182 results on '"membrane channels"'
Search Results
2. Structural insights into the orthosteric inhibition of P2X receptors by non-ATP analog antagonists
- Author
-
Danqi Sheng, Chen-Xi Yue, Fei Jin, Yao Wang, Muneyoshi Ichikawa, Ye Yu, Chang-Run Guo, and Motoyuki Hattori
- Subjects
membrane channels ,receptors ,electron microscopy ,electrophysiology ,Medicine ,Science ,Biology (General) ,QH301-705.5 - Abstract
P2X receptors are extracellular ATP-gated ion channels that form homo- or heterotrimers and consist of seven subtypes. They are expressed in various tissues, including neuronal and nonneuronal cells, and play critical roles in physiological processes such as neurotransmission, inflammation, pain, and cancer. As a result, P2X receptors have attracted considerable interest as drug targets, and various competitive inhibitors have been developed. However, although several P2X receptor structures from different subtypes have been reported, the limited structural information of P2X receptors in complex with competitive antagonists hampers the understanding of orthosteric inhibition, hindering the further design and optimization of those antagonists for drug discovery. We determined the cryogenic electron microscopy (cryo-EM) structures of the mammalian P2X7 receptor in complex with two classical competitive antagonists of pyridoxal-5'-phosphate derivatives, pyridoxal-5'-phosphate-6-(2'-naphthylazo-6'-nitro-4',8'-disulfonate) (PPNDS) and pyridoxal phosphate-6-azophenyl-2′,5′-disulfonic acid (PPADS), and performed structure-based mutational analysis by patch-clamp recording as well as molecular dynamics (MD) simulations. Our structures revealed the orthosteric site for PPADS/PPNDS, and structural comparison with the previously reported apo- and ATP-bound structures showed how PPADS/PPNDS binding inhibits the conformational changes associated with channel activation. In addition, structure-based mutational analysis identified key residues involved in the PPNDS sensitivity of P2X1 and P2X3, which are known to have higher affinity for PPADS/PPNDS than other P2X subtypes.
- Published
- 2024
- Full Text
- View/download PDF
3. Proteome and Membrane Channels
- Author
-
Pasquarelli, Alberto and Pasquarelli, Alberto
- Published
- 2021
- Full Text
- View/download PDF
4. Anesthetics and Cell–Cell Communication: Potential Ca 2+ -Calmodulin Role in Gap Junction Channel Gating by Heptanol, Halothane and Isoflurane.
- Author
-
Peracchia, Camillo
- Subjects
- *
ISOFLURANE , *CAFFEINE , *ANESTHETICS , *PHORBOL esters , *ION channels , *FORSKOLIN , *CALMODULIN , *THEOPHYLLINE - Abstract
Cell–cell communication via gap junction channels is known to be inhibited by the anesthetics heptanol, halothane and isoflurane; however, despite numerous studies, the mechanism of gap junction channel gating by anesthetics is still poorly understood. In the early nineties, we reported that gating by anesthetics is strongly potentiated by caffeine and theophylline and inhibited by 4-Aminopyridine. Neither Ca2+ channel blockers nor 3-isobutyl-1-methylxanthine (IBMX), forskolin, CPT-cAMP, 8Br-cGMP, adenosine, phorbol ester or H7 had significant effects on gating by anesthetics. In our publication, we concluded that neither cytosolic Ca2+i nor pHi were involved, and suggested a direct effect of anesthetics on gap junction channel proteins. However, while a direct effect cannot be excluded, based on the potentiating effect of caffeine and theophylline added to anesthetics and data published over the past three decades, we are now reconsidering our earlier interpretation and propose an alternative hypothesis that uncoupling by heptanol, halothane and isoflurane may actually result from a rise in cytosolic Ca2+ concentration ([Ca2+]i) and consequential activation of calmodulin linked to gap junction proteins. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
5. The murburn precepts for cellular ionic homeostasis and electrophysiology.
- Author
-
Manoj, Kelath Murali, Bazhin, Nikolai, and Tamagawa, Hirohisa
- Subjects
- *
MOLECULAR structure , *HOMEOSTASIS , *MONOVALENT cations , *CALCIUM ions , *ACTION potentials , *SOLUBILIZATION , *ELECTROPHYSIOLOGY - Abstract
Starting from the basic molecular structure and redox properties of its components, we build a macroscopic cellular electrophysiological model. We first present a murburn purview that could explain ion distribution in bulk‐milieu/membrane‐interface and support the origin of trans‐membrane potential (TMP) in cells. In particular, the discussion focuses on how cells achieve disparity in the distribution of monovalent and divalent cations within (K+ > Na+ > Mg2+ > Ca2+) and outside (Na+ > K+ > Ca2+ > Mg2+). We explore how TMP could vary for resting/graded/action potentials generation and project a model for impulse conduction in neurons. Outcomes based on murburn bioenergetic equilibriums leading to solubilization of ion‐pairs, membrane's permittivity, protein channels' fluxes, and proteins' innate ability to bind/adsorb ions selectively are projected as the integral rationale. We also provide experimental modalities to ratify the projections. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
6. Digging into the biophysical features of cell membranes with lipid-DNA conjugates.
- Author
-
Ali, Ahsan Ausaf, Bagheri, Yousef, and You, Mingxu
- Subjects
- *
CELL membranes , *BIOPHYSICS , *MEMBRANE lipids , *DNA probes - Abstract
Lipid-DNA conjugates have emerged as highly useful tools to modify the cell membranes. These conjugates generally consist of a lipid anchor for membrane modification and a functional DNA nanostructure for membrane analysis or regulation. There are several unique properties of these lipid-DNA conjugates, especially including their programmability, fast and efficient membrane insertion, and precise sequence-specific assembly. These unique properties have enabled a broad range of biophysical applications on live cell membranes. In this review, we will mainly focus on recent tremendous progress, especially during the past three years, in regulating the biophysical features of these lipid-DNA conjugates and their key applications in studying cell membrane biophysics. Some insights into the current challenges and future directions of this interdisciplinary field have also been provided. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
7. Molecular mechanism of thiamine pyrophosphate import into mitochondria: a molecular simulation study.
- Author
-
Van Liefferinge, F., Krammer, E.-M., Waeytens, J., and Prévost, M.
- Subjects
- *
THIAMIN pyrophosphate , *MOLECULAR dynamics , *PLANT mitochondria , *MITOCHONDRIA , *BINDING sites , *MITOCHONDRIAL membranes - Abstract
The import of thiamine pyrophosphate (TPP) through both mitochondrial membranes was studied using a total of 3-µs molecular dynamics simulations. Regarding the translocation through the mitochondrial outer membrane, our simulations support the conjecture that TPP uses the voltage-dependent anion channel, the major pore of this membrane, for its passage to the intermembrane space, as its transport presents significant analogies with that used by other metabolites previously studied, in particular with ATP. As far as passing through the mitochondrial inner membrane is concerned, our simulations show that the specific carrier of TPP has a single binding site that becomes accessible, through an alternating access mechanism. The preference of this transporter for TPP can be rationalized mainly by three residues located in the binding site that differ from those identified in the ATP/ADP carrier, the most studied member of the mitochondrial carrier family. The simulated transport mechanism of TPP highlights the essential role, at the energetic level, of the contributions coming from the formation and breakage of two networks of salt bridges, one on the side of the matrix and the other on the side of the intermembrane space, as well as the interactions, mainly of an ionic nature, formed by TPP upon its binding. The energy contribution provided by the cytosolic network establishes a lower barrier than that of the matrix network, which can be explained by the lower interaction energy of TPP on the matrix side or possibly a uniport activity. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
8. A Visible‐Light‐Regulated Chloride Transport Channel Inspired by Rhodopsin.
- Author
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Quan, Jiaxin, Zhu, Fei, Dhinakaran, Manivannan Kalavathi, Yang, Yingying, Johnson, Robert P., and Li, Haibing
- Subjects
- *
CHLORIDE channels , *RHODOPSIN , *BIOLOGICAL transport , *CHEMICAL models , *VISIBLE spectra , *CUCURBITURIL - Abstract
Inspired by the light‐regulating capabilities of naturally occurring rhodopsin, we have constructed a visible‐light‐regulated Cl−‐transport membrane channel based on a supramolecular host–guest interaction. A natural retinal chromophore, capable of a visible‐light response, is used as the guest and grafted into the artificial channel. Upon introduction of an ethyl‐urea‐derived pillar[6]arene (Urea‐P6) host, threading or de‐threading of the retinal and selective bonding of Cl− can be utilized to regulate ion transport. Based on the visible‐light responsiveness of the host–guest interaction, Cl− transport can be regulated by visible light between ON and OFF states. Visible‐light‐regulated Cl− transport as a chemical model permits to understand comparable biological ion‐selective transport behaviors. Furthermore, this result also supplies a smart visible‐light‐responsive Cl− transporter, which may have applications in natural photoelectric conversion and photo‐controlled delivery systems. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
9. Structural insights into the orthosteric inhibition of P2X receptors by non-ATP analog antagonists.
- Author
-
Sheng D, Yue CX, Jin F, Wang Y, Ichikawa M, Yu Y, Guo CR, and Hattori M
- Subjects
- Animals, Mammals, Molecular Dynamics Simulation, Adenosine Triphosphate chemistry
- Abstract
P2X receptors are extracellular ATP-gated ion channels that form homo- or heterotrimers and consist of seven subtypes. They are expressed in various tissues, including neuronal and nonneuronal cells, and play critical roles in physiological processes such as neurotransmission, inflammation, pain, and cancer. As a result, P2X receptors have attracted considerable interest as drug targets, and various competitive inhibitors have been developed. However, although several P2X receptor structures from different subtypes have been reported, the limited structural information of P2X receptors in complex with competitive antagonists hampers the understanding of orthosteric inhibition, hindering the further design and optimization of those antagonists for drug discovery. We determined the cryogenic electron microscopy (cryo-EM) structures of the mammalian P2X7 receptor in complex with two classical competitive antagonists of pyridoxal-5'-phosphate derivatives, pyridoxal-5'-phosphate-6-(2'-naphthylazo-6'-nitro-4',8'-disulfonate) (PPNDS) and pyridoxal phosphate-6-azophenyl-2',5'-disulfonic acid (PPADS), and performed structure-based mutational analysis by patch-clamp recording as well as molecular dynamics (MD) simulations. Our structures revealed the orthosteric site for PPADS/PPNDS, and structural comparison with the previously reported apo- and ATP-bound structures showed how PPADS/PPNDS binding inhibits the conformational changes associated with channel activation. In addition, structure-based mutational analysis identified key residues involved in the PPNDS sensitivity of P2X1 and P2X3, which are known to have higher affinity for PPADS/PPNDS than other P2X subtypes., Competing Interests: DS, CY, FJ, YW, MI, YY, CG, MH No competing interests declared, (© 2023, Sheng, Yue et al.)
- Published
- 2024
- Full Text
- View/download PDF
10. Effects of Moderate Static Magnetic Field on Neural Systems Is a Non-invasive Mechanical Stimulation of the Brain Possible Theoretically?
- Author
-
Antonio Hernando, Fernando Galvez, Miguel A. García, Vanesa Soto-León, Carlos Alonso-Bonilla, Juan Aguilar, and Antonio Oliviero
- Subjects
static magnetic field ,Zeeman energy ,membrane channels ,non-invasive brain stimulation ,mechanical stimulation ,Neurosciences. Biological psychiatry. Neuropsychiatry ,RC321-571 - Abstract
Static magnetic fields have been shown to induce effects on the human brain. Different experiments seem to support the idea that moderate static magnetic field can exert some influence on the gating processes of the membrane channels. In this article we visit the order of magnitude of the energy magnetic terms associated with moderate applied field (between 10 and 200 milliteslas). It is shown that gradients of the Zeeman energy associated with the inhomogeneous applied fields can induce pressures of the order of 10–2Pa. The surface tension generated by the magnetic pressure, on the surface delimiting the brain region subject to relevant field and gradients, is found to range between 10–1 and 1 mN⋅m–1. These pressures seem to be strong enough to interfere with the elastic and electrostatic energies involved in the channel activation-inactivation-deactivation mechanisms of biological membranes. It has been described that small mechanical force can activate voltage gated potassium channels. Moreover, stretch-activated ion channels are widely described in different biological tissues. Virtually, all these channels can modify their activity if stressed by a sufficient pressure delivered for enough time. We propose mechanical stimulation – possibly not exclusively – as a candidate mechanism how static magnetic field can produce effects in biological systems. It must be emphasized, that such field gradients were not previously proposed as a possible source of neural activity modification.
- Published
- 2020
- Full Text
- View/download PDF
11. Apolipoprotein L-1 renal risk variants form active channels at the plasma membrane driving cytotoxicity
- Author
-
Joseph A Giovinazzo, Russell P Thomson, Nailya Khalizova, Patrick J Zager, Nirav Malani, Enrique Rodriguez-Boulan, Jayne Raper, and Ryan Schreiner
- Subjects
protein trafficking ,membrane channels ,ion channel ,apolipoprotein l1 ,polymorphism ,Medicine ,Science ,Biology (General) ,QH301-705.5 - Abstract
Recently evolved alleles of Apolipoprotein L-1 (APOL1) provide increased protection against African trypanosome parasites while also significantly increasing the risk of developing kidney disease in humans. APOL1 protects against trypanosome infections by forming ion channels within the parasite, causing lysis. While the correlation to kidney disease is robust, there is little consensus concerning the underlying disease mechanism. We show in human cells that the APOL1 renal risk variants have a population of active channels at the plasma membrane, which results in an influx of both Na+ and Ca2+. We propose a model wherein APOL1 channel activity is the upstream event causing cell death, and that the activate-state, plasma membrane-localized channel represents the ideal drug target to combat APOL1-mediated kidney disease.
- Published
- 2020
- Full Text
- View/download PDF
12. Direct binding of phosphatidylglycerol at specific sites modulates desensitization of a ligand-gated ion channel
- Author
-
Ailing Tong, John T Petroff II, Fong-Fu Hsu, Philipp AM Schmidpeter, Crina M Nimigean, Liam Sharp, Grace Brannigan, and Wayland WL Cheng
- Subjects
mass spectrometry ,membrane channels ,phospholipids ,desensitization ,Medicine ,Science ,Biology (General) ,QH301-705.5 - Abstract
Pentameric ligand-gated ion channels (pLGICs) are essential determinants of synaptic transmission, and are modulated by specific lipids including anionic phospholipids. The exact modulatory effect of anionic phospholipids in pLGICs and the mechanism of this effect are not well understood. Using native mass spectrometry, coarse-grained molecular dynamics simulations and functional assays, we show that the anionic phospholipid, 1-palmitoyl-2-oleoyl phosphatidylglycerol (POPG), preferentially binds to and stabilizes the pLGIC, Erwinia ligand-gated ion channel (ELIC), and decreases ELIC desensitization. Mutations of five arginines located in the interfacial regions of the transmembrane domain (TMD) reduce POPG binding, and a subset of these mutations increase ELIC desensitization. In contrast, a mutation that decreases ELIC desensitization, increases POPG binding. The results support a mechanism by which POPG stabilizes the open state of ELIC relative to the desensitized state by direct binding at specific sites.
- Published
- 2019
- Full Text
- View/download PDF
13. Effects of Moderate Static Magnetic Field on Neural Systems Is a Non-invasive Mechanical Stimulation of the Brain Possible Theoretically?
- Author
-
Hernando, Antonio, Galvez, Fernando, García, Miguel A., Soto-León, Vanesa, Alonso-Bonilla, Carlos, Aguilar, Juan, and Oliviero, Antonio
- Subjects
BRAIN stimulation ,CYBERNETICS ,MAGNETIC fields ,BIOLOGICAL membranes ,POTASSIUM channels ,TISSUES - Abstract
Static magnetic fields have been shown to induce effects on the human brain. Different experiments seem to support the idea that moderate static magnetic field can exert some influence on the gating processes of the membrane channels. In this article we visit the order of magnitude of the energy magnetic terms associated with moderate applied field (between 10 and 200 milliteslas). It is shown that gradients of the Zeeman energy associated with the inhomogeneous applied fields can induce pressures of the order of 10
–2 Pa. The surface tension generated by the magnetic pressure, on the surface delimiting the brain region subject to relevant field and gradients, is found to range between 10–1 and 1 mN⋅m–1 . These pressures seem to be strong enough to interfere with the elastic and electrostatic energies involved in the channel activation-inactivation-deactivation mechanisms of biological membranes. It has been described that small mechanical force can activate voltage gated potassium channels. Moreover, stretch-activated ion channels are widely described in different biological tissues. Virtually, all these channels can modify their activity if stressed by a sufficient pressure delivered for enough time. We propose mechanical stimulation – possibly not exclusively – as a candidate mechanism how static magnetic field can produce effects in biological systems. It must be emphasized, that such field gradients were not previously proposed as a possible source of neural activity modification. [ABSTRACT FROM AUTHOR]- Published
- 2020
- Full Text
- View/download PDF
14. Calmodulin-Mediated Regulation of Gap Junction Channels.
- Author
-
Peracchia, Camillo
- Subjects
- *
CALMODULIN , *CONNEXINS , *CELL death , *NINETEENTH century - Abstract
Evidence that neighboring cells uncouple from each other as one dies surfaced in the late 19th century, but it took almost a century for scientists to start understanding the uncoupling mechanism (chemical gating). The role of cytosolic free calcium (Ca2+ i) in cell–cell channel gating was first reported in the mid-sixties. In these studies, only micromolar [Ca2+]i were believed to affect gating—concentrations reachable only in cell death, which would discard Ca2+ i as a fine modulator of cell coupling. More recently, however, numerous researchers, including us, have reported the effectiveness of nanomolar [Ca2+]i. Since connexins do not have high-affinity calcium sites, the effectiveness of nanomolar [Ca2+]i suggests the role of Ca-modulated proteins, with calmodulin (CaM) being most obvious. Indeed, in 1981 we first reported that a CaM-inhibitor prevents chemical gating. Since then, the CaM role in gating has been confirmed by studies that tested it with a variety of approaches such as treatments with CaM-inhibitors, inhibition of CaM expression, expression of CaM mutants, immunofluorescent co-localization of CaM and gap junctions, and binding of CaM to peptides mimicking connexin domains identified as CaM targets. Our gating model envisions Ca2+-CaM to directly gate the channels by acting as a plug (“Cork” gating model), and probably also by affecting connexin conformation. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
15. Major regulatory mechanisms involved in sperm motility
- Author
-
Rute Pereira, Rosália Sá, Alberto Barros, and Mário Sousa
- Subjects
antioxidants ,calcium ,membrane channels ,protein kinases ,sperm genetic abnormalities ,sperm motility ,Diseases of the genitourinary system. Urology ,RC870-923 - Abstract
The genetic bases and molecular mechanisms involved in the assembly and function of the flagellum components as well as in the regulation of the flagellar movement are not fully understood, especially in humans. There are several causes for sperm immotility, of which some can be avoided and corrected, whereas other are related to genetic defects and deserve full investigation to give a diagnosis to patients. This review was performed after an extensive literature search on the online databases PubMed, ScienceDirect, and Web of Science. Here, we review the involvement of regulatory pathways responsible for sperm motility, indicating possible causes for sperm immotility. These included the calcium pathway, the cAMP-dependent protein kinase pathway, the importance of kinases and phosphatases, the function of reactive oxygen species, and how the regulation of cell volume and osmolarity are also fundamental components. We then discuss main gene defects associated with specific morphological abnormalities. Finally, we slightly discuss some preventive and treatments approaches to avoid development of conditions that are associated with unspecified sperm immotility. We believe that in the near future, with the development of more powerful techniques, the genetic causes of sperm immotility and the regulatory mechanisms of sperm motility will be better understand, thus enabling to perform a full diagnosis and uncover new therapies.
- Published
- 2017
- Full Text
- View/download PDF
16. TMC1 is an essential component of a leak channel that modulates tonotopy and excitability of auditory hair cells in mice
- Author
-
Shuang Liu, Shufeng Wang, Linzhi Zou, Jie Li, Chenmeng Song, Jiaofeng Chen, Qun Hu, Lian Liu, Pingbo Huang, and Wei Xiong
- Subjects
TMC1 ,mechanotransduction ,leak conductance ,membrane channels ,tonotopy ,hair cells ,Medicine ,Science ,Biology (General) ,QH301-705.5 - Abstract
Hearing sensation relies on the mechano-electrical transducer (MET) channel of cochlear hair cells, in which transmembrane channel-like 1 (TMC1) and transmembrane channel-like 2 (TMC2) have been proposed to be the pore-forming subunits in mammals. TMCs were also found to regulate biological processes other than MET in invertebrates, ranging from sensations to motor function. However, whether TMCs have a non-MET role remains elusive in mammals. Here, we report that in mouse hair cells, TMC1, but not TMC2, provides a background leak conductance, with properties distinct from those of the MET channels. By cysteine substitutions in TMC1, we characterized four amino acids that are required for the leak conductance. The leak conductance is graded in a frequency-dependent manner along the length of the cochlea and is indispensable for action potential firing. Taken together, our results show that TMC1 confers a background leak conductance in cochlear hair cells, which may be critical for the acquisition of sound-frequency and -intensity.
- Published
- 2019
- Full Text
- View/download PDF
17. Structural and functional characterization of an otopetrin family proton channel
- Author
-
Qingfeng Chen, Weizhong Zeng, Ji She, Xiao-chen Bai, and Youxing Jiang
- Subjects
otopetrin ,proton ,membrane channels ,cryo-EM ,Medicine ,Science ,Biology (General) ,QH301-705.5 - Abstract
The otopetrin (OTOP) proteins were recently characterized as proton channels. Here we present the cryo-EM structure of OTOP3 from Xenopus tropicalis (XtOTOP3) along with functional characterization of the channel. XtOTOP3 forms a homodimer with each subunit containing 12 transmembrane helices that can be divided into two structurally homologous halves; each half assembles as an α-helical barrel that could potentially serve as a proton conduction pore. Both pores open from the extracellular half before becoming occluded at a central constriction point consisting of three highly conserved residues – Gln232/585-Asp262/Asn623-Tyr322/666 (the constriction triads). Mutagenesis shows that the constriction triad from the second pore is less amenable to perturbation than that of the first pore, suggesting an unequal contribution between the two pores to proton transport. We also identified several key residues at the interface between the two pores that are functionally important, particularly Asp509, which confers intracellular pH-dependent desensitization to OTOP channels.
- Published
- 2019
- Full Text
- View/download PDF
18. Structural basis of Ca2+-dependent activation and lipid transport by a TMEM16 scramblase
- Author
-
Maria E Falzone, Jan Rheinberger, Byoung-Cheol Lee, Thasin Peyear, Linda Sasset, Ashleigh M Raczkowski, Edward T Eng, Annarita Di Lorenzo, Olaf S Andersen, Crina M Nimigean, and Alessio Accardi
- Subjects
Scrambling ,membrane structure ,membrane channels ,phospholipids ,Medicine ,Science ,Biology (General) ,QH301-705.5 - Abstract
The lipid distribution of plasma membranes of eukaryotic cells is asymmetric and phospholipid scramblases disrupt this asymmetry by mediating the rapid, nonselective transport of lipids down their concentration gradients. As a result, phosphatidylserine is exposed to the outer leaflet of membrane, an important step in extracellular signaling networks controlling processes such as apoptosis, blood coagulation, membrane fusion and repair. Several TMEM16 family members have been identified as Ca2+-activated scramblases, but the mechanisms underlying their Ca2+-dependent gating and their effects on the surrounding lipid bilayer remain poorly understood. Here, we describe three high-resolution cryo-electron microscopy structures of a fungal scramblase from Aspergillus fumigatus, afTMEM16, reconstituted in lipid nanodiscs. These structures reveal that Ca2+-dependent activation of the scramblase entails global rearrangement of the transmembrane and cytosolic domains. These structures, together with functional experiments, suggest that activation of the protein thins the membrane near the transport pathway to facilitate rapid transbilayer lipid movement.
- Published
- 2019
- Full Text
- View/download PDF
19. Structure and Function of Ion Channels Regulating Sperm Motility—An Overview
- Author
-
Karolina Nowicka-Bauer and Monika Szymczak-Cendlak
- Subjects
sperm motility ,ion channels ,membrane channels ,calcium ,potassium ,chloride ,Biology (General) ,QH301-705.5 ,Chemistry ,QD1-999 - Abstract
Sperm motility is linked to the activation of signaling pathways that trigger movement. These pathways are mainly dependent on Ca2+, which acts as a secondary messenger. The maintenance of adequate Ca2+ concentrations is possible thanks to proper concentrations of other ions, such as K+ and Na+, among others, that modulate plasma membrane potential and the intracellular pH. Like in every cell, ion homeostasis in spermatozoa is ensured by a vast spectrum of ion channels supported by the work of ion pumps and transporters. To achieve success in fertilization, sperm ion channels have to be sensitive to various external and internal factors. This sensitivity is provided by specific channel structures. In addition, novel sperm-specific channels or isoforms have been found with compositions that increase the chance of fertilization. Notably, the most significant sperm ion channel is the cation channel of sperm (CatSper), which is a sperm-specific Ca2+ channel required for the hyperactivation of sperm motility. The role of other ion channels in the spermatozoa, such as voltage-gated Ca2+ channels (VGCCs), Ca2+-activated Cl-channels (CaCCs), SLO K+ channels or voltage-gated H+ channels (VGHCs), is to ensure the activation and modulation of CatSper. As the activation of sperm motility differs among metazoa, different ion channels may participate; however, knowledge regarding these channels is still scarce. In the present review, the roles and structures of the most important known ion channels are described in regard to regulation of sperm motility in animals.
- Published
- 2021
- Full Text
- View/download PDF
20. Biomimetic DNA Nanotubes: Nanoscale Channel Design and Applications.
- Author
-
Liu, Xiaoguo, Zhao, Yan, Liu, Pi, Wang, Lihua, Lin, Jianping, and Fan, Chunhai
- Subjects
- *
NANOTUBES , *DNA , *DNA nanotechnology , *CONSTRUCTION materials , *DNA primers - Abstract
Biomacromolecular nanotubes play important physiological roles in transmembrane ion/molecule channeling, intracellular transport, and inter‐cellular communications. While genetically encoded protein nanotubes are prevalent in vivo, the in vitro construction of biomimetic DNA nanotubes has attracted intense interest with the rise of structural DNA nanotechnology. The abiotic use of DNA assembly provides a powerful bottom‐up approach for the rational construction of complex materials with arbitrary size and shape at the nanoscale. More specifically, a typical DNA nanotube can be assembled either with parallel‐aligned DNA duplexes or by closing DNA tile lattices. These artificial DNA nanotubes can be tailored and site‐specifically modified to realize biomimetic functions including ionic or molecular channeling, bioreactors, drug delivery, and biomolecular sensing. In this Minireview, we aim to summarize recent advances in design strategies, including the characterization and applications of biomimetic DNA nanotubes. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
21. Small‐Molecule Permeation across Membrane Channels: Chemical Modification to Quantify Transport across OmpF.
- Author
-
Wang, Jiajun, Bafna, Jayesh Arun, Bhamidimarri, Satya Prathyusha, and Winterhalter, Mathias
- Subjects
- *
CURRENT fluctuations , *BACTERIAL cell membranes , *ACTIVATION energy , *NORFLOXACIN - Abstract
Biological channels facilitate the exchange of molecules across membranes, but general tools to quantify transport are missing. Electrophysiology is the method of choice to study the functional properties of channels. However, analyzing the current fluctuation of channels typically does not identify successful transport, that is, distinguishing translocation from binding. To distinguish both processes, we added an additional barrier at the channel exit acting as a molecular counter. To identify permeation, we compare the molecule residence time in the native channel with one that is chemically modified at the exit. We use the well‐studied outer membrane channel from E. coli, OmpF. Position 181, which is below the constriction region, was subsequently mutated into cysteine (E181C) in an otherwise cysteine‐free system, then functionalized by covalent binding with one of the two blockers MTSES or GLT. We measured the passage of model peptides, mono‐, tri‐, hepta‐arginine and of norfloxacin, as an example for antibiotic permeation. A molecule counter, added at the channel exit of a bacterial cell membrane pore creates an additional energy barrier to quantify molecules that permeate. The efficiency with charged peptides was tested. In a second series the antibiotic norfloxacin was tested. Introducing the partial channel blocker allows to distinguish binding from translocation for a broad range of molecules. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
22. Calmodulin-Mediated Regulation of Gap Junction Channels
- Author
-
Camillo Peracchia
- Subjects
gap junctions ,connexins ,innexins ,calmodulin ,membrane channels ,channel gating ,calcium ,ph ,chemical gating ,voltage gating ,Biology (General) ,QH301-705.5 ,Chemistry ,QD1-999 - Abstract
Evidence that neighboring cells uncouple from each other as one dies surfaced in the late 19th century, but it took almost a century for scientists to start understanding the uncoupling mechanism (chemical gating). The role of cytosolic free calcium (Ca2+i) in cell−cell channel gating was first reported in the mid-sixties. In these studies, only micromolar [Ca2+]i were believed to affect gating—concentrations reachable only in cell death, which would discard Ca2+i as a fine modulator of cell coupling. More recently, however, numerous researchers, including us, have reported the effectiveness of nanomolar [Ca2+]i. Since connexins do not have high-affinity calcium sites, the effectiveness of nanomolar [Ca2+]i suggests the role of Ca-modulated proteins, with calmodulin (CaM) being most obvious. Indeed, in 1981 we first reported that a CaM-inhibitor prevents chemical gating. Since then, the CaM role in gating has been confirmed by studies that tested it with a variety of approaches such as treatments with CaM-inhibitors, inhibition of CaM expression, expression of CaM mutants, immunofluorescent co-localization of CaM and gap junctions, and binding of CaM to peptides mimicking connexin domains identified as CaM targets. Our gating model envisions Ca2+-CaM to directly gate the channels by acting as a plug (“Cork” gating model), and probably also by affecting connexin conformation.
- Published
- 2020
- Full Text
- View/download PDF
23. Gap Junction Channel Structure
- Author
-
Yeager, Mark, Harris, Andrew L., editor, and Locke, Darren, editor
- Published
- 2009
- Full Text
- View/download PDF
24. Cation selectivity of the presequence translocase channel Tim23 is crucial for efficient protein import
- Author
-
Niels Denkert, Alexander Benjamin Schendzielorz, Mariam Barbot, Lennart Versemann, Frank Richter, Peter Rehling, and Michael Meinecke
- Subjects
mitochondria ,protein trafficking ,Tim23 ,electrophysiology ,mitochondrial biogenesis ,membrane channels ,Medicine ,Science ,Biology (General) ,QH301-705.5 - Abstract
Virtually all mitochondrial matrix proteins and a considerable number of inner membrane proteins carry a positively charged, N-terminal presequence and are imported by the TIM23 complex (presequence translocase) located in the inner mitochondrial membrane. The voltage-regulated Tim23 channel constitutes the actual protein-import pore wide enough to allow the passage of polypeptides with a secondary structure. In this study, we identify amino acids important for the cation selectivity of Tim23. Structure based mutants show that selectivity is provided by highly conserved, pore-lining amino acids. Mutations of these amino acid residues lead to reduced selectivity properties, reduced protein import capacity and they render the Tim23 channel insensitive to substrates. We thus show that the cation selectivity of the Tim23 channel is a key feature for substrate recognition and efficient protein import.
- Published
- 2017
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25. Major regulatory mechanisms involved in sperm motility.
- Author
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Pereira, Rute, Sá, Rosália, Barros, Alberto, and Sousa, Mário
- Abstract
The genetic bases and molecular mechanisms involved in the assembly and function of the flagellum components as well as in the regulation of the flagellar movement are not fully understood, especially in humans. There are several causes for sperm immotility, of which some can be avoided and corrected, whereas other are related to genetic defects and deserve full investigation to give a diagnosis to patients. This review was performed after an extensive literature search on the online databases PubMed, ScienceDirect, and Web of Science. Here, we review the involvement of regulatory pathways responsible for sperm motility, indicating possible causes for sperm immotility. These included the calcium pathway, the cAMP‑dependent protein kinase pathway, the importance of kinases and phosphatases, the function of reactive oxygen species, and how the regulation of cell volume and osmolarity are also fundamental components. We then discuss main gene defects associated with specific morphological abnormalities. Finally, we slightly discuss some preventive and treatments approaches to avoid development of conditions that are associated with unspecified sperm immotility. We believe that in the near future, with the development of more powerful techniques, the genetic causes of sperm immotility and the regulatory mechanisms of sperm motility will be better understand, thus enabling to perform a full diagnosis and uncover new therapies. [ABSTRACT FROM AUTHOR]
- Published
- 2017
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- View/download PDF
26. Proton currents constrain structural models of voltage sensor activation
- Author
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Aaron L Randolph, Younes Mokrab, Ashley L Bennett, Mark SP Sansom, and Ian Scott Ramsey
- Subjects
proton transport ,membrane channels ,channel gating ,voltage sensor ,protein structure ,Medicine ,Science ,Biology (General) ,QH301-705.5 - Abstract
The Hv1 proton channel is evidently unique among voltage sensor domain proteins in mediating an intrinsic ‘aqueous’ H+ conductance (GAQ). Mutation of a highly conserved ‘gating charge’ residue in the S4 helix (R1H) confers a resting-state H+ ‘shuttle’ conductance (GSH) in VGCs and Ci VSP, and we now report that R1H is sufficient to reconstitute GSH in Hv1 without abrogating GAQ. Second-site mutations in S3 (D185A/H) and S4 (N4R) experimentally separate GSH and GAQ gating, which report thermodynamically distinct initial and final steps, respectively, in the Hv1 activation pathway. The effects of Hv1 mutations on GSH and GAQ are used to constrain the positions of key side chains in resting- and activated-state VS model structures, providing new insights into the structural basis of VS activation and H+ transfer mechanisms in Hv1.
- Published
- 2016
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- View/download PDF
27. Low noise patch‐clamp current amplification by nanoparticles plasmonic–photonic coupling (analysis and modelling).
- Author
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Haberal, E. O., SalmanOgli, A., and Nasseri, B.
- Abstract
In this article, a patch‐clamp low noise current amplification based on nanoparticles plasmonic radiation is analyzed. It is well‐known, a very small current is flowing from different membrane channels and so, for extra processing the current amplification is necessary. It is notable that there are some problems in traditional electronic amplifier due to its noise and bandwidth problem. Because of the important role of the patch‐clamp current in cancer research and especially its small amplitude, it is vital to intensify it without adding any noises. In this study, the current amplification is performed firstly: from the excitement of nanoparticles by the patch‐clamp pico‐ampere current and then, the effect of nanoparticles plasmonic far‐field radiation on conductor's carriers, which will cause the current amplification. This relates to the plasmonic‐photonic coupling and their effect on conductor carriers as the current perturbation agent. In the steady state, the current amplification can reach to 1000 times of initial level. Furthermore, we investigated the nanoparticles morphology changing effect such as size, nanoparticles inter‐distance, and nanoparticles distance from the conductor on the amplifier parameters. Finally, it should note that the original aim is to use nanoparticles plasmonic engineering and their coupling to photonics for output current manipulating. [ABSTRACT FROM AUTHOR]
- Published
- 2016
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28. Peroxisomal Pex11 is a pore-forming protein homologous to TRPM channels.
- Author
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Mindthoff, Sabrina, Grunau, Silke, Steinfort, Laura L., Girzalsky, Wolfgang, Hiltunen, J. Kalervo, Erdmann, Ralf, and Antonenkov, Vasily D.
- Subjects
- *
PEROXISOMES , *LIPID metabolism , *TRP channels , *GENETIC mutation , *GENETIC overexpression , *MEMBRANE proteins , *ORIGIN of life - Abstract
More than 30 proteins (Pex proteins) are known to participate in the biogenesis of peroxisomes—ubiquitous oxidative organelles involved in lipid and ROS metabolism. The Pex11 family of homologous proteins is responsible for division and proliferation of peroxisomes. We show that yeast Pex11 is a pore-forming protein sharing sequence similarity with TRPM cation-selective channels. The Pex11 channel with a conductance of Λ = 4.1 nS in 1.0 M KCl is moderately cation-selective ( P K + / P Cl − = 1.85) and resistant to voltage-dependent closing. The estimated size of the channel's pore (r ~ 0.6 nm) supports the notion that Pex11 conducts solutes with molecular mass below 300–400 Da. We localized the channel's selectivity determining sequence. Overexpression of Pex11 resulted in acceleration of fatty acids β-oxidation in intact cells but not in the corresponding lysates. The β-oxidation was affected in cells by expression of the Pex11 protein carrying point mutations in the selectivity determining sequence. These data suggest that the Pex11-dependent transmembrane traffic of metabolites may be a rate-limiting step in the β-oxidation of fatty acids. This conclusion was corroborated by analysis of the rate of β-oxidation in yeast strains expressing Pex11 with mutations mimicking constitutively phosphorylated (S165D, S167D) or unphosphorylated (S165A, S167A) protein. The results suggest that phosphorylation of Pex11 is a mechanism that can control the peroxisomal β-oxidation rate. Our results disclose an unexpected function of Pex11 as a non-selective channel responsible for transfer of metabolites across peroxisomal membrane. The data indicate that peroxins may be involved in peroxisomal metabolic processes in addition to their role in peroxisome biogenesis. [ABSTRACT FROM AUTHOR]
- Published
- 2016
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29. Introduction to the Theme on Membrane Channels
- Author
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von Heijne, Gunnar and von Heijne, Gunnar
- Abstract
This volume of the Annual Review of Biochemistry contains three reviews on membrane channel proteins: the first by Szczot et al., titled The Form and Function of PIEZO2; the second by Ruprecht & Kunji, titled Structural Mechanism of Transport of Mitochondrial Carriers; and the third by McIlwain et al., titled Membrane Exporters of Fluoride Ion. These reviews provide nice illustrations of just how far evolution has been able to play with the basic helix-bundle architecture of integral membrane proteins to produce membrane channels and transporters of widely different functions.
- Published
- 2021
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30. Molecular mechanism of thiamine pyrophosphate import into mitochondria: a molecular simulation study
- Author
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Van Liefferinge, François, Krammer, Eva-Maria, Waeytens, Jehan, Prévost, Martine, Van Liefferinge, François, Krammer, Eva-Maria, Waeytens, Jehan, and Prévost, Martine
- Abstract
The import of thiamine pyrophosphate (TPP) through both mitochondrial membranes was studied using a total of 3-µs molecular dynamics simulations. Regarding the translocation through the mitochondrial outer membrane, our simulations support the conjecture that TPP uses the voltage-dependent anion channel, the major pore of this membrane, for its passage to the intermembrane space, as its transport presents significant analogies with that used by other metabolites previously studied, in particular with ATP. As far as passing through the mitochondrial inner membrane is concerned, our simulations show that the specific carrier of TPP has a single binding site that becomes accessible, through an alternating access mechanism. The preference of this transporter for TPP can be rationalized mainly by three residues located in the binding site that differ from those identified in the ATP/ADP carrier, the most studied member of the mitochondrial carrier family. The simulated transport mechanism of TPP highlights the essential role, at the energetic level, of the contributions coming from the formation and breakage of two networks of salt bridges, one on the side of the matrix and the other on the side of the intermembrane space, as well as the interactions, mainly of an ionic nature, formed by TPP upon its binding. The energy contribution provided by the cytosolic network establishes a lower barrier than that of the matrix network, which can be explained by the lower interaction energy of TPP on the matrix side or possibly a uniport activity., SCOPUS: ar.j, info:eu-repo/semantics/published
- Published
- 2021
31. The Ciliary Muscle and Zonules of Zinn Modulate Lens Intracellular Hydrostatic Pressure Through Transient Receptor Potential Vanilloid Channels
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Paul J. Donaldson, Caterina Sellitto, Thomas W. White, Richard T. Mathias, Leping Li, Junyuan Gao, and Yadi Chen
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0301 basic medicine ,TRPV4 ,membrane transport ,Hydrostatic pressure ,TRPV1 ,microcirculation ,TRPV ,03 medical and health sciences ,Transient receptor potential channel ,Lens ,0302 clinical medicine ,Ciliary body ,Transient Receptor Potential Channels ,Lens, Crystalline ,medicine ,Hydrostatic Pressure ,Chemistry ,lens epithelium ,Ciliary Body ,Accommodation, Ocular ,membrane channels ,030104 developmental biology ,medicine.anatomical_structure ,Ciliary muscle ,030221 ophthalmology & optometry ,Biophysics ,Intracellular - Abstract
Purpose Lenses have an intracellular hydrostatic pressure gradient to drive fluid from central fiber cells to surface epithelial cells. Pressure is regulated by a feedback control system that relies on transient receptor potential vanilloid (TRPV)1 and TRPV4 channels. The ciliary muscle transmits tension to the lens through the zonules of Zinn. Here, we have examined if ciliary muscle tension influenced the lens intracellular hydrostatic pressure gradient. Methods We measured the ciliary body position and intracellular hydrostatic pressures in mouse lenses while pharmacologically causing relaxation or contraction of the ciliary muscle. We also used inhibitors of TRPV1 and TRPV4, in addition to phosphoinositide 3-kinase (PI3K) p110α knockout mice and immunostaining of phosphorylated protein kinase B (Akt), to determine how changes in ciliary muscle tension resulted in altered hydrostatic pressure. Results Ciliary muscle relaxation increased the distance between the ciliary body and the lens and caused a decrease in intracellular hydrostatic pressure that was dependent on intact zonules and could be blocked by inhibition of TRPV4. Ciliary contraction moved the ciliary body toward the lens and caused an increase in intracellular hydrostatic pressure and Akt phosphorylation that required intact zonules and was blocked by either inhibition of TRPV1 or genetic deletion of the p110α catalytic subunit of PI3K. Conclusions These results show that the hydrostatic pressure gradient within the lens was influenced by the tension exerted on the lens by the ciliary muscle through the zonules of Zinn. Modulation of the gradient of intracellular hydrostatic pressure in the lens could alter the water content, and the gradient of refractive index.
- Published
- 2019
32. Ion movements in cell death: from protection to execution
- Author
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LUIS FELIPE BARROS, JOEL CASTRO, and CARLA X. BITTNER
- Subjects
Cell death ,membrane channels ,apoptosis ,necrosis ,Biology (General) ,QH301-705.5 - Abstract
Cell death is preceded by severe disruption of inorganic ion homeostasis. Seconds to minutes after an injury, calcium, protons, sodium, potassium and chloride are exchanged between the cell and its environment. Simultaneously, ions are shifted between membrane compartments inside the cell, whereby mitochondria and endoplasmic reticulum play a crucial role. Depending of the type and severity of injury, two mutually exclusive metastable states can be reached, which predict the final outcome. Cells characterized by large increases in cytosolic [Ca2+], [Na+]; and [Mg2+] swell and die by necrosis; alternatively, cells characterized by high [H+]and low [K+], with normal [Na+] and normal to moderate [Ca2+] increases die by apoptosis. The levels of these ions represent central determinants in signaling events leading to cell death. Their movements are explained mechanistically by specific modulation of membrane transport proteins including channels, pumps and carriers
- Published
- 2002
33. BK channel overexpression on plasma membrane of fibroblasts from Hutchinson-Gilford progeria syndrome
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Gastone Castellani, Giovanna Lattanzi, Entele Gavoci, Isabella Zironi, Angela Virelli, Daniel Remondini, Fabrizio Amorini, Zironi, Isabella, Gavoçi, Entelë, Lattanzi, Giovanna, Virelli, Angela, Amorini, Fabrizio, Remondini, Daniel, and Castellani, Gastone
- Subjects
0301 basic medicine ,Adult ,BK channel ,congenital, hereditary, and neonatal diseases and abnormalities ,Adolescent ,patch clamp ,LMNA ,03 medical and health sciences ,K current + ,Young Adult ,0302 clinical medicine ,Progeria ,Gene expression ,medicine ,Cell Adhesion ,Humans ,Large-Conductance Calcium-Activated Potassium Channels ,LMNA gene ,Child ,Aged ,Cell Proliferation ,cellular proliferation ,Aged, 80 and over ,biology ,membrane channel ,integumentary system ,Chemistry ,aging ,Cell Membrane ,nutritional and metabolic diseases ,Cell Biology ,Fibroblasts ,medicine.disease ,Progerin ,Lamin Type A ,K+ current ,Potassium channel ,Chromatin ,Cell biology ,membrane channels ,030104 developmental biology ,Gene Expression Regulation ,030220 oncology & carcinogenesis ,gene LMNA ,biology.protein ,Hutchinson-Gilford Progeria Syndrome (HGPS) ,Lamin ,Research Paper - Abstract
Hutchinson-Gilford progeria syndrome (HGPS) is an extremely rare genetic disorder wherein symptoms resembling aspects of aging are manifested at a very early age. It is a genetic condition that occurs due to a de novo mutation in the LMNA gene encoding for the nuclear structural protein lamin A. The lamin family of proteins are thought to be involved in nuclear stability, chromatin structure and gene expression and this leads to heavy effects on the regulation and functionality of the cell machinery. The functional role of the large-conductance calcium-activated potassium channels (BKCa) is still unclear, but has been recently described a strong relationship with their membrane expression, progerin nuclear levels and the ageing process. In this study, we found that: i) the outward potassium membrane current amplitude and the fluorescence intensity of the BKCa channel probe showed higher values in human dermal fibroblast obtained from patients affected by HGPS if compared to that from healthy young subjects; ii) this result appears to correlate with a basic cellular activity such as the replicative boost. We suggest that studying the HGPS also from the electrophysiological point of view might reveal new clues about the normal process of aging.
- Published
- 2018
34. Towards Understanding Different Spatial and Temporal Scales.
- Author
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Zerbetto, Francesco
- Subjects
- *
MOLECULAR dynamics , *CONTINUUM mechanics , *QUANTUM theory , *QUANTUM chemistry , *SIMULATION methods & models , *PHYSICAL & theoretical chemistry - Abstract
Through the illustration of five examples of recent work, I try to show the interplay that exists between the macroscopic description of the physical chemistry properties and dynamics of molecules and the insight that can be obtained by atomistic simulations. The difficulties and problems of bridging the gaps between the different scales with atomistic simulations are highlighted with the general intent of trying to assess at which point in time or in space the continuum or engineering type of treatment switches to the discrete level. [ABSTRACT FROM AUTHOR]
- Published
- 2007
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35. Efim Liberman toward the comprehension of the phenomenon of life.
- Author
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Skulachev, Vladimir P.
- Subjects
- *
BIOLOGICAL membranes , *OXIDATIVE phosphorylation , *ARTIFICIAL membranes , *BIOPHYSICS , *CELL membranes - Abstract
Efim Liberman was a proud scholar of biophysics—a genuine scientific discipline that strives for high accuracy in contrast to descriptive biology. He played a major role at the Pushchino Institute of Biophysics and participated in Gelfand's famous seminar. He developed a groundbreaking model of neural impulses and discovered the decisive role of cell membranes and membrane channels in neural cell excitation. Efim Liberman studied artificial and biological membranes, and conducted seminal experiments to proof Mitchell's hypothesis of oxidative phosphorylation. He discovered penetrating ions in pioneering studies of mitochondrial electrical energetics. He put forward a trailblazing idea of an intracell analog-digital molecular computer capable of using genetically coded algorithms for processing information. His ideas and research gave impetus to academic studies in various areas, such as a role of small RNАs as universal regulators of life. Efim Liberman was an outstanding, versatile and bright personality whose lifelong journey was to pursue the comprehension of the Universe and to understand the phenomenon of life. [ABSTRACT FROM AUTHOR]
- Published
- 2022
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36. Effect of lauric arginate, nisin Z, and a combination against several food-related bacteria.
- Author
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Rinrada Pattanayaiying, Aran H.-Kittikun, and Cutter, Catherine N.
- Subjects
- *
ANTI-infective agents , *NISIN , *ESCHERICHIA coli O157:H7 , *SCANNING electron microscopy , *TRANSMISSION electron microscopy , *LYSIS , *FOOD microbiology , *BACTERIOCINS - Abstract
The effects of lauric arginate (LAE) and nisin Z, alone or in combination, on cell damage were investigated against Escherichia coli O157:H7, Listeria monocytogenes and Brochothrix thermosphacta, by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations, efflux of potassium and phosphate ions, and growth inhibition. A combination of LAE with nisin Z caused severe and dramatic changes in the cytoplasmic membrane and cell lysis of both Gram-positive and Gram-negative bacteria. The combination treatment also caused significant potassium and phosphate ion leakage of E. coli O157:H7, L. monocytogenes and B. thermosphacta, when compared with other treatments: 16.62 ± 1.05, 50.35 ± 0.81 and 45.47 ± 1.15 mg/L of potassium ion and 122.66 ± 8.81, 97.96 ± 3.31 and 26.47 ± 13.97 mg/L of phosphate ion after treatment for 6 h, respectively. Bacteria were reduced by approximately 7 log10 CFU/mL within the first hour of treatment and then cells were unable to grow for the remainder of the experiment. Treatment with LAE alone resulted in changes in cellular morphology, coagulation of the cytoplasm, and low level leakage of potassium and phosphate ions in all bacteria tested. Treatment of L. monocytogenes and B. thermosphacta with nisin Z (320 AU/mL of final concentration) resulted in the formation of membrane channels and leakage of potassium and phosphate ions at rather high levels; but the bacteriocin was not effective against E. coli O157:H7. LAE or nisin Z reduced growth of both L. monocytogenes and B. thermosphacta by approximately 7 log10 CFU/mL. Conversely, E. coli O157:H7 was not inhibited by treatments with nisin Z, but decreased by approximately 4.45 log10 CFU/mL after treatment with LAE. These findings provide additional information on the mode of action of these compounds on bacterial populations. [ABSTRACT FROM AUTHOR]
- Published
- 2014
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- View/download PDF
37. Peroxisomal membrane channel Pxmp2 in the mammary fat pad is essential for stromal lipid homeostasis and for development of mammary gland epithelium in mice.
- Author
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Vapola, Miia H., Rokka, Aare, Sormunen, Raija T., Alhonen, Leena, Schmitz, Werner, Conzelmann, Ernst, Wärri, Anni, Grunau, Silke, Antonenkov, Vasily D., and Hiltunen, J. Kalervo
- Subjects
- *
PEROXISOMES , *HOMEOSTASIS , *LIPIDS , *MAMMARY glands , *LABORATORY mice , *FAT cells - Abstract
Abstract: To understand the functional role of the peroxisomal membrane channel Pxmp2, mice with a targeted disruption of the Pxmp2 gene were generated. These mice were viable, grew and bred normally. However, Pxmp2 −/− female mice were unable to nurse their pups. Lactating mammary gland epithelium displayed secretory lipid droplets and milk proteins, but the size of the ductal system was greatly reduced. Examination of mammary gland development revealed that retarded mammary ductal outgrowth was due to reduced proliferation of epithelial cells during puberty. Transplantation experiments established the Pxmp2 −/− mammary stroma as a tissue responsible for suppression of epithelial growth. Morphological and biochemical examination confirmed the presence of peroxisomes in the mammary fat pad adipocytes, and functional Pxmp2 was detected in the stroma of wild-type mammary glands. Deletion of Pxmp2 led to an elevation in the expression of peroxisomal proteins in the mammary fat pad but not in liver or kidney of transgenic mice. Lipidomics of Pxmp2 −/− mammary fat pad showed a decrease in the content of myristic acid (C14), a principal substrate for protein myristoylation and a potential peroxisomal β-oxidation product. Analysis of complex lipids revealed a reduced concentration of a variety of diacylglycerols and phospholipids containing mostly polyunsaturated fatty acids that may be caused by activation of lipid peroxidation. However, an antioxidant-containing diet did not stimulate mammary epithelial proliferation in Pxmp2 −/− mice. The results point to disturbances of lipid metabolism in the mammary fat pad that in turn may result in abnormal epithelial growth. The work reveals impaired mammary gland development as a new category of peroxisomal disorders. [Copyright &y& Elsevier]
- Published
- 2014
- Full Text
- View/download PDF
38. Diphtheria toxin conformational switching at acidic pH.
- Author
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Leka, Oneda, Vallese, Francesca, Pirazzini, Marco, Berto, Paola, Montecucco, Cesare, and Zanotti, Giuseppe
- Subjects
- *
DIPHTHERIA toxin , *CONFORMATIONAL analysis , *PH effect , *BACTERIAL toxins , *BILAYER lipid membranes , *CRYSTALLIZATION - Abstract
Diphtheria toxin ( DT), the etiological agent of the homonymous disease, like other bacterial toxins, has to undergo a dramatic structural change in order to be internalized into the cytosol, where it finally performs its function. The molecular mechanism of toxin transit across the membrane is not well known, but the available experimental evidence indicates that one of the three domains of the toxin, called the central α-helical domain, inserts into the lipid bilayer, so favoring the translocation of the catalytic domain. This process is driven by the acidic pH of the endosomal lumen. Here, we describe the crystal structure of DT grown at acidic pH in the presence of bicelles. We were unable to freeze the moment of DT insertion into the lipid bilayer, but our crystal structure indicates that the low pH causes the unfolding of the TH2, TH3 and TH4 α-helices. This event gives rise to the exposure of a hydrophobic surface that includes the TH5 and TH8 α-helices, and the loop region connecting the TH8 and TH9 α-helices. Their exposure is probably favored by the presence of lipid bilayers in the crystallization solution, and they appear to be ready to insert into the membrane. Database Coordinates and structure factors have been deposited in the Protein Data Bank under accession number . [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
39. Membrane channels as integrators of G-protein-mediated signaling.
- Author
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Inanobe, Atsushi and Kurachi, Yoshihisa
- Subjects
- *
MEMBRANE proteins , *BIOLOGICAL membranes , *IMMUNE response , *STIMULUS & response (Biology) , *G proteins , *CYTOSKELETON - Abstract
Abstract: A variety of extracellular stimuli regulate cellular responses via membrane receptors. A well-known group of seven-transmembrane domain-containing proteins referred to as G protein-coupled receptors, directly couple with the intracellular GTP-binding proteins (G proteins) across cell membranes and trigger various cellular responses by regulating the activity of several enzymes as well as ion channels. Many specific populations of ion channels are directly controlled by G proteins; however, indirect modulation of some channels by G protein-dependent phosphorylation events and lipid metabolism is also observed. G protein-mediated diverse modifications affect the ion channel activities and spatio-temporally regulate membrane potentials as well as of intracellular Ca2+ concentrations in both excitatory and non-excitatory cells. This article is part of a Special Issue entitled: Reciprocal influences between cell cytoskeleton and membrane channels, receptors and transporters. Guest Editor: Jean Claude Hervé. [Copyright &y& Elsevier]
- Published
- 2014
- Full Text
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40. Apolipoprotein L-1 renal risk variants form active channels at the plasma membrane driving cytotoxicity
- Author
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Enrique Rodriguez-Boulan, Jayne Raper, Nirav Malani, Patrick J. Zager, Nailya Khalizova, Russell Thomson, Ryan Schreiner, and Joseph A Giovinazzo
- Subjects
0301 basic medicine ,Apolipoprotein B ,Apolipoprotein L1 ,030232 urology & nephrology ,Endoplasmic Reticulum ,Kidney ,Ion Channels ,polymorphism ,0302 clinical medicine ,Risk Factors ,Biology (General) ,education.field_of_study ,Cell Death ,biology ,Cytotoxins ,General Neuroscience ,General Medicine ,Hydrogen-Ion Concentration ,membrane channels ,Cell biology ,Medicine ,Kidney Diseases ,Apolipoprotein L ,protein trafficking ,Research Article ,Human ,Programmed cell death ,QH301-705.5 ,Science ,Population ,CHO Cells ,General Biochemistry, Genetics and Molecular Biology ,03 medical and health sciences ,Cricetulus ,medicine ,Animals ,Humans ,Human Biology and Medicine ,education ,Ion channel ,apolipoprotein l1 ,General Immunology and Microbiology ,Sodium ,Cell Membrane ,Cell Biology ,medicine.disease ,HEK293 Cells ,030104 developmental biology ,Microscopy, Fluorescence ,ion channel ,Potassium ,biology.protein ,Membrane channel ,Kidney disease - Abstract
Recently evolved alleles of Apolipoprotein L-1 (APOL1) provide increased protection against African trypanosome parasites while also significantly increasing the risk of developing kidney disease in humans. APOL1 protects against trypanosome infections by forming ion channels within the parasite, causing lysis. While the correlation to kidney disease is robust, there is little consensus concerning the underlying disease mechanism. We show in human cells that the APOL1 renal risk variants have a population of active channels at the plasma membrane, which results in an influx of both Na+and Ca2+. We propose a model wherein APOL1 channel activity is the upstream event causing cell death, and that the activate-state, plasma membrane-localized channel represents the ideal drug target to combat APOL1-mediated kidney disease.
- Published
- 2020
41. Direct binding of phosphatidylglycerol at specific sites modulates desensitization of a ligand-gated ion channel
- Author
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Fong-Fu Hsu, Grace Brannigan, Ailing Tong, Wayland W.L. Cheng, Liam Sharp, Crina M. Nimigean, Philipp A. M. Schmidpeter, and John T. Petroff
- Subjects
Protein Conformation ,QH301-705.5 ,Structural Biology and Molecular Biophysics ,Science ,DNA Mutational Analysis ,Phospholipid ,desensitization ,Molecular Dynamics Simulation ,Synaptic Transmission ,General Biochemistry, Genetics and Molecular Biology ,03 medical and health sciences ,chemistry.chemical_compound ,0302 clinical medicine ,Desensitization (telecommunications) ,Allosteric Regulation ,None ,Biology (General) ,Ion channel ,phospholipids ,030304 developmental biology ,mass spectrometry ,Phosphatidylglycerol ,0303 health sciences ,General Immunology and Microbiology ,General Neuroscience ,Phosphatidylglycerols ,General Medicine ,Ligand-Gated Ion Channels ,membrane channels ,Transmembrane domain ,chemistry ,Structural biology ,Biophysics ,Membrane channel ,Ligand-gated ion channel ,Medicine ,lipids (amino acids, peptides, and proteins) ,030217 neurology & neurosurgery ,Research Article ,Protein Binding - Abstract
Pentameric ligand-gated ion channels (pLGICs) are essential determinants of synaptic transmission, and are modulated by specific lipids including anionic phospholipids. The exact modulatory effect of anionic phospholipids in pLGICs and the mechanism of this effect are not well understood. Using native mass spectrometry, coarse-grained molecular dynamics simulations and functional assays, we show that the anionic phospholipid, 1-palmitoyl-2-oleoyl phosphatidylglycerol (POPG), preferentially binds to and stabilizes the pLGIC, Erwinia ligand-gated ion channel (ELIC), and decreases ELIC desensitization. Mutations of five arginines located in the interfacial regions of the transmembrane domain (TMD) reduce POPG binding, and a subset of these mutations increase ELIC desensitization. In contrast, a mutation that decreases ELIC desensitization, increases POPG binding. The results support a mechanism by which POPG stabilizes the open state of ELIC relative to the desensitized state by direct binding at specific sites.
- Published
- 2019
42. Filter gate closure inhibits ion but not water transport through potassium channels.
- Author
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Hoomann, Torben, Jahnke, Nadin, Horner, Andreas, Keller, Sandro, and Pohl, Peter
- Subjects
- *
POTASSIUM channels , *CARBONYL group , *AMINO acids , *SOLUBILIZATION , *HYDRATION , *MOLECULAR structure of water - Abstract
The selectivity filter of K+ channels is conserved throughout all kingdoms of life. Carbonyl groups of highly conserved amino acids point toward the lumen to act as surrogates for the water molecules of K+ hydration. Ion conductivity is abrogated if some of these carbonyl groups flip out of the lumen, which happens (i) in the process of C-type inactivation or (ii) during filter collapse in the absence of K+. Here, we show that K+ channels remain permeable to water, even after entering such an electrically silent conformation. We reconstituted fluorescently labeled and constitutively open mutants of the bacterial K+ channel KcsA into lipid vesicles that were either C-type inactivating or noninactivating. Fluorescence correlation spectroscopy allowed us to count both the number of proteoliposomes and the number of protein-containing micelles after solubilization, providing the number of reconstituted channels per proteoliposome. Quantification of the per-channel increment in proteoliposome water permeability with the aid of stopped-flow experiments yielded a unitary water permeability pf of (6.9 ± 0.6) × 10-13 cm3·s-1 for both mutants. "Collapse" of the selectivity filter upon K+ removal did not alter pf and was fully reversible, as demonstrated by current measurements through planar bilayers in a K+-containing medium to which K+-free proteoliposomes were fused. Water flow through KcsA is halved by 200 mM K+ in the aqueous solution, which indicates an effective K+ dissociation constant in that range for a singly occupied channel. This questions the widely accepted hypothesis that multiple K+ ions in the selectivity filter act to mutually destabilize binding. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
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43. The role of renal water channels in health and disease
- Author
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Holmes, Ross P.
- Subjects
- *
AQUAPORINS , *GENE expression , *CELL membranes , *KIDNEY diseases , *EPITHELIAL cells , *GENETIC mutation , *GENETIC polymorphisms , *TRANSCRIPTION factors - Abstract
Abstract: Seven members of the aquaporin (AQP) family are expressed in different regions of the kidney. AQP1–4 are localized in plasma membranes of renal epithelial cells and are intimately involved in water reabsorption by the kidney. AQP7 is also localized in the plasma membrane and may facilitate glycerol transport. AQP6 and AQP11 are localized within the cell, with AQP6 involved in anion transport and AQP11 water transport. Mutations in AQP2 can result in diabetes insipidus, whereas mutations in other AQPs have not yet been shown to be disease-associated. Genetic polymorphisms may contribute to the susceptibility to defects in urine concentrating mechanisms associated with some diseases. Most of the AQPs are subject to transcriptional regulation and post-translational modifications by a range of biological modifiers. As a result a number of chronic kidney and systemic diseases produce changes in the abundance of AQPs. The more recent developments in this field are reviewed. [Copyright &y& Elsevier]
- Published
- 2012
- Full Text
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44. The pivotal twin histidines and aromatic triad of the Escherichia coil ammonium channel AmtB can be replaced.
- Author
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Hall, Jason A. and Kustu, Sydney
- Subjects
- *
HISTIDINE , *CELL membranes , *ESCHERICHIA coli , *BIOLOGICAL transport , *MUTAGENESIS - Abstract
In Escherichia coli, each subunit of the trimeric channel protein AmtB carries a hydrophobic pore for transport of NH4+ across the cytoplasmic membrane. Positioned along this substrate conduction pathway are two conserved elements-a pair of hydrogen-bonded histidines (H168/H318) located within the pore itself and a set of aromatic residues (F107/W148/F215) at its periplasmic entrance-thought to be critical to AmtB function. Using site-directed mutagenesis and suppressor genetics, we examined the requirement for these elements in NH4+ transport. This analysis shows that AmtB can accommodate, by either direct substitution or suppressor generation, acidic residues at one or both positions of the H168/H318 twin-histidine site while retaining near wild-type activity. Similarly, study of the F107/W148/F215 triad indicates that good-to-excellent AmtB function is preserved upon individual and simultaneous replacement of these aromatic amino acids with aliphatic residues. Our findings lead us to conclude that these elements and their component parts are not required for AmtB function, but instead serve to optimize its performance. [ABSTRACT FROM AUTHOR]
- Published
- 2011
- Full Text
- View/download PDF
45. Plant aquaporins with non-aqua functions: deciphering the signature sequences.
- Author
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Hove, Runyararo and Bhave, Mrinal
- Abstract
Research in recent years on plant Major Intrinsic Proteins (MIPs), commonly referred to as 'aquaporins', has seen a vast expansion in the substrates found to be transported via these membrane channels. The diversity in sizes, chemical nature and physiological significance of these substrates has meant a need to critically analyse the possible structural and biochemical properties of MIPs that transport these, in order to understand their roles. In this work we have undertaken a comprehensive analysis of all plant MIPs, coming from different families, that have been proven to transport ammonia, boron, carbon dioxide, hydrogen peroxide, silicon and urea. The sequences were analysed for all primary selectivity-related motifs (NPA motifs, ar/R filter, P1-P5 residues). In addition, the putative regulatory phosphorylation and glycosylation sites and mechanistic regulators such as loop lengths have been analysed. Further, nine specificity-determining positions (SDPs) were predicted for each group. The results show the ar/R filter residues, P2-P4 positions and some of the SDPs are characteristic for certain groups, and O-glycosylation sites are unique to a subgroup while N-glycosylation was characteristic of the other MIPs. Certain residues, especially in loop C, and structural parameters such as loop lengths also contribute to the uniqueness of groups. The comprehensive analysis makes significant inroads into appraising the intriguing diversity of plant MIPs and their roles in fundamental life processes, and provides tools for plant selections, protein engineering and transgenics. [ABSTRACT FROM AUTHOR]
- Published
- 2011
- Full Text
- View/download PDF
46. Melatonin and the pathophysiology of cellular membranes.
- Author
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Reiter, Russel J., Fuentes-Broto, Lorena, Paredes, Sergio D., Dun-Xian Tan, and Garcia, Joaquin J.
- Subjects
- *
MELATONIN , *PATHOLOGICAL physiology , *CELL membranes , *UNICELLULAR organisms , *LIPIDS , *FREE radicals , *MANAGEMENT science - Abstract
The ability of melatonin to influence the physiology of cell membranes is reviewed in this report. Publications related to this field from 1993 - present. Melatonin is a ubiquitously acting indoleamine which is associated with a variety of important functions within both unicellular and multicellular organisms. By virtue of its ability to protect lipids from free radical damage, melatonin is remarkably beneficial in preserving the morphological and functional integrity of cell membranes. In doing so, it reduces the quantity of oxidized lipids in membranes and maintains them at optimal fluidity, i.e., prevents them from becoming rigid. This contributes significantly to the function of proteins (receptors, channels, pores, etc.) in the cell membranes and helps in preserving the normal physiology of the cells. In addition to these indirect effects of melatonin on membrane function, there is evidence that this indoleamine also may act directly on channels assisting membranes in maintaining proper ion gradients and current. The role of melatonin in the functioning of membrane channels and pores is an area of research that should be experimentally exploited. [ABSTRACT FROM AUTHOR]
- Published
- 2010
47. Membrane Channels
- Author
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Rédei, George P.
- Published
- 2008
- Full Text
- View/download PDF
48. An involvement of yeast peroxisomal channels in transmembrane transfer of glyoxylate cycle intermediates
- Author
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Antonenkov, Vasily D., Mindthoff, Sabrina, Grunau, Silke, Erdmann, Ralf, and Hiltunen, J. Kalervo
- Subjects
- *
PEROXISOMES , *YEAST , *CYTOSOL , *SACCHAROMYCES cerevisiae , *BILAYER lipid membranes , *CYTOPLASM , *INTERMEDIATES (Chemistry) - Abstract
Abstract: The separate localization of glyoxylate cycle enzymes in the peroxisomes and the cytosol of the yeast Saccharomyces cerevisiae indicates that the peroxisomal membrane must permit the flow of metabolites between the two compartments. The transfer of these metabolites may require peroxisomal membrane channel(s). We used an electrophysiological approach (reconstitution assay in lipid bilayers) to assess the ability of peroxisomal membrane channels to conduct different solutes including metabolites of the glyoxylate cycle. At least two distinct channel-forming activities were detected in peroxisomal preparations. One of these activities was highly inducible by dithiothreitol and showed large-amplitude current increments when 1M KCl was used as a bath solution. Single-channel analysis revealed that the inducible channel is anion-selective and displays flickering at holding potentials over ±30mV directed upward or downward relative to the main open state of the channel. The channel inducible by DTT facilitates the transfer of solutes with a molecular mass up to 400Da, sufficient to allow the transmembrane trafficking of glyoxylate cycle intermediates between the peroxisomal lumen and the cytoplasm. [Copyright &y& Elsevier]
- Published
- 2009
- Full Text
- View/download PDF
49. Optimal control of metabolite transport across cell membranes driven by the membrane potential
- Author
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Marinoschi, Gabriela
- Subjects
- *
METABOLITES , *CELL membranes , *BIOMOLECULES , *RESPECT - Abstract
Abstract: The movement of the metabolites crossing biological membranes is essentially controlled by the action of the membrane potential. In biophysics, the interest is on the way in which the membrane potential drives the particle motion and makes more probable its translocation, i.e., the transit through the channel and the escape through the opposite side with respect to the entrance. Our investigation will focus on the determination of the membrane potential which allows the particle escape from the channel and may possibly limit the particle lifetime inside it. In mathematical terms, the purpose of this work is to study some mathematical nonlinear control problems, consisting in the determination of an optimal potential which makes the channel more efficient in a certain sense. Some physically significant variations of this basic problem are also investigated and a discussion of the possible extension of the model to time-dependent situations is made. Finally, numerical results are presented. [Copyright &y& Elsevier]
- Published
- 2009
- Full Text
- View/download PDF
50. Connexins, pannexins, innexins: novel roles of “hemi-channels”.
- Author
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Scemes, Eliana, Spray, David C., and Meda, Paolo
- Subjects
- *
CONNEXINS , *GAP junctions (Cell biology) , *PROTEINS , *MEMBRANE proteins , *GENETIC regulation , *GENE expression - Abstract
The article focuses on the combination of different connexin proteins to form vertebrate gap junction channels. It states the dependence of transmembrane fluxes in the formation of channels and the similarity of the proteins to that of innexins which represent vertebrate homologs. In addition, it highlights that gene expression is significantly perturbed after loss of individual connexin.
- Published
- 2009
- Full Text
- View/download PDF
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