Search

The Zrt/Irt-like protein (ZIP) family contributes to the metal homeostasis by regulating the transport of divalent metal cations such as Fe2+, Zn2+, Mn2+, Cd2+ and sometimes even Cu2+. Most ZIP members have a long variable loop between transmembrane domains (TMDs) III and IV; this region is predicted to be located in the cytoplasm and is postulated to be the metal ion binding site. In this study, we looked at the thermodynamic behavior and coordination chemistry of Zn2+, Ni2+ and Cu2+ complexes with the histidine-rich domain, Ac-(185)RAHAAHHRHSH(195)-NH2 (HRD), from the yeast TjZNT1 protein, located between TMDs III and IV. The sequence is conserved also in higher species like Thlaspi japonicum. The stability of complexes increases in the series Ni2+ < Zn2+ ≪ Cu2+. The geometry of complexes is very different for each metal and in the case of Zn2+ complexes, high specificity in binding is observed. Moreover, the stability of HRD-Cu2+ complexes was compared with the five His residues containing peptide from Hpn protein (Helicobacter pylori). The results suggest a high ability of HRD in the binding of all three studied metals. [ABSTRACT FROM AUTHOR]

Abstract: Alzheimer''s disease (AD) is the leading cause of senile dementia. One of the main hallmarks of AD is the presence of amyloid plaques in the brain, primarily formed by fibrils of the amyloid-β (Aβ) peptide. Transition metal ions, such as Cu2+ and Zn2+ have been found at high concentrations in senile plaques isolated from AD patients and evidence have been reached that (i) Aβ aggregation is greatly affected by Cu2+ and Zn2+ and (ii) Cu2+, implicated in the formation of reactive oxygen species, leads to mitochondrial dysfunctions ultimately leading to neuronal cells death. Aβ, apart from being toxic to neural cells, induces reactive astrocytosis in cell culture. Astrocytes play many crucial roles to sustain normal brain function by maintaining the cerebral homeostasis, modulating the synaptic transmission, and providing a metabolic support for neuronal growth. Although many studies have shown that Aβ fibrils interfere in the main astrocytic functions aimed at supporting the neuronal activity, nothing is known about the effects of Zn2+- and Cu2+‐induced Aβ aggregates on astrocyte functions. In this study the effects of treatments with Aβ42, either in absence or in the presence of Cu2+ and Zn2+, on astrocyte cell cultures were evaluated by using classical cellular assay and by looking at changes in metabolic profiles in the cellular medium by using nuclear magnetic resonance spectroscopy (NMR). Our results indicate that metal induced Aβ aggregation strongly affects the metabolites involved in the neurotransmission activity supporting a deleterious impact of Cu2+ and Zn2+ Aβ amyloidogenesis on astrocyte functions. [Copyright &y& Elsevier]

Abstract: The C-terminal region of Escherichia coli SlyD is unstructured and extremely rich in potential metal-binding amino acids, especially in histidine residues. SlyD is able to bind two to seven nickel ions per molecule, in a variety of coordination geometries and coordination numbers. This protein contributes to the insertion of nickel into the hydrogenase precursor protein and it has a peptidyl-prolyl cis/trans-isomerase activity which can be regulated through nickel ions. This inspired us to undertake systematic studies on the coordination ability of two histidine-rich peptides from the C-terminus of the SlyD protein with nickel. Also, it is known that histidine-rich regions are part of a Cu2+ binding domain involved in copper uptake under conditions of metal starvation in vivo in other bacteria. For this reason we decided to examine the complex formation of Ac-AHGHVHGAHDHHHD-NH2 and Ac-GHGHDHGHEHG-NH2 fragments with copper ions, which are also reference metal ions in this study. Experiments were performed in a DMSO/water 30:70 solvent. The Ac-AHGHVHGAHDHHHD-NH2 and Ac-GHGHDHGHEHG-NH2 fragments were synthesized and their interactions with Ni2+ and Cu2+ ions were studied by potentiometric, mass spectrometric, UV–vis, CD, EPR, and NMR spectroscopic techniques in solution. The results show that the Ac-GHGHDHGHEHG-NH2 fragment forms equimolar complexes with both nickel and copper ions. At physiological pH, the metal ion is bound only through nitrogens from imidazole sidechain of histidine residues. On the contrary, Ac-AHGHVHGAHDHHHD-NH2 binds 2 metal ions per molecule, at pH range 5 to 7, even if the 1:2 metal:peptide ratios were used. NMR studies indicate the involvement of all His residues in this pH-range in metal binding of the latter peptide. At higher pH, the stoichiometry changes to 1:1 and the His residues are displaced by amide nitrogens. [Copyright &y& Elsevier]

The fragment of the zebrafish prion-like protein (PrP-rel-2), encompassing residues 74-86 and unprotected at N-terminus (zf74-86) represents a good model to understand Cu2+and Zn2+binding to ligands containing multi-potential metal donor sites. Zf(74-86) contains four His and His-1 N-terminal amine groups which constitute both copper and zinc anchoring sites. The presence of His at the first position additionally provides the histamine-like binding mode which could compete with the multi-His binding mode. In this study the speciation profiles of the Cu2+and Zn2+complexes with zf74-86 have been obtained. The main species, dominating at physiological pH, have been fully characterized by using different spectroscopic techniques. The detected NMR chemical shift variations and line broadening enhancements, caused by Zn2+and Cu2+respectively, allowed to determine the metal binding sites. Both metal ions showed common binding donor atoms, being 2 or 3 His imidazoles and the N-terminal group involved in Cu2+and Zn2+binding. [ABSTRACT FROM AUTHOR]

Abstract: Both human (h) and chicken (Ch) prion proteins (PrP) bind copper ions within the so called “tandem repeat” N-terminal region. Outside this region, hPrP possesses two additional copper binding sites, localized at His-96 and His-111 in the so called “amylodogenic” or neurotoxic region (residues 91–126). Also ChPrP possesses a similar region (ChPrP105−140) containing two His (His-110 and His-124) and an identical hydrophobic tail of 15 amino acids rich in Ala and Gly. The copper binding abilities within such region of ChPrP were investigated by NMR, CD and potentiometry using Ni2+ as diamagnetic probe. The formation of diamagnetic metal complexes allowed to monitor the chemical shift and signal intensity variations and to determine the structural and kinetic features of the His-110 and His-124 metal binding sites. Finally a comparison between the hPrP and ChPrP metal binding abilities was performed. We found that the two prion proteins exhibited different copper and nickel preferences with the favoured metal binding sites localized at opposite His: His-110 for ChPrP, and His-111 for hPrP. [Copyright &y& Elsevier]

Human Prion Protein (hPrPC) is able to bind up to six Cu2+ions. Four of them can be allocated in the “octarepeat domain”, a region of the unstructured N-terminal domain containing four tandem-repetitions of the sequence PHGGGWGQ. It is widely accepted that the additional binding sites correspond to His-96 and His-111 residues. However, recent literature does not agree on the role and the behavior of these sites in Cu2+complexation to hPrPC. In order to shed more light on this topic, some peptidic analogues of the PrP92–113fragment were synthesized: (H96A)PrP92–113, (H111A)PrP92–113, (H96Nτ-Me-His)PrP92–113, (H111Nτ-Me-His)PrP92–113, (H96Nτ-Me-His)PrP92–100, (H111Nτ-Me-His)PrP106–113, where an alanine or a histidine methylated at the τ nitrogen atom of its imidazole ring have been substituted to His-96 or His-111. The first two ligands allowed to confirm that His-111 binding site is stronger than His-96 one: they act as independent sites even at Cu2+-ion substoichiometric levels. Neither multi-histidine binding nor bis-complex formation has been detected at neutral pH. Nτmethylation gave evidence that τ nitrogens of imidazole residues can participate in complex-formation only at acidic pH, where displacement of amidic protons by Cu2+ions is not allowed. Finally, the length of the fragment does not appear to have any significant influence on the behavior of the two His-96 and His-111 binding sites, from the point of view of either the coordination geometry or their relative strength. [ABSTRACT FROM AUTHOR]

Prion protein (PrP) misfolding is one of the pivotal issues in understanding the rudiments of neurodegenerative disorders. The conformational change of mammalian cellular PrP to scrapie PrP is caused by an unknown agent, but there is reasonable evidence supporting the key role of copper ions in this process. The structure of the avian PrP was found to be very similar to the mammalian protein, although there is only 30% homology in the secondary structure. This work shows that copper ions are very effectively bound by hexarepeat fragments of chicken prion protein, although not as effectively as it was found in the case of mammalian protein. By means of potentiometric and spectroscopic techniques (nuclear magnetic resonance, circular dichroism, UV-vis, and electronic paramagnetic resonance), it was shown that CuII ions coordinate to the chicken PrP hexapeptide domain in physiological pH via imidazole nitrogen donors of His residue(s). The binding pattern changes the structure of peptide involved, indicating a possible impact of CuII ions in the biology and pathology of nonmammalian PrP, which could be similar to that found for mammalian PrP. The present study shows that, similar to the human prion octapeptide repeats, chicken prion hexapeptide repeats might bind copper ions in two different ways, depending on the number of repeats and metal/ligand molar ratio: (i) an intra-repeat coordination mode in which copper ion is chelated by His imidazole and deprotonated amide nitrogen in monomeric peptide and (ii) an inter-repeat coordination mode in which a polymeric peptide ligand (dimer and trimer) forms polyimidazole complexes that are very stable at physiological pH. Two proline residues inserted into the hexapeptide unit have a critical impact on the metal-binding ability. [ABSTRACT FROM AUTHOR]

The reactions of human β-amyloid peptide 1-28 (Aβ28) with AlIII and FeIII ions were investigated by 1H NMR and electrospray ionization mass spectrometry (ESI-MS) under pH conditions close to physiological ones. 1H NMR titrations, performed in the 5.3-8.0 pH range, revealed that no measurable amounts of Aβ28-AlIII or Aβ28-FeIII adducts are formed; such metal adducts could not be obtained even by changing a number of experimental conditions, e.g., temperature, buffer, nature of the salt, etc. These observations were later confirmed by ESI-MS. It is thus demonstrated that Aβ28, at physiological pH, is not able to form binary complexes with AlIII and FeIII ions of sufficient stability to compete with metal hydroxide precipitation. The biological implications of these findings are discussed in the frame of current literature. [ABSTRACT FROM AUTHOR]

The reaction at the ruthenium(ll) complex fac[Ru(CO)3Cl2· (N¹-thz)] (I hereafter; thz = 1,3-thiazole) with human β-amyloid peptide 1-28 (Aβ2e) and the resulting (Ru(CO)3)2+ peptide adduct was investigated by a variety of biophysical methods. ¹H NMFt titrations highlighted a selective interaction ot (Ru(CO)3)2+ with Aβ28 histidine residues; circular dichroism revealed the occurrence of a substantial contormational rearrangement at Mxo; electraspray ionization mass spectrometry (ESI-MS) suggested a prevalent 1:1 metal/peptide stoichiometry and disclosed the nature at peptide-bound metallic fragments. Notably, very similar ESI-MS results were obtained when I was reacted with Aβ42. The implications ot the above tindings tar a possible use at ruthenium compounds in Alzheimer's disease are discussed. [ABSTRACT FROM AUTHOR]

The interaction between Zn2+and the single repeat of PrP-rel-2 of zebrafish at physiological pH was investigated by NMR spectroscopy; the chemical shift mapping and the proton–proton distances were used to obtain the structural model of the Zn2+complex. [ABSTRACT FROM AUTHOR]

Amyloidogenic proteins are associated with severe neurodegenerative disorders afflicting millions of people worldwide. The main hallmarks of these diseases are the presence of amyloid plaques in the brain, primarily formed by fibrils of misfolded cellular proteins. The process leading to protein aggregation, is far from completely understood. However, it is well accepted that many factors are able to influence the morphology and kinetics of amyloids formation. In the last years, a plethora of studies have suggested that the aggregation process is greatly influenced by the interactions of these proteins with copper and membranes. Amyloidogenic proteins undergo large conformational changes in the presence of membranes and show the presence of stable α helix structures in the presence of high concentrations of unilamellar vesicles or detergent micelles. The regions involved in the helicoidal rearrangements are those which are critical for protein aggregation. In addition, the α helix structuring of amyloidogenic proteins may strongly affect copper binding, in terms of donor atoms and complex stability since metal binding domains are often located near regions experiencing transitions from random-coil to α helix conformations. [ABSTRACT FROM AUTHOR]

α-Synuclein (αSyn) constitutes the main protein component of Lewy bodies, which are the pathologic hallmark in Parkinson's disease. αSyn is unstructured in solution but the interaction of αSyn with lipid membrane modulates its conformation by inducing an α-helical structure of the N-terminal region. In addition, the interaction with metal ions can trigger αSyn conformation upon binding and/or through the metal-promoted generation of reactive oxygen species which lead to a cascade of structural alterations. For these reasons, the ternary interaction between αSyn, copper, and membranes needs to be elucidated in detail. Here, we investigated the structural properties of copper-αSyn binding through NMR, EPR, and XAS analyses, with particular emphasis on copper(I) coordination since the reduced state is particularly relevant for oxygen activation chemistry. The analysis was performed in different membrane model systems, such as micellar sodium dodecyl sulfate (SDS) and unilamellar vesicles, comparing the binding of full-length αSyn and N-terminal peptide fragments. The presence of membrane-like environments induced the formation of a copper:αSyn = 1:2 complex where Cu+ was bound to the Met1 and Met5 residues of two helical peptide chains. In this coordination, Cu+ is stabilized and is unreactive in the presence of O2 in catechol substrate oxidation. [ABSTRACT FROM AUTHOR]

Galantamine is a natural alkaloid extracted from the Amaryllidaceae plants and is used as the active ingredient of a drug approved for the treatment of the early stages of Alzheimer's disease. It mainly acts as an acetylcholinesterase (AChE) inhibitor, increasing concentrations of the acetylcholine neurotransmitter. Recent cellular studies have also shown the ability of galantamine to protect SH-SY5Y cell lines against amyloid-β (Aβ)-induced toxicity. Such investigations have supported and validated further in-depth studies for understanding the chemical and molecular features associated with galantamine-protective abilities. In addition to galantamine, other natural alkaloids are known to possess AChE inhibitory activity; among them lycorine has been extensively investigated for its antibacterial, anti-inflammatory and antitumoral activities as well. Despite its interesting biological properties, lycorine's neuroprotective functions against Aβ-induced damages have not been explored so far. In this research study, the ability of galantamine and lycorine to suppress Aβ-induced in vitro neuronal toxicity was evaluated by investigating the chemical interactions of the two alkaloids with Aβ peptide. A multi-technique spectroscopic analysis and cellular cytotoxicity assays were applied to obtain new insights on these molecular associations. The comparison between the behaviors exhibited by the two alkaloids indicates that both compounds possess analogue abilities to interact with the amyloidogenic peptide and protect cells. [ABSTRACT FROM AUTHOR]

The heteroaromatic base 5,6-dimethylbenzo-1,3-imidazole (DMBI) proved to be a Brönsted base in an anhydrous ethanol solution, which contained fac , trans -[Ru(CO) 3 Cl 2 ] 2 at 55 °C in air when the DMBI:Ru molar ratio was 2:1. The reaction produced colorless anhydrous single crystals of {(HDMBI) + Cl − }, C 9 H 11 ClN 2 , which were collected and analyzed using X-ray diffraction (XRD) techniques. A network of N–H⋯Cl hydrogen bond type interactions linking the protonated hetero-aromatic base to the chloride anions (bridging bases) stabilizes the crystal and mimics the N–H⋯Cl − interactions that play important roles in CCl channel biological systems. The shortest N⋯Cl contact distance and corresponding N–H⋯Cl angle are 3.073(3) Å and 173(3)°, respectively. The packing is also assisted by weaker C–H⋯Cl − hydrogen bond-type interactions and an extensive network of π⋯π stacking interactions involving HDMBI + cations. Density functional calculations at the B3LYP/6-31G ∗∗ and /6-311++G ∗∗ levels for models of fragments of the crystal structure allowed for the evaluation of geometric parameters, hydrogen bond-type interaction formation energies, and infrared parameters for {(HDMBI) + Cl − } and {(HDMBI) + ⋯Cl − ⋯(HDMBI) + }. [ABSTRACT FROM AUTHOR]

The reaction of [Ru II 2 (CO) 6 Cl 2 ], 1 , in methanol with azoles affords complexes that contain the fa c-{Ru II (CO) 3 } 2+ - core . The complexes presented in this paper have the general formula fac -[Ru II (CO) 3 Cl 2 L], with a molecule L of imidazole (IM), 2 , or N-methyl-imidazole (MIM), 3 , as a ligand in the pseudo -octahedral coordination sphere that is completed by two chlorido ligands cis to each other. The compounds show an appreciable solubility in water (up to ca 1 g/L) at 25 °C, and are well soluble in other solvents, such as alcohol, acetone, dicholoromethane, dimethylsulfoxide, and in mixtures of solvents. In the case where water is present in the medium (10% v/v or higher), significant dissociation of the Ru–N bond that is trans to a carbonyl ligand occurs, and a series of substitutions and other types of reactions may take place afterwards, depending on the reactants and the applied experimental conditions. The synthesis and isolation of single crystals of 2 was performed by reacting the starting dimer 1 with 1-acetylimidazole in alcohol medium. DFT structure simulations/optimizations were carried out at Becke3lyp level of theory by using several basis sets up to 6-311++G ∗∗ for C, H, Cl, N and O atoms, and the Lanl2DZ pseudo -potential for Ru. In vitro cytotoxicity tests for 2 , 3 and fac -[Ru II (CO) 3 Cl 2 (THZ)] (THZ = 1,3-thiazole), 4 , showed IC 50 values mostly in the range 100–200 μM in CH1 (ovarian carcinoma) and SW480 (colon carcinoma) cell lines. ESI-MS studies revealed the ability of these complexes to link the model proteins Lysozyme and Cytochrome c and similar binding patterns are highlighted; interestingly, protein binding is accompanied by a partial release of the original ligands. Fragments of the type [Ru II (CO) 2 ] 2+ or [Ru II (CO)] 2+ are found associated to the proteins. [ABSTRACT FROM AUTHOR]

The aggregation of alpha-synuclein (AS) in a critical step in the etiology of parkinson's disease (PD). A central, unresolved question in the pathophysiology of PD relates to the role of AS-metal interaction in amyloid fibril formation and neurodegeneration. Our previous works established a hierarchy in alpha-synuclein-metal ion interactions, where Cu(II) binds specifically to the protein and triggers be aggregation under conditions that might he relevant for the development of PD. Two independent, non-interacting copper-binding sites were identified at the N-terminal region of AS, with significant difference in their affinities for the metal ion. In this work we have solved unknown details related to the structural binding specificity and aggregation enhancement mediated by Cu(II). The high-resolution structural characterization of the highest affinity N-terminus AS-Cu(II) complex is reported here. Through the measurement of AS aggregation kinetics we proved conclusively that the copper-enhanced AS amyloid formation is a direct consequence of the formation of the AS-Cu(II) complex at the highest affinity binding site. The kinetic behavior was not influenced by the His residue at position 50, arguing against an active rate for this residue in the structural and biological events involved is the mechanism of copper-mediated AS aggregation. These new findings are central to elucidate the mechanism through which the metal ion participates in the fibrillization of AS and represent relevant progress in the understanding of the bionorganic chemistry of PD. [ABSTRACT FROM AUTHOR]

Abstract: Laccase, isolated from Cerrena unicolor, is able to transform 3-amino-4-hydroxybenzensulfonic acid into a water soluble phenoxazine dye with an extinction coefficient (ɛ) of 8600M−1 cm−1. The dye has been characterized using a variety of different analytic and spectroscopic techniques like UV–vis spectroscopy, HPLC (High Performance Liquid Chromatography), ESI/MS (Electrospray Ionization Mass Spectrometry) and the following NMR experiments: 1H, 13C, TOCSY (Total Correlation Spectroscopy), HSQC (Heteronuclear Single Quantum Coherence), HMBC (Heteronuclear Multiple Bond Coherence) showing the structure of 2-amino-3-oxo-3H-phenoxazine-8-sulfonic acid. The advantages of the presented biocatalytic system, in alignment with chemical system to obtain Curie_22, are eco-sustainability and one step performance. [Copyright &y& Elsevier]

Alzheimer's disease (AD) is a neurodegenerative disorder, affecting millions of people worldwide, a number expected to exponentially increase in the future since no effective treatments are available so far. AD is characterized by severe cognitive dysfunctions associated with neuronal loss and connection disruption, mainly occurring in specific brain areas such as the hippocampus, cerebral cortex, and amygdala, compromising memory, language, reasoning, and social behavior. Proteomics and redox proteomics are powerful techniques used to identify altered proteins and pathways in AD, providing relevant insights on cellular pathways altered in the disease and defining novel targets exploitable for drug development. Here, we review the main results achieved by both -omics techniques, focusing on the changes occurring in AD mitochondria under oxidative stress and upon copper exposure. Relevant information arises by the comparative analysis of these results, evidencing alterations of common mitochondrial proteins, metabolic cycles, and cascades. Our analysis leads to three shared mitochondrial proteins, playing key roles in metabolism, ATP generation, oxidative stress, and apoptosis. Their potential as targets for development of innovative AD treatments is thus suggested. Despite the relevant efforts, no effective drugs against AD have been reported so far; nonetheless, various compounds targeting mitochondria have been proposed and investigated, reporting promising results. [ABSTRACT FROM AUTHOR]

14-3-3 are regulatory proteins that through protein–protein interactions (PPI) with numerous binding partners could be involved in several human diseases, including cancer, neurodegenerative disorders, and pathogens infections. Following our research interest in the development of 14-3-3 PPI inhibitors, here we exploited the privileged 4-aminoantipyrine scaffold in the design and synthesis of some derivatives endowed with antiproliferative activity against K-562 cells, and capable of binding to recombinant 14-3-3σ as evidenced by NMR spectroscopy. The binding mode was further explored by molecular modelling, while coupling confocal microscopy with intensitometric analysis showed that compound 1 was able to promote the nuclear translocation of c-Abl at low micromolar concentrations. Overall, 1 is chemically stable compared to parent 14-3-3 PPI inhibitors, and thus emerged as a confirmed hit for further development. [ABSTRACT FROM AUTHOR]

The N-terminal fragment of Aβ (β = beta) peptide is able to bind essential transition metal ions like, copper, zinc and iron. Metal binding usually occurs via the imidazole nitrogens of the three His residues which play a key role in the coordination chemistry. Among all the investigated systems, the interaction between copper and Amyloid β assume a biological relevance because of the interplay between the two copper oxidation states, Cu(II) and Cu(I), and their involvement in redox reactions. Both copper ions share the ability to bind Amyloid β. A huge number of investigations have demonstrated that Cu(II) anchors to the N-terminal amino and His6, His13/14 imidazole groups, while Cu(I) forms a linear complex by coordinating to the His13 and His14 dyad. In this study we have analyzed Cu(I) interaction with the Amyloid β fragment encompassing the first 16 amino-acids. Our data were obtained by means of NMR spectroscopy which provided relevant structural details of the metal complexes. Our findings are consistent with the involvement of two or three His in the Cu(I) coordination sphere and indicate that His6 effectively participates to the metal binding. Cu(I) interaction with the N-terminal fragment of amyloid β. Unlabelled Image • His6, His13 and His14 are the primary Cu(I) binding sites of Aβ (β = beta). • Upon Cu(I) binding, Aβ16 undergoes to specific structural rearrangements. • In the metal complex His6 is close to the His13 His14 dyad. • His6 Nδ, His13 and His14 Nε are the Cu(I) binding donor atoms. • Ag(I) has strong potential in probing Cu(I) interaction with Aβ16. [ABSTRACT FROM AUTHOR]

Plants have evolved a set of mechanisms that control and respond to the uptake and accumulation of both essential and non-essential metals, including chelation and sequestration of these elements by thiol ligands, such as glutathione and phytochelatins. Indeed, such thiol peptides can chelate some metals, quickly form thiol-metal complexes, and segregate them in the vacuolar compartment. Reasonably, conceptually similar mechanisms can be assumed to be responsible for the transport of metal complexes ̶ in particular thiol-cadmium complexes ̶ across the plasma membrane, with the consequent release of this toxic metal in the extracellular environment. Such hypothesis, focusing on prevention and detoxification mechanisms, was here verified in axenically-grown gametophytes of the model liverwort Marchantia polymorpha , exposed to three different cadmium concentrations over five exposure times. From the data obtained, it can be deduced that the cell wall of M. polymorpha moderately reduced the influx of cadmium into the cells, since it was rapidly saturated by this metal. At an intracellular level, cadmium induced the activity, but not the gene expression, of the phytochelatin synthase enzyme, leading to synthesis of phytochelatins. Moreover, both glutathione and phytochelatins chelated cadmium at the cytosolic level and allowed its detoxification, possibly involving tonoplast transporters belonging to type-C ABC subfamily (Mp7g13860 and Mp4g11930). Likewise, cadmium, glutathione and phytochelatins were released extracellularly, thus highlighting a possible novel role in cadmium detoxification, in a pH-dependent manner. The overall results suggest that, in M. polymorpha , glutathione and phytochelatins can accomplish intracellular and extracellular detoxification of cadmium. [Display omitted] • Marchantia polymorpha cell wall only partially counteracts cadmium entry inside the cell. • Cadmium stimulates phytochelatin synthase enzymatic activity, but not its gene expression. • Phytochelatins allow intracellular detoxification of cadmium. • Glutathione and phytochelatins can also be released extracellularly. • Glutathione forms intra- and extracellular complexes with cadmium in a pH-dependent way. [ABSTRACT FROM AUTHOR]

Highlights: [•] Recent NMR findings on metal interactions with disordered protein domains are discussed. [•] Flexible domains derived either from amyloidogenic proteins or from metal chaperones are considered. [•] The NMR behaviors of different transition metal ions are discussed and compared. [•] The use of NMR to determine (i) the metal coordination sphere, (ii) the structure, (iii) the dynamics and (iv) the binding affinity is discussed. [•] All the benefits and drawbacks of the NMR method are addressed as well. [ABSTRACT FROM AUTHOR]

Transmissible spongiform encephalopathies are associated with the misfolding of the cellular Prion Protein (PrP) to an abnormal protein isoform, called scrapie prion protein (PrP). The structural rearrangement of the fragment of N-terminal domain of the protein spanning residues 91-127 is critical for the observed structural transition. The amyloidogenic domain of the protein encloses two copper-binding sites corresponding to His-96 and His-111 residues that act as anchors for metal ion binding. Previous studies have shown that Cu(II) sequestration by both sites may modulate the peptide's tendency to aggregation as it inflicts the hairpin-like structure that stabilizes the transition states leading to β-sheet formation. On the other hand, since both His sites differ in their ability to Cu(II) sequestration, with His-111 as a preferred binding site, we found it interesting to test the role of Cu(II) coordination to this single site on the structural properties of amyloidogenic domain. The obtained results reveal that copper binding to His-111 site imposes precise backbone bending and weakens the natural tendency of apo peptide to β-sheet formation. [ABSTRACT FROM AUTHOR]

Abstract: In this review, we summarize the most recent observations on some very effective binding sites (e.g. ATCUN motif, poly-His, poly-Cys, or Met-containing sequences) for biologically relevant metals in proteins and peptides. In addition, the influence of the specific sequence on the binding stability, besides the donor atoms, is described (e.g. Pro residues as in PrP or poly-Gln sequences). It is well known that some disorders are connected with proteins which need metal ions for biological activity. Often metal ions coordinate to binding sites located in loops or unstructured regions of those proteins. These rather recent discoveries make metal ion binding to proteins slightly more enigmatic than in the case of an insertion of metal into an “organized” site. Although in the latter cases, we still may need chaperons helping to select the proper metal ion, some selectivity is provided by the pre-organized structure of the donor site itself in the protein. The metal ion binding usually exerts a distinct impact on the binding pocket structure due to the secondary or tertiary structure donors from the residues being often very far away in the peptide sequence. Recently, several metallo-proteins were discovered whose structures are rather disordered (e.g. α-synuclein, prions or β-amyloid peptide involved in Alzheimer disease). Also some specific metal chaperons, consisting of long poly-His sequences being very effective binders of metals, do not show any specific secondary structure. Examples of these might be bacterial nickel accessory proteins, involved in the complicated pathway of metal uptake, delivery and regulation in microorganisms. Recently, several observations were reported on the homeostasis of nickel in Helicobacter pylori, a Gram-negative bacterium that colonizes the gastric mucosa in humans, and is the causative agent of acute and chronic gastritis, peptic ulcer disease, gastric carcinoma, and gastric lymphoma. The homeostasis of nickel is crucial for the survival of this bacterium in the extremely acidic environment of the stomach; the metal is delivered to urease and hydrogenase by a set of accessory proteins. Zinc often plays a structural or regulatory role in those nickel chaperones. It can also be one of the metal ion which interferes with the homeostasis of Ni2+, since the affinity of the two metals toward His- and Cys-rich sequences can sometimes be comparable. [Copyright &y& Elsevier]

Abstract: The basic role of metal ions including copper, zinc and iron in neurological pathologies is generally accepted. The relationship between the development of disease and particular metal ions is very complicated and complex. Thus, comprehension of metal homeostasis, details of transport and interactions with biomolecules is essential for understanding the normal and pathological processes occurring in the living system. Homeostasis of metal ions usually involves a huge set of proteins which regulate the proper metal biology. Disorder in metal homeostasis may result in serious pathologies including neurodegenerative diseases. Metal ions, especially copper, zinc and iron play very important roles in neurodegeneration having impact on both protein structure (misfolding) and oxidative stress. Metal ion binding to proteins involved in neurodegeneration is therefore an important factor for whole brain damage processes. All these aspects are discussed in the review. [Copyright &y& Elsevier]

Abstract: Metal ions, especially redox active copper, are thought to play critical roles in neurodegenerative disorders. As a matter of fact, metal binding may result into severe conformational changes of proteins involved in neurodegeneration. The present review describes the interactions of metal ions with model peptides mimicking metal binding sites of such proteins, including the prion protein, the β-amyloid and the α-synuclein that have been related to the pathological onset of spongiform encephalopathies, Alzheimer''s disease and Parkinson''s disease, respectively. Using short protein fragments provides successful tools for characterizing the metal ion interaction with protein domains devoid of any defined secondary structure, and allows one to gain structural information on the metal ion binding properties of the corresponding proteins. Moreover, such an approach based on simplified models yields a multidimensional knowledge that would be never accessible for the natural systems, thus providing a significant and powerful tool for biochemical studies. [Copyright &y& Elsevier]

Abstract: Teicoplanin, a member of the “last chance” antibiotic family has a similar structure and the same mechanism of action as parent drug vancomycin, which is proved to be an effective binder of Cu(II) ions. However, the potentiometric and spectroscopic studies (UV–visible, CD, NMR) have shown that the modification of the N-terminal structure of the peptide backbone in teicoplanin affects considerably the binding ability towards Cu(II) ions. While vancomycin forms almost instantly the stable 3N complex species involving the N-terminal and two amide nitrogen donors, in case of teicoplanin only two nitrogen donors derived from the N-terminal amino group and adjacent peptide bond are coordinated to Cu(II) ion within the whole pH range studied. The major factor influencing the binding mode is most likely the structure of the N-terminus of the peptide unit in the antibiotic ligand. [Copyright &y& Elsevier]

Abstract: Metal ions, especially with high chemical activity (e.g. redox-active Cu and Fe) must be carefully managed in biological systems. The “uncontrolled” activity, e.g. catalysis of Fenton-like reactions by ions like Cu(I) or Fe(II), is so damaging for the biological milieu that right from their entry, metal ions need to be strictly controlled until they arrive at their storage site. This chaperoning occurs usually by proteins which are involved in transport, delivery and distribution processes. In this review some aspects of the metal homeostasis for major metal ions (Cu, Fe, and Zn) are presented. The impact of these metals on some disorders are also discussed. [Copyright &y& Elsevier]

Abstract: The bis-chelate complex of Zn2+ with 2-hydroxy-(4-methylthio)butanoate (MHA-H the anion derived from the so-called methionine hydroxy-analogue, MHA) is an effective, bioavailable mineral supplement for animal feeding. It can be obtained in two solid forms: the anhydrous [Zn(OC(O)CH2CH(OH)CH2CH2SCH3)2] and the corresponding dihydrate species, both well distinguishable by IR spectroscopy and powder X-ray diffraction. The crystal and molecular structure of the dihydrate form has been solved by single-crystal X-ray diffraction. It consists of dinuclear bis-chelate species with a bridging carboxylate group, both zinc atoms displaying hexacoordination involving all the hydroxyl and carboxyl groups from the four MHA-H anions and three oxygens from different water molecules. The fourth water molecule does not participate in coordination. Therefore, the dihydrate complex must be formulated as [Zn2(OC(O)CH2CH(OH)CH2CH2SCH3)4(H2O)3]·H2O (1). A molecular computational analysis has been carried out by density functional theory (DFT) on three possible MHA-H zinc chelates, i.e. the dinuclear bis-chelate observed in the solid state, the mononuclear bis-chelate diaquo-complex, and the monochelate tetraaquo-complex. Calculations have suggested that between the dinuclear and mononuclear bis-chelates, the preferred form in aqueous solution may be the second one. Moreover, both 1H (chemical shifts and relaxation rates) and 13C NMR data provide further evidence for the formation of Zn/MHA-H chelates in solution. [Copyright &y& Elsevier]

Abstract: The prion proteins may play a critical role in copper homeostasis and the antioxidant activity in the brain. This review presents the state of art in the studies on Cu2+ prion systems. The proteins discussed are from different species from mammals to fishes. All proteins are His-rich and the research discussed clearly indicates the basic role of imidazole side chains and the adjacent amide nitrogen atoms in metal ion binding. Prions represent the family of proteins with new mode of Cu2+ binding which includes the amide nitrogen coordination. The multi-imidazole coordination is also likely and it can play a critical role in the antioxidant activity of the copper–prion complexes. The combination of the imidazole and amide nitrogen atoms to Cu2+ ions could also be relevant in histidine-rich peptide antibiotics including demegen. The impact of peptide sequence and His positions on copper binding ability is also discussed. [Copyright &y& Elsevier]

Abstract: Sinefungin (SFG) is an antifungal and antiparasitic nucleoside antibiotic composed by ornithine and adenosine moieties both having the potential to bind copper(II). NMR studies performed at physiological pH have shown that the α-amino and the carboxylate groups in the ornithine unit are the preferred donor sites for Cu(II) binding. On the contrary, at acidic pH, Cu(II) complexation starts from adenosine nitrogen being the α-amino group still protonated and not available for metal binding. The proton paramagnetic relaxation enhancements measured at neutral pH allowed to obtain the 3D structure of the 1:2 Cu(II)–SFG complex. Molecular dynamics calculations were revealing for the existence of secondary Cu(II) interaction with the purine nitrogens of the adenosine moiety. [Copyright &y& Elsevier]

The synthetic peptide encompassing residues 106-126 (PrP106-126, KTNMKHMAGAAAAGAVVGGLG) of the human prion protein was considered for its binding properties toward copper(II), manganese(II) and zinc(II) at pH 5.7. ¹H and 13C 1D spectra, ¹H spin--lattice relaxation rates, and ¹H--15N and ¹H--13C HSQC 2D experiments were obtained in the absence and in the presence of metal ions. While Zn(II) was found to yield negligible effects upon any NMR parameter, metal--peptide association was demonstrated by the paramagnetic effects of Cu(II) and Mn(II) upon 1D and 2D spectra. Delineation of structures of metal complexes was sought by interpreting the paramagnetic effect on ¹H spin--lattice relaxation rates. Exchange of peptide molecules from the metal coordination sphere was shown to provide sizable contribution to the observed relaxation rates. Such contribution was calculated in the case of Cu(II); whereas the faster paramagnetic rates of peptide molecules bound to Mn(II) were determining spin--lattice. relaxation rates at most exclusively dominated by exchange. Proton -- metal distances were therefore evaluated in the case of the Cu(II) complex only and used as restraints in molecular dynamics calculations wherefrom the structure of the complex was obtained. The peptide was shown to bind copper through the imidazole nitrogen and the ionized amide nitrogen of His-111 and the amino-terminal group with the terminal carboxyl stabilizing the coordination sphere through ionic interactions. The data were interpreted, as to demonstrate that the hydrophobic C-terminal region was not affecting the copper-binding properties of the peptide and that this hydrophobic tail is left free to interact with other target molecules. As for the complex with Mn(II), qualitative information was obtained on carbonyl oxygens of Gly-124 and Leu-125, beyond the terminal Gly-126 carboxyl, being at close distance from the metal ion, that also interacts, most likely, through a hydrogen bond of metal-bound water, with the imidazole ring of His-111. [ABSTRACT FROM AUTHOR]

Often, in the search for a highly defined scientific phenomenon, a different one becomes apparent. This was also the case of this work, in the scope of which we planned to search for metal-enhanced, novel antibacterial/antifungal compounds. Instead, we denied the existence of such and revealed the details of the bioinorganic chemistry of Zn(II)-alloferon complexes. Zinc(II) complexes of alloferon 1 and 2, ligands with a sequential difference of one amino acid only, show a substantially different coordination pattern at physiological pH. In the case of Zn(II)-alloferon 1 species, a histamine-like binding mode is observed (N-terminal amine and imidazole of His-1) and the coordination sphere is completed with the imidazole nitrogens of His-6 and His-9; His-12 is not involved in binding. In the case of Zn(II)-alloferon 2, the N-terminal amine and all the three imidazoles present in the sequence participate in the coordination, however, with the chemical shift of His-5 being less affected than those of other imidazoles. The histamine-like binding in Zn(II)-alloferon 1 complex strongly enhances its thermodynamic stability in comparison to the His-1 lacking alloferon 2 analogue. Despite previous reports on the antibacterial and antifungal activity of alloferon 1, no such activity was detected, neither for alloferon 1 and 2 nor for their Zn(II) complexes. Unlabelled Image • Impact of Zn(II) on the change of structure and function of alloferons is discussed. • Despite previous reports, no antibacterial/ anitifungal activity is detected. • Zn(II) binding sites thermodynamics of Zn-alloferon 1 and 2 complexes are discussed. • Ligands which differ in only one amino acid, show a different coordination pattern. [ABSTRACT FROM AUTHOR]

Alzheimer's disease is a severe disorder that affects millions of people worldwide. It is a very debilitating disease with no cure at the moment. The necessity of finding an effective treatment is very demanding, and the entire scientific community is putting in a lot of effort to address this issue. The major hallmark of Alzheimer's disease is the presence of toxic aggregated species in the brain, impaired metal homeostasis, and high levels of oxidative stress. Rosmarinic acid is a well-known potent antioxidant molecule, the efficacy of which has been proved both in vitro and in vivo. In this study, we investigated the possible role played by rosmarinic acid as a mediator of the copper(II)-induced neurotoxicity. Several spectroscopic techniques and biological assays were applied to characterize the metal complexes and to evaluate the cytotoxicity and the mutagenicity of rosmarinic acid and its Cu(II) complex. Our data indicate that rosmarinic acid is able to interfere with the interaction between amyloid β and Cu(II) by forming an original ternary association. [ABSTRACT FROM AUTHOR]

Diabetes mellitus, a complex metabolic disorder, presents a growing global health challenge. In 2021, there were 529 million diabetics worldwide. At the super-regional level, Oceania, the Middle East, and North Africa had the highest age-standardized rates. The majority of cases of diabetes in 2021 (>90.0%) were type 2 diabetes, which is largely indicative of the prevalence of diabetes in general, particularly in older adults (K. L. Ong, et al. , Global, regional, and national burden of diabetes from 1990 to 2021, with projections of prevalence to 2050: a systematic analysis for the Global Burden of Disease Study 2021, Lancet , 2023, 402 (10397), 203-234). Nowadays, slowing the progression of diabetic complications is the only effective way to manage diabetes with the available therapeutic options. However, novel biomarkers and treatments are urgently needed to control cytokine secretion, advanced glycation end products (AGEs) production, vascular inflammatory effects, and cellular death. Emerging research has highlighted the intricate interplay between reactive oxygen species (ROS) and protein aggregation in the pathogenesis of diabetes. In this scenario, the main aim of this paper is to provide a comprehensive review of the current understanding of the molecular mechanisms underlying ROS-induced cellular damage and protein aggregation, specifically focusing on their contribution to diabetes development. The role of ROS as key mediators of oxidative stress in diabetes is discussed, emphasizing their impact on cellular components and signaling. Additionally, the involvement of protein aggregation in impairing cellular function and insulin signaling is explored. The synergistic effects of ROS and protein aggregation in promoting β-cell dysfunction and insulin resistance are examined, shedding light on potential targets for therapeutic intervention., Competing Interests: All authors declare that they have no conflicts of interest that could inappropriately influence this manuscript., (This journal is © The Royal Society of Chemistry.)