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629 results on '"Spudich, John L."'

6. Platymonas subcordiformis Channelrhodopsin-2 Function I. THE PHOTOCHEMICAL REACTION CYCLE*

Author

Szundi, Istvan, Li, Hai, Chen, Eefei, Bogomolni, Roberto, Spudich, John L, and Kliger, David S

Subjects
1.1 Normal biological development and functioning, Underpinning research, Chlorophyta, Kinetics, Light, Photochemistry, Rhodopsin, channelrhodopsin, optogenetics, photocycle, photoreceptor, phototaxis, protein dynamic, rhodopsin, time-resolved spectroscopy, ultraviolet-visible spectroscopy, Chemical Sciences, Biological Sciences, Medical and Health Sciences, Biochemistry & Molecular Biology
Abstract

The photocycle kinetics of Platymonas subcordiformis channelrhodopsin-2 (PsChR2), among the most highly efficient light-gated cation channels and the most blue-shifted channelrhodopsin, was studied by time-resolved absorption spectroscopy in the 340-650-nm range and in the 100-ns to 3-s time window. Global exponential fitting of the time dependence of spectral changes revealed six lifetimes: 0.60 μs, 5.3 μs, 170 μs, 1.4 ms, 6.7 ms, and 1.4 s. The sequential intermediates derived for a single unidirectional cycle scheme based on these lifetimes were found to contain mixtures of K, L, M, O, and P molecular states, named in analogy to photointermediates in the bacteriorhodopsin photocycle. The photochemistry is described by the superposition of two independent parallel photocycles. The analysis revealed that 30% of the photoexcited receptor molecules followed Cycle 1 through the K, M, O, and P states, whereas 70% followed Cycle 2 through the K, L, M, and O states. The recovered state, R, is spectrally close, but not identical, to the dark state on the seconds time scale. The two-cycle model of this high efficiency channelrhodopsin-2 (ChR) opens new perspectives in understanding the mechanism of channelrhodopsin function.

Published
2015

12. Genome Sequence of Halobacterium Species NRC-1

Author

Ng, Wailap Victor, Kennedy, Sean P., Mahairas, Gregory G., Berquist, Brian, Pan, Min, Shukla, Hem Dutt, Lasky, Stephen R., Baliga, Nitin S., Thorsson, Vesteinn, Sbrogna, Jennifer, Swartzell, Steven, Weir, Douglas, Hall, John, Dahl, Timothy A., Welti, Russell, Goo, Young Ah, Leithauser, Brent, Keller, Kim, Cruz, Randy, Danson, Michael J., Hough, David W., Maddocks, Deborah G., Jablonski, Peter E., Krebs, Mark P., Angevine, Christine M., Dale, Heather, Isenbarger, Thomas A., Peck, Ronald F., Pohlschroder, Mechthild, Spudich, John L., Jung, Kwang-Hwan, Alam, Maqsudul, Freitas, Tracey, Hou, Shaobin, Daniels, Charles J., Dennis, Patrick P., Omer, Arina D., Ebhardt, Holger, Lowe, Todd M., Liang, Ping, Riley, Monica, Hood, Leroy, and DasSarma, Shiladitya

Published
2000

24. Structures of channelrhodopsin paralogs in peptidiscs explain their contrasting K+ and Na+ selectivities.

Author

Morizumi, Takefumi, Kim, Kyumhyuk, Li, Hai, Govorunova, Elena G., Sineshchekov, Oleg A., Wang, Yumei, Zheng, Lei, Bertalan, Éva, Bondar, Ana-Nicoleta, Askari, Azam, Brown, Leonid S., Spudich, John L., and Ernst, Oliver P.

Subjects
POTASSIUM, SODIUM channels, ATOMIC structure, POTASSIUM channels, PERMEABILITY, MUTAGENESIS, MICROSCOPY
Abstract

Kalium channelrhodopsin 1 from Hyphochytrium catenoides (HcKCR1) is a light-gated channel used for optogenetic silencing of mammalian neurons. It selects K+ over Na+ in the absence of the canonical tetrameric K+ selectivity filter found universally in voltage- and ligand-gated channels. The genome of H. catenoides also encodes a highly homologous cation channelrhodopsin (HcCCR), a Na+ channel with >100-fold larger Na+ to K+ permeability ratio. Here, we use cryo-electron microscopy to determine atomic structures of these two channels embedded in peptidiscs to elucidate structural foundations of their dramatically different cation selectivity. Together with structure-guided mutagenesis, we show that K+ versus Na+ selectivity is determined at two distinct sites on the putative ion conduction pathway: in a patch of critical residues in the intracellular segment (Leu69/Phe69, Ile73/Ser73 and Asp116) and within a cluster of aromatic residues in the extracellular segment (primarily, Trp102 and Tyr222). The two filters are on the opposite sides of the photoactive site involved in channel gating. Recently discovered kalium channelrhodopsins (KCRs) are optogenetic tools for neuronal silencing. Here, authors report cryo-electron microscopy structures of KCR1 from Hyphochytriumcatenoides and a highly homologous but sodium-selective channel from the same organism. [ABSTRACT FROM AUTHOR]

Published
2023
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44. Cation and Anion Channelrhodopsins: Sequence Motifs and Taxonomic Distribution

Author

Govorunova, Elena G., primary, Sineshchekov, Oleg A., additional, Li, Hai, additional, Wang, Yumei, additional, Brown, Leonid S., additional, Palmateer, Alyssa, additional, Melkonian, Michael, additional, Cheng, Shifeng, additional, Carpenter, Eric, additional, Patterson, Jordan, additional, Wong, Gane K.-S., additional, and Spudich, John L., additional

Published
2021
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48. Conductance Mechanisms of Rapidly Desensitizing Cation Channelrhodopsins from Cryptophyte Algae

Author

Sineshchekov, Oleg A., Govorunova, Elena G., Li, Hai, Wang, Yumei, Melkonian, Michael, Wong, Gane K-S, Brown, Leonid S., Spudich, John L., Sineshchekov, Oleg A., Govorunova, Elena G., Li, Hai, Wang, Yumei, Melkonian, Michael, Wong, Gane K-S, Brown, Leonid S., and Spudich, John L.

Abstract

Channelrhodopsins guide algal phototaxis and are widely used as optogenetic probes for control of membrane potential with light. Bacteriorhodopsin-like cation channelrhodopsins (BCCRs) from cryptophytes differ in primary structure from other CCRs, lacking usual residues important for their cation conductance. Instead, the sequences of BCCR match more closely those of rhodopsin proton pumps, containing residues responsible for critical proton transfer reactions. We report 19 new BCCRs which, together with the earlier 6 known members of this family, form three branches (subfamilies) of a phylogenetic tree. Here, we show that the conductance mechanisms in two subfamilies differ with respect to involvement of the homolog of the proton donor in rhodopsin pumps. Two BCCRs from the genus Rhodomonas generate photocurrents that rapidly desensitize under continuous illumination. Using a combination of patch clamp electrophysiology, absorption, Raman spectroscopy, and flash photolysis, we found that the desensitization is due to rapid accumulation of a long-lived nonconducting intermediate of the photocycle with unusually blue-shifted absorption with a maximum at 330 nm. These observations reveal diversity within the BCCR family and contribute to deeper understanding of their independently evolved cation channel function. IMPORTANCE Cation channelrhodopsins, light-gated channels from flagellate green algae, are extensively used as optogenetic photoactivators of neurons in research and recently have progressed to clinical trials for vision restoration. However, the molecular mechanisms of their photoactivation remain poorly understood. We recently identified cryptophyte cation channelrhodopsins, structurally different from those of green algae, which have separately evolved to converge on light-gated cation conductance. This study reveals diversity within this new protein family and describes a subclade with unusually rapid desensitization that results in short transient photoc

Published
2020

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