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Astashkin R, Kovalev K, Bukhdruker S, Vaganova S, Kuzmin A, Alekseev A, Balandin T, Zabelskii D, Gushchin I, Royant A, Volkov D, Bourenkov G, Koonin E, Engelhard M, Bamberg E, Gordeliy V. Structural insights into light-driven anion pumping in cyanobacteria. Nat Commun 2022; 13:6460. [PMID: 36309497 PMCID: PMC9617919 DOI: 10.1038/s41467-022-34019-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2022] [Accepted: 10/11/2022] [Indexed: 12/25/2022] Open
Abstract
Transmembrane ion transport is a key process in living cells. Active transport of ions is carried out by various ion transporters including microbial rhodopsins (MRs). MRs perform diverse functions such as active and passive ion transport, photo-sensing, and others. In particular, MRs can pump various monovalent ions like Na+, K+, Cl-, I-, NO3-. The only characterized MR proposed to pump sulfate in addition to halides belongs to the cyanobacterium Synechocystis sp. PCC 7509 and is named Synechocystis halorhodopsin (SyHR). The structural study of SyHR may help to understand what makes an MR pump divalent ions. Here we present the crystal structure of SyHR in the ground state, the structure of its sulfate-bound form as well as two photoreaction intermediates, the K and O states. These data reveal the molecular origin of the unique properties of the protein (exceptionally strong chloride binding and proposed pumping of divalent anions) and sheds light on the mechanism of anion release and uptake in cyanobacterial halorhodopsins. The unique properties of SyHR highlight its potential as an optogenetics tool and may help engineer different types of anion pumps with applications in optogenetics.
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Affiliation(s)
- R. Astashkin
- grid.450307.50000 0001 0944 2786Univ. Grenoble Alpes, CEA, CNRS, Institut de Biologie Structurale (IBS), Grenoble, France
| | - K. Kovalev
- grid.475756.20000 0004 0444 5410European Molecular Biology Laboratory, Hamburg unit c/o DESY, Hamburg, Germany
| | - S. Bukhdruker
- grid.5398.70000 0004 0641 6373European Synchrotron Radiation Facility Grenoble, Grenoble, France ,grid.8385.60000 0001 2297 375XInstitute of Biological Information Processing (IBI-7: Structural Biochemistry), Forschungszentrum Jülich, Jülich, Germany ,grid.8385.60000 0001 2297 375XJuStruct: Jülich Center for Structural Biology, Forschungszentrum Jülich, Jülich, Germany
| | - S. Vaganova
- grid.8385.60000 0001 2297 375XInstitute of Biological Information Processing (IBI-7: Structural Biochemistry), Forschungszentrum Jülich, Jülich, Germany ,grid.8385.60000 0001 2297 375XJuStruct: Jülich Center for Structural Biology, Forschungszentrum Jülich, Jülich, Germany
| | - A. Kuzmin
- grid.18763.3b0000000092721542Research Center for Molecular Mechanisms of Aging and Age-related Diseases, Moscow Institute of Physics and Technology, Dolgoprudny, Russia
| | - A. Alekseev
- grid.18763.3b0000000092721542Research Center for Molecular Mechanisms of Aging and Age-related Diseases, Moscow Institute of Physics and Technology, Dolgoprudny, Russia
| | - T. Balandin
- grid.8385.60000 0001 2297 375XInstitute of Biological Information Processing (IBI-7: Structural Biochemistry), Forschungszentrum Jülich, Jülich, Germany ,grid.8385.60000 0001 2297 375XJuStruct: Jülich Center for Structural Biology, Forschungszentrum Jülich, Jülich, Germany
| | - D. Zabelskii
- grid.434729.f0000 0004 0590 2900European XFEL GmbH, Schenefeld, Germany
| | - I. Gushchin
- grid.18763.3b0000000092721542Research Center for Molecular Mechanisms of Aging and Age-related Diseases, Moscow Institute of Physics and Technology, Dolgoprudny, Russia
| | - A. Royant
- grid.450307.50000 0001 0944 2786Univ. Grenoble Alpes, CEA, CNRS, Institut de Biologie Structurale (IBS), Grenoble, France ,grid.5398.70000 0004 0641 6373European Synchrotron Radiation Facility Grenoble, Grenoble, France
| | - D. Volkov
- grid.8385.60000 0001 2297 375XInstitute of Biological Information Processing (IBI-7: Structural Biochemistry), Forschungszentrum Jülich, Jülich, Germany ,grid.8385.60000 0001 2297 375XJuStruct: Jülich Center for Structural Biology, Forschungszentrum Jülich, Jülich, Germany
| | - G. Bourenkov
- grid.475756.20000 0004 0444 5410European Molecular Biology Laboratory, Hamburg unit c/o DESY, Hamburg, Germany
| | - E. Koonin
- grid.419234.90000 0004 0604 5429National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD USA
| | - M. Engelhard
- grid.418441.c0000 0004 0491 3333Department Structural Biochemistry, Max Planck Institute of Molecular Physiology, 44227 Dortmund, Germany
| | - E. Bamberg
- grid.419494.50000 0001 1018 9466Max Planck Institute of Biophysics, Frankfurt am Main, Germany
| | - V. Gordeliy
- grid.450307.50000 0001 0944 2786Univ. Grenoble Alpes, CEA, CNRS, Institut de Biologie Structurale (IBS), Grenoble, France ,grid.8385.60000 0001 2297 375XInstitute of Biological Information Processing (IBI-7: Structural Biochemistry), Forschungszentrum Jülich, Jülich, Germany ,grid.8385.60000 0001 2297 375XJuStruct: Jülich Center for Structural Biology, Forschungszentrum Jülich, Jülich, Germany
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2
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Shionoya T, Mizuno M, Kandori H, Mizutani Y. Contact-Mediated Retinal-Opsin Coupling Enables Proton Pumping in Gloeobacter Rhodopsin. J Phys Chem B 2022; 126:7857-7869. [PMID: 36173382 DOI: 10.1021/acs.jpcb.2c04208] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
When a chromophore embedded in a photoreceptive protein undergoes a reaction upon photoexcitation, the photoreaction triggers structural changes in the protein moiety that are necessary for the function of the protein. It is thus essential to elucidate the coupling between the chromophore and protein moiety to understand the functional mechanism for photoreceptive proteins, but the mechanism by which this coupling occurs remains poorly understood. Here, we show that nonbonded atomic contacts play an essential role in driving functionally important structural changes following photoisomerization of the chromophore in Gloeobacter rhodopsin (GR). Time-resolved ultraviolet resonance Raman spectroscopy revealed that the substitution of Trp222, which contacts with methyl groups of the retinal chromophore, with a Phe residue reduced the extent of structural change. The proton-pumping activity of the GR mutant was as small as 9% of that of the wild type. Time-resolved visible absorption and resonance Raman spectra showed that the photocycle of the mutant proceeded to the L intermediate following the all-trans to 13-cis photoisomerization step but did not result in the deprotonation of the chromophore. The present results demonstrate that the atomic contacts between the chromophore and the Trp222 side chain induce the structural changes necessary for proton transfer. The requirement for dense atomic packing in a protein structure for the efficient propagation of structural changes through a coupling mechanism is discussed.
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Affiliation(s)
- Tomomi Shionoya
- Department of Chemistry, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan
| | - Misao Mizuno
- Department of Chemistry, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan
| | - Hideki Kandori
- Department of Life Science and Applied Chemistry, Nagoya Institute of Technology, Showa-ku, Nagoya, Aichi 466-8555, Japan
| | - Yasuhisa Mizutani
- Department of Chemistry, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan
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3
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Kozlova MI, Bushmakin IM, Belyaeva JD, Shalaeva DN, Dibrova DV, Cherepanov DA, Mulkidjanian AY. Expansion of the "Sodium World" through Evolutionary Time and Taxonomic Space. BIOCHEMISTRY. BIOKHIMIIA 2020; 85:1518-1542. [PMID: 33705291 DOI: 10.1134/s0006297920120056] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
In 1986, Vladimir Skulachev and his colleagues coined the term "Sodium World" for the group of diverse organisms with sodium (Na)-based bioenergetics. Albeit only few such organisms had been discovered by that time, the authors insightfully noted that "the great taxonomic variety of organisms employing the Na-cycle points to the ubiquitous distribution of this novel type of membrane-linked energy transductions". Here we used tools of bioinformatics to follow expansion of the Sodium World through the evolutionary time and taxonomic space. We searched for those membrane protein families in prokaryotic genomes that correlate with the use of the Na-potential for ATP synthesis by different organisms. In addition to the known Na-translocators, we found a plethora of uncharacterized protein families; most of them show no homology with studied proteins. In addition, we traced the presence of Na-based energetics in many novel archaeal and bacterial clades, which were recently identified by metagenomic techniques. The data obtained support the view that the Na-based energetics preceded the proton-dependent energetics in evolution and prevailed during the first two billion years of the Earth history before the oxygenation of atmosphere. Hence, the full capacity of Na-based energetics in prokaryotes remains largely unexplored. The Sodium World expanded owing to the acquisition of new functions by Na-translocating systems. Specifically, most classes of G-protein-coupled receptors (GPCRs), which are targeted by almost half of the known drugs, appear to evolve from the Na-translocating microbial rhodopsins. Thereby the GPCRs of class A, with 700 representatives in human genome, retained the Na-binding site in the center of the transmembrane heptahelical bundle together with the capacity of Na-translocation. Mathematical modeling showed that the class A GPCRs could use the energy of transmembrane Na-potential for increasing both their sensitivity and selectivity. Thus, GPCRs, the largest protein family coded by human genome, stem from the Sodium World, which encourages exploration of other Na-dependent enzymes of eukaryotes.
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Affiliation(s)
- M I Kozlova
- School of Physics, Osnabrueck University, Osnabrueck, 49069, Germany. .,Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119992, Russia
| | - I M Bushmakin
- School of Bioengineering and Bioinformatics, Lomonosov Moscow State University, Moscow, 119992, Russia.
| | - J D Belyaeva
- School of Bioengineering and Bioinformatics, Lomonosov Moscow State University, Moscow, 119992, Russia.
| | - D N Shalaeva
- School of Physics, Osnabrueck University, Osnabrueck, 49069, Germany.
| | - D V Dibrova
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119992, Russia.
| | - D A Cherepanov
- Semenov Institute of Chemical Physics, Russian Academy of Sciences, Moscow, 119991, Russia.
| | - A Y Mulkidjanian
- School of Physics, Osnabrueck University, Osnabrueck, 49069, Germany. .,Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119992, Russia.,School of Bioengineering and Bioinformatics, Lomonosov Moscow State University, Moscow, 119992, Russia
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4
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Yun JH, Ohki M, Park JH, Ishimoto N, Sato-Tomita A, Lee W, Jin Z, Tame JRH, Shibayama N, Park SY, Lee W. Pumping mechanism of NM-R3, a light-driven bacterial chloride importer in the rhodopsin family. SCIENCE ADVANCES 2020; 6:eaay2042. [PMID: 32083178 PMCID: PMC7007266 DOI: 10.1126/sciadv.aay2042] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/29/2019] [Accepted: 11/25/2019] [Indexed: 06/10/2023]
Abstract
A newly identified microbial rhodopsin, NM-R3, from the marine flavobacterium Nonlabens marinus, was recently shown to drive chloride ion uptake, extending our understanding of the diversity of mechanisms for biological energy conversion. To clarify the mechanism underlying its function, we characterized the crystal structures of NM-R3 in both the dark state and early intermediate photoexcited states produced by laser pulses of different intensities and temperatures. The displacement of chloride ions at five different locations in the model reflected the detailed anion-conduction pathway, and the activity-related key residues-Cys105, Ser60, Gln224, and Phe90-were identified by mutation assays and spectroscopy. Comparisons with other proteins, including a closely related outward sodium ion pump, revealed key motifs and provided structural insights into light-driven ion transport across membranes by the NQ subfamily of rhodopsins. Unexpectedly, the response of the retinal in NM-R3 to photostimulation appears to be substantially different from that seen in bacteriorhodopsin.
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Affiliation(s)
- Ji-Hye Yun
- Department of Biochemistry, College of Life Science and Biotechnology, Yonsei University, Seoul 03722, South Korea
| | - Mio Ohki
- Research Complex at Harwell, Rutherford Appleton Laboratory, OX11 0FA Didcot, UK
- Drug Design Laboratory, Graduate School of Medical Life Science, Yokohama City University, Tsurumi, Yokohama 230-0045, Japan
| | - Jae-Hyun Park
- Department of Biochemistry, College of Life Science and Biotechnology, Yonsei University, Seoul 03722, South Korea
| | - Naito Ishimoto
- Drug Design Laboratory, Graduate School of Medical Life Science, Yokohama City University, Tsurumi, Yokohama 230-0045, Japan
| | - Ayana Sato-Tomita
- Division of Biophysics, Department of Physiology, Jichi Medical University, 3311-1 Yakushiji, Shimotsuke, Tochigi 329-0498, Japan
| | - Wonbin Lee
- Department of Biochemistry, College of Life Science and Biotechnology, Yonsei University, Seoul 03722, South Korea
| | - Zeyu Jin
- Department of Biochemistry, College of Life Science and Biotechnology, Yonsei University, Seoul 03722, South Korea
| | - Jeremy R. H. Tame
- Drug Design Laboratory, Graduate School of Medical Life Science, Yokohama City University, Tsurumi, Yokohama 230-0045, Japan
| | - Naoya Shibayama
- Division of Biophysics, Department of Physiology, Jichi Medical University, 3311-1 Yakushiji, Shimotsuke, Tochigi 329-0498, Japan
| | - Sam-Yong Park
- Drug Design Laboratory, Graduate School of Medical Life Science, Yokohama City University, Tsurumi, Yokohama 230-0045, Japan
| | - Weontae Lee
- Department of Biochemistry, College of Life Science and Biotechnology, Yonsei University, Seoul 03722, South Korea
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5
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Mizuno M, Shimoo Y, Kandori H, Mizutani Y. Effect of a bound anion on the structure and dynamics of halorhodopsin from Natronomonas pharaonis. STRUCTURAL DYNAMICS (MELVILLE, N.Y.) 2019; 6:054703. [PMID: 31673569 PMCID: PMC6811361 DOI: 10.1063/1.5125621] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/24/2019] [Accepted: 10/09/2019] [Indexed: 06/10/2023]
Abstract
Active ion transport across membranes is vital to maintaining the electrochemical gradients of ions in cells and is mediated by transmembrane proteins. Halorhodopsin (HR) functions as a light-driven inward pump for chloride ions. The protein contains all-trans-retinal bound to a specific lysine residue through a protonated Schiff base. Interaction between the bound chloride ion and the protonated Schiff base is crucial for ion transport because chloride ion movement is driven by the flipping of the protonated Schiff base upon photoisomerization. However, it remains unknown how this interaction evolves in the HR photocycle. Here, we addressed the effect of the bound anion on the structure and dynamics of HR from Natronomonas pharaonis in the early stage of the photocycle. Comparison of the chloride-bound, formate-bound, and anion-depleted forms provided insights into the interaction between the bound anion and the chromophore/protein moiety. In the unphotolyzed state, the bound anion affects the π-conjugation of the polyene chain and the hydrogen bond of the protonated Schiff base of the retinal chromophore. Picosecond time scale measurements showed that the band intensities of the W16 and W18 modes of the tryptophan residues decreased instantaneously upon photoexcitation of the formate-bound form. In contrast, these intensity decreases were delayed for the chloride-bound and anion-depleted forms. These observations suggest the stronger interactions of the bound formate ion with the retinal chromophore and the chromophore pocket. On the nanosecond to microsecond timescales, we found that the interaction between the protonated Schiff base and the bound ion is broken upon formation of the K intermediate and is recovered following translocation of the bound anion toward the protonated Schiff base in the L intermediate. Our results demonstrate that the hydrogen-bonding ability of the bound anion plays an essential role in the ion transport of light-driven anion pumps.
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Affiliation(s)
- Misao Mizuno
- Department of Chemistry, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan
| | - Yumi Shimoo
- Department of Chemistry, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan
| | - Hideki Kandori
- Department of Life Science and Applied Chemistry, Nagoya Institute of Technology, Showa-ku, Nagoya, Aichi 466-8555, Japan
| | - Yasuhisa Mizutani
- Department of Chemistry, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan
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6
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Dombrowski T, Rankovic V, Moser T. Toward the Optical Cochlear Implant. Cold Spring Harb Perspect Med 2019; 9:cshperspect.a033225. [PMID: 30323016 DOI: 10.1101/cshperspect.a033225] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
When hearing fails, cochlear implants (CIs) provide open speech perception to most of the currently half a million CI users. CIs bypass the defective sensory organ and stimulate the auditory nerve electrically. The major bottleneck of current CIs is the poor coding of spectral information, which results from wide current spread from each electrode contact. As light can be more conveniently confined, optical stimulation of the auditory nerve presents a promising perspective for a fundamental advance of CIs. Moreover, given the improved frequency resolution of optical excitation and its versatility for arbitrary stimulation patterns the approach also bears potential for auditory research. Here, we review the current state of the art focusing on the emerging concept of optogenetic stimulation of the auditory pathway. Developing optogenetic stimulation for auditory research and future CIs requires efforts toward viral gene transfer to the neurons, design and characterization of appropriate optogenetic actuators, as well as engineering of multichannel optical implants.
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Affiliation(s)
- Tobias Dombrowski
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center, 37075 Göttingen, Germany.,Department of Otorhinolaryngology, Head and Neck Surgery, Ruhr University Bochum, St. Elisabeth Hospital, 44787 Bochum, Germany
| | - Vladan Rankovic
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center, 37075 Göttingen, Germany.,Auditory Neuroscience and Optogenetics Group, German Primate Center, 37077 Göttingen, Germany
| | - Tobias Moser
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center, 37075 Göttingen, Germany.,Auditory Neuroscience and Optogenetics Group, German Primate Center, 37077 Göttingen, Germany.,Auditory Neuroscience Group, Max-Planck-Institute for Experimental Medicine, 37075 Göttingen, Germany
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7
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Kouyama T, Ihara K, Maki K, Chan SK. Three-Step Isomerization of the Retinal Chromophore during the Anion Pumping Cycle of Halorhodopsin. Biochemistry 2018; 57:6013-6026. [PMID: 30211543 DOI: 10.1021/acs.biochem.8b00631] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
The anion pumping cycle of halorhodopsin from Natronomonas pharaonis ( pHR) is initiated when the all- trans/15- anti isomer of retinal is photoisomerized into the 13- cis/15- anti configuration. A recent crystallographic study suggested that a reaction state with 13- cis/15- syn retinal occurred during the anion release process, i.e., after the N state with the 13- cis/15- anti retinal and before the O state with all- trans/15- anti retinal. In this study, we investigated the retinal isomeric composition in a long-living reaction state at various bromide ion concentrations. It was found that the 13- cis isomer (csHR'), in which the absorption spectrum was blue-shifted by ∼8 nm compared with that of the trans isomer (taHR), accumulated significantly when a cold suspension of pHR-rich claret membranes in 4 M NaBr was illuminated with continuous light. Analysis of flash-induced absorption changes suggested that the branching of the trans photocycle into the 13- cis isomer (csHR') occurs during the decay of an O-like state (O') with 13- cis/15- syn retinal; i.e., O' can decay to either csHR' or O with all- trans/15- anti retinal. The efficiency of the branching reaction was found to be dependent on the bromide ion concentration. At a very high bromide ion concentration, the anion pumping cycle is described by the scheme taHR -( hν) → K → L1a ↔ L1b ↔ N ↔ N' ↔ O' ↔ csHR' ↔ taHR. At a low bromide ion concentration, on the other hand, O' decays into taHR via O.
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Affiliation(s)
- Tsutomu Kouyama
- Department of Physics, Graduate School of Science , Nagoya University , Furo-cho, Chikusa-ku, Nagoya 464-8602 , Japan
| | - Kunio Ihara
- Center for Gene Research , Nagoya University , Nagoya 464-8602 , Japan
| | - Kosuke Maki
- Department of Physics, Graduate School of Science , Nagoya University , Furo-cho, Chikusa-ku, Nagoya 464-8602 , Japan
| | - Siu Kit Chan
- Department of Physics, Graduate School of Science , Nagoya University , Furo-cho, Chikusa-ku, Nagoya 464-8602 , Japan
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8
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Sakajiri Y, Sugano E, Watanabe Y, Sakajiri T, Tabata K, Kikuchi T, Tomita H. Natronomonas pharaonis halorhodopsin Ser81 plays a role in maintaining chloride ions near the Schiff base. Biochem Biophys Res Commun 2018; 503:2326-2332. [PMID: 29964009 DOI: 10.1016/j.bbrc.2018.06.156] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2018] [Accepted: 06/27/2018] [Indexed: 02/02/2023]
Abstract
Optogenetic technologies have often been used as tools for neuronal activation or silencing by light. Natronomonas pharaonis halorhodopsin (NpHR) is a light-driven chloride ion pump. Upon light absorption, a chloride ion passes through the cell membrane, which is accompanied by the temporary binding of a chloride ion with Thr126 at binding site-1 (BS1) near the protonated Schiff base in NpHR. However, the mechanism of stabilization of the binding state between a chloride ion and BS1 has not been investigated. Therefore, to identify a key component of the chloride ion transport pathway as well as to acquire dynamic information about the chloride ion-BS1 binding state, we performed a rough analysis of the chloride ion pathway shape followed by molecular dynamics (MD) simulations for both wild-type and mutant NpHR structures. The MD simulations showed that the hydrogen bond between Thr126 and the chloride ion was retained in the wild-type protein, while the chloride ion could not be retained at and tended to leave BS1 in the S81A mutant. We found that the direction of the Thr126 side chain was fixed by a hydroxyl group of Ser81 through a hydrogen bond and that Thr126 bound to a chloride ion in the wild-type protein, while this interaction was lost in the S81A mutant, resulting in rotation of the Thr126 side chain and reduction in the interaction between Thr126 and a chloride ion. To confirm the role of S81, patch clamp recordings were performed using cells expressing NpHR S81A mutant protein. Considered together with the results that the NpHR S81A-expressing cells did not undergo hyperpolarization under light stimulation, our results indicate that Ser81 plays a key role in chloride migration. Our findings might be relevant to ongoing clinical trials using optogenetic gene therapy in blind patients.
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Affiliation(s)
- Yuko Sakajiri
- The United Graduate School of Agricultural Sciences, Iwate University, 3-18-8 Ueda, Morioka, Iwate, 020-8550, Japan.
| | - Eriko Sugano
- The United Graduate School of Agricultural Sciences, Iwate University, 3-18-8 Ueda, Morioka, Iwate, 020-8550, Japan; Laboratory of Visual Neuroscience, Graduate Course in Biological Sciences, Iwate University, 4-3-5 Ueda, Morioka, Iwate, 020-8551, Japan.
| | - Yoshito Watanabe
- Laboratory of Visual Neuroscience, Graduate Course in Biological Sciences, Iwate University, 4-3-5 Ueda, Morioka, Iwate, 020-8551, Japan.
| | - Tetsuya Sakajiri
- Department of Applied Life Sciences, Graduate School of Life and Environmental Sciences, Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku, Sakai, Osaka, 599-8531, Japan.
| | - Kitako Tabata
- Laboratory of Visual Neuroscience, Graduate Course in Biological Sciences, Iwate University, 4-3-5 Ueda, Morioka, Iwate, 020-8551, Japan.
| | - Takeshi Kikuchi
- Department of Bioinformatics, College of Life Sciences, Ritsumeikan University, 1-1-1 Noji-higashi, Kusatsu Shiga, 525-8577, Japan.
| | - Hiroshi Tomita
- The United Graduate School of Agricultural Sciences, Iwate University, 3-18-8 Ueda, Morioka, Iwate, 020-8550, Japan; Laboratory of Visual Neuroscience, Graduate Course in Biological Sciences, Iwate University, 4-3-5 Ueda, Morioka, Iwate, 020-8551, Japan; Clinical Research, Innovation and Education Center, Tohoku University Hospital, 1-1 Seiryo, Aoba, Sendai, Miyagi, 980-8574, Japan.
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9
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Engelhard C, Chizhov I, Siebert F, Engelhard M. Microbial Halorhodopsins: Light-Driven Chloride Pumps. Chem Rev 2018; 118:10629-10645. [DOI: 10.1021/acs.chemrev.7b00715] [Citation(s) in RCA: 48] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Affiliation(s)
| | - Igor Chizhov
- Institute for Biophysical Chemistry, Hannover Medical School, OE8830 Carl-Neuberg-Straße 1, 30625 Hannover, Germany
| | - Friedrich Siebert
- Institut für Molekulare Medizin und Zellforschung, Sektion Biophysik, Albert-Ludwigs-Universität Freiburg, Hermann-Herderstr. 9, 79104 Freiburg, Germany
| | - Martin Engelhard
- Max Planck Institute for Molecular Physiology, Otto Hahn Str. 11, 44227 Dortmund, Germany
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10
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High frequency neural spiking and auditory signaling by ultrafast red-shifted optogenetics. Nat Commun 2018; 9:1750. [PMID: 29717130 PMCID: PMC5931537 DOI: 10.1038/s41467-018-04146-3] [Citation(s) in RCA: 92] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2017] [Accepted: 04/06/2018] [Indexed: 11/29/2022] Open
Abstract
Optogenetics revolutionizes basic research in neuroscience and cell biology and bears potential for medical applications. We develop mutants leading to a unifying concept for the construction of various channelrhodopsins with fast closing kinetics. Due to different absorption maxima these channelrhodopsins allow fast neural photoactivation over the whole range of the visible spectrum. We focus our functional analysis on the fast-switching, red light-activated Chrimson variants, because red light has lower light scattering and marginal phototoxicity in tissues. We show paradigmatically for neurons of the cerebral cortex and the auditory nerve that the fast Chrimson mutants enable neural stimulation with firing frequencies of several hundred Hz. They drive spiking at high rates and temporal fidelity with low thresholds for stimulus intensity and duration. Optical cochlear implants restore auditory nerve activity in deaf mice. This demonstrates that the mutants facilitate neuroscience research and future medical applications such as hearing restoration. Optogenetic applications would benefit from channelrhodopsins (ChRs) with faster photostimulation, increased tissue transparency and lower phototoxicity. Here, the authors develop fast red-shifted ChR variants and show the abilities for temporal precise spiking of cerebral interneurons and restoring auditory activity in deaf mice.
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Abstract
Microbial rhodopsins (MRs) are a large family of photoactive membrane proteins, found in microorganisms belonging to all kingdoms of life, with new members being constantly discovered. Among the MRs are light-driven proton, cation and anion pumps, light-gated cation and anion channels, and various photoreceptors. Due to their abundance and amenability to studies, MRs served as model systems for a great variety of biophysical techniques, and recently found a great application as optogenetic tools. While the basic aspects of microbial rhodopsins functioning have been known for some time, there is still a plenty of unanswered questions. This chapter presents and summarizes the available knowledge, focusing on the functional and structural studies.
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Affiliation(s)
- Ivan Gushchin
- Moscow Institute of Physics and Technology, Dolgoprudniy, Russia.
| | - Valentin Gordeliy
- Moscow Institute of Physics and Technology, Dolgoprudniy, Russia.
- University of Grenoble Alpes, CEA, CNRS, IBS, Grenoble, France.
- Institute of Complex Systems (ICS), ICS-6: Structural Biochemistry, Research Centre Jülich, Jülich, Germany.
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12
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Chen XR, Huang YC, Yi HP, Yang CS. A Unique Light-Driven Proton Transportation Signal in Halorhodopsin from Natronomonas pharaonis. Biophys J 2017; 111:2600-2607. [PMID: 28002736 DOI: 10.1016/j.bpj.2016.11.003] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2016] [Revised: 11/03/2016] [Accepted: 11/07/2016] [Indexed: 11/26/2022] Open
Abstract
Halorhodopsin (HR) is a seven-transmembrane retinylidene protein from haloarchaea that is commonly known to function as a light-driven inward chloride pump. However, previous studies have indicated that despite the general characteristics that most HRs share, HRs from distinct species differ in many aspects. We present indium-tin-oxide-based photocurrent measurements that reveal a light-induced signal generated by proton release that is observed solely in NpHR via purified protein-based assays, demonstrating that indeed HRs are not all identical. We conducted mutagenesis studies on several conserved residues that are considered critical for chloride stability among HRs. Intriguingly, the photocurrent signals were eliminated after specific point mutations. We propose an NpHR light-driven, cytoplasmic-side proton circulation model to explain the unique light-induced photocurrent recorded in NpHR. Notably, the photocurrent and various photocycle intermediates were recorded simultaneously. This approach provides a high-resolution method for further investigations of the proton-assisted chloride translocation mechanism.
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Affiliation(s)
- Xiao-Ru Chen
- Department of Biochemical Science and Technology, National Taiwan University, Taipei, Taiwan
| | - Yuan-Chi Huang
- Department of Biochemical Science and Technology, National Taiwan University, Taipei, Taiwan
| | - Hsiu-Ping Yi
- Department of Biochemical Science and Technology, National Taiwan University, Taipei, Taiwan
| | - Chii-Shen Yang
- Department of Biochemical Science and Technology, National Taiwan University, Taipei, Taiwan.
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13
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Schreiner M, Schlesinger R, Heberle J, Niemann HH. Crystal structure of Halobacterium salinarum halorhodopsin with a partially depopulated primary chloride-binding site. Acta Crystallogr F Struct Biol Commun 2016; 72:692-9. [PMID: 27599860 PMCID: PMC5012209 DOI: 10.1107/s2053230x16012796] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2016] [Accepted: 08/08/2016] [Indexed: 05/17/2023] Open
Abstract
The transmembrane pump halorhodopsin in halophilic archaea translocates chloride ions from the extracellular to the cytoplasmic side upon illumination. In the ground state a tightly bound chloride ion occupies the primary chloride-binding site (CBS I) close to the protonated Schiff base that links the retinal chromophore to the protein. The light-triggered trans-cis isomerization of retinal causes structural changes in the protein associated with movement of the chloride ion. In reverse, chemical depletion of CBS I in Natronomonas pharaonis halorhodopsin (NpHR) through deprotonation of the Schiff base results in conformational changes of the protein: a state thought to mimic late stages of the photocycle. Here, crystals of Halobacterium salinarum halorhodopsin (HsHR) were soaked at high pH to provoke deprotonation of the Schiff base and loss of chloride. The crystals changed colour from purple to yellow and the occupancy of CBS I was reduced from 1 to about 0.5. In contrast to NpHR, this chloride depletion did not cause substantial conformational changes in the protein. Nevertheless, two observations indicate that chloride depletion could eventually result in structural changes similar to those found in NpHR. Firstly, the partially chloride-depleted form of HsHR has increased normalized B factors in the region of helix C that is close to CBS I and changes its conformation in NpHR. Secondly, prolonged soaking of HsHR crystals at high pH resulted in loss of diffraction. In conclusion, the conformation of the chloride-free protein may not be compatible with this crystal form of HsHR despite a packing arrangement that hardly restrains helices E and F that presumably move during ion transport.
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Affiliation(s)
- Madeleine Schreiner
- Department of Chemistry, Bielefeld University, Universitätsstrasse 25, 33615 Bielefeld, Germany
| | - Ramona Schlesinger
- Genetic Biophysics, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - Joachim Heberle
- Experimental Molecular Biophysics, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - Hartmut H. Niemann
- Department of Chemistry, Bielefeld University, Universitätsstrasse 25, 33615 Bielefeld, Germany
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14
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Kouyama T, Kawaguchi H, Nakanishi T, Kubo H, Murakami M. Crystal structures of the L1, L2, N, and O states of pharaonis halorhodopsin. Biophys J 2016; 108:2680-90. [PMID: 26039169 PMCID: PMC4457492 DOI: 10.1016/j.bpj.2015.04.027] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2015] [Revised: 04/17/2015] [Accepted: 04/20/2015] [Indexed: 01/15/2023] Open
Abstract
Halorhodopsin from Natronomonas pharaonis (pHR) functions as a light-driven halide ion pump. In the presence of halide ions, the photochemical reaction of pHR is described by the scheme: K→ L1 → L2 → N → O → pHR′ → pHR. Here, we report light-induced structural changes of the pHR-bromide complex observed in the C2 crystal. In the L1-to-L2 transition, the bromide ion that initially exists in the extracellular vicinity of retinal moves across the retinal Schiff base. Upon the formation of the N state with a bromide ion bound to the cytoplasmic vicinity of the retinal Schiff base, the cytoplasmic half of helix F moves outward to create a water channel in the cytoplasmic interhelical space, whereas the extracellular half of helix C moves inward. During the transition from N to an N-like reaction state with retinal assuming the 13-cis/15-syn configuration, the translocated bromide ion is released into the cytoplasmic medium. Subsequently, helix F relaxes into its original conformation, generating the O state. Anion uptake from the extracellular side occurs when helix C relaxes into its original conformation. These structural data provide insight into the structural basis of unidirectional anion transport.
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Affiliation(s)
- Tsutomu Kouyama
- Department of Physics, Graduate School of Science, Nagoya University, Nagoya, Japan; RIKEN Harima Branch, 1-1-1, Kouto, Sayo, Hyogo, Japan.
| | - Haruki Kawaguchi
- Department of Physics, Graduate School of Science, Nagoya University, Nagoya, Japan
| | - Taichi Nakanishi
- Department of Physics, Graduate School of Science, Nagoya University, Nagoya, Japan
| | - Hiroki Kubo
- Department of Physics, Graduate School of Science, Nagoya University, Nagoya, Japan
| | - Midori Murakami
- Department of Physics, Graduate School of Science, Nagoya University, Nagoya, Japan
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Shalaeva DN, Galperin MY, Mulkidjanian AY. Eukaryotic G protein-coupled receptors as descendants of prokaryotic sodium-translocating rhodopsins. Biol Direct 2015; 10:63. [PMID: 26472483 PMCID: PMC4608122 DOI: 10.1186/s13062-015-0091-4] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2015] [Accepted: 10/12/2015] [Indexed: 12/20/2022] Open
Abstract
Abstract Microbial rhodopsins and G-protein coupled receptors (GPCRs, which include animal rhodopsins) are two distinct (super) families of heptahelical (7TM) membrane proteins that share obvious structural similarities but no significant sequence similarity. Comparison of the recently solved high-resolution structures of the sodium-translocating bacterial rhodopsin and various Na+-binding GPCRs revealed striking similarity of their sodium-binding sites. This similarity allowed us to construct a structure-guided sequence alignment for the two (super)families, which highlighted their evolutionary relatedness. Our analysis supports a common underlying molecular mechanism for both families that involves a highly conserved aromatic residue playing a pivotal role in rotation of the 6th transmembrane helix. Reviewers This article was reviewed by Oded Beja, G. P. S. Raghava and L. Aravind. Electronic supplementary material The online version of this article (doi:10.1186/s13062-015-0091-4) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Daria N Shalaeva
- School of Physics, Osnabrueck University, 49069, Osnabrueck, Germany. .,School of Bioengineering and Bioinformatics, Lomonosov Moscow State University, Moscow, 119992, Russia.
| | - Michael Y Galperin
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD, 20894, USA.
| | - Armen Y Mulkidjanian
- School of Physics, Osnabrueck University, 49069, Osnabrueck, Germany. .,School of Bioengineering and Bioinformatics, Lomonosov Moscow State University, Moscow, 119992, Russia. .,A.N. Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119992, Russia.
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Jardón-Valadez E, Bondar AN, Tobias DJ. Electrostatic interactions and hydrogen bond dynamics in chloride pumping by halorhodopsin. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2015; 1837:1964-1972. [PMID: 25256652 DOI: 10.1016/j.bbabio.2014.09.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2014] [Revised: 09/15/2014] [Accepted: 09/17/2014] [Indexed: 10/24/2022]
Abstract
Translocation of negatively charged ions across cell membranes by ion pumps raises the question as to how protein interactions control the location and dynamics of the ion. Here we address this question by performing extensive molecular dynamics simulations of wild type and mutant halorhodopsin, a seven-helical transmembrane protein that translocates chloride ions upon light absorption. We find that inter-helical hydrogen bonds mediated by a key arginine group largely govern the dynamics of the protein and water groups coordinating the chloride ion.
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Affiliation(s)
- Eduardo Jardón-Valadez
- Departamento de Recursos de la Tierra, Universidad Autónoma Metropolitana-Lerma, Lerma de Villada, Estado de México 52005, México
| | - Ana-Nicoleta Bondar
- Theoretical Molecular Biophysics Department of Physics, Freie University Arnimallee 14, Berlin 14195, Germany.
| | - Douglas J Tobias
- Department of Chemistry, University of California, Irvine, CA 92697-2025, USA
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17
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Schreiner M, Schlesinger R, Heberle J, Niemann HH. Structure of Halorhodopsin from Halobacterium salinarum in a new crystal form that imposes little restraint on the E-F loop. J Struct Biol 2015; 190:373-8. [PMID: 25916754 DOI: 10.1016/j.jsb.2015.04.010] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2015] [Accepted: 04/13/2015] [Indexed: 10/23/2022]
Abstract
Halorhodopsin from the halophilic archaeon Halobacterium salinarum is a membrane located light-driven chloride pump. Upon illumination Halorhodopsin undergoes a reversible photocycle initiated by the all-trans to 13-cis isomerization of the covalently bound retinal chromophore. The photocycle consists of several spectroscopically distinct intermediates. The structural basis of the chloride transport mechanism remains elusive, presumably because packing contacts have so far precluded protein conformational changes in the available crystals. With the intention to structurally characterize late photocycle intermediates by X-ray crystallography we crystallized Halorhodopsin in a new crystal form using the vesicle fusion method. In the new crystal form lateral contacts are mediated by helices A and G. Helices E and F that were suggested to perform large movements during the photocycle are almost unrestrained by packing contacts. This feature might permit the displacement of these helices without disrupting the crystal lattice. Therefore, this new crystal form might be an excellent system for the structural characterization of late Halorhodopsin photocycle intermediates by trapping or by time resolved experiments, especially at XFELs.
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Affiliation(s)
- Madeleine Schreiner
- Department of Chemistry, Bielefeld University, Universitätsstraße 25, 33615 Bielefeld, Germany
| | - Ramona Schlesinger
- Genetic Biophysics, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - Joachim Heberle
- Experimental Molecular Biophysics, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - Hartmut H Niemann
- Department of Chemistry, Bielefeld University, Universitätsstraße 25, 33615 Bielefeld, Germany.
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Müller M, Bamann C, Bamberg E, Kühlbrandt W. Light-induced helix movements in channelrhodopsin-2. J Mol Biol 2014; 427:341-9. [PMID: 25451024 DOI: 10.1016/j.jmb.2014.11.004] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2014] [Revised: 10/10/2014] [Accepted: 11/02/2014] [Indexed: 11/26/2022]
Abstract
Channelrhodopsin-2 (ChR2) is a cation-selective light-gated channel from Chlamydomonas reinhardtii (Nagel G, Szellas T, Huhn W, Kateriya S, Adeishvili N, Berthold P, et al. Channelrhodopsin-2, a directly light-gated cation-selective membrane channel. Proc Natl Acad Sci USA 2003;100:13940-5), which has become a powerful tool in optogenetics. Two-dimensional crystals of the slow photocycling C128T ChR2 mutant were exposed to 473 nm light and rapidly frozen to trap the open state. Projection difference maps at 6Å resolution show the location, extent and direction of light-induced conformational changes in ChR2 during the transition from the closed state to the ion-conducting open state. Difference peaks indicate that transmembrane helices (TMHs) TMH2, TMH6 and TMH7 reorient or rearrange during the photocycle. No major differences were found near TMH3 and TMH4 at the dimer interface. While conformational changes in TMH6 and TMH7 are known from other microbial-type rhodopsins, our results indicate that TMH2 has a key role in light-induced channel opening and closing in ChR2.
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Affiliation(s)
- Maria Müller
- Max Planck Institute of Biophysics Department of Structural Biology, Max von Laue Strasse 3, 60438 Frankfurt, Germany
| | - Christian Bamann
- Max Planck Institute of Biophysics Department of Biophysical Chemistry, Max von Laue Strasse 3, 60438 Frankfurt, Germany
| | - Ernst Bamberg
- Max Planck Institute of Biophysics Department of Biophysical Chemistry, Max von Laue Strasse 3, 60438 Frankfurt, Germany
| | - Werner Kühlbrandt
- Max Planck Institute of Biophysics Department of Structural Biology, Max von Laue Strasse 3, 60438 Frankfurt, Germany.
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Chan SK, Kitajima-Ihara T, Fujii R, Gotoh T, Murakami M, Ihara K, Kouyama T. Crystal structure of Cruxrhodopsin-3 from Haloarcula vallismortis. PLoS One 2014; 9:e108362. [PMID: 25268964 PMCID: PMC4182453 DOI: 10.1371/journal.pone.0108362] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2014] [Accepted: 08/26/2014] [Indexed: 01/09/2023] Open
Abstract
Cruxrhodopsin-3 (cR3), a retinylidene protein found in the claret membrane of Haloarcula vallismortis, functions as a light-driven proton pump. In this study, the membrane fusion method was applied to crystallize cR3 into a crystal belonging to space group P321. Diffraction data at 2.1 Å resolution show that cR3 forms a trimeric assembly with bacterioruberin bound to the crevice between neighboring subunits. Although the structure of the proton-release pathway is conserved among proton-pumping archaeal rhodopsins, cR3 possesses the following peculiar structural features: 1) The DE loop is long enough to interact with a neighboring subunit, strengthening the trimeric assembly; 2) Three positive charges are distributed at the cytoplasmic end of helix F, affecting the higher order structure of cR3; 3) The cytoplasmic vicinity of retinal is more rigid in cR3 than in bacteriorhodopsin, affecting the early reaction step in the proton-pumping cycle; 4) the cytoplasmic part of helix E is greatly bent, influencing the proton uptake process. Meanwhile, it was observed that the photobleaching of retinal, which scarcely occurred in the membrane state, became significant when the trimeric assembly of cR3 was dissociated into monomers in the presence of an excess amount of detergent. On the basis of these observations, we discuss structural factors affecting the photostabilities of ion-pumping rhodopsins.
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Affiliation(s)
- Siu Kit Chan
- Department of Physics, Graduate School of Science, Nagoya University, Nagoya, Japan
| | | | - Ryudoh Fujii
- Department of Physics, Graduate School of Science, Nagoya University, Nagoya, Japan
| | - Toshiaki Gotoh
- Department of Physics, Graduate School of Science, Nagoya University, Nagoya, Japan
| | - Midori Murakami
- Department of Physics, Graduate School of Science, Nagoya University, Nagoya, Japan
| | - Kunio Ihara
- Center for Gene Research, Nagoya University, Nagoya, Japan
| | - Tsutomu Kouyama
- Department of Physics, Graduate School of Science, Nagoya University, Nagoya, Japan
- RIKEN Harima Institute/SPring-8, Mikazuki, Sayo, Hyogo, Japan
- * E-mail:
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Sattig T, Rickert C, Bamberg E, Steinhoff HJ, Bamann C. Light-Induced Movement of the Transmembrane Helix B in Channelrhodopsin-2. Angew Chem Int Ed Engl 2013; 52:9705-8. [DOI: 10.1002/anie.201301698] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2013] [Revised: 06/12/2013] [Indexed: 11/06/2022]
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21
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Sattig T, Rickert C, Bamberg E, Steinhoff HJ, Bamann C. Light-Induced Movement of the Transmembrane Helix B in Channelrhodopsin-2. Angew Chem Int Ed Engl 2013. [DOI: 10.1002/ange.201301698] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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