1
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Asido M, Boumrifak C, Weissbecker J, Bamberg E, Wachtveitl J. Vibrational Study of the Inward Proton Pump Xenorhodopsin NsXeR: Switch Order Determines Vectoriality. J Mol Biol 2024; 436:168447. [PMID: 38244766 DOI: 10.1016/j.jmb.2024.168447] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2023] [Revised: 01/12/2024] [Accepted: 01/12/2024] [Indexed: 01/22/2024]
Abstract
Common proton pumps, e.g. HsBR and PR, transport protons out of the cell. Xenorhodopsins (XeR) were the first discovered microbial rhodopsins which come as natural inward proton pumps. In this work we combine steady-state (cryo-)FTIR and Raman spectroscopy with time-resolved IR and UV/Vis measurements to roadmap the inward proton transport of NsXeR and pinpoint the most important mechanistic features. Through the assignment of characteristic bands of the protein backbone, the retinal chromophore, the retinal Schiff base and D220, we could follow the switching processes for proton accessibility in accordance with the isomerization / switch / transfer model. The corresponding transient IR signatures suggest that the initial assignment of D220 as the proton acceptor needs to be questioned due to the temporal mismatch of the Schiff base and D220 protonation steps. The switching events in the K-L and MCP-MEC transitions are finely tuned by changes of the protein backbone and rearrangements of the Schiff base. This finely tuned mechanism is disrupted at cryogenic temperatures, being reflected in the replacement of the previously reported long-lived intermediate GS* by an actual redshifted (O-like) intermediate.
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Affiliation(s)
- Marvin Asido
- Institute of Physical and Theoretical Chemistry, Goethe University Frankfurt, Max-von-Laue Straße 7, 60438 Frankfurt am Main, Germany
| | - Chokri Boumrifak
- Institute of Physical and Theoretical Chemistry, Goethe University Frankfurt, Max-von-Laue Straße 7, 60438 Frankfurt am Main, Germany
| | - Juliane Weissbecker
- Department of Biophysical Chemistry, Max-Planck-Institute of Biophysics, Max-von-Laue-Straße 3, 60438 Frankfurt am Main, Germany
| | - Ernst Bamberg
- Department of Biophysical Chemistry, Max-Planck-Institute of Biophysics, Max-von-Laue-Straße 3, 60438 Frankfurt am Main, Germany
| | - Josef Wachtveitl
- Institute of Physical and Theoretical Chemistry, Goethe University Frankfurt, Max-von-Laue Straße 7, 60438 Frankfurt am Main, Germany.
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2
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Lim J, Shin M, Ha T, Su WW, Yoon J, Choi JW. A Nano-Biohybrid-Based Bio-Solar Cell to Regulate the Electrical Signal Transmission to Living Cells for Biomedical Application. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2023; 35:e2303125. [PMID: 37435979 DOI: 10.1002/adma.202303125] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/04/2023] [Revised: 07/07/2023] [Accepted: 07/07/2023] [Indexed: 07/13/2023]
Abstract
Bio-solar cells are studied as sustainable and biocompatible energy sources with significant potential for biomedical applications. However, they are composed of light-harvesting biomolecules with narrow absorption wavelengths and weak transient photocurrent generation. In this study, a nano-biohybrid-based bio-solar cell composed of bacteriorhodopsin, chlorophyllin, and Ni/TiO2 nanoparticles is developed to overcome the current limitations and verify the possibility of biomedical applications. Bacteriorhodopsin and chlorophyllin are introduced as light-harvesting biomolecules to broaden the absorption wavelength. As a photocatalyst, Ni/TiO2 nanoparticles are introduced to generate a photocurrent and amplify the photocurrent generated by the biomolecules. The developed bio-solar cell absorbs a broad range of visible wavelengths and generates an amplified stationary photocurrent density (152.6 nA cm-2 ) with a long lifetime (up to 1 month). Besides, the electrophysiological signals of muscle cells at neuromuscular junctions are precisely regulated by motor neurons excited by the photocurrent of the bio-solar cell, indicating that the bio-solar cell can control living cells by signal transmission through other types of living cells. The proposed nano-biohybrid-based bio-solar cell can be used as a sustainable and biocompatible energy source for the development of wearable and implantable biodevices and bioelectronic medicines for humans.
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Affiliation(s)
- Joungpyo Lim
- Department of Chemical & Biomolecular Engineering, Sogang University, 35 Baekbeom-ro, Mapo-gu, Seoul, 04107, Republic of Korea
| | - Minkyu Shin
- Department of Chemical & Biomolecular Engineering, Sogang University, 35 Baekbeom-ro, Mapo-gu, Seoul, 04107, Republic of Korea
| | - Taehyung Ha
- Department of Chemical & Biomolecular Engineering, Sogang University, 35 Baekbeom-ro, Mapo-gu, Seoul, 04107, Republic of Korea
| | - Wei Wen Su
- Department of Molecular Biosciences and Bioengineering, University of Hawaii at Manoa, Honolulu, HI, 96822, USA
| | - Jinho Yoon
- Department of Biomedical-Chemical Engineering, The Catholic University of Korea, 43 Jibong-ro, Wonmi-gu, Bucheon-si, Gyeonggi-do, 14662, Republic of Korea
| | - Jeong-Woo Choi
- Department of Chemical & Biomolecular Engineering, Sogang University, 35 Baekbeom-ro, Mapo-gu, Seoul, 04107, Republic of Korea
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3
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Meng X, Ganapathy S, van Roemburg L, Post M, Brinks D. Voltage Imaging with Engineered Proton-Pumping Rhodopsins: Insights from the Proton Transfer Pathway. ACS PHYSICAL CHEMISTRY AU 2023; 3:320-333. [PMID: 37520318 PMCID: PMC10375888 DOI: 10.1021/acsphyschemau.3c00003] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/20/2023] [Revised: 04/13/2023] [Accepted: 04/13/2023] [Indexed: 08/01/2023]
Abstract
Voltage imaging using genetically encoded voltage indicators (GEVIs) has taken the field of neuroscience by storm in the past decade. Its ability to create subcellular and network level readouts of electrical dynamics depends critically on the kinetics of the response to voltage of the indicator used. Engineered microbial rhodopsins form a GEVI subclass known for their high voltage sensitivity and fast response kinetics. Here we review the essential aspects of microbial rhodopsin photocycles that are critical to understanding the mechanisms of voltage sensitivity in these proteins and link them to insights from efforts to create faster, brighter and more sensitive microbial rhodopsin-based GEVIs.
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Affiliation(s)
- Xin Meng
- Department
of Imaging Physics, Delft University of
Technology, 2628 CJ Delft, The
Netherlands
| | - Srividya Ganapathy
- Department
of Imaging Physics, Delft University of
Technology, 2628 CJ Delft, The
Netherlands
- Department
of Pediatrics & Cellular and Molecular Medicine, UCSD School of Medicine, La Jolla, California 92093, United States
| | - Lars van Roemburg
- Department
of Imaging Physics, Delft University of
Technology, 2628 CJ Delft, The
Netherlands
| | - Marco Post
- Department
of Imaging Physics, Delft University of
Technology, 2628 CJ Delft, The
Netherlands
| | - Daan Brinks
- Department
of Imaging Physics, Delft University of
Technology, 2628 CJ Delft, The
Netherlands
- Department
of Molecular Genetics, Erasmus University
Medical Center, 3015 GD Rotterdam, The Netherlands
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4
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Brown LS. Light-driven proton transfers and proton transport by microbial rhodopsins - A biophysical perspective. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2022; 1864:183867. [PMID: 35051382 DOI: 10.1016/j.bbamem.2022.183867] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/29/2021] [Revised: 12/30/2021] [Accepted: 01/10/2022] [Indexed: 12/31/2022]
Abstract
In the last twenty years, our understanding of the rules and mechanisms for the outward light-driven proton transport (and underlying proton transfers) by microbial rhodopsins has been changing dramatically. It transitioned from a very detailed atomic-level understanding of proton transport by bacteriorhodopsin, the prototypical proton pump, to a confounding variety of sequence motifs, mechanisms, directions, and modes of transport in its newly found homologs. In this review, we will summarize and discuss experimental data obtained on new microbial rhodopsin variants, highlighting their contribution to the refinement and generalization of the ideas crystallized in the previous century. In particular, we will focus on the proton transport (and transfers) vectoriality and their structural determinants, which, in many cases, remain unidentified.
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Affiliation(s)
- Leonid S Brown
- Department of Physics and Biophysics Interdepartmental Group, University of Guelph, Ontario N1G 2W1, Canada.
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Rokitskaya TI, Maliar N, Kovalev KV, Volkov O, Gordeliy VI, Antonenko YN. Rhodopsin Channel Activity Can Be Evaluated by Measuring the Photocurrent Voltage Dependence in Planar Bilayer Lipid Membranes. BIOCHEMISTRY (MOSCOW) 2021; 86:409-419. [PMID: 33941063 DOI: 10.1134/s0006297921040039] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The studies of the functional properties of retinal-containing proteins often include experiments in model membrane systems, e.g., measurements of electric current through planar bilayer lipid membranes (BLMs) with proteoliposomes adsorbed on one of the membrane surfaces. However, the possibilities of this method have not been fully explored yet. We demonstrated that the voltage dependence of stationary photocurrents for two light-sensitive proteins, bacteriorhodopsin (bR) and channelrhodopsin 2 (ChR2), in the presence of protonophore had very different characteristics. In the case of the bR (proton pump), the photocurrent through the BLM did not change direction when the polarity of the applied voltage was switched. In the case of the photosensitive channel protein ChR2, the photocurrent increased with the increase in voltage and the current polarity changed with the change in the voltage polarity. The protonophore 4,5,6,7-tetrachloro-2-trifluoromethyl benzimidazole (TTFB) was more efficient in the maximizing stationary photocurrents. In the presence of carbonyl cyanide-m-chlorophenylhydrazone (CCCP), the amplitude of the measured photocurrents for bR significantly decreased, while in the case of ChR2, the photocurrents virtually disappeared. The difference between the effects of TTFB and CCCP was apparently due to the fact that, in contrast to TTFB, CCCP transfers protons across the liposome membranes with a higher rate than through the decane-containing BLM used as a surface for the proteoliposome adsorption.
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Affiliation(s)
- Tatyana I Rokitskaya
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119991, Russia.
| | - Nina Maliar
- Moscow Institute of Physics and Technology, Dolgoprudny, Moscow Region, 141701, Russia
| | - Kirill V Kovalev
- Moscow Institute of Physics and Technology, Dolgoprudny, Moscow Region, 141701, Russia.,Institut de Biologie Structurale (IBS), Université Grenoble Alpes, CEA, CNRS, Grenoble, 38044, France
| | - Oleksandr Volkov
- Institute of Biological Information Processing (IBI-7: Structural Biochemistry), Forschungszentrum Jülich GmbH, Juelich, 52425, Germany.,JuStruct: Jülich Center for Structural Biology, Forschungszentrum Jülich GmbH, Juelich, 52425, Germany
| | - Valentin I Gordeliy
- Moscow Institute of Physics and Technology, Dolgoprudny, Moscow Region, 141701, Russia.,Institut de Biologie Structurale (IBS), Université Grenoble Alpes, CEA, CNRS, Grenoble, 38044, France.,Institute of Biological Information Processing (IBI-7: Structural Biochemistry), Forschungszentrum Jülich GmbH, Juelich, 52425, Germany.,JuStruct: Jülich Center for Structural Biology, Forschungszentrum Jülich GmbH, Juelich, 52425, Germany
| | - Yuri N Antonenko
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119991, Russia
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Oleinikov VA, Solovyeva DO, Zaitsev SY. Nanohybrid Structures Based on Plasmonic or Fluorescent Nanoparticles and Retinal-Containing Proteins. BIOCHEMISTRY (MOSCOW) 2020; 85:S196-S212. [PMID: 32087060 DOI: 10.1134/s0006297920140102] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Rhodopsins are light-sensitive membrane proteins enabling transmembrane charge separation (proton pump) on absorption of a light quantum. Bacteriorhodopsin (BR) is a transmembrane protein from halophilic bacteria that belongs to the rhodopsin family. Potential applications of BR are considered so promising that the number of studies devoted to the use of BR itself, its mutant variants, as well as hybrid materials containing BR in various areas grows steadily. Formation of hybrid structures combining BR with nanoparticles is an essential step in promotion of BR-based devices. However, rapid progress, continuous emergence of new data, as well as challenges of analyzing the entire data require regular reviews of the achievements in this area. This review is devoted to the issues of formation of materials based on hybrids of BR with fluorescent semiconductor nanocrystals (quantum dots) and with noble metal (silver, gold) plasmonic nanoparticles. Recent data on formation of thin (mono-) and thick (multi-) layers from materials containing BR and BR/nanoparticle hybrids are presented.
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Affiliation(s)
- V A Oleinikov
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, 117997, Russia. .,Institute of Engineering Physics for Biomedicine, National Research Nuclear University MEPhI, Moscow, 115409, Russia
| | - D O Solovyeva
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, 117997, Russia.,Institute of Engineering Physics for Biomedicine, National Research Nuclear University MEPhI, Moscow, 115409, Russia
| | - S Yu Zaitsev
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, 117997, Russia.,L. K. Ernst Federal Science Center for Animal Husbandry, Dubrovitsy, Moscow Region, 142132, Russia
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7
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Dong B, Sánchez-Magraner L, Luecke H. Structure of an Inward Proton-Transporting Anabaena Sensory Rhodopsin Mutant: Mechanistic Insights. Biophys J 2017; 111:963-72. [PMID: 27602724 DOI: 10.1016/j.bpj.2016.04.055] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2015] [Revised: 04/08/2016] [Accepted: 04/12/2016] [Indexed: 02/03/2023] Open
Abstract
Microbial rhodopsins are light-activated, seven-α-helical, retinylidene transmembrane proteins that have been identified in thousands of organisms across archaea, bacteria, fungi, and algae. Although they share a high degree of sequence identity and thus similarity in structure, many unique functions have been discovered and characterized among them. Some function as outward proton pumps, some as inward chloride pumps, whereas others function as light sensors or ion channels. Unique among the microbial rhodopsins characterized thus far, Anabaena sensory rhodopsin (ASR) is a photochromic sensor that interacts with a soluble 14-kDa cytoplasmic transducer that is encoded on the same operon. The sensor itself stably interconverts between all-trans-15-anti and 13-cis-15-syn retinal forms depending on the wavelength of illumination, although only the former participates in a photocycle with a signaling M intermediate. A mutation in the cytoplasmic half-channel of the protein, replacing Asp217 with Glu (D217E), results in the creation of a light-driven, single-photon, inward proton transporter. We present the 2.3 Å structure of dark-adapted D217E ASR, which reveals significant changes in the water network surrounding Glu217, as well as a shift in the carbon backbone near retinal-binding Lys210, illustrating a possible pathway leading to the protonation of Glu217 in the cytoplasmic half-channel, located 15 Å from the Schiff base. Crystallographic evidence for the protonation of nearby Glu36 is also discussed, which was described previously by Fourier transform infrared spectroscopy analysis. Finally, two histidine residues near the extracellular surface and their possible role in proton uptake are discussed.
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Affiliation(s)
- Bamboo Dong
- Department of Molecular Biology and Biochemistry, University of California Irvine, Irvine, California
| | | | - Hartmut Luecke
- Department of Molecular Biology and Biochemistry, University of California Irvine, Irvine, California.
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8
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Hung CC, Chen XR, Ko YK, Kobayashi T, Yang CS, Yabushita A. Schiff Base Proton Acceptor Assists Photoisomerization of Retinal Chromophores in Bacteriorhodopsin. Biophys J 2017. [PMID: 28636908 DOI: 10.1016/j.bpj.2017.05.015] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022] Open
Abstract
In this study, we investigated the ultrafast dynamics of bacteriorhodopsins (BRs) from Haloquadratum walsbyi (HwBR) and Haloarcula marismortui (HmBRI and HmBRII). First, the ultrafast dynamics were studied for three HwBR samples: wild-type, D93N mutation, and D104N mutation. The residues of the D93 and D104 mutants correspond to the control by the Schiff base proton acceptor and donor of the proton translocation subchannels. Measurements indicated that the negative charge from the Schiff base proton acceptor residue D93 interacts with the ultrafast and substantial change of the electrostatic potential associated with chromophore isomerization. By contrast, the Schiff base proton donor assists the restructuring of the chromophore cavity hydrogen-bond network during the thermalization of the vibrational hot state. Second, the ultrafast dynamics of the wild-types of HwBR, HmBRI, and HmBRII were compared. Measurements demonstrated that the hydrogen-bond network in the extracellular region in HwBR and HmBRII slows the photoisomerization of retinal chromophores, and the negatively charged helices on the cytoplasmic side of HwBR and HmBRII accelerate the thermalization of the vibrational hot state of retinal chromophores. The similarity of the correlation spectra of the wild-type HmBRI and D104N mutant of HwBR indicates that inactivation of the Schiff base proton donor induces a positive charge on the helices of the cytoplasmic side.
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Affiliation(s)
- Chih-Chang Hung
- Department of Electrophysics, National Chiao-Tung University, Hsinchu, Taiwan
| | - Xiao-Ru Chen
- Department of Biochemical Science and Technology, National Taiwan University, Taipei, Taiwan
| | - Ying-Kuan Ko
- Department of Electrophysics, National Chiao-Tung University, Hsinchu, Taiwan
| | - Takayoshi Kobayashi
- Brain Science Inspired Life Support Research Center, The University of Electro-Communications, Tokyo, Japan; Research Center for Water Frontier Science and Technology, Tokyo University of Science, Tokyo, Japan
| | - Chii-Shen Yang
- Department of Biochemical Science and Technology, National Taiwan University, Taipei, Taiwan.
| | - Atsushi Yabushita
- Department of Electrophysics, National Chiao-Tung University, Hsinchu, Taiwan; Faculty of Engineering, Kanagawa University, Yokohama, Japan.
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9
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Lu Z, Wang J, Li R, Qiao Y, Zhou M, Li CM. Controllable stationary photocurrents generated from a bacteriorhodopsin/upconversion nanoparticle-based bionanosystem under NIR illumination. NANOSCALE 2016; 8:18524-18530. [PMID: 27782261 DOI: 10.1039/c6nr06930d] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
In the past few decades, tremendous effort has been dedicated to develop bacteriorhodopsin (bR)-based photo-electronic devices for generating a stationary photocurrent and further for use as a component of artificial retinas in constant illumination sensing. However, an IR-triggered stationary photocurrent with controllable amplitudes has never been realized to date. Herein, NaYF4:Yb,Er and NaYF4:Yb,Tm upconversion nanoparticles (UCNPs) with green and blue emissions, respectively, were synthesized and further incorporated with bR to build a bionanosystem. Under 980 nm NIR irradiation the UCNPs function as internal green and blue light sources to initiate the photocycle and speed up the transition of bR from M410 to the ground state, consequently accelerating the bR photocycle for the generation of a stationary photocurrent. Moreover, the photocurrent profile could be tailored by changing the blue/green emission intensity ratio. The mechanism is analysed to explore the scientific insights. The system consisting of controllable blue and green light sources may not only hold great promise to construct new types of bR-based optical devices, but also offers a useful setup to investigate the fundamental science underlying the bR photoresponse.
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Affiliation(s)
- Zhisong Lu
- Institute for Clean Energy & Advance Materials, Southwest University, 1 Tiansheng Road, Chongqing 400715, P. R. China and Chongqing Key Laboratory for Advanced Materials & Technologies of Clean Energies, Southwest University, 1 Tiansheng Road, Chongqing 400715, P. R. China.
| | - Jing Wang
- Institute for Clean Energy & Advance Materials, Southwest University, 1 Tiansheng Road, Chongqing 400715, P. R. China and Chongqing Key Laboratory for Advanced Materials & Technologies of Clean Energies, Southwest University, 1 Tiansheng Road, Chongqing 400715, P. R. China.
| | - Rui Li
- Hubei Key Laboratory of Genetic Regulation and Integrative Biology, School of Life Sciences, Central China Normal University, Wuhan 430079, P. R. China
| | - Yan Qiao
- Institute for Clean Energy & Advance Materials, Southwest University, 1 Tiansheng Road, Chongqing 400715, P. R. China and Chongqing Key Laboratory for Advanced Materials & Technologies of Clean Energies, Southwest University, 1 Tiansheng Road, Chongqing 400715, P. R. China.
| | - Mengyao Zhou
- Institute for Clean Energy & Advance Materials, Southwest University, 1 Tiansheng Road, Chongqing 400715, P. R. China and Chongqing Key Laboratory for Advanced Materials & Technologies of Clean Energies, Southwest University, 1 Tiansheng Road, Chongqing 400715, P. R. China.
| | - Chang Ming Li
- Institute for Clean Energy & Advance Materials, Southwest University, 1 Tiansheng Road, Chongqing 400715, P. R. China and Chongqing Key Laboratory for Advanced Materials & Technologies of Clean Energies, Southwest University, 1 Tiansheng Road, Chongqing 400715, P. R. China. and Institute for Materials Science and Devices, Suzhou University of Science and Technology, Suzhou 215011, P.R. China
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10
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Conversion of a light-driven proton pump into a light-gated ion channel. Sci Rep 2015; 5:16450. [PMID: 26597707 PMCID: PMC4657025 DOI: 10.1038/srep16450] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2015] [Accepted: 10/14/2015] [Indexed: 12/19/2022] Open
Abstract
Interest in microbial rhodopsins with ion pumping activity has been revitalized in the context of optogenetics, where light-driven ion pumps are used for cell hyperpolarization and voltage sensing. We identified an opsin-encoding gene (CsR) in the genome of the arctic alga Coccomyxa subellipsoidea C-169 that can produce large photocurrents in Xenopus oocytes. We used this property to analyze the function of individual residues in proton pumping. Modification of the highly conserved proton shuttling residue R83 or its interaction partner Y57 strongly reduced pumping power. Moreover, this mutation converted CsR at moderate electrochemical load into an operational proton channel with inward or outward rectification depending on the amino acid substitution. Together with molecular dynamics simulations, these data demonstrate that CsR-R83 and its interacting partner Y57 in conjunction with water molecules forms a proton shuttle that blocks passive proton flux during the dark-state but promotes proton movement uphill upon illumination.
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11
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Ranaghan MJ, Greco JA, Wagner NL, Grewal R, Rangarajan R, Koscielecki JF, Wise KJ, Birge RR. Photochromic bacteriorhodopsin mutant with high holographic efficiency and enhanced stability via a putative self-repair mechanism. ACS APPLIED MATERIALS & INTERFACES 2014; 6:2799-2808. [PMID: 24498928 PMCID: PMC3985900 DOI: 10.1021/am405363z] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/25/2013] [Accepted: 02/05/2014] [Indexed: 06/03/2023]
Abstract
The Q photoproduct of bacteriorhodopsin (BR) is the basis of several biophotonic technologies that employ BR as the photoactive element. Several blue BR (bBR) mutants, generated by using directed evolution, were investigated with respect to the photochemical formation of the Q state. We report here a new bBR mutant, D85E/D96Q, which is capable of efficiently converting the entire sample to and from the Q photoproduct. At pH 8.5, where Q formation is optimal, the Q photoproduct requires 65 kJ mol(-1) of amber light irradiation (590 nm) for formation and 5 kJ mol(-1) of blue light (450 nm) for reversion, respectively. The melting temperature of the resting state and Q photoproduct, measured via differential scanning calorimetry, is observed at 100 °C and 89 °C at pH 8.5 or 91 °C and 82 °C at pH 9.5, respectively. We hypothesize that the protein stability of D85E/D96Q compared to other blue mutants is associated with a rapid equilibrium between the blue form E85(H) and the purple form E85(-) of the protein, the latter providing enhanced structural stability. Additionally, the protein is shown to be stable and functional when suspended in an acrylamide matrix at alkaline pH. Real-time photoconversion to and from the Q state is also demonstrated with the immobilized protein. Finally, the holographic efficiency of an ideal thin film using the Q state of D85E/D96Q is calculated to be 16.7%, which is significantly better than that provided by native BR (6-8%) and presents the highest efficiency of any BR mutant to date.
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Affiliation(s)
- Matthew J. Ranaghan
- Department of Molecular and Cell Biology, University of Connecticut, 91 North Eagleville Road, Storrs, Connecticut 06269, United States
| | - Jordan A. Greco
- Department of Chemistry, University of Connecticut, 55 North Eagleville Road, Storrs, Connecticut 06269, United States
| | - Nicole L. Wagner
- Department of Molecular and Cell Biology, University of Connecticut, 91 North Eagleville Road, Storrs, Connecticut 06269, United States
| | - Rickinder Grewal
- Department of Molecular and Cell Biology, University of Connecticut, 91 North Eagleville Road, Storrs, Connecticut 06269, United States
| | - Rekha Rangarajan
- Department of Molecular and Cell Biology, University of Connecticut, 91 North Eagleville Road, Storrs, Connecticut 06269, United States
| | - Jeremy F. Koscielecki
- Department of Chemistry, University of Connecticut, 55 North Eagleville Road, Storrs, Connecticut 06269, United States
| | - Kevin J. Wise
- Department of Molecular and Cell Biology, University of Connecticut, 91 North Eagleville Road, Storrs, Connecticut 06269, United States
| | - Robert R. Birge
- Department of Molecular and Cell Biology, University of Connecticut, 91 North Eagleville Road, Storrs, Connecticut 06269, United States
- Department of Chemistry, University of Connecticut, 55 North Eagleville Road, Storrs, Connecticut 06269, United States
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12
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Zaitsev SY, Solovyeva DO, Nabiev IR. Nanobiohybrid structures based on the organized films of photosensitive membrane proteins. RUSSIAN CHEMICAL REVIEWS 2014. [DOI: 10.1070/rc2014v083n01abeh004372] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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13
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14
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Schulten K, Humphrey W, Logunov I, Sheves M, Xu D. Molecular Dynamics Studies of Bacteriorhodopsin's Photocycles. Isr J Chem 2013. [DOI: 10.1002/ijch.199500042] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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15
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Honig B, Ottolenghi M, Sheves M. Acid-Base Equilibria and the Proton Pump in Bacteriorhodopsin. Isr J Chem 2013. [DOI: 10.1002/ijch.199500041] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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16
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17
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Moltke S, Alexiev U, Heyn MP. Kinetics of Light-Induced Intramolecular Charge Transfer and Proton Release in Bacteriorhodopsin. Isr J Chem 2013. [DOI: 10.1002/ijch.199500039] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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18
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Spudich JL, Zacks DN, Bogomolni RA. Microbial Sensory Rhodopsins: Photochemistry and Function. Isr J Chem 2013. [DOI: 10.1002/ijch.199500045] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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19
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Saint Clair EC, Ogren JI, Mamaev S, Russano D, Kralj JM, Rothschild KJ. Near-IR resonance Raman spectroscopy of archaerhodopsin 3: effects of transmembrane potential. J Phys Chem B 2012. [PMID: 23189985 DOI: 10.1021/jp309996a] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Archaerhodopsin 3 (AR3) is a light driven proton pump from Halorubrum sodomense that has been used as a genetically targetable neuronal silencer and an effective fluorescent sensor of transmembrane potential. Unlike the more extensively studied bacteriorhodopsin (BR) from Halobacterium salinarum, AR3 readily incorporates into the plasma membrane of both E. coli and mammalian cells. Here, we used near-IR resonance Raman confocal microscopy to study the effects of pH and membrane potential on the AR3 retinal chromophore structure. Measurements were performed both on AR3 reconstituted into E. coli polar lipids and in vivo in E. coli expressing AR3 in the absence and presence of a negative transmembrane potential. The retinal chromophore structure of AR3 is in an all-trans configuration almost identical to BR over the entire pH range from 3 to 11. Small changes are detected in the retinal ethylenic stretching frequency and Schiff Base (SB) hydrogen bonding strength relative to BR which may be related to a different water structure near the SB. In the case of the AR3 mutant D95N, at neutral pH an all-trans retinal O-like species (O(all-trans)) is found. At higher pH a second 13-cis retinal N-like species (N(13-cis)) is detected which is attributed to a slowly decaying intermediate in the red-light photocycle of D95N. However, the amount of N(13-cis) detected is less in E. coli cells but is restored upon addition of carbonyl cyanide m-chlorophenyl hydrazone (CCCP) or sonication, both of which dissipate the normal negative membrane potential. We postulate that these changes are due to the effect of membrane potential on the N(13-cis) to M(13-cis) levels accumulated in the D95N red-light photocycle and on a molecular level by the effects of the electric field on the protonation/deprotonation of the cytoplasmic accessible SB. This mechanism also provides a possible explanation for the observed fluorescence dependence of AR3 and other microbial rhodopsins on transmembrane potential.
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Affiliation(s)
- Erica C Saint Clair
- Department of Physics, Photonics Center and Molecular Biophysics Laboratory, Boston University, Boston, Massachusetts 02215, USA
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20
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Zaitsev SY, Solovyeva DO, Nabiev I. Thin films and assemblies of photosensitive membrane proteins and colloidal nanocrystals for engineering of hybrid materials with advanced properties. Adv Colloid Interface Sci 2012; 183-184:14-29. [PMID: 22906866 DOI: 10.1016/j.cis.2012.07.003] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2012] [Revised: 07/15/2012] [Accepted: 07/24/2012] [Indexed: 11/16/2022]
Abstract
The development and study of nano-bio hybrid materials engineered from membrane proteins (the key functional elements of various biomembranes) and nanoheterostructures (inorganic colloidal nanoparticles, transparent electrodes, and films) is a rapidly growing field at the interface of materials and life sciences. The mainspring of the development of bioinspired materials and devices is the fact that biological evolution has solved many problems similar to those that humans are attempting to solve in the field of light-harvesting and energy-transferring inorganic compounds. Along this way, bioelectronics and biophotonics have shown considerable promise. A number of proteins have been explored in terms of bioelectronic device applications, but bacteriorhodopsin (bR, a photosensitive membrane protein from purple membranes of the bacterium Halobacterium salinarum) and bacterial photosynthetic reaction centres have received the most attention. The energy harvesting in plants has a maximum efficiency of 5%, whereas bR, in the absence of a specific light-harvesting system, allows bacteria to utilize only 0.1-0.5% of the solar light. Recent nano-bioengineering approaches employing colloidal semiconductor and metal nanoparticles conjugated with biosystems permit the enhancement of the light-harvesting capacity of photosensitive proteins, thus providing a strong impetus to protein-based device optimisation. Fabrication of ultrathin and highly oriented films from biological membranes and photosensitive proteins is the key task for prospective bioelectronic and biophotonic applications. In this review, the main advances in techniques of preparation of such films are analyzed. Comparison of the techniques for obtaining thin films leads to the conclusion that the homogeneity and orientation of biomembrane fragments or proteins in these films depend on the method of their fabrication and increase in the following order: electrophoretic sedimentation < Langmuir-Blodgett and Langmuir-Schaefer methods < self-assembly and layer-by-layer methods. The key advances in the techniques of preparation of the assemblies or complexes of colloidal nanocrystals with bR, purple membranes, or photosynthetic reaction centres are also reviewed. Approaches to the fabrication of the prototype photosensitive nano-bio hybrid materials with advanced photovoltaic, energy transfer, and optical switching properties and future prospects in this field are analyzed in the concluding part of the review.
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Affiliation(s)
- Sergei Yu Zaitsev
- Laboratory of Nano-Bioengineering, Moscow Engineering Physics Institute, 31 Kashirskoe sh., 115409 Moscow, Russian Federation.
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21
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Imhof M, Rhinow D, Linne U, Hampp N. Two-Photon-Induced Selective Decarboxylation of Aspartic Acids D85 and D212 in Bacteriorhodopsin. J Phys Chem Lett 2012; 3:2991-2994. [PMID: 26292239 DOI: 10.1021/jz301292n] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The interest in microbial opsins stems from their photophysical properties, which are superior to most organic dyes. Microbial rhodopsins like bacteriorhodopsin (BR) from Halobacterium salinarum have an astonishingly high cross-section for two-photon-absorption (TPA), which is of great interest for technological applications such as data storage. Irradiation of BR with intense laser pulses at 532 nm leads to formation of a bathochromic photoproduct, which is further converted to a photochemical species absorbing in the UV range. As demonstrated earlier, the photochemical conversions are induced by resonant TPA. However, the molecular basis of these conversions remained unresolved. In this work we use mass spectroscopy to demonstrate that TPA of BR leads to selective decarboxylation of two aspartic acids in the vicinity of the retinal chromphore. These photochemical conversions are the basis of permanent two-photon data storage in BR and are of critical importance for application of microbial opsins in optogenetics.
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Affiliation(s)
- Martin Imhof
- †Philipps-University of Marburg, Department of Chemistry, Hans-Meerwein-Str., D-35032 Marburg, Germany
| | - Daniel Rhinow
- ‡Max-Planck-Institute of Biophysics, Department of Structural Biology, Max-von-Laue-Str. 3, D-60438 Frankfurt, Germany
| | - Uwe Linne
- †Philipps-University of Marburg, Department of Chemistry, Hans-Meerwein-Str., D-35032 Marburg, Germany
| | - Norbert Hampp
- †Philipps-University of Marburg, Department of Chemistry, Hans-Meerwein-Str., D-35032 Marburg, Germany
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22
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Herz J, Verhoefen MK, Weber I, Bamann C, Glaubitz C, Wachtveitl J. Critical role of Asp227 in the photocycle of proteorhodopsin. Biochemistry 2012; 51:5589-600. [PMID: 22738119 DOI: 10.1021/bi3003764] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The photocycle of the proton acceptor complex mutant D227N of the bacterial retinal protein proteorhodopsin is investigated employing steady state pH-titration experiments in the UV-visible range as well as femtosecond-pump-probe spectroscopy and flash photolysis in the visible spectral range. The evaluation of the pH-dependent spectra showed that the neutralization of the charge at position 227 has a remarkable influence on the ground state properties of the protein. Both the pK(a) values of the primary proton acceptor and of the Schiff base are considerably decreased. Femtosecond-time-resolved measurements demonstrate that the general S(1) deactivation pathway; that is, the K-state formation is preserved in the D227N mutant. However, the pH-dependence of the reaction rate is lost by the substitution of Asp227 with an asparagine. Also no significant kinetic differences are observed upon deuteration. This is explained by the lack of a strongly hydrogen-bonded water in the vicinity of Asp97, Asp227, and the Schiff base or a change in the hydrogen bonding of it (Ikeda et al. (2007) Biochemistry 46, 5365-5373). The flash photolysis measurements prove a considerably elongated photocycle with pronounced pH-dependence. Interestingly, at pH 9 the M-state is visible until the end of the reaction cycle, leading to the conclusion that the mutation does not only lower the pK(a) of the Schiff base in the unphotolyzed ground state but also prevents an efficient reprotonation reaction.
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Affiliation(s)
- Julia Herz
- Institute of Physical and Theoretical Chemistry, Johann Wolfgang Goethe-University, Max von Laue-Strasse 7, 60438 Frankfurt am Main, Germany
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23
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Optical recording of action potentials in mammalian neurons using a microbial rhodopsin. Nat Methods 2011; 9:90-5. [PMID: 22120467 PMCID: PMC3248630 DOI: 10.1038/nmeth.1782] [Citation(s) in RCA: 323] [Impact Index Per Article: 24.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2011] [Accepted: 10/25/2011] [Indexed: 11/27/2022]
Abstract
Reliable optical detection of single action potentials in mammalian neurons has been one of the longest-standing challenges in neuroscience. Here we achieve this goal by using the endogenous fluorescence of a microbial rhodopsin protein, Archaerhodopsin 3 (Arch) from Halorubrum sodomense, expressed in cultured rat hippocampal neurons. This genetically encoded voltage indicator exhibited an approximately 10-fold improvement in sensitivity and speed over existing protein-based voltage indicators, with a roughly linear two-fold increase in brightness between −150 mV and +150 mV and a sub-millisecond response time. Arch detected single electrically triggered action potentials with an optical signal-to-noise ratio > 10. The mutant Arch(D95N) lacked endogenous proton pumping and showed 50% greater sensitivity than wild-type, but had a slower response (41 ms). Nonetheless, Arch(D95N) also resolved individual action potentials. Microbial rhodopsin-based voltage indicators promise to enable optical interrogation of complex neural circuits, and electrophysiology in systems for which electrode-based techniques are challenging.
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24
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Kawanabe A, Furutani Y, Jung KH, Kandori H. An inward proton transport using Anabaena sensory rhodopsin. J Microbiol 2011; 49:1-6. [PMID: 21369972 DOI: 10.1007/s12275-011-0547-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2010] [Accepted: 01/14/2011] [Indexed: 11/24/2022]
Abstract
ATP is synthesized by an enzyme that utilizes proton motive force and thus nature creates various proton pumps. The best understood proton pump is bacteriorhodopsin (BR), an outward-directed light-driven proton pump in Halobacterium salinarum. Many archaeal and eubacterial rhodopsins are now known to show similar proton transport activity. Proton pumps must have a specific mechanism to exclude transport in the reverse direction to maintain a proton gradient, and in the case of BR, a highly hydrophobic cytoplasmic domain may constitute such machinery. Although an inward proton pump has neither been created naturally nor artificially, we recently reported that an inward-directed proton transport can be engineered from a bacterial rhodopsin by a single amino acid replacement Anabaena sensory rhodopsin (ASR) is a photochromic sensor in freshwater cyanobacteria, possessing little proton transport activity. When we replace Asp217 at the cytoplasmic domain (distance ∼ 15 Å from the retinal chromophore) to Glu, ASR is converted into an inward proton transport, driven by absorption of a single photon. FTIR spectra clearly show an increased proton affinity for Glu217, which presumably controls the unusual directionality opposite to normal proton pumps.
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Affiliation(s)
- Akira Kawanabe
- Department of Frontier Materials, Nagoya Institute of Technology, Showa-ku, Nagoya, 466-8555, Japan
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25
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Ranaghan MJ, Shima S, Ramos L, Poulin DS, Whited G, Rajasekaran S, Stuart JA, Albert AD, Birge RR. Photochemical and thermal stability of green and blue proteorhodopsins: implications for protein-based bioelectronic devices. J Phys Chem B 2011; 114:14064-70. [PMID: 20964279 DOI: 10.1021/jp106633w] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The photochemical and thermal stability of the detergent-solubilized blue- and green-absorbing proteorhodpsins, BPR and GPR, respectively, are investigated to determine the viability of these proteins for photonic device applications. Photochemical stability is studied by using pulsed laser excitation and differential UV-vis spectroscopy to assign the photocyclicity. GPR, with a cyclicity of 7 × 10(4) photocycles protein(-1), is 4-5 times more stable than BPR (9 × 10(3) photocycles protein(-1)), but is less stable than native bacteriorhodopsin (9 × 10(5) photocycles protein(-1)) or the 4-keto-bacteriorhodopsin analogue (1 × 10(5) photocycles protein(-1)). The thermal stabilities are assigned by using differential scanning calorimetry and thermal bleaching experiments. Both proteorhodopsins display excellent thermal stability, with melting temperatures above 85 °C, and remain photochemically stable up to 75 °C. The biological relevance of our results is also discussed. The lower cyclicity of BPR is found to be adequate for the long-term biological function of the host organism at ocean depths of 50 m or more.
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Affiliation(s)
- Matthew J Ranaghan
- Department of Molecular and Cell Biology, University of Connecticut, 91 North Eagleville Road, Storrs, Connecticut 06269, USA
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26
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Baumann RP, Eussner J, Hampp N. pH-dependent bending in and out of purple membranes comprising BR-D85T. Phys Chem Chem Phys 2011; 13:21375-82. [DOI: 10.1039/c1cp22098e] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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27
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Rhinow D, Chizhik I, Baumann RP, Noll F, Hampp N. Crystallinity of Purple Membranes Comprising the Chloride-Pumping Bacteriorhodopsin Variant D85T and Its Modulation by pH and Salinity. J Phys Chem B 2010; 114:15424-8. [DOI: 10.1021/jp108502p] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Daniel Rhinow
- Max-Planck-Institute of Biophysics, Department of Structural Biology, Max-von-Laue-Str. 3, D-60438 Frankfurt, Germany, Philipps-University of Marburg, Department of Chemistry, Hans-Meerwein-Str. Bldg. H, D-35032 Marburg, Germany, and Material Sciences Center, D-35032 Marburg, Germany
| | - Ivan Chizhik
- Max-Planck-Institute of Biophysics, Department of Structural Biology, Max-von-Laue-Str. 3, D-60438 Frankfurt, Germany, Philipps-University of Marburg, Department of Chemistry, Hans-Meerwein-Str. Bldg. H, D-35032 Marburg, Germany, and Material Sciences Center, D-35032 Marburg, Germany
| | - Roelf-Peter Baumann
- Max-Planck-Institute of Biophysics, Department of Structural Biology, Max-von-Laue-Str. 3, D-60438 Frankfurt, Germany, Philipps-University of Marburg, Department of Chemistry, Hans-Meerwein-Str. Bldg. H, D-35032 Marburg, Germany, and Material Sciences Center, D-35032 Marburg, Germany
| | - Frank Noll
- Max-Planck-Institute of Biophysics, Department of Structural Biology, Max-von-Laue-Str. 3, D-60438 Frankfurt, Germany, Philipps-University of Marburg, Department of Chemistry, Hans-Meerwein-Str. Bldg. H, D-35032 Marburg, Germany, and Material Sciences Center, D-35032 Marburg, Germany
| | - Norbert Hampp
- Max-Planck-Institute of Biophysics, Department of Structural Biology, Max-von-Laue-Str. 3, D-60438 Frankfurt, Germany, Philipps-University of Marburg, Department of Chemistry, Hans-Meerwein-Str. Bldg. H, D-35032 Marburg, Germany, and Material Sciences Center, D-35032 Marburg, Germany
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28
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Kawanabe A, Furutani Y, Jung KH, Kandori H. Engineering an inward proton transport from a bacterial sensor rhodopsin. J Am Chem Soc 2010; 131:16439-44. [PMID: 19848403 DOI: 10.1021/ja904855g] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
ATP is synthesized by an enzyme that utilizes proton motive force, and thus, nature has created various proton pumps. The best-understood proton pump is bacteriorhodopsin (BR), an outward-directed, light-driven proton pump in Halobacterium salinarum. Many archaeal and eubacterial rhodopsins are now known to show similar proton transport activity. We previously converted BR into an inward-directed chloride ion pump, but an inward proton pump has never been created. Proton pumps must have a specific mechanism to exclude transport in the reverse direction in order to maintain a proton gradient, and in the case of BR, a highly hydrophobic cytoplasmic domain may constitute such machinery. Here we report that an inward-directed proton transport can be engineered from a bacterial rhodopsin by a single amino acid replacement. Anabaena sensory rhodopsin (ASR) is a photochromic sensor in freshwater cyanobacteria that possesses little proton pump activity. When we replaced Asp217 in the cytoplasmic domain (a distance of approximately 15 A from the retinal chromophore) by Glu, ASR exhibited an inward proton transport activity driven by absorption of a single photon. FTIR spectra clearly showed an increased proton affinity for Glu217, which presumably controls the unusual directionality opposite to that in normal proton pumps.
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Affiliation(s)
- Akira Kawanabe
- Department of Materials Science and Engineering, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555, Japan
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29
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Ultrafast optogenetic control. Nat Neurosci 2010; 13:387-92. [DOI: 10.1038/nn.2495] [Citation(s) in RCA: 566] [Impact Index Per Article: 40.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2009] [Accepted: 01/04/2010] [Indexed: 11/08/2022]
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30
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Lörinczi É, Verhoefen MK, Wachtveitl J, Woerner AC, Glaubitz C, Engelhard M, Bamberg E, Friedrich T. Voltage- and pH-Dependent Changes in Vectoriality of Photocurrents Mediated by Wild-type and Mutant Proteorhodopsins upon Expression in Xenopus Oocytes. J Mol Biol 2009; 393:320-41. [DOI: 10.1016/j.jmb.2009.07.055] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2009] [Revised: 06/15/2009] [Accepted: 07/17/2009] [Indexed: 10/20/2022]
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31
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Verhoefen MK, Lenz MO, Amarie S, Klare JP, Tittor J, Oesterhelt D, Engelhard M, Wachtveitl J. Primary Reaction of Sensory Rhodopsin II Mutant D75N and the Influence of Azide. Biochemistry 2009; 48:9677-83. [DOI: 10.1021/bi901197c] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Mirka-Kristin Verhoefen
- Institute of Physical and Theoretical Chemistry, Institute of Biophysics, Johann Wolfgang Goethe-University Frankfurt, Max von Laue-Strasse 7, 60438 Frankfurt am Main, Germany
| | - Martin O. Lenz
- Institute of Physical and Theoretical Chemistry, Institute of Biophysics, Johann Wolfgang Goethe-University Frankfurt, Max von Laue-Strasse 7, 60438 Frankfurt am Main, Germany
| | - Sergiu Amarie
- Institute of Physical and Theoretical Chemistry, Institute of Biophysics, Johann Wolfgang Goethe-University Frankfurt, Max von Laue-Strasse 7, 60438 Frankfurt am Main, Germany
| | - Johann P. Klare
- Max-Planck-Institute of Molecular Physiology, Otto-Hahn-Strasse 11, 44139 Dortmund, Germany
| | - Jörg Tittor
- Max-Planck-Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany
| | - Dieter Oesterhelt
- Max-Planck-Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany
| | - Martin Engelhard
- Max-Planck-Institute of Molecular Physiology, Otto-Hahn-Strasse 11, 44139 Dortmund, Germany
| | - Josef Wachtveitl
- Institute of Physical and Theoretical Chemistry, Institute of Biophysics, Johann Wolfgang Goethe-University Frankfurt, Max von Laue-Strasse 7, 60438 Frankfurt am Main, Germany
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32
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Sobotta C, Braun M, Tittor J, Oesterhelt D, Zinth W. Influence of the charge at D85 on the initial steps in the photocycle of bacteriorhodopsin. Biophys J 2009; 97:267-76. [PMID: 19580764 DOI: 10.1016/j.bpj.2009.04.021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2008] [Revised: 03/25/2009] [Accepted: 04/06/2009] [Indexed: 10/20/2022] Open
Abstract
Studies have shown that trans-cis isomerization of retinal is the primary photoreaction in the photocycle of the light-driven proton pump bacteriorhodopsin (BR) from Halobacterium salinarum, as well as in the photocycle of the chloride pump halorhodopsin (HR). The transmembrane proteins HR and BR show extensive structural similarities, but differ in the electrostatic surroundings of the retinal chromophore near the protonated Schiff base. Point mutation of BR of the negatively charged aspartate D85 to a threonine T (D85T) in combination with variation of the pH value and anion concentration is used to study the ultrafast photoisomerization of BR and HR for well-defined electrostatic surroundings of the retinal chromophore. Variations of the pH value and salt concentration allow a switch in the isomerization dynamics of the BR mutant D85T between BR-like and HR-like behaviors. At low salt concentrations or a high pH value (pH 8), the mutant D85T shows a biexponential initial reaction similar to that of HR. The combination of high salt concentration and a low pH value (pH 6) leads to a subpopulation of 25% of the mutant D85T whose stationary and dynamic absorption properties are similar to those of native BR. In this sample, the combination of low pH and high salt concentration reestablishes the electrostatic surroundings originally present in native BR, but only a minor fraction of the D85T molecules have the charge located exactly at the position required for the BR-like fast isomerization reaction. The results suggest that the electrostatics in the native BR protein is optimized by evolution. The accurate location of the fixed charge at the aspartate D85 near the Schiff base in BR is essential for the high efficiency of the primary reaction.
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Affiliation(s)
- Constanze Sobotta
- Lehrstuhl für BioMolekulare Optik, Fakultät für Physik, Ludwig-Maximilians-Universität München, Munich, Germany
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33
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Koyama K, Miyasaka T, Needleman R, Lanyi JK. Photoelectrochemical Verification of Proton-Releasing Groups in Bacteriorhodopsin. Photochem Photobiol 2008. [DOI: 10.1111/j.1751-1097.1998.tb09699.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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34
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Mutagenic Analysis of Membrane Protein Functional Mechanisms: Bacteriorhodopsin as a Model Example. Methods Cell Biol 2008. [DOI: 10.1016/s0091-679x(07)84016-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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35
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Tittor J, Oesterhelt D, Bamberg E. Bacteriorhodopsin mutants D85N, D85T and D85,96N as proton pumps. Biophys Chem 2007; 56:153-7. [PMID: 17023320 DOI: 10.1016/0301-4622(95)00027-u] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Proton translocation in the BR mutants D85N, D85T and D85,96N was studied by attachment of purple membranes to planar lipid bilayers. Pump currents in these mutants were measured via capacitive coupling and by use of the appropriate ionophores. All mutants have a reduced pK of their Schiff bases around 8-8.5 in common. At physiological pH, a mixture of chromophores absorbing at 410 nm (deprotonated form) and around 600 nm (protonated form) coexists. Excitation with continuous blue light induces in all three mutants an outwardly directed stationary pump current. These currents are enhanced upon addition of azide in D85N and D85,96N by a factor of 50, but no azide enhancement is observed in D85T. Yellow light alone induces transient inwardly directed currents in the mutants but additional blue light leads to a stationary current with the same direction. All the observed currents are carried by protons, so that the consecutive absorption of a yellow and a blue photon leads to inverted stationary photocurrents by the mutants, as observed with halorhodopsin (HR). A mechanistic model describing the inversion of proton pumping is discussed by the cis-trans, trans-cis isomerization of the retinal and the different proton accessibility of the Schiff base from the extracellular or the cytoplasmic side of the membrane.
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Affiliation(s)
- J Tittor
- Max-Planck-Institut für Biochemie, D-82152 Martinsried, Germany
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36
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Horn C, Steinem C. Photocurrents generated by bacteriorhodopsin adsorbed on nano-black lipid membranes. Biophys J 2005; 89:1046-54. [PMID: 15908580 PMCID: PMC1366590 DOI: 10.1529/biophysj.105.059550] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Purple membranes were adsorbed on freestanding lipid bilayers, termed nano-black lipid membranes (nano-BLMs), suspending the pores of porous alumina substrates with average pore diameters of 280 nm. Nano-BLMs were obtained by first coating the upper surface of the highly ordered porous alumina substrates with a thin gold layer followed by chemisorption of 1,2-dipalmitoyl-sn-glycero-3-phosphothioethanol and subsequent addition of a droplet of 1,2-diphytanoyl-sn-glycero-3-phosphocholine and octadecylamine dissolved in n-decane onto the hydrophobic submonolayer. By means of impedance spectroscopy, the quality of the nano-BLMs was verified. The electrical parameters confirm the formation of single lipid bilayers with high membrane resistances covering the porous matrix. Adsorption of purple membranes on the nano-BLMs was followed by recording the photocurrents generated by bacteriorhodopsin upon continuous light illumination. The membrane system exhibits a very high long-term stability with the advantage that not only transient but also stationary currents are recordable. By adding the proton ionophore carbonyl cyanide-m-chlorophenylhydrazone the conductivity of the nano-BLMs increases, resulting in a higher stationary current, which proves that proton conductance occurs across the nano-BLMs.
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Affiliation(s)
- Christian Horn
- Institut für Analytische Chemie, Chemo- und Biosensorik, Universität Regensburg, Germany
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37
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Abstract
The dynamics of proton dissociation from an acidic moiety and its subsequent dispersion in the bulk is regulated by the physical chemical properties of the solvent. The solvent has to provide a potential well to accommodate the discharged proton, screen it from the negative charge of the conjugated base, and provide an efficient mode for the diffusion of the proton to the bulk. On measuring the dynamics of proton dissociation in the time-resolved domain, the kinetic analysis of the reaction can quantitate the properties of the immediate environment. In this review we implement the kinetic analysis for evaluating the properties of small cavities in proteins and the diffusion of protons within narrow channels. On the basis of this analysis,we discuss how the clustering of proton-binding sites on a surface can endow the surface with enhanced capacity to attract protons and to funnel them toward a specific site.
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Affiliation(s)
- M Gutman
- Laser Laboratory for Fast Reactions in Biochemical Systems, Department of Biochemistry, Tel-Aviv University, Tel-Aviv, Israel 69978
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38
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Dioumaev AK, Wang JM, Bálint Z, Váró G, Lanyi JK. Proton transport by proteorhodopsin requires that the retinal Schiff base counterion Asp-97 be anionic. Biochemistry 2003; 42:6582-7. [PMID: 12767242 DOI: 10.1021/bi034253r] [Citation(s) in RCA: 82] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
At pH >7, proteorhodopsin functions as an outward-directed proton pump in cell membranes, and Asp-97 and Glu-108, the homologues of the Asp-85 and Asp-96 in bacteriorhodopsin, are the proton acceptor and donor to the retinal Schiff base, respectively. It was reported, however [Friedrich, T. et al. (2002) J. Mol. Biol., 321, 821-838], that proteorhodopsin transports protons also at pH <7 where Asp-97 is protonated and in the direction reverse from that at higher pH. To explore the roles of Asp-97 and Glu-108 in the proposed pumping with variable vectoriality, we compared the photocycles of D97N and E108Q mutants, and the effects of azide on the photocycle of the E108Q mutant, at low and high pH. Unlike at high pH, at a pH low enough to protonate Asp-97 neither the mutations nor the effects of azide revealed evidence for the participation of the acidic residues in proton transfer, and as in the photocycle of the wild-type protein, no intermediate with unprotonated Schiff base accumulated. In view of these findings, and the doubts raised by absence of charge transfer after flash excitation at low pH, we revisited the question whether transport occurs at all under these conditions. In both oriented membrane fragments and liposomes reconstituted with proteorhodopsin, we found transport at high pH but not at low pH. Instead, proton transport activity followed the titration curve for Asp-97, with an apparent pK(a) of 7.1, and became zero at the pH where Asp-97 is fully protonated.
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Affiliation(s)
- Andrei K Dioumaev
- Department of Physiology and Biophysics, University of California, Irvine, California 92697, USA
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39
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Seitz A, Schneider F, Pasternack R, Fuchsbauer HL, Hampp N. Enzymatic cross-linking of purple membranes catalyzed by bacterial transglutaminase. Biomacromolecules 2002; 2:233-8. [PMID: 11749178 DOI: 10.1021/bm0056207] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
It was found that bacterial transglutaminase (TGase) facilitates selective cross-linking of bacteriorhodopsin (BR) in purple membrane (PM) form under mild conditions. Fluorescent probes were used to detect that the membrane protein BR may act as a glutamine donor as well as a lysine donor for TGase. The binding sites were determined to be Gln-3 as the reactive glutamine, and Lys-129 is the corresponding lysine residue. Upon incubation of PM with TGase, cross-linking of PM patches can be achieved without an additional spacer molecule. To our knowledge, this is the first time that an intermembrane cross-linking of membrane-bound proteins is reported. Furthermore, this finding may provide the ability to achieve covalent linkage of complete purple membrane patches to synthetic polymers.
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Affiliation(s)
- A Seitz
- Institute for Physical Chemistry, University of Marburg, D-35032 Marburg, Germany
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40
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Dolfi A, Aloisi G, Guidelli R. Photoelectric response of purple membrane fragments adsorbed on a lipid monolayer supported by mercury and characterization of the resulting interphase. Bioelectrochemistry 2002; 57:155-66. [PMID: 12160613 DOI: 10.1016/s1567-5394(02)00117-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Purple membrane (PM) fragments were adsorbed on a dioleoylphosphatidylcholine (DOPC) monolayer supported by mercury to investigate the kinetics of light-driven proton transport by bacteriorhodopsin (bR). PM fragments were also adsorbed on a mercury-supported triethyleneoxythiol (TET) monolayer. On both monolayers, the light-on current exhibits a finite, potential dependent stationary component that decreases linearly with a positive shift in the applied potential. The light-on and light-off capacitive photocurrents were interpreted on the basis of a simple equivalent circuit, which accounts for the potential dependence of the stationary light-on current. The potential of zero stationary current is about equal to +0.010 V vs. saturated calomel electrode (SCE) on DOPC-coated mercury. The absolute potential difference across the PM fragments adsorbed at this applied potential was estimated on the basis of extrathermodynamic considerations and amounts to about +260 mV; it compares favorably with the value, +250 mV, of the transmembrane potential of zero stationary current across an oocyte plasma membrane incorporating bR [Biophys. J. 74 (1998) 403.]. The effect of the proton pumping activity of photoexcited PM fragments on the electroreduction kinetics of ubiquinone-10 incorporated in the DOPC monolayer underlying the PM fragments was investigated.
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Affiliation(s)
- Andrea Dolfi
- Department of Chemistry, Polo Scientifico, University of Florence, Via della Lastruccia 3, 50019 Sesto Fiorentino, Florence, Italy
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41
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Taneva SG, Goñi FM, Tuparev NP, Petkanchin I, Dér A, Muga A. Effect of Asp85 replacement by Thr on the conformation, surface electric properties and stability of bacteriorhodopsin. Colloids Surf A Physicochem Eng Asp 2002. [DOI: 10.1016/s0927-7757(02)00180-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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42
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Martinez LC, Turner GJ. High-throughput screening of bacteriorhodopsin mutants in whole cell pastes. BIOCHIMICA ET BIOPHYSICA ACTA 2002; 1564:91-8. [PMID: 12101000 DOI: 10.1016/s0005-2736(02)00406-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
A high-throughput screening method has been developed which enables functional analysis of bacteriorhodpsin in whole cell pastes. Reflectance spectra, from as little as 5 ml of Halobacterium salinarum cells, show close correspondence to that obtained from the purified purple membrane (PM), containing bacteriorhodopsin (BR) as the sole protein component. We demonstrate accurate quantification of BR accumulation by ratiometric analysis of BR (A(max) 568) and a membrane-bound cytochrome (A(max) 410). In addition, ground-state light- and dark-adapted (LA and DA, respectively) spectral differences were determined with high accuracy and precision. Using cells expressing the BR mutant D85N, we monitored transitions between intermediate-state homologues of the reprotonation phase of the light-activated proton pumping mechanism. We demonstrate that phenotypes of three mutants (D85N/T170C, D85N/D96N, and D85N/R82Q) previously characterized for their effect on photocycle transitions are reproduced in the whole cell samples. D85N/T170C stabilizes accumulation of the N state while D85N/D96N accumulates no N state. D85N/R82Q was found to have perturbed the pK(a) of M accumulation. These studies illustrate the correspondence between pH-dependent ground-state transitions accessed by D85N and the transitions accessed by the wild-type protein following photoexcitation. We demonstrate that whole cell reflectance spectroscopy can be used to efficiently characterize the large numbers of mutants generated by engineering strategies that exploit saturation mutagenesis.
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Affiliation(s)
- Lynell C Martinez
- Department of Physiology and Biophysics and the Neurosciences Program, The University of Miami School of Medicine, Miami, FL 33101, USA
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43
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Nachliel E, Gutman M, Tittor J, Oesterhelt D. Proton transfer dynamics on the surface of the late M state of bacteriorhodopsin. Biophys J 2002; 83:416-26. [PMID: 12080130 PMCID: PMC1302157 DOI: 10.1016/s0006-3495(02)75179-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
The cytoplasmic surface of the BR (initial) state of bacteriorhodopsin is characterized by a cluster of three carboxylates that function as a proton-collecting antenna. Systematic replacement of most of the surface carboxylates indicated that the cluster is made of D104, E161, and E234 (Checover, S., Y. Marantz, E. Nachliel, M. Gutman, M. Pfeiffer, J. Tittor, D. Oesterhelt, and N. Dencher. 2001. Biochemistry. 40:4281-4292), yet the BR state is a resting configuration; thus, its proton-collecting antenna can only indicate the presence of its role in the photo-intermediates where the protein is re-protonated by protons coming from the cytoplasmic matrix. In the present study we used the D96N and the triple (D96G/F171C/F219L) mutant for monitoring the proton-collecting properties of the protein in its late M state. The protein was maintained in a steady M state by continuous illumination and subjected to reversible pulse protonation caused by repeated excitation of pyranine present in the reaction mixture. The re-protonation dynamics of the pyranine anion was subjected to kinetic analysis, and the rate constants of the reaction of free protons with the surface groups and the proton exchange reactions between them were calculated. The reconstruction of the experimental signal indicated that the late M state of bacteriorhodopsin exhibits an efficient mechanism of proton delivery to the unoccupied-most basic-residue on its cytoplasmic surface (D38), which exceeds that of the BR configuration of the protein. The kinetic analysis was carried out in conjunction with the published structure of the M state (Sass, H., G. Büldt, R. Gessenich, D. Hehn, D. Neff, R. Schlesinger, J. Berendzen, and P. Ormos. 2000. Nature. 406:649-653), the model that resolves most of the cytoplasmic surface. The combination of the kinetic analysis and the structural information led to identification of two proton-conducting tracks on the protein's surface that are funneling protons to D38. One track is made of the carboxylate moieties of residues D36 and E237, while the other is made of D102 and E232. In the late M state the carboxylates of both tracks are closer to D38 than in the BR (initial) state, accounting for a more efficient proton equilibration between the bulk and the protein's proton entrance channel. The triple mutant resembles in the kinetic properties of its proton conducting surface more the BR-M state than the initial state confirming structural similarities with the BR-M state and differences to the BR initial state.
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Affiliation(s)
- Esther Nachliel
- Laser Laboratory for Fast Reactions in Biology, Department of Biochemistry, Tel Aviv University, Tel Aviv 69978, Israel
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Paula S, Tittor J, Oesterhelt D. Roles of cytoplasmic arginine and threonine in chloride transport by the bacteriorhodopsin mutant D85T. Biophys J 2001; 80:2386-95. [PMID: 11325738 PMCID: PMC1301427 DOI: 10.1016/s0006-3495(01)76208-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In the light-driven anion pump halorhodopsin (HR), the residues arginine 200 and threonine 203 are involved in anion release at the cytoplasmic side of the membrane. Because of large sequence homology and great structural similarities between HR and bacteriorhodopsin (BR), it has been suggested that anion translocation by HR and by the chloride-pumping BR mutant BR-D85T occurs by the same mechanism. Consequently, the functions of the R200/T203 pair in HR should be the same as those of the corresponding pair in BR-D85T (R175/T178). We have put this hypothesis to a test by creating two mutants of BR-D85T in which R175 and T178 were replaced by glutamine and valine, respectively. Chloride transport activities were essentially the same for all three mutants, whereas chloride binding and the kinetics of parts of the photocycle were markedly affected by the replacement of T178. In contrast, the consequences of mutating R175 proved to be less significant. These findings are consistent with evidence obtained on HR and therefore support the idea that the respective mechanistic roles of the cytoplasmic arginine/threonine pairs in HR and BR-D85T are equal.
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Affiliation(s)
- S Paula
- Department of Membrane Biochemistry, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany
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45
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Schmies G, Engelhard M, Wood PG, Nagel G, Bamberg E. Electrophysiological characterization of specific interactions between bacterial sensory rhodopsins and their transducers. Proc Natl Acad Sci U S A 2001; 98:1555-9. [PMID: 11171989 PMCID: PMC29295 DOI: 10.1073/pnas.98.4.1555] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The halobacterial phototaxis receptors sensory rhodopsin I and II (SRI, SRII) enable the bacteria to seek optimal light conditions for ion pumping by bacteriorhodopsin and/or halorhodopsin. The incoming signal is transferred across the plasma membrane by means of receptor-specific transducer proteins that bind tightly to their corresponding photoreceptors. To investigate the receptor/transducer interaction, advantage is taken of the observation that both SRI and SRII can function as proton pumps. SRI from Halobacterium salinarum, which triggers the positive phototaxis, the photophobic receptor SRII from Natronobacterium pharaonis (pSRII), as well as the mutant pSRII-F86D were expressed in Xenopus oocytes. Voltage-clamp studies confirm that SRI and pSRII function as light-driven, outwardly directed proton pumps with a much stronger voltage dependence than the ion pumps bacteriorhodopsin and halorhodopsin. Coexpression of SRI and pSRII-F86D with their corresponding transducers suppresses the proton transport, revealing a tight binding and specific interaction of the two proteins. These latter results may be exploited to further analyze the binding interaction of the photoreceptors with their downstream effectors.
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Affiliation(s)
- G Schmies
- Max-Planck-Institut für Molekulare Physiologie, Otto-Hahn-Strasse 11, 44227 Dortmund, Germany
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46
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Electrophysiological characterization of specific interactions between bacterial sensory rhodopsins and their transducers. Proc Natl Acad Sci U S A 2001. [PMID: 11171989 PMCID: PMC29295 DOI: 10.1073/pnas.031562298] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The halobacterial phototaxis receptors sensory rhodopsin I and II (SRI, SRII) enable the bacteria to seek optimal light conditions for ion pumping by bacteriorhodopsin and/or halorhodopsin. The incoming signal is transferred across the plasma membrane by means of receptor-specific transducer proteins that bind tightly to their corresponding photoreceptors. To investigate the receptor/transducer interaction, advantage is taken of the observation that both SRI and SRII can function as proton pumps. SRI from Halobacterium salinarum, which triggers the positive phototaxis, the photophobic receptor SRII from Natronobacterium pharaonis (pSRII), as well as the mutant pSRII-F86D were expressed in Xenopus oocytes. Voltage-clamp studies confirm that SRI and pSRII function as light-driven, outwardly directed proton pumps with a much stronger voltage dependence than the ion pumps bacteriorhodopsin and halorhodopsin. Coexpression of SRI and pSRII-F86D with their corresponding transducers suppresses the proton transport, revealing a tight binding and specific interaction of the two proteins. These latter results may be exploited to further analyze the binding interaction of the photoreceptors with their downstream effectors.
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47
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Zinth W, Sieg A, Huppmann P, Blankenhorn T, Oesterhelt D, Nonella M. Femtosecond Spectroscopy and model calculations for an understanding of the primary reaction in bacteriorhodopsin. ULTRAFAST PHENOMENA XII 2001. [DOI: 10.1007/978-3-642-56546-5_202] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/09/2023]
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48
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Swartz TE, Szundi I, Spudich JL, Bogomolni RA. New photointermediates in the two photon signaling pathway of sensory rhodopsin-I. Biochemistry 2000; 39:15101-9. [PMID: 11106488 DOI: 10.1021/bi0013290] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Sensory rhodopsin-I (SRI) functions as a color discriminating receptor in halobacterial phototaxis. SRI exists in the membrane as a molecular complex with a signal transducer protein. Excitation of its thermally stable form, SRI(587), generates a long-lived photointermediate of its photocycle, S(373), and an attractant phototactic response. S(373) decays thermally in a few seconds into SRI(587.) However, when S(373) is excited by UV-blue light, it photoconverts into SRI(587) in less than a second, generating a repellent phototactic response. Only one intermediate of this back-photoreaction, S(b)(510), is known. We studied the back-photoreaction in both native SRI and its transducer free form fSRI by measuring laser flash induced absorption changes of S(373) photoproducts from 100 ns to 1 s in the 350-750 nm range. Using global exponential fitting, we determined the spectra and kinetics of the photointermediates. S(373) and fS(373) when pumped with 355 nm laser light generate in less than 100 ns two intermediate species: a previously undetected species that absorbs maximally at about 410 nm, S(b)(410), and the previously described S(b)(510). These two intermediates appear to be in a rapid equilibrium, which probably entails protonation change of the Schiff base chromophore. At pH 6 this system relaxes to SRI(587) via another intermediate absorbing maximally around 550 nm, which thermally decays back to the ground state. The same intermediates are seen in the presence and absence of transducer; however, the kinetics are affected by binding of the transducer.
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Affiliation(s)
- T E Swartz
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, California 95064, USA
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49
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Lanyi JK. Molecular Mechanism of Ion Transport in Bacteriorhodopsin: Insights from Crystallographic, Spectroscopic, Kinetic, and Mutational Studies. J Phys Chem B 2000. [DOI: 10.1021/jp0023718] [Citation(s) in RCA: 114] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Janos K. Lanyi
- Department of Physiology & Biophysics, University of California, Irvine, California 92697
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50
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Balashov SP. Protonation reactions and their coupling in bacteriorhodopsin. BIOCHIMICA ET BIOPHYSICA ACTA 2000; 1460:75-94. [PMID: 10984592 DOI: 10.1016/s0005-2728(00)00131-6] [Citation(s) in RCA: 130] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Light-induced changes of the proton affinities of amino acid side groups are the driving force for proton translocation in bacteriorhodopsin. Recent progress in obtaining structures of bacteriorhodopsin and its intermediates with an increasingly higher resolution, together with functional studies utilizing mutant pigments and spectroscopic methods, have provided important information on the molecular architecture of the proton transfer pathways and the key groups involved in proton transport. In the present paper I consider mechanisms of light-induced proton release and uptake and intramolecular proton transport and mechanisms of modulation of proton affinities of key groups in the framework of these data. Special attention is given to some important aspects that have surfaced recently. These are the coupling of protonation states of groups involved in proton transport, the complex titration of the counterion to the Schiff base and its origin, the role of the transient protonation of buried groups in catalysis of the chromophore's thermal isomerization, and the relationship between proton affinities of the groups and the pH dependencies of the rate constants of the photocycle and proton transfer reactions.
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Affiliation(s)
- S P Balashov
- Center for Biophysics and Computational Biology, Department of Cell and Structural Biology, University of Illinois at Urbana-Champaign, B107 CLSL, 601 S. Goodwin Ave., 61801, Urbana, IL, USA.
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