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Nishikino T, Sugimoto T, Kandori H. Low-temperature FTIR spectroscopy of the L/Q switch of proteorhodopsin. Phys Chem Chem Phys 2024; 26:22959-22967. [PMID: 39171479 DOI: 10.1039/d4cp02248c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/23/2024]
Abstract
Rhodopsins are photoreceptive membrane proteins containing a retinal chromophore, and the color tuning mechanism in rhodopsins is one of the important topics. Color switch is a color-determining residue at the same position, where replacement of red- and blue-shifting amino acids in two wild-type rhodopsins causes spectral blue- and red-shifts, respectively. The first and most famous color switch in microbial rhodopsins is the L/Q switch in proteorhodopsins (PRs). Green- or blue-absorbing PR (GPR or BPR) contains Leu and Gln at position 105 of the C-helix (TM3), respectively, and their replacement converted absorbing colors. The L/Q switch enables bacteria to absorb green or blue light in shallow or deep ocean waters, respectively. Although Gln and Leu are hydrophilic and hydrophobic residues, respectively, a comprehensive mutation study of position 105 in GPR revealed that the λmax correlated with the volume of residues, not the hydropathy index. To gain structural insights into the mechanism, we applied low-temperature FTIR spectroscopy of L105Q GPR, and the obtained spectra were compared with those of GPR and BPR. The difference FTIR spectra of L105Q GPR were similar to those of BPR, not GPR, implying that the L/Q switch converts the GPR structure into a BPR structure in terms of the local environments of the retinal chromophore. It includes retinal skeletal vibration, hydrogen-bonding strength of the protonated Schiff base, amide-A vibration (peptide backbone), and protein-bound water molecules. Consequently color is switched accompanying such structural alterations, and known as the L/Q switch.
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Affiliation(s)
- Tatsuro Nishikino
- Department of Life Science and Applied Chemistry, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555, Japan.
- OptoBioTechnology Research Center, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555, Japan
| | - Teppei Sugimoto
- Department of Life Science and Applied Chemistry, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555, Japan.
| | - Hideki Kandori
- Department of Life Science and Applied Chemistry, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555, Japan.
- OptoBioTechnology Research Center, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555, Japan
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2
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Marín MDC, Jaffe AL, West PT, Konno M, Banfield JF, Inoue K. Biophysical characterization of microbial rhodopsins with DSE motif. Biophys Physicobiol 2023; 20:e201023. [PMID: 38362324 PMCID: PMC10865882 DOI: 10.2142/biophysico.bppb-v20.s023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2023] [Accepted: 03/07/2023] [Indexed: 03/09/2023] Open
Abstract
Microbial rhodopsins are photoreceptive transmembrane proteins that transport ions or regulate other intracellular biological processes. Recent genomic and metagenomic analyses found many microbial rhodopsins with unique sequences distinct from known ones. Functional characterization of these new types of microbial rhodopsins is expected to expand our understanding of their physiological roles. Here, we found microbial rhodopsins having a DSE motif in the third transmembrane helix from members of the Actinobacteria. Although the expressed proteins exhibited blue-green light absorption, either no or extremely small outward H+ pump activity was observed. The turnover rate of the photocycle reaction of the purified proteins was extremely slow compared to typical H+ pumps, suggesting these rhodopsins would work as photosensors or H+ pumps whose activities are enhanced by an unknown regulatory system in the hosts. The discovery of this rhodopsin group with the unique motif and functionality expands our understanding of the biological role of microbial rhodopsins.
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Affiliation(s)
- María del Carmen Marín
- The Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - Alexander L. Jaffe
- Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720-3102, USA
- Department of Earth System Science, Stanford University, Stanford, CA 94305-4216, USA
| | - Patrick T. West
- Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720-3102, USA
| | - Masae Konno
- The Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan
- PRESTO, Japan Science and Technology Agency, Kawaguchi, Saitama 332-0012, Japan
| | - Jillian F. Banfield
- Innovative Genomics Institute, University of California, Berkeley, CA 94720-2151, USA
- Department of Earth and Planetary Science, University of California, Berkeley, CA 94720-4767, USA
- Department of Environmental Science, Policy, and Management, University of California, Berkeley, CA 94720-3114, USA
| | - Keiichi Inoue
- The Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan
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de Grip WJ, Ganapathy S. Rhodopsins: An Excitingly Versatile Protein Species for Research, Development and Creative Engineering. Front Chem 2022; 10:879609. [PMID: 35815212 PMCID: PMC9257189 DOI: 10.3389/fchem.2022.879609] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2022] [Accepted: 05/16/2022] [Indexed: 01/17/2023] Open
Abstract
The first member and eponym of the rhodopsin family was identified in the 1930s as the visual pigment of the rod photoreceptor cell in the animal retina. It was found to be a membrane protein, owing its photosensitivity to the presence of a covalently bound chromophoric group. This group, derived from vitamin A, was appropriately dubbed retinal. In the 1970s a microbial counterpart of this species was discovered in an archaeon, being a membrane protein also harbouring retinal as a chromophore, and named bacteriorhodopsin. Since their discovery a photogenic panorama unfolded, where up to date new members and subspecies with a variety of light-driven functionality have been added to this family. The animal branch, meanwhile categorized as type-2 rhodopsins, turned out to form a large subclass in the superfamily of G protein-coupled receptors and are essential to multiple elements of light-dependent animal sensory physiology. The microbial branch, the type-1 rhodopsins, largely function as light-driven ion pumps or channels, but also contain sensory-active and enzyme-sustaining subspecies. In this review we will follow the development of this exciting membrane protein panorama in a representative number of highlights and will present a prospect of their extraordinary future potential.
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Affiliation(s)
- Willem J. de Grip
- Leiden Institute of Chemistry, Department of Biophysical Organic Chemistry, Leiden University, Leiden, Netherlands
- Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, Netherlands
| | - Srividya Ganapathy
- Department of Imaging Physics, Delft University of Technology, Netherlands
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4
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Smedley GD, McElroy KE, Feller KD, Serb JM. Additive and epistatic effects influence spectral tuning in molluscan retinochrome opsin. J Exp Biol 2022; 225:275511. [DOI: 10.1242/jeb.242929] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2021] [Accepted: 04/26/2022] [Indexed: 11/20/2022]
Abstract
The relationship between genotype and phenotype is nontrivial due to often complex molecular pathways that make it difficult to unambiguously relate phenotypes to specific genotypes. Photopigments, an opsin apoprotein bound to a light-absorbing chromophore, present an opportunity to directly relate the amino acid sequence to an absorbance peak phenotype (λmax). We examined this relationship by conducting a series of site-directed mutagenesis experiments of retinochrome, a non-visual opsin, from two closely related species: the common bay scallop, Argopecten irradians, and the king scallop, Pecten maximus. Using protein folding models, we identified three amino acid sites of likely functional importance and expressed mutated retinochrome proteins in vitro. Our results show that the mutation of amino acids lining the opsin binding pocket are responsible for fine spectral tuning, or small changes in the λmax of these light sensitive proteins Mutations resulted in a blue or red shift as predicted, but with dissimilar magnitudes. Shifts ranged from a 16 nm blue shift to a 12 nm red shift from the wild-type λmax. These mutations do not show an additive effect, but rather suggests the presence of epistatic interactions. This work highlights the importance of binding pocket shape in the evolution of spectral tuning and builds on our ability to relate genotypic changes to phenotypes in an emerging model for opsin functional analysis.
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Affiliation(s)
- G. Dalton Smedley
- Department of Ecology, Evolution, and Organismal Biology, Iowa State University, Ames, Iowa, USA
| | - Kyle E. McElroy
- Department of Ecology, Evolution, and Organismal Biology, Iowa State University, Ames, Iowa, USA
| | - Kathryn D. Feller
- Department of Biological Sciences, Union College, Schenectady, New York, USA
| | - Jeanne M. Serb
- Department of Ecology, Evolution, and Organismal Biology, Iowa State University, Ames, Iowa, USA
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5
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Sumikawa M, Abe-Yoshizumi R, Uchihashi T, Kandori H. Molecular Origin of the Anomalous pH Effect in Blue Proteorhodopsin. J Phys Chem Lett 2021; 12:12225-12229. [PMID: 34928158 DOI: 10.1021/acs.jpclett.1c03355] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Proteorhodopsin (PR) is a light-driven proton pump found in marine bacteria, and thousands of PRs are classified into blue-absorbing PR (BPR; λmax ∼ 490 nm) and green-absorbing PR (GPR; λmax ∼ 525 nm). We previously presented conversion of BPR into GPR using the anomalous pH effect. When we lowered the pH of a BPR to pH 2 and returned to pH 7, the protein absorbs green light. This suggests the existence of the critical point of the irreversible process at around pH 2, but the mechanism of anomalous pH effect was fully unknown. The present size exclusion chromatography (SEC) and atomic force microscope (AFM) analysis of BPR from Vibrio califitulae (VcBPR) revealed the anomalous pH effect because of the conversion from pentamer to monomer. The different pKa of the Schiff base counterion between pentamer and monomer leads to different colors at the same pH.
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Affiliation(s)
- Mizuki Sumikawa
- Department of Life Science and Applied Chemistry, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555, Japan
| | - Rei Abe-Yoshizumi
- Department of Life Science and Applied Chemistry, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555, Japan
| | | | - Hideki Kandori
- Department of Life Science and Applied Chemistry, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555, Japan
- OptoBioTechnology Research Center, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555, Japan
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Abstract
Rhodopsins are photoreceptive membrane proteins consisting of a common heptahelical transmembrane architecture that contains a retinal chromophore. Rhodopsin was first discovered in the animal retina in 1876, but a different type of rhodopsin, bacteriorhodopsin, was reported to be present in the cell membrane of an extreme halophilic archaeon, Halobacterium salinarum, 95 years later. Although these findings were made by physiological observation of pigmented tissue and cell bodies, recent progress in genomic and metagenomic analyses has revealed that there are more than 10,000 microbial rhodopsins and 9000 animal rhodopsins with large diversity and tremendous new functionality. In this Cell Science at a Glance article and accompanying poster, we provide an overview of the diversity of functions, structures, color discrimination mechanisms and optogenetic applications of these two rhodopsin families, and will also highlight the third distinctive rhodopsin family, heliorhodopsin.
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Affiliation(s)
- Takashi Nagata
- The Institute for Solid State Physics, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581, Japan.,PRESTO, Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan
| | - Keiichi Inoue
- The Institute for Solid State Physics, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581, Japan
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7
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Pro219 is an electrostatic color determinant in the light-driven sodium pump KR2. Commun Biol 2021; 4:1185. [PMID: 34645937 PMCID: PMC8514524 DOI: 10.1038/s42003-021-02684-z] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2021] [Accepted: 09/19/2021] [Indexed: 11/13/2022] Open
Abstract
Color tuning in animal and microbial rhodopsins has attracted the interest of many researchers, as the color of their common retinal chromophores is modulated by the amino acid residues forming the chromophore cavity. Critical cavity amino acid residues are often called “color switches”, as the rhodopsin color is effectively tuned through their substitution. Well-known color switches are the L/Q and A/TS switches located in the C and G helices of the microbial rhodopsin structure respectively. Recently, we reported on a third G/P switch located in the F helix of the light-driven sodium pumps of KR2 and JsNaR causing substantial spectral red-shifts in the latter with respect to the former. In order to investigate the molecular-level mechanism driving such switching function, here we present an exhaustive mutation, spectroscopic and computational investigation of the P219X mutant set of KR2. To do so, we study the changes in the absorption band of the 19 possible mutants and construct, semi-automatically, the corresponding hybrid quantum mechanics/molecular mechanics models. We found that the P219X feature a red-shifted light absorption with the only exception of P219R. The analysis of the corresponding models indicate that the G/P switch induces red-shifting variations via electrostatic interactions, while replacement-induced chromophore geometrical (steric) distortions play a minor role. However, the same analysis indicates that the P219R blue-shifted variant has a more complex origin involving both electrostatic and steric changes accompanied by protonation state and hydrogen bond networks modifications. These results make it difficult to extract simple rules or formulate theories for predicting how a switch operates without considering the atomistic details and environmental consequences of the side chain replacement. Nakajima, Pedraza-González et al. provide a comprehensive investigation of amino acid mutations at position 219 of the sodium pump rhodopsin, KR2, and their role in the color tuning of the retinal chromophore. They prepared P219X (X= A, C, D, E, F, G, H, I, K, L, M, N, Q, R, S, T, V, W, Y) mutants of KR2, and find that all mutants are red-shifted, except for P219R, highlighting its role as a color determinant in the light-driven pump KR2.
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Kawamura I, Seki H, Tajima S, Makino Y, Shigeta A, Okitsu T, Wada A, Naito A, Sudo Y. Structure of a retinal chromophore of dark-adapted middle rhodopsin as studied by solid-state nuclear magnetic resonance spectroscopy. Biophys Physicobiol 2021; 18:177-185. [PMID: 34434690 PMCID: PMC8354847 DOI: 10.2142/biophysico.bppb-v18.019] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2021] [Accepted: 07/12/2021] [Indexed: 12/01/2022] Open
Abstract
Middle rhodopsin (MR) found from the archaeon Haloquadratum walsbyi is evolutionarily located between two different types of rhodopsins, bacteriorhodopsin (BR) and sensory rhodopsin II (SRII). Some isomers of the chromophore retinal and the photochemical reaction of MR are markedly different from those of BR and SRII. In this study, to obtain the structural information regarding its active center (i.e., retinal), we subjected MR embedded in lipid bilayers to solid-state magic-angle spinning nuclear magnetic resonance (NMR) spectroscopy. The analysis of the isotropic 13C chemical shifts of the retinal chromophore revealed the presence of three types of retinal configurations of dark-adapted MR: (13-trans, 15-anti (all-trans)), (13-cis, 15-syn), and 11-cis isomers. The higher field resonance of the 20-C methyl carbon in the all-trans retinal suggested that Trp182 in MR has an orientation that is different from that in other microbial rhodopsins, owing to the changes in steric hindrance associated with the 20-C methyl group in retinal. 13Cζ signals of Tyr185 in MR for all-trans and 13-cis, 15-syn isomers were discretely observed, representing the difference in the hydrogen bond strength of Tyr185. Further, 15N NMR analysis of the protonated Schiff base corresponding to the all-trans and 13-cis, 15-syn isomers in MR showed a strong electrostatic interaction with the counter ion. Therefore, the resulting structural information exhibited the property of stable retinal conformations of dark-adapted MR.
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Affiliation(s)
- Izuru Kawamura
- Graduate School of Engineering, Yokohama National University, Yokohama, Kanagawa 240-8501, Japan.,Graduate School of Engineering Science, Yokohama National University, Yokohama, Kanagawa 240-8501, Japan
| | - Hayato Seki
- Graduate School of Engineering, Yokohama National University, Yokohama, Kanagawa 240-8501, Japan
| | - Seiya Tajima
- Graduate School of Engineering Science, Yokohama National University, Yokohama, Kanagawa 240-8501, Japan
| | - Yoshiteru Makino
- Graduate School of Engineering, Yokohama National University, Yokohama, Kanagawa 240-8501, Japan.,Present address: Graduate School of Medicine, Kobe University, Kobe, Hyogo 657-8501, Japan
| | - Arisu Shigeta
- Graduate School of Engineering, Yokohama National University, Yokohama, Kanagawa 240-8501, Japan
| | - Takashi Okitsu
- Laboratory of Organic Chemistry for Life Science, Kobe Pharmaceutical University, Kobe, Hyogo 658-8558, Japan
| | - Akimori Wada
- Laboratory of Organic Chemistry for Life Science, Kobe Pharmaceutical University, Kobe, Hyogo 658-8558, Japan
| | - Akira Naito
- Graduate School of Engineering, Yokohama National University, Yokohama, Kanagawa 240-8501, Japan
| | - Yuki Sudo
- Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama 700-8530, Japan
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Abstract
Schizorhodopsins (SzRs), a new rhodopsin family identified in Asgard archaea, are phylogenetically located at an intermediate position between type-1 microbial rhodopsins and heliorhodopsins. SzRs work as light-driven inward H+ pumps as xenorhodopsins in bacteria. Although E81 plays an essential role in inward H+ release, the H+ is not metastably trapped in such a putative H+ acceptor, unlike the other H+ pumps. It remains elusive why SzR exhibits different kinetic behaviors in H+ release. Here, we report the crystal structure of SzR AM_5_00977 at 2.1 Å resolution. The SzR structure superimposes well on that of bacteriorhodopsin rather than heliorhodopsin, suggesting that SzRs are classified with type-1 rhodopsins. The structure-based mutagenesis study demonstrated that the residues N100 and V103 around the β-ionone ring are essential for color tuning in SzRs. The cytoplasmic parts of transmembrane helices 2, 6, and 7 are shorter than those in the other microbial rhodopsins, and thus E81 is located near the cytosol and easily exposed to the solvent by light-induced structural change. We propose a model of untrapped inward H+ release; H+ is released through the water-mediated transport network from the retinal Schiff base to the cytosol by the side of E81. Moreover, most residues on the H+ transport pathway are not conserved between SzRs and xenorhodopsins, suggesting that they have entirely different inward H+ release mechanisms.
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Exploration of natural red-shifted rhodopsins using a machine learning-based Bayesian experimental design. Commun Biol 2021; 4:362. [PMID: 33742139 PMCID: PMC7979833 DOI: 10.1038/s42003-021-01878-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2020] [Accepted: 02/19/2021] [Indexed: 12/16/2022] Open
Abstract
Microbial rhodopsins are photoreceptive membrane proteins, which are used as molecular tools in optogenetics. Here, a machine learning (ML)-based experimental design method is introduced for screening rhodopsins that are likely to be red-shifted from representative rhodopsins in the same subfamily. Among 3,022 ion-pumping rhodopsins that were suggested by a protein BLAST search in several protein databases, the ML-based method selected 65 candidate rhodopsins. The wavelengths of 39 of them were able to be experimentally determined by expressing proteins with the Escherichia coli system, and 32 (82%, p = 7.025 × 10-5) actually showed red-shift gains. In addition, four showed red-shift gains >20 nm, and two were found to have desirable ion-transporting properties, indicating that they would be potentially useful in optogenetics. These findings suggest that data-driven ML-based approaches play effective roles in the experimental design of rhodopsin and other photobiological studies. (141/150 words).
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11
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Shtyrov AA, Nikolaev DM, Mironov VN, Vasin AV, Panov MS, Tveryanovich YS, Ryazantsev MN. Simple Models to Study Spectral Properties of Microbial and Animal Rhodopsins: Evaluation of the Electrostatic Effect of Charged and Polar Residues on the First Absorption Band Maxima. Int J Mol Sci 2021; 22:ijms22063029. [PMID: 33809708 PMCID: PMC8002287 DOI: 10.3390/ijms22063029] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2021] [Accepted: 03/05/2021] [Indexed: 01/22/2023] Open
Abstract
A typical feature of proteins from the rhodopsin family is the sensitivity of their absorption band maximum to protein amino acid composition. For this reason, studies of these proteins often require methodologies that determine spectral shift caused by amino acid substitutions. Generally, quantum mechanics/molecular mechanics models allow for the calculation of a substitution-induced spectral shift with high accuracy, but their application is not always easy and requires special knowledge. In the present study, we propose simple models that allow us to estimate the direct effect of a charged or polar residue substitution without extensive calculations using only rhodopsin three-dimensional structure and plots or tables that are provided in this article. The models are based on absorption maximum values calculated at the SORCI+Q level of theory for cis- and trans-forms of retinal protonated Schiff base in an external electrostatic field of charges and dipoles. Each value corresponds to a certain position of a charged or polar residue relative to the retinal chromophore. The proposed approach was evaluated against an example set consisting of twelve bovine rhodopsin and sodium pumping rhodopsin mutants. The limits of the applicability of the models are also discussed. The results of our study can be useful for the interpretation of experimental data and for the rational design of rhodopsins with required spectral properties.
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Affiliation(s)
- Andrey A. Shtyrov
- Nanotechnology Research and Education Centre RAS, Saint Petersburg Academic University, 8/3 Khlopina Street, 194021 St. Petersburg, Russia; (A.A.S.); (D.M.N.); (V.N.M.)
| | - Dmitrii M. Nikolaev
- Nanotechnology Research and Education Centre RAS, Saint Petersburg Academic University, 8/3 Khlopina Street, 194021 St. Petersburg, Russia; (A.A.S.); (D.M.N.); (V.N.M.)
| | - Vladimir N. Mironov
- Nanotechnology Research and Education Centre RAS, Saint Petersburg Academic University, 8/3 Khlopina Street, 194021 St. Petersburg, Russia; (A.A.S.); (D.M.N.); (V.N.M.)
- Institute of Chemistry, Saint Petersburg State University, 7/9 Universitetskaya Nab., 199034 St. Petersburg, Russia; (M.S.P.); (Y.S.T.)
| | - Andrey V. Vasin
- Institute of Biomedical Systems and Botechnologies, Peter the Great St. Petersburg Polytechnic University, 29 Polytechnicheskaya Street, 195251 St. Petersburg, Russia;
| | - Maxim S. Panov
- Institute of Chemistry, Saint Petersburg State University, 7/9 Universitetskaya Nab., 199034 St. Petersburg, Russia; (M.S.P.); (Y.S.T.)
| | - Yuri S. Tveryanovich
- Institute of Chemistry, Saint Petersburg State University, 7/9 Universitetskaya Nab., 199034 St. Petersburg, Russia; (M.S.P.); (Y.S.T.)
| | - Mikhail N. Ryazantsev
- Nanotechnology Research and Education Centre RAS, Saint Petersburg Academic University, 8/3 Khlopina Street, 194021 St. Petersburg, Russia; (A.A.S.); (D.M.N.); (V.N.M.)
- Institute of Chemistry, Saint Petersburg State University, 7/9 Universitetskaya Nab., 199034 St. Petersburg, Russia; (M.S.P.); (Y.S.T.)
- Correspondence:
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12
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Abstract
Microbial rhodopsins are distributed through many microorganisms. Heliorhodopsins are newly discovered but have an unclear function. They have seven transmembrane helices similar to type-I and type-II rhodopsins, but they are different in that the N-terminal region of heliorhodopsin is cytoplasmic. We chose 13 representative heliorhodopsins from various microorganisms, expressed and purified with an N-terminal His tag, and measured the absorption spectra. The 13 natural variants had an absorption maximum (λmax) in the range 530–556 nm similar to proteorhodopsin (λmax = 490–525 nm). We selected several candidate residues that influence rhodopsin color-tuning based on sequence alignment and constructed mutants via site-directed mutagenesis to confirm the spectral changes. We found two important residues located near retinal chromophore that influence λmax. We also predict the 3D structure via homology-modeling of Thermoplasmatales heliorhodopsin. The results indicate that the color-tuning mechanism of type-I rhodopsin can be applied to understand the color-tuning of heliorhodopsin.
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13
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El‐Tahawy MMT, Conti I, Bonfanti M, Nenov A, Garavelli M. Tailoring Spectral and Photochemical Properties of Bioinspired Retinal Mimics by in Silico Engineering. Angew Chem Int Ed Engl 2020. [DOI: 10.1002/ange.202008644] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Mohsen M. T. El‐Tahawy
- Dipartimento di Chimica industriale “Toso Montanari” Università di Bologna Viale del Risorigmento 4 40136 Bologna Italy
- Chemistry Department Faculty of Science Damanhour University Damanhour 22511 Egypt
| | - Irene Conti
- Dipartimento di Chimica industriale “Toso Montanari” Università di Bologna Viale del Risorigmento 4 40136 Bologna Italy
| | - Matteo Bonfanti
- Dipartimento di Chimica industriale “Toso Montanari” Università di Bologna Viale del Risorigmento 4 40136 Bologna Italy
| | - Artur Nenov
- Dipartimento di Chimica industriale “Toso Montanari” Università di Bologna Viale del Risorigmento 4 40136 Bologna Italy
| | - Marco Garavelli
- Dipartimento di Chimica industriale “Toso Montanari” Università di Bologna Viale del Risorigmento 4 40136 Bologna Italy
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14
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Novel Modular Rhodopsins from Green Algae Hold Great Potential for Cellular Optogenetic Modulation Across the Biological Model Systems. Life (Basel) 2020; 10:life10110259. [PMID: 33126644 PMCID: PMC7693036 DOI: 10.3390/life10110259] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2020] [Revised: 10/18/2020] [Accepted: 10/19/2020] [Indexed: 01/07/2023] Open
Abstract
Light-gated ion channel and ion pump rhodopsins are widely used as optogenetic tools and these can control the electrically excitable cells as (1) they are a single-component system i.e., their light sensing and ion-conducting functions are encoded by the 7-transmembrane domains and, (2) they show fast kinetics with small dark-thermal recovery time. In cellular signaling, a signal receptor, modulator, and the effector components are involved in attaining synchronous regulation of signaling. Optical modulation of the multicomponent network requires either receptor to effector encoded in a single ORF or direct modulation of the effector domain through bypassing all upstream players. Recently discovered modular rhodopsins like rhodopsin guanylate cyclase (RhoGC) and rhodopsin phosphodiesterase (RhoPDE) paves the way to establish a proof of concept for utilization of complex rhodopsin (modular rhodopsin) for optogenetic applications. Light sensor coupled modular system could be expressed in any cell type and hence holds great potential in the advancement of optogenetics 2.0 which would enable manipulating the entire relevant cell signaling system. Here, we had identified 50 novel modular rhodopsins with variant domains and their diverse cognate signaling cascades encoded in a single ORF, which are associated with specialized functions in the cells. These novel modular algal rhodopsins have been characterized based on their sequence and structural homology with previously reported rhodopsins. The presented novel modular rhodopsins with various effector domains leverage the potential to expand the optogenetic tool kit to regulate various cellular signaling pathways across the diverse biological model systems.
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15
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El‐Tahawy MMT, Conti I, Bonfanti M, Nenov A, Garavelli M. Tailoring Spectral and Photochemical Properties of Bioinspired Retinal Mimics by in Silico Engineering. Angew Chem Int Ed Engl 2020; 59:20619-20627. [DOI: 10.1002/anie.202008644] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2020] [Indexed: 11/08/2022]
Affiliation(s)
- Mohsen M. T. El‐Tahawy
- Dipartimento di Chimica industriale “Toso Montanari” Università di Bologna Viale del Risorigmento 4 40136 Bologna Italy
- Chemistry Department Faculty of Science Damanhour University Damanhour 22511 Egypt
| | - Irene Conti
- Dipartimento di Chimica industriale “Toso Montanari” Università di Bologna Viale del Risorigmento 4 40136 Bologna Italy
| | - Matteo Bonfanti
- Dipartimento di Chimica industriale “Toso Montanari” Università di Bologna Viale del Risorigmento 4 40136 Bologna Italy
| | - Artur Nenov
- Dipartimento di Chimica industriale “Toso Montanari” Università di Bologna Viale del Risorigmento 4 40136 Bologna Italy
| | - Marco Garavelli
- Dipartimento di Chimica industriale “Toso Montanari” Università di Bologna Viale del Risorigmento 4 40136 Bologna Italy
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16
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Red-shifting mutation of light-driven sodium-pump rhodopsin. Nat Commun 2019; 10:1993. [PMID: 31040285 PMCID: PMC6491443 DOI: 10.1038/s41467-019-10000-x] [Citation(s) in RCA: 41] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2018] [Accepted: 04/12/2019] [Indexed: 11/08/2022] Open
Abstract
Microbial rhodopsins are photoreceptive membrane proteins that transport various ions using light energy. While they are widely used in optogenetics to optically control neuronal activity, rhodopsins that function with longer-wavelength light are highly demanded because of their low phototoxicity and high tissue penetration. Here, we achieve a 40-nm red-shift in the absorption wavelength of a sodium-pump rhodopsin (KR2) by altering dipole moment of residues around the retinal chromophore (KR2 P219T/S254A) without impairing its ion-transport activity. Structural differences in the chromophore of the red-shifted protein from that of the wildtype are observed by Fourier transform infrared spectroscopy. QM/MM models generated with an automated protocol show that the changes in the electrostatic interaction between protein and chromophore induced by the amino-acid replacements, lowered the energy gap between the ground and the first electronically excited state. Based on these insights, a natural sodium pump with red-shifted absorption is identified from Jannaschia seosinensis. Microbial rhodopsins are photoreceptive and widely used in optogenetics for which they should preferable function with longer-wavelength light. Here, authors achieve a 40-nm red-shift in the absorption wavelength of a sodium-pump rhodopsin (KR2) by altering the distribution of the retinal chromophore.
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17
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Morzan UN, Alonso de Armiño DJ, Foglia NO, Ramírez F, González Lebrero MC, Scherlis DA, Estrin DA. Spectroscopy in Complex Environments from QM–MM Simulations. Chem Rev 2018; 118:4071-4113. [DOI: 10.1021/acs.chemrev.8b00026] [Citation(s) in RCA: 97] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- Uriel N. Morzan
- Departamento de Química Inorgánica, Analítica y Química Física/INQUIMAE-CONICET, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pab. II, C1428EHA Buenos Aires, Argentina
| | - Diego J. Alonso de Armiño
- Departamento de Química Inorgánica, Analítica y Química Física/INQUIMAE-CONICET, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pab. II, C1428EHA Buenos Aires, Argentina
| | - Nicolás O. Foglia
- Departamento de Química Inorgánica, Analítica y Química Física/INQUIMAE-CONICET, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pab. II, C1428EHA Buenos Aires, Argentina
| | - Francisco Ramírez
- Departamento de Química Inorgánica, Analítica y Química Física/INQUIMAE-CONICET, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pab. II, C1428EHA Buenos Aires, Argentina
| | - Mariano C. González Lebrero
- Departamento de Química Inorgánica, Analítica y Química Física/INQUIMAE-CONICET, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pab. II, C1428EHA Buenos Aires, Argentina
| | - Damián A. Scherlis
- Departamento de Química Inorgánica, Analítica y Química Física/INQUIMAE-CONICET, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pab. II, C1428EHA Buenos Aires, Argentina
| | - Darío A. Estrin
- Departamento de Química Inorgánica, Analítica y Química Física/INQUIMAE-CONICET, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pab. II, C1428EHA Buenos Aires, Argentina
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18
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Inoue S, Yoshizawa S, Nakajima Y, Kojima K, Tsukamoto T, Kikukawa T, Sudo Y. Spectroscopic characteristics ofRubricoccus marinusxenorhodopsin (RmXeR) and a putative model for its inward H+transport mechanism. Phys Chem Chem Phys 2018; 20:3172-3183. [DOI: 10.1039/c7cp05033j] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
On the basis of functional and spectroscopic characterization, we propose a model for the inward proton transport inRmXeR, a newly discovered microbial rhodopsin.
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Affiliation(s)
- Saki Inoue
- Graduate School of Medicine
- Dentistry and Pharmaceutical Sciences
- Okayama University
- Okayama 700-8530
- Japan
| | - Susumu Yoshizawa
- Atmosphere and Ocean Research Institute
- The University of Tokyo
- Chiba 277-8564
- Japan
| | - Yu Nakajima
- Atmosphere and Ocean Research Institute
- The University of Tokyo
- Chiba 277-8564
- Japan
| | - Keiichi Kojima
- Graduate School of Medicine
- Dentistry and Pharmaceutical Sciences
- Okayama University
- Okayama 700-8530
- Japan
| | - Takashi Tsukamoto
- Graduate School of Medicine
- Dentistry and Pharmaceutical Sciences
- Okayama University
- Okayama 700-8530
- Japan
| | - Takashi Kikukawa
- Faculty of Advanced Life Science
- Hokkaido University
- Sapporo 060-0810
- Japan
- Global Station for Soft Matter
| | - Yuki Sudo
- Graduate School of Medicine
- Dentistry and Pharmaceutical Sciences
- Okayama University
- Okayama 700-8530
- Japan
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19
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Kaneko A, Inoue K, Kojima K, Kandori H, Sudo Y. Conversion of microbial rhodopsins: insights into functionally essential elements and rational protein engineering. Biophys Rev 2017; 9:861-876. [PMID: 29178082 DOI: 10.1007/s12551-017-0335-x] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2017] [Accepted: 11/07/2017] [Indexed: 01/16/2023] Open
Abstract
Technological progress has enabled the successful application of functional conversion to a variety of biological molecules, such as nucleotides and proteins. Such studies have revealed the functionally essential elements of these engineered molecules, which are difficult to characterize at the level of an individual molecule. The functional conversion of biological molecules has also provided a strategy for their rational and atomistic design. The engineered molecules can be used in studies to improve our understanding of their biological functions and to develop protein-based tools. In this review, we introduce the functional conversion of membrane-embedded photoreceptive retinylidene proteins (also called rhodopsins) and discuss these proteins mainly on the basis of results obtained from our own studies. This information provides insights into the molecular mechanism of light-induced protein functions and their use in optogenetics, a technology which involves the use of light to control biological activities.
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Affiliation(s)
- Akimasa Kaneko
- Faculty of Pharmaceutical Sciences, Okayama University, Okayama, 700-8530, Japan
| | - Keiichi Inoue
- Department of Frontier Materials, Nagoya Institute of Technology, Showa-ku, Nagoya, 466-8555, Japan
- OptoBioTechnology Research Center, Nagoya Institute of Technology, Showa-ku, Nagoya, 466-8555, Japan
- Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency (JST), 4-1-8 Honcho Kawaguchi, Saitama, 332-0012, Japan
| | - Keiichi Kojima
- Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, 1-1-1 Tsushima-naka, Kita-ku, Okayama, 700-8530, Japan
| | - Hideki Kandori
- Department of Frontier Materials, Nagoya Institute of Technology, Showa-ku, Nagoya, 466-8555, Japan
- OptoBioTechnology Research Center, Nagoya Institute of Technology, Showa-ku, Nagoya, 466-8555, Japan
| | - Yuki Sudo
- Faculty of Pharmaceutical Sciences, Okayama University, Okayama, 700-8530, Japan.
- Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, 1-1-1 Tsushima-naka, Kita-ku, Okayama, 700-8530, Japan.
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20
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Lamarche LB, Kumar RP, Trieu MM, Devine EL, Cohen-Abeles LE, Theobald DL, Oprian DD. Purification and Characterization of RhoPDE, a Retinylidene/Phosphodiesterase Fusion Protein and Potential Optogenetic Tool from the Choanoflagellate Salpingoeca rosetta. Biochemistry 2017; 56:5812-5822. [PMID: 28976747 DOI: 10.1021/acs.biochem.7b00519] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
RhoPDE is a type I rhodopsin/phosphodiesterase gene fusion product from the choanoflagellate Salpingoeca rosetta. The gene was discovered around the time that a similar type I rhodopsin/guanylyl cyclase fusion protein, RhoGC, was shown to control phototaxis of an aquatic fungus through a cGMP signaling pathway. RhoPDE has potential as an optogenetic tool catalyzing the hydrolysis of cyclic nucleotides. Here we provide an expression and purification system for RhoPDE, as well as a crystal structure of the C-terminal phosphodiesterase catalytic domain. We show that RhoPDE contains an even number of transmembrane segments, with N- and C-termini both located on the cytoplasmic surface of the cell membrane. The purified protein exhibits an absorption maximum at 490 nm in the dark state, which shifts to 380 nm upon exposure to light. The protein acts as a cGMP-selective phosphodiesterase. However, the activity does not appear to be modulated by light. The protein is also active with cAMP as a substrate, but with a roughly 5-7-fold lower kcat. A truncation consisting solely of the phosphodiesterase domain is also active with a kcat for cGMP roughly 6-9-fold lower than that of the full-length protein. The isolated PDE domain was crystallized, and the X-ray structure showed the protein to be a dimer similar to human PDE9. We anticipate that the purification system introduced here will enable further structural and biochemical experiments to improve our understanding of the function and mechanism of this unique fusion protein.
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Affiliation(s)
- Lindsey B Lamarche
- Department of Biochemistry, Brandeis University , Waltham, Massachusetts 02454, United States
| | - Ramasamy P Kumar
- Department of Biochemistry, Brandeis University , Waltham, Massachusetts 02454, United States
| | - Melissa M Trieu
- Department of Biochemistry, Brandeis University , Waltham, Massachusetts 02454, United States
| | - Erin L Devine
- Department of Biochemistry, Brandeis University , Waltham, Massachusetts 02454, United States
| | - Luke E Cohen-Abeles
- Department of Biochemistry, Brandeis University , Waltham, Massachusetts 02454, United States
| | - Douglas L Theobald
- Department of Biochemistry, Brandeis University , Waltham, Massachusetts 02454, United States
| | - Daniel D Oprian
- Department of Biochemistry, Brandeis University , Waltham, Massachusetts 02454, United States
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21
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Yamauchi Y, Konno M, Ito S, Tsunoda SP, Inoue K, Kandori H. Molecular properties of a DTD channelrhodopsin from Guillardia theta. Biophys Physicobiol 2017. [PMID: 28630812 PMCID: PMC5468465 DOI: 10.2142/biophysico.14.0_57] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Microbial rhodopsins are membrane proteins found widely in archaea, eubacteria and eukaryotes (fungal and algal species). They have various functions, such as light-driven ion pumps, light-gated ion channels, light sensors and light-activated enzymes. A light-driven proton pump bacteriorhodopsin (BR) contains a DTD motif at positions 85, 89, and 96, which is unique to archaeal proton pumps. Recently, channelrhodopsins (ChRs) containing the DTD motif, whose sequential identity is ~20% similar to BR and to cation ChRs in Chlamydomonas reinhardtii (CrCCRs), were found. While extensive studies on ChRs have been performed with CrCCR2, the molecular properties of DTD ChRs remain an intrigue. In this paper, we studied a DTD rhodopsin from G. theta (GtCCR4) using electrophysiological measurements, flash photolysis, and low-temperature difference FTIR spectroscopy. Electrophysiological measurements clearly showed that GtCCR4 functions as a light-gated cation channel, similar to other G. theta DTD ChRs (GtCCR1-3). Light-driven proton pump activity was also suggested for GtCCR4. Both electrophysiological and flash photolysis experiments showed that channel closing occurs upon reprotonation of the Schiff base, suggesting that the dynamics of retinal and channels are tightly coupled in GtCCR4. From Fourier transform infrared (FTIR) spectroscopy at 77 K, we found that the primary reaction is an all-trans to a 13-cis photoisomerization, like other microbial rhodopsins, although perturbations in the secondary structure were much smaller in GtCCR4 than in CrCCR2.
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Affiliation(s)
- Yumeka Yamauchi
- Department of Life Science and Applied Chemistry, Nagoya Institute of Technology, Nagoya, Aichi 466-8555, Japan
| | - Masae Konno
- Department of Life Science and Applied Chemistry, Nagoya Institute of Technology, Nagoya, Aichi 466-8555, Japan.,OptoBioTechnology Research Center, Nagoya Institute of Technology, Nagoya, Aichi 466-8555, Japan
| | - Shota Ito
- Department of Life Science and Applied Chemistry, Nagoya Institute of Technology, Nagoya, Aichi 466-8555, Japan
| | - Satoshi P Tsunoda
- Department of Life Science and Applied Chemistry, Nagoya Institute of Technology, Nagoya, Aichi 466-8555, Japan.,OptoBioTechnology Research Center, Nagoya Institute of Technology, Nagoya, Aichi 466-8555, Japan.,PRESTO, Japan Science and Technology Agency, Kawaguchi, Saitama 332-0012, Japan
| | - Keiichi Inoue
- Department of Life Science and Applied Chemistry, Nagoya Institute of Technology, Nagoya, Aichi 466-8555, Japan.,OptoBioTechnology Research Center, Nagoya Institute of Technology, Nagoya, Aichi 466-8555, Japan.,PRESTO, Japan Science and Technology Agency, Kawaguchi, Saitama 332-0012, Japan.,Frontier Research Institute for Material Science, Nagoya Institute of Technology, Nagoya, Aichi 466-8555, Japan
| | - Hideki Kandori
- Department of Life Science and Applied Chemistry, Nagoya Institute of Technology, Nagoya, Aichi 466-8555, Japan.,OptoBioTechnology Research Center, Nagoya Institute of Technology, Nagoya, Aichi 466-8555, Japan
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22
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Urmann D, Lorenz C, Linker SM, Braun M, Wachtveitl J, Bamann C. Photochemical Properties of the Red-shifted Channelrhodopsin Chrimson. Photochem Photobiol 2017; 93:782-795. [DOI: 10.1111/php.12741] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2016] [Accepted: 01/02/2017] [Indexed: 01/03/2023]
Affiliation(s)
- David Urmann
- Institute of Physical and Theoretical Chemistry; Johann Wolfgang Goethe University Frankfurt; Frankfurt am Main Germany
| | - Charlotte Lorenz
- Department of Biophysical Chemistry; Max Planck Institute of Biophysics; Frankfurt am Main Germany
| | - Stephanie M. Linker
- Department of Biophysical Chemistry; Max Planck Institute of Biophysics; Frankfurt am Main Germany
| | - Markus Braun
- Institute of Physical and Theoretical Chemistry; Johann Wolfgang Goethe University Frankfurt; Frankfurt am Main Germany
| | - Josef Wachtveitl
- Institute of Physical and Theoretical Chemistry; Johann Wolfgang Goethe University Frankfurt; Frankfurt am Main Germany
| | - Christian Bamann
- Department of Biophysical Chemistry; Max Planck Institute of Biophysics; Frankfurt am Main Germany
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23
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Yoshida K, Tsunoda SP, Brown LS, Kandori H. A unique choanoflagellate enzyme rhodopsin exhibits light-dependent cyclic nucleotide phosphodiesterase activity. J Biol Chem 2017; 292:7531-7541. [PMID: 28302718 DOI: 10.1074/jbc.m117.775569] [Citation(s) in RCA: 65] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2017] [Revised: 03/13/2017] [Indexed: 12/28/2022] Open
Abstract
Photoactivated adenylyl cyclase (PAC) and guanylyl cyclase rhodopsin increase the concentrations of intracellular cyclic nucleotides upon illumination, serving as promising second-generation tools in optogenetics. To broaden the arsenal of such tools, it is desirable to have light-activatable enzymes that can decrease cyclic nucleotide concentrations in cells. Here, we report on an unusual microbial rhodopsin that may be able to meet the demand. It is found in the choanoflagellate Salpingoeca rosetta and contains a C-terminal cyclic nucleotide phosphodiesterase (PDE) domain. We examined the enzymatic activity of the protein (named Rh-PDE) both in HEK293 membranes and whole cells. Although Rh-PDE was constitutively active in the dark, illumination increased its hydrolytic activity 1.4-fold toward cGMP and 1.6-fold toward cAMP, as measured in isolated crude membranes. Purified full-length Rh-PDE displayed maximal light absorption at 492 nm and formed the M intermediate with the deprotonated Schiff base upon illumination. The M state decayed to the parent spectral state in 7 s, producing long-lasting activation of the enzyme domain with increased activity. We discuss a possible mechanism of the Rh-PDE activation by light. Furthermore, Rh-PDE decreased cAMP concentration in HEK293 cells in a light-dependent manner and could do so repeatedly without losing activity. Thus, Rh-PDE may hold promise as a potential optogenetic tool for light control of intracellular cyclic nucleotides (e.g. to study cyclic nucleotide-associated signal transduction cascades).
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Affiliation(s)
- Kazuho Yoshida
- From the Department of Life Science and Applied Chemistry and
| | - Satoshi P Tsunoda
- From the Department of Life Science and Applied Chemistry and .,JST PRESTO, 4-1-8 Honcho, Kawaguchi, Saitama, 332-0012, Japan, and.,the OptoBioTechnology Research Center, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555, Japan
| | - Leonid S Brown
- the Department of Physics, University of Guelph, Guelph, Ontario N1G 2W1, Canada
| | - Hideki Kandori
- From the Department of Life Science and Applied Chemistry and .,the OptoBioTechnology Research Center, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555, Japan
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24
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Kato HE, Kamiya M, Sugo S, Ito J, Taniguchi R, Orito A, Hirata K, Inutsuka A, Yamanaka A, Maturana AD, Ishitani R, Sudo Y, Hayashi S, Nureki O. Atomistic design of microbial opsin-based blue-shifted optogenetics tools. Nat Commun 2015; 6:7177. [PMID: 25975962 PMCID: PMC4479019 DOI: 10.1038/ncomms8177] [Citation(s) in RCA: 65] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2014] [Accepted: 04/14/2015] [Indexed: 12/31/2022] Open
Abstract
Microbial opsins with a bound chromophore function as photosensitive ion transporters and have been employed in optogenetics for the optical control of neuronal activity. Molecular engineering has been utilized to create colour variants for the functional augmentation of optogenetics tools, but was limited by the complexity of the protein-chromophore interactions. Here we report the development of blue-shifted colour variants by rational design at atomic resolution, achieved through accurate hybrid molecular simulations, electrophysiology and X-ray crystallography. The molecular simulation models and the crystal structure reveal the precisely designed conformational changes of the chromophore induced by combinatory mutations that shrink its π-conjugated system which, together with electrostatic tuning, produce large blue shifts of the absorption spectra by maximally 100 nm, while maintaining photosensitive ion transport activities. The design principle we elaborate is applicable to other microbial opsins, and clarifies the underlying molecular mechanism of the blue-shifted action spectra of microbial opsins recently isolated from natural sources.
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Affiliation(s)
- Hideaki E Kato
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, 2-11-16 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan
| | - Motoshi Kamiya
- Department of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
| | - Seiya Sugo
- Department of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
| | - Jumpei Ito
- Department of Bioengineering Sciences, Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan
| | - Reiya Taniguchi
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, 2-11-16 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan
| | - Ayaka Orito
- Department of Bioengineering Sciences, Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan
| | | | - Ayumu Inutsuka
- Department of Neuroscience II, Research Institute of Environmental Medicine, Nagoya University, Nagoya 464-8601, Japan
| | - Akihiro Yamanaka
- Department of Neuroscience II, Research Institute of Environmental Medicine, Nagoya University, Nagoya 464-8601, Japan
| | - Andrés D Maturana
- Department of Bioengineering Sciences, Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan
| | - Ryuichiro Ishitani
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, 2-11-16 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan
| | - Yuki Sudo
- Division of Pharmaceutical Sciences, Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, Okayama University, 1-1-1 Tsushima-naka, Kita-ku, Okayama 700-8530, Japan
| | - Shigehiko Hayashi
- Department of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
| | - Osamu Nureki
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, 2-11-16 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan
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25
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Inoue K, Tsukamoto T, Shimono K, Suzuki Y, Miyauchi S, Hayashi S, Kandori H, Sudo Y. Converting a Light-Driven Proton Pump into a Light-Gated Proton Channel. J Am Chem Soc 2015; 137:3291-9. [DOI: 10.1021/ja511788f] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Affiliation(s)
- Keiichi Inoue
- Department
of Frontier Materials, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555, Japan
- OptoBioTechnology
Research Center, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555, Japan
- PRESTO, Japan Science and Technology Agency, 4-1-8 Honcho Kawaguchi, Saitama 332-0012, Japan
| | - Takashi Tsukamoto
- Division
of Pharmaceutical Sciences, Graduate School of Medicine, Dentistry,
and Pharmaceutical Sciences, Okayama University, 1-1-1 Tsushima-naka, Kita-ku, Okayama 700-8530, Japan
| | - Kazumi Shimono
- Faculty
of Pharmaceutical Sciences, Toho University, Funabashi 274-8510, Japan
| | - Yuto Suzuki
- Department
of Frontier Materials, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555, Japan
| | - Seiji Miyauchi
- Faculty
of Pharmaceutical Sciences, Toho University, Funabashi 274-8510, Japan
| | - Shigehiko Hayashi
- Department
of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
| | - Hideki Kandori
- Department
of Frontier Materials, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555, Japan
- OptoBioTechnology
Research Center, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555, Japan
| | - Yuki Sudo
- Division
of Pharmaceutical Sciences, Graduate School of Medicine, Dentistry,
and Pharmaceutical Sciences, Okayama University, 1-1-1 Tsushima-naka, Kita-ku, Okayama 700-8530, Japan
- Japan Science and Technology Agency, CREST, K’s Gobancho, 7 Gobancho, Chiyoda-ku, Tokyo 102-0076, Japan
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26
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Rozin R, Wand A, Jung KH, Ruhman S, Sheves M. pH Dependence of Anabaena Sensory Rhodopsin: Retinal Isomer Composition, Rate of Dark Adaptation, and Photochemistry. J Phys Chem B 2014; 118:8995-9006. [DOI: 10.1021/jp504688y] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Affiliation(s)
- Rinat Rozin
- Department
of Organic Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Amir Wand
- Institute
of Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, Jerusalem 91904, Israel
| | - Kwang-Hwan Jung
- Department
of Life Science and Institute of Biological Interfaces, Sogang University, Shinsu-Dong 1, Mapo-Gu, Seoul 121-742, South Korea
| | - Sanford Ruhman
- Institute
of Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, Jerusalem 91904, Israel
| | - Mordechai Sheves
- Department
of Organic Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel
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27
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Cheminal A, Léonard J, Kim S, Jung KH, Kandori H, Haacke S. Steady state emission of the fluorescent intermediate of Anabaena Sensory Rhodopsin as a function of light adaptation conditions. Chem Phys Lett 2013. [DOI: 10.1016/j.cplett.2013.09.044] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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28
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Wang W, Geiger JH, Borhan B. The photochemical determinants of color vision: revealing how opsins tune their chromophore's absorption wavelength. Bioessays 2013; 36:65-74. [PMID: 24323922 DOI: 10.1002/bies.201300094] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The evolution of a variety of important chromophore-dependent biological processes, including microbial light sensing and mammalian color vision, relies on protein modifications that alter the spectral characteristics of a bound chromophore. Three different color opsins share the same chromophore, but have three distinct absorptions that together cover the entire visible spectrum, giving rise to trichromatic vision. The influence of opsins on the absorbance of the chromophore has been studied through methods such as model compounds, opsin mutagenesis, and computational modeling. The recent development of rhodopsin mimic that uses small soluble proteins to recapitulate the binding and wavelength tuning of the native opsins provides a new platform for studying protein-regulated spectral tuning. The ability to achieve far-red shifted absorption in the rhodopsin mimic system was attributed to a combination of the lack of a counteranion proximal to the iminium, and a uniformly neutral electrostatic environment surrounding the chromophore.
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Affiliation(s)
- Wenjing Wang
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA, USA
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Tsukamoto T, Inoue K, Kandori H, Sudo Y. Thermal and spectroscopic characterization of a proton pumping rhodopsin from an extreme thermophile. J Biol Chem 2013; 288:21581-92. [PMID: 23740255 DOI: 10.1074/jbc.m113.479394] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
So far retinylidene proteins (∼rhodopsin) have not been discovered in thermophilic organisms. In this study we investigated and characterized a microbial rhodopsin derived from the extreme thermophilic bacterium Thermus thermophilus, which lives in a hot spring at around 75 °C. The gene for the retinylidene protein, named thermophilic rhodopsin (TR), was chemically synthesized with codon optimization. The codon optimized TR protein was functionally expressed in the cell membranes of Escherichia coli cells and showed active proton transport upon photoillumination. Spectroscopic measurements revealed that the purified TR bound only all-trans-retinal as a chromophore and showed an absorption maximum at 530 nm. In addition, TR exhibited both photocycle kinetics and pH-dependent absorption changes, which are characteristic of rhodopsins. Of note, time-dependent thermal denaturation experiments revealed that TR maintained its absorption even at 75 °C, and the denaturation rate constant of TR was much lower than those of other proton pumping rhodopsins such as archaerhodopsin-3 (200 ×), Haloquadratum walsbyi bacteriorhodopsin (by 10-times), and Gloeobacter rhodopsin (100 ×). Thus, these results suggest that microbial rhodopsins are also distributed among thermophilic organisms and have high stability. TR should allow the investigation of the molecular mechanisms of ion transport and protein folding.
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Affiliation(s)
- Takashi Tsukamoto
- Division of Biological Science, Graduate School of Science, Nagoya University, Nagoya 464-8602, Japan
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Inoue K, Tsukamoto T, Sudo Y. Molecular and evolutionary aspects of microbial sensory rhodopsins. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2013; 1837:562-77. [PMID: 23732219 DOI: 10.1016/j.bbabio.2013.05.005] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2013] [Revised: 05/14/2013] [Accepted: 05/16/2013] [Indexed: 02/03/2023]
Abstract
Retinal proteins (~rhodopsins) are photochemically reactive membrane-embedded proteins, with seven transmembrane α-helices which bind the chromophore retinal (vitamin A aldehyde). They are widely distributed through all three biological kingdoms, eukarya, bacteria and archaea, indicating the biological significance of the retinal proteins. Light absorption by the retinal proteins triggers a photoisomerization of the chromophore, leading to the biological function, light-energy conversion or light-signal transduction. This article reviews molecular and evolutionary aspects of the light-signal transduction by microbial sensory receptors and their related proteins. This article is part of a Special Issue entitled: Retinal Proteins - You can teach an old dog new tricks.
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Affiliation(s)
- Keiichi Inoue
- Department of Frontier Materials, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555, Japan; Japan Science and Technology Agency (JST), PRESTO, 4-1-8 Honcho Kawaguchi, Saitama 332-0012, Japan
| | - Takashi Tsukamoto
- Division of Biological Science, Graduate School of Science, Nagoya University, Nagoya, 464-8602, Japan
| | - Yuki Sudo
- Japan Science and Technology Agency (JST), PRESTO, 4-1-8 Honcho Kawaguchi, Saitama 332-0012, Japan; Division of Biological Science, Graduate School of Science, Nagoya University, Nagoya, 464-8602, Japan; Department of Life and Coordination-Complex Molecular Science, Institute for Molecular Science, 38 Nishigo-Naka, Myodaiji, Okazaki, Japan.
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31
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Mori A, Yagasaki J, Homma M, Reissig L, Sudo Y. Investigation of the chromophore binding cavity in the 11-cis acceptable microbial rhodopsin MR. Chem Phys 2013. [DOI: 10.1016/j.chemphys.2012.11.020] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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32
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Sudo Y, Okazaki A, Ono H, Yagasaki J, Sugo S, Kamiya M, Reissig L, Inoue K, Ihara K, Kandori H, Takagi S, Hayashi S. A blue-shifted light-driven proton pump for neural silencing. J Biol Chem 2013; 288:20624-32. [PMID: 23720753 DOI: 10.1074/jbc.m113.475533] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Ion-transporting rhodopsins are widely utilized as optogenetic tools both for light-induced neural activation and silencing. The most studied representative is Bacteriorhodopsin (BR), which absorbs green/red light (∼570 nm) and functions as a proton pump. Upon photoexcitation, BR induces a hyperpolarization across the membrane, which, if incorporated into a nerve cell, results in its neural silencing. In this study, we show that several residues around the retinal chromophore, which are completely conserved among BR homologs from the archaea, are involved in the spectral tuning in a BR homolog (HwBR) and that the combination mutation causes a large spectral blue shift (λmax = 498 nm) while preserving the robust pumping activity. Quantum mechanics/molecular mechanics calculations revealed that, compared with the wild type, the β-ionone ring of the chromophore in the mutant is rotated ∼130° because of the lack of steric hindrance between the methyl groups of the retinal and the mutated residues, resulting in the breakage of the π conjugation system on the polyene chain of the retinal. By the same mutations, similar spectral blue shifts are also observed in another BR homolog, archearhodopsin-3 (also called Arch). The color variant of archearhodopsin-3 could be successfully expressed in the neural cells of Caenorhabditis elegans, and illumination with blue light (500 nm) led to the effective locomotory paralysis of the worms. Thus, we successfully produced a blue-shifted proton pump for neural silencing.
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Affiliation(s)
- Yuki Sudo
- Division of Biological Science, Graduate School of Science, Nagoya University, Nagoya 464-8602, Japan.
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Yamashita H, Inoue K, Shibata M, Uchihashi T, Sasaki J, Kandori H, Ando T. Role of trimer-trimer interaction of bacteriorhodopsin studied by optical spectroscopy and high-speed atomic force microscopy. J Struct Biol 2013; 184:2-11. [PMID: 23462099 DOI: 10.1016/j.jsb.2013.02.011] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2012] [Revised: 12/22/2012] [Accepted: 02/12/2013] [Indexed: 10/27/2022]
Abstract
Bacteriorhodopsin (bR) trimers form a two-dimensional hexagonal lattice in the purple membrane of Halobacterium salinarum. However, the physiological significance of forming the lattice has long been elusive. Here, we study this issue by comparing properties of assembled and non-assembled bR trimers using directed mutagenesis, high-speed atomic force microscopy (HS-AFM), optical spectroscopy, and a proton pumping assay. First, we show that the bonds formed between W12 and F135 amino acid residues are responsible for trimer-trimer association that leads to lattice assembly; the lattice is completely disrupted in both W12I and F135I mutants. HS-AFM imaging reveals that both crystallized D96N and non-crystallized D96N/W12I mutants undergo a large conformational change (i.e., outward E-F loop displacement) upon light-activation. However, lattice disruption significantly reduces the rate of conformational change under continuous light illumination. Nevertheless, the quantum yield of M-state formation, measured by low-temperature UV-visible spectroscopy, and proton pumping efficiency are unaffected by lattice disruption. From these results, we conclude that trimer-trimer association plays essential roles in providing bound retinal with an appropriate environment to maintain its full photo-reactivity and in maintaining the natural photo-reaction pathway.
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Affiliation(s)
- Hayato Yamashita
- Department of Physics, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan
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Hayashi T, Matsuura A, Sato H, Sakurai M. Full-Quantum chemical calculation of the absorption maximum of bacteriorhodopsin: a comprehensive analysis of the amino acid residues contributing to the opsin shift. Biophysics (Nagoya-shi) 2012; 8:115-25. [PMID: 27493528 PMCID: PMC4629650 DOI: 10.2142/biophysics.8.115] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2012] [Accepted: 06/14/2012] [Indexed: 12/01/2022] Open
Abstract
Herein, the absorption maximum of bacteriorhodopsin (bR) is calculated using our recently developed method in which the whole protein can be treated quantum mechanically at the level of INDO/S-CIS//ONIOM (B3LYP/6-31G(d,p): AMBER). The full quantum mechanical calculation is shown to reproduce the so-called opsin shift of bR with an error of less than 0.04 eV. We also apply the same calculation for 226 different bR mutants, each of which was constructed by replacing any one of the amino acid residues of the wild-type bR with Gly. This substitution makes it possible to elucidate the extent to which each amino acid contributes to the opsin shift and to estimate the inter-residue synergistic effect. It was found that one of the most important contributions to the opsin shift is the electron transfer from Tyr185 to the chromophore upon excitation. We also indicate that some aromatic (Trp86, Trp182) and polar (Ser141, Thr142) residues, located in the vicinity of the retinal polyene chain and the β-ionone ring, respectively, play an important role in compensating for the large blue-shift induced by both the counterion residues (Asp85, Asp212) and an internal water molecule (W402) located near the Schiff base linkage. In particular, the effect of Trp86 is comparable to that of Tyr185. In addition, Ser141 and Thr142 were found to contribute to an increase in the dipole moment of bR in the excited state. Finally, we provide a complete energy diagram for the opsin shift together with the contribution of the chromophore-protein steric interaction.
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Affiliation(s)
- Tomohiko Hayashi
- Center for Biological Resources and Informatics, Tokyo Institute of Technology, B-62 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8501, Japan
| | - Azuma Matsuura
- Fujitsu Laboratories, Ltd., 10-1 Morinosato-Wakamiya, Atsugi 243-0197, Japan
| | - Hiroyuki Sato
- Fujitsu Laboratories, Ltd., 10-1 Morinosato-Wakamiya, Atsugi 243-0197, Japan
| | - Minoru Sakurai
- Center for Biological Resources and Informatics, Tokyo Institute of Technology, B-62 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8501, Japan
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Sudo Y, Homma M. [Photosensing by membrane-embedded receptors and its application for the life scientists]. YAKUGAKU ZASSHI 2012; 132:407-16. [PMID: 22465915 DOI: 10.1248/yakushi.132.407] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Light is one of the most important energy sources and signals providing critical information to biological systems. The photoreceptor rhodopsin, which possesses retinal chromophore (vitamin A aldehyde) surrounded by seven transmembrane alpha-helices, is widely dispersed in prokaryotes and in eukaryotes. Although rhodopsin molecules work as distinctly different photoreceptors, they can be divided according to their two basic functions such as light-energy conversion and light-signal transduction. Thus rhodopsin molecules have great potential for controlling cellular activity by light. Indeed, a light-energy converter channel rhodopsin is used to control neural activity. From 2001, we have been working on various microbial sensory rhodopsins functioning as light-signal converters. In this review, we will introduce rhodopsin molecules from microbes, and will describe artificial and light-dependent protein expression system in Escherichia coli using Anabeana sensory rhodopsin (ASR). The newly developed tools would be widely useful for life scientists.
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Affiliation(s)
- Yuki Sudo
- Division of Biological Science, Graduate School of Science, Nagoya University, Nagoya, Japan.
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Wand A, Rozin R, Eliash T, Jung KH, Sheves M, Ruhman S. Asymmetric Toggling of a Natural Photoswitch: Ultrafast Spectroscopy of Anabaena Sensory Rhodopsin. J Am Chem Soc 2011; 133:20922-32. [DOI: 10.1021/ja208371g] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Amir Wand
- Institute of Chemistry and Farkash Center for Light-Induced Processes, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
| | - Rinat Rozin
- Department of Organic Chemistry, The Weizmann Institute of Science, Rehovot 76100, Israel
| | - Tamar Eliash
- Department of Organic Chemistry, The Weizmann Institute of Science, Rehovot 76100, Israel
| | - Kwang-Hwan Jung
- Department of Life Science and Institute of Biological Interfaces, Sogang University, Shinsu-Dong 1, Mapo-Gu, Seoul 121-742, South Korea
| | - Mordechai Sheves
- Department of Organic Chemistry, The Weizmann Institute of Science, Rehovot 76100, Israel
| | - Sanford Ruhman
- Institute of Chemistry and Farkash Center for Light-Induced Processes, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
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37
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Yamashita Y, Kikukawa T, Tsukamoto T, Kamiya M, Aizawa T, Kawano K, Miyauchi S, Kamo N, Demura M. Expression of salinarum halorhodopsin in Escherichia coli cells: solubilization in the presence of retinal yields the natural state. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2011; 1808:2905-12. [PMID: 21925140 DOI: 10.1016/j.bbamem.2011.08.035] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/29/2011] [Revised: 08/27/2011] [Accepted: 08/30/2011] [Indexed: 11/29/2022]
Abstract
Salinarum halorhodopsin (HsHR), a light-driven chloride ion pump of haloarchaeon Halobacterium salinarum, was heterologously expressed in Escherichia coli. The expressed HsHR had no color in the E. coli membrane, but turned purple after solubilization in the presence of all-trans retinal. This colored HsHR was purified by Ni-chelate chromatography in a yield of 3-4 mg per liter culture. The purified HsHR showed a distinct chloride pumping activity by incorporation into the liposomes, and showed even in the detergent-solubilized state, its typical behaviors in both the unphotolyzed and photolyzed states. Upon solubilization, HsHR expressed in the E. coli membrane attains the proper folding and a trimeric assembly comparable to those in the native membranes.
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Affiliation(s)
- Yasutaka Yamashita
- Faculty of Advanced Life Science, Hokkaido University, Sapporo 060-0810, Japan
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38
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Wada T, Shimono K, Kikukawa T, Hato M, Shinya N, Kim SY, Kimura-Someya T, Shirouzu M, Tamogami J, Miyauchi S, Jung KH, Kamo N, Yokoyama S. Crystal Structure of the Eukaryotic Light-Driven Proton-Pumping Rhodopsin, Acetabularia Rhodopsin II, from Marine Alga. J Mol Biol 2011; 411:986-98. [DOI: 10.1016/j.jmb.2011.06.028] [Citation(s) in RCA: 95] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2011] [Accepted: 06/15/2011] [Indexed: 11/29/2022]
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Sudo Y, Yuasa Y, Shibata J, Suzuki D, Homma M. Spectral tuning in sensory rhodopsin I from Salinibacter ruber. J Biol Chem 2011; 286:11328-36. [PMID: 21288897 DOI: 10.1074/jbc.m110.187948] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Organisms utilize light as energy sources and as signals. Rhodopsins, which have seven transmembrane α-helices with retinal covalently linked to a conserved Lys residue, are found in various organisms as distant in evolution as bacteria, archaea, and eukarya. One of the most notable properties of rhodopsin molecules is the large variation in their absorption spectrum. Sensory rhodopsin I (SRI) and sensory rhodopsin II (SRII) function as photosensors and have similar properties (retinal composition, photocycle, structure, and function) except for their λ(max) (SRI, ∼560 nm; SRII, ∼500 nm). An expression system utilizing Escherichia coli and the high protein stability of a newly found SRI-like protein, SrSRI, enables studies of mutant proteins. To determine the residue contributing to the spectral shift from SRI to SRII, we constructed various SRI mutants, in which individual residues were substituted with the corresponding residues of SRII. Three such mutants of SrSRI showed a large spectral blue-shift (>14 nm) without a large alteration of their retinal composition. Two of them, A136Y and A200T, are newly discovered color tuning residues. In the triple mutant, the λ(max) was 525 nm. The inverse mutation of SRII (F134H/Y139A/T204A) generated a spectral-shifted SRII toward longer wavelengths, although the effect is smaller than in the case of SRI, which is probably due to the lack of anion binding in the SRII mutant. Thus, half of the spectral shift from SRI to SRII could be explained by only those three residues taking into account the effect of Cl(-) binding.
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Affiliation(s)
- Yuki Sudo
- Division of Biological Science, Graduate School of Science, Nagoya University, Nagoya, Japan.
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Nakao Y, Kikukawa T, Shimono K, Tamogami J, Kimitsuki N, Nara T, Unno M, Ihara K, Kamo N. Photochemistry of a putative new class of sensory rhodopsin (SRIII) coded by xop2 of Haloarcular marismortui. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY 2011; 102:45-54. [DOI: 10.1016/j.jphotobiol.2010.09.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2010] [Revised: 08/31/2010] [Accepted: 09/03/2010] [Indexed: 11/30/2022]
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Sudo Y, Ihara K, Kobayashi S, Suzuki D, Irieda H, Kikukawa T, Kandori H, Homma M. A microbial rhodopsin with a unique retinal composition shows both sensory rhodopsin II and bacteriorhodopsin-like properties. J Biol Chem 2010; 286:5967-76. [PMID: 21135094 DOI: 10.1074/jbc.m110.190058] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Rhodopsins possess retinal chromophore surrounded by seven transmembrane α-helices, are widespread in prokaryotes and in eukaryotes, and can be utilized as optogenetic tools. Although rhodopsins work as distinctly different photoreceptors in various organisms, they can be roughly divided according to their two basic functions, light-energy conversion and light-signal transduction. In microbes, light-driven proton transporters functioning as light-energy converters have been modified by evolution to produce sensory receptors that relay signals to transducer proteins to control motility. In this study, we cloned and characterized two newly identified microbial rhodopsins from Haloquadratum walsbyi. One of them has photochemical properties and a proton pumping activity similar to the well known proton pump bacteriorhodopsin (BR). The other, named middle rhodopsin (MR), is evolutionarily transitional between BR and the phototactic sensory rhodopsin II (SRII), having an SRII-like absorption maximum, a BR-like photocycle, and a unique retinal composition. The wild-type MR does not have a light-induced proton pumping activity. On the other hand, a mutant MR with two key hydrogen-bonding residues located at the interaction surface with the transducer protein HtrII shows robust phototaxis responses similar to SRII, indicating that MR is potentially capable of the signaling. These results demonstrate that color tuning and insertion of the critical threonine residue occurred early in the evolution of sensory rhodopsins. MR may be a missing link in the evolution from type 1 rhodopsins (microorganisms) to type 2 rhodopsins (animals), because it is the first microbial rhodopsin known to have 11-cis-retinal similar to type 2 rhodopsins.
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Affiliation(s)
- Yuki Sudo
- Division of Biological Science, Graduate School of Science, Nagoya University, Nagoya, 464-8602, Japan.
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Photoreactions and structural changes of anabaena sensory rhodopsin. SENSORS 2009; 9:9741-804. [PMID: 22303148 PMCID: PMC3267196 DOI: 10.3390/s91209741] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/18/2009] [Revised: 10/14/2009] [Accepted: 10/23/2009] [Indexed: 12/05/2022]
Abstract
Anabaena sensory rhodopsin (ASR) is an archaeal-type rhodopsin found in eubacteria. The gene encoding ASR forms a single operon with ASRT (ASR transducer) which is a 14 kDa soluble protein, suggesting that ASR functions as a photochromic sensor by activating the soluble transducer. This article reviews the detailed photoreaction processes of ASR, which were studied by low-temperature Fourier-transform infrared (FTIR) and UV-visible spectroscopy. The former research reveals that the retinal isomerization is similar to bacteriorhodopsin (BR), but the hydrogen-bonding network around the Schiff base and cytoplasmic region is different. The latter study shows the stable photoproduct of the all-trans form is 100% 13-cis, and that of the 13-cis form is 100% all-trans. These results suggest that the structural changes of ASR in the cytoplasmic domain play important roles in the activation of the transducer protein, and photochromic reaction is optimized for its sensor function.
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Sudo Y, Okada A, Suzuki D, Inoue K, Irieda H, Sakai M, Fujii M, Furutani Y, Kandori H, Homma M. Characterization of a Signaling Complex Composed of Sensory Rhodopsin I and Its Cognate Transducer Protein from the Eubacterium Salinibacter ruber. Biochemistry 2009; 48:10136-45. [DOI: 10.1021/bi901338d] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Yuki Sudo
- Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan
- PRESTO, Japan Science and Technology Agency (JST), 4-1-8 Honcho Kawaguchi, Saitama 332-0012, Japan
| | - Akiko Okada
- Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan
| | - Daisuke Suzuki
- Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan
| | - Keiichi Inoue
- Chemical Resources Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8503, Japan
| | - Hiroki Irieda
- Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan
| | - Makoto Sakai
- Chemical Resources Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8503, Japan
| | - Masaaki Fujii
- Chemical Resources Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8503, Japan
| | - Yuji Furutani
- Department of Frontier Materials, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555, Japan
| | - Hideki Kandori
- Department of Frontier Materials, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555, Japan
| | - Michio Homma
- Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan
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Suzuki D, Furutani Y, Inoue K, Kikukawa T, Sakai M, Fujii M, Kandori H, Homma M, Sudo Y. Effects of chloride ion binding on the photochemical properties of salinibacter sensory rhodopsin I. J Mol Biol 2009; 392:48-62. [PMID: 19560470 DOI: 10.1016/j.jmb.2009.06.050] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2009] [Revised: 05/31/2009] [Accepted: 06/18/2009] [Indexed: 10/20/2022]
Abstract
Microbial organisms utilize light not only as energy sources but also as signals by which rhodopsins (containing retinal as a chromophore) work as photoreceptors. Sensory rhodopsin I (SRI) is a dual photoreceptor that regulates both negative and positive phototaxis in microbial organisms, such as the archaeon Halobacterium salinarum and the eubacterium Salinibacter ruber. These organisms live in highly halophilic environments, suggesting the possibility of the effects of salts on the function of SRI. However, such effects remain unclear because SRI proteins from H. salinarum (HsSRI) are unstable in dilute salt solutions. Recently, we characterized a new SRI protein (SrSRI) that is stable even in the absence of salts, thus allowing us to investigate the effects of salts on the photochemical properties of SRI. In this study, we report that the absorption maximum of SrSRI is shifted from 542 to 556 nm in a Cl(-)-dependent manner with a K(m) of 307+/-56 mM, showing that Cl(-)-binding sites exist in SRI. The bathochromic shift was caused not only by NaCl but also by other salts (NaI, NaBr, and NaNO(3)), implying that I(-), Br(-), and NO(3)(-) can also bind to SrSRI. In addition, the photochemical properties during the photocycle are also affected by chloride ion binding. Mutagenesis studies strongly suggested that a conserved residue, His131, is involved in the Cl(-)-binding site. In light of these results, we discuss the effects of the Cl(-) binding to SRI and the roles of Cl(-) binding in its function.
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Kitade Y, Furutani Y, Kamo N, Kandori H. Proton Release Group of pharaonis Phoborhodopsin Revealed by ATR-FTIR Spectroscopy. Biochemistry 2009; 48:1595-603. [DOI: 10.1021/bi801984u] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Yuya Kitade
- Department of Frontier Materials, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555, Japan, and Graduate School of Pharmaceutical Sciences, Hokkaido University, Sapporo 060-0810, Japan
| | - Yuji Furutani
- Department of Frontier Materials, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555, Japan, and Graduate School of Pharmaceutical Sciences, Hokkaido University, Sapporo 060-0810, Japan
| | - Naoki Kamo
- Department of Frontier Materials, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555, Japan, and Graduate School of Pharmaceutical Sciences, Hokkaido University, Sapporo 060-0810, Japan
| | - Hideki Kandori
- Department of Frontier Materials, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555, Japan, and Graduate School of Pharmaceutical Sciences, Hokkaido University, Sapporo 060-0810, Japan
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46
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Kitajima-Ihara T, Furutani Y, Suzuki D, Ihara K, Kandori H, Homma M, Sudo Y. Salinibacter sensory rhodopsin: sensory rhodopsin I-like protein from a eubacterium. J Biol Chem 2008; 283:23533-41. [PMID: 18566451 PMCID: PMC3259787 DOI: 10.1074/jbc.m802990200] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2008] [Revised: 06/05/2008] [Indexed: 11/06/2022] Open
Abstract
Halobacterium salinarum sensory rhodopsin I (HsSRI), a dual receptor regulating both negative and positive phototaxis in haloarchaea, transmits light signals through changes in protein-protein interactions with its transducer, halobacterial transducer protein I (HtrI). Haloarchaea also have another sensor pigment, sensory rhodopsin II (SRII), which functions as a receptor regulating negative phototaxis. Compared with HsSRI, the signal relay mechanism of SRII is well characterized because SRII from Natronomonus pharaonis (NpSRII) is much more stable than HsSRI and HsSRII, especially in dilute salt solutions and is much more resistant to detergents. Two genes encoding SRI homologs were identified from the genome sequence of the eubacterium Salinibacter ruber. Those sequences are distantly related to HsSRI ( approximately 40% identity) and contain most of the amino acid residues identified as necessary for its function. To determine whether those genes encode functional protein(s), we cloned and expressed them in Escherichia coli. One of them (SrSRI) was expressed well as a recombinant protein having all-trans retinal as a chromophore. UV-Vis, low-temperature UV-Vis, pH-titration, and flash photolysis experiments revealed that the photochemical properties of SrSRI are similar to those of HsSRI. In addition to the expression system, the high stability of SrSRI makes it possible to prepare large amounts of protein and enables studies of mutant proteins that will allow new approaches to investigate the photosignaling process of SRI-HtrI.
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Affiliation(s)
- Tomomi Kitajima-Ihara
- Division of Biological Science, Graduate
School of Science and the Center for Gene
Research, Nagoya University, Chikusa-Ku, Nagoya, 464-8602, Japan and the
Department of Materials Science and Engineering,
Nagoya Institute of Technology, Showa-ku, Nagoya, 466-8555, Japan
| | - Yuji Furutani
- Division of Biological Science, Graduate
School of Science and the Center for Gene
Research, Nagoya University, Chikusa-Ku, Nagoya, 464-8602, Japan and the
Department of Materials Science and Engineering,
Nagoya Institute of Technology, Showa-ku, Nagoya, 466-8555, Japan
| | - Daisuke Suzuki
- Division of Biological Science, Graduate
School of Science and the Center for Gene
Research, Nagoya University, Chikusa-Ku, Nagoya, 464-8602, Japan and the
Department of Materials Science and Engineering,
Nagoya Institute of Technology, Showa-ku, Nagoya, 466-8555, Japan
| | - Kunio Ihara
- Division of Biological Science, Graduate
School of Science and the Center for Gene
Research, Nagoya University, Chikusa-Ku, Nagoya, 464-8602, Japan and the
Department of Materials Science and Engineering,
Nagoya Institute of Technology, Showa-ku, Nagoya, 466-8555, Japan
| | - Hideki Kandori
- Division of Biological Science, Graduate
School of Science and the Center for Gene
Research, Nagoya University, Chikusa-Ku, Nagoya, 464-8602, Japan and the
Department of Materials Science and Engineering,
Nagoya Institute of Technology, Showa-ku, Nagoya, 466-8555, Japan
| | - Michio Homma
- Division of Biological Science, Graduate
School of Science and the Center for Gene
Research, Nagoya University, Chikusa-Ku, Nagoya, 464-8602, Japan and the
Department of Materials Science and Engineering,
Nagoya Institute of Technology, Showa-ku, Nagoya, 466-8555, Japan
| | - Yuki Sudo
- Division of Biological Science, Graduate
School of Science and the Center for Gene
Research, Nagoya University, Chikusa-Ku, Nagoya, 464-8602, Japan and the
Department of Materials Science and Engineering,
Nagoya Institute of Technology, Showa-ku, Nagoya, 466-8555, Japan
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47
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Abstract
Pharaonis phoborhodopsin (ppR, also called pharaonis sensory rhodopsin II) is a seven transmembrane helical retinal protein. ppR forms a signaling complex with pharaonis Halobacterial transducer II (pHtrII) in the membrane that transmits a light signal to the sensory system in the cytoplasm. The M-state during the photocycle of ppR (lambda(max) = 386 nm) is one of the active (signaling) intermediates. However, progress in characterizing the M-state at physiological temperature has been slow because its lifetime is very short (decay half-time is approximately 1 s). In this study, we identify a highly stable photoproduct that can be trapped at room temperature in buffer solution containing n-octyl-beta-d-glucoside, with a decay half-time and an absorption maximum of approximately 2 h and 386 nm, respectively. HPLC analysis revealed that this stable photoproduct contains 13-cis-retinal as a chromophore. Previously, we reported that water-soluble hydroxylamine reacts selectively with the M-state, and we found that this stable photoproduct also reacts selectively with that reagent. These results suggest that the physical properties of the stable photoproduct (named the M-like state) are very similar with the M-state during the photocycle. By utilizing the high stability of the M-like state, we analyzed interactions of the M-like state and directly estimated the pK(a) value of the Schiff base in the M-like state. These results suggest that the dissociation constant of the ppR(M-like)/pHtrII complex greatly increases (to 5 muM) as the pK(a) value greatly decreases (from 12 to 1.5). The proton transfer reaction of ppR from the cytoplasmic to the extracellular side is proposed to be caused by this change in pK(a).
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48
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Altun A, Yokoyama S, Morokuma K. Quantum mechanical/molecular mechanical studies on spectral tuning mechanisms of visual pigments and other photoactive proteins. Photochem Photobiol 2008; 84:845-54. [PMID: 18331400 DOI: 10.1111/j.1751-1097.2008.00308.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The protein environments surrounding the retinal tune electronic absorption maximum from 350 to 630 nm. Hybrid quantum mechanical/molecular mechanical (QM/MM) methods can be used in calculating excitation energies of retinal in its native protein environments and in studying the molecular basis of spectral tuning. We hereby review recent QM/MM results on the phototransduction of bovine rhodopsin, bacteriorhodopsin, sensory rhodopsin II, nonretinal photoactive yellow protein and their mutants.
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Affiliation(s)
- Ahmet Altun
- Cherry L. Emerson Center for Scientific Computation and Department of Chemistry, Emory University, Atlanta, GA, USA
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49
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Iwasa T, Abe E, Yakura Y, Yoshida H, Kamo N. Tryptophan 171 in Pharaonis phoborhodopsin (sensory rhodopsin II) interacts with the chromophore retinal and its substitution with alanine or threonine slowed down the decay of M- and O-intermediate. Photochem Photobiol 2007; 83:328-35. [PMID: 17029563 DOI: 10.1562/2006-06-15-ra-928] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Pharaonis phoborhodopsin (ppR), also called pharaonis sensory rhodopsin II, NpSRII, is a photoreceptor for the photophobic response of Natronomonas pharaonis. Tryptophan 182 (W182) of bacteriorhodopsin (bR) is near the chromophore retinal and has been suggested to interact with retinal during the photoreaction and also to be involved in the hydrogen-bonding network around the retinal. W182 of bR is conserved in ppR as tryptophan 171 (W171). To elucidate whether W171 of ppR interacts with retinal during the photoreaction and/or is involved in the hydrogen-bonding network as in bR, we formed W171-substituted mutants of ppR, W171A and W171T. Our low-temperature spectroscopic study has revealed that the substitution of W171 to Ala or Thr resulted in the stabilization of M- and O-intermediates. The stability of M and absorption spectral changes during the M-decay were different depending on the substituted residue. These findings suggest that W171 in ppR interacts with retinal and the degree of the interaction depends on the substituted residues, which might be rate determining in the M-decay. In addition, the involvement of W171 in the hydrogen-bonding network is suggested by the O-decay. We also found that glycerol slowed the decay of M and not of O.
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Affiliation(s)
- Tatsuo Iwasa
- Department of Materials Science and Engineering, Muroran Institute of Technology, Muroran, Japan.
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50
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Hoffmann M, Wanko M, Strodel P, König PH, Frauenheim T, Schulten K, Thiel W, Tajkhorshid E, Elstner M. Color tuning in rhodopsins: the mechanism for the spectral shift between bacteriorhodopsin and sensory rhodopsin II. J Am Chem Soc 2007; 128:10808-18. [PMID: 16910676 DOI: 10.1021/ja062082i] [Citation(s) in RCA: 166] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The mechanism of color tuning in the rhodopsin family of proteins has been studied by comparing the optical properties of the light-driven proton pump bacteriorhodopsin (bR) and the light detector sensory rhodopsin II (sRII). Despite a high structural similarity, the maximal absorption is blue-shifted from 568 nm in bR to 497 nm in sRII. The molecular mechanism of this shift is still a matter of debate, and its clarification sheds light onto the general mechanisms of color tuning in retinal proteins. The calculations employ a combined quantum mechanical/molecular mechanical (QM/MM) technique, using a DFT-based method for ground state properties and the semiempirical OM2/MRCI method and ab initio SORCI method for excited state calculations. The high efficiency of the methodology has allowed us to study a wide variety of aspects including dynamical effects. The absorption shift as well as various mutation experiments and vibrational properties have been successfully reproduced. Our results indicate that several sources contribute to the spectral shift between bR and sRII. The main factors are the counterion region at the extracellular side of retinal and the amino acid composition of the binding pocket. Our analysis allows a distinction and identification of the different effects in detail and leads to a clear picture of the mechanism of color tuning, which is in good agreement with available experimental data.
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Affiliation(s)
- Michael Hoffmann
- Theoretische Physik, Universität Paderborn, Warburger Str. 100, 33098 Paderborn, Germany
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