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Urui T, Shionoya T, Mizuno M, Inoue K, Kandori H, Mizutani Y. Chromophore-Protein Interactions Affecting the Polyene Twist and π-π* Energy Gap of the Retinal Chromophore in Schizorhodopsins. J Phys Chem B 2024; 128:2389-2397. [PMID: 38433395 DOI: 10.1021/acs.jpcb.3c08465] [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: 03/05/2024]
Abstract
The properties of a prosthetic group are broadened by interactions with its neighboring residues in proteins. The retinal chromophore in rhodopsins absorbs light, undergoes structural changes, and drives functionally important structural changes in proteins during the photocycle. It is therefore crucial to understand how chromophore-protein interactions regulate the molecular structure and electronic state of chromophores in rhodopsins. Schizorhodopsin is a newly discovered subfamily of rhodopsins found in the genomes of Asgard archaea, which are extant prokaryotes closest to the last common ancestor of eukaryotes and of other microbial species. Here, we report the effects of a hydrogen bond between a retinal Schiff base and its counterion on the twist of the polyene chain and the color of the retinal chromophore. Correlations between spectral features revealed the unexpected fact that the twist of the polyene chain is reduced as the hydrogen bond becomes stronger, suggesting that the twist is caused by tight atomic contacts between the chromophore and nearby residues. In addition, the strength of the hydrogen bond is the primary factor affecting the color-tuning of the retinal chromophore in schizorhodopsins. The findings of this study are valuable for manipulating the molecular structure and electronic state of the chromophore by controlling chromophore-protein interactions.
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Affiliation(s)
- Taito Urui
- Department of Chemistry, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan
| | - Tomomi Shionoya
- Department of Chemistry, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan
| | - Misao Mizuno
- Department of Chemistry, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan
| | - Keiichi Inoue
- The Institute for Solid State Physics, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581, Japan
| | - Hideki Kandori
- Department of Life Science and Applied Chemistry, Nagoya Institute of Technology, Showa-ku, Nagoya, Aichi 466-8555, Japan
| | - Yasuhisa Mizutani
- Department of Chemistry, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan
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Mannen K, Nagata T, Rozenberg A, Konno M, Del Carmen Marín M, Bagherzadeh R, Béjà O, Uchihashi T, Inoue K. Multiple Roles of a Conserved Glutamate Residue for Unique Biophysical Properties in a New Group of Microbial Rhodopsins Homologous to TAT Rhodopsin. J Mol Biol 2024; 436:168331. [PMID: 37898385 DOI: 10.1016/j.jmb.2023.168331] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2023] [Revised: 10/02/2023] [Accepted: 10/21/2023] [Indexed: 10/30/2023]
Abstract
TAT rhodopsin, a microbial rhodopsin found in the marine SAR11 bacterium HIMB114, uniquely possesses a Thr-Ala-Thr (TAT) motif in the third transmembrane helix. Because of a low pKa value of the retinal Schiff base (RSB), TAT rhodopsin exhibits both a visible light-absorbing state with the protonated RSB and a UV-absorbing state with the deprotonated RSB at a neutral pH. The UV-absorbing state, in contrast to the visible light-absorbing one, converts to a long-lived photointermediate upon light absorption, implying that TAT rhodopsin functions as a pH-dependent light sensor. Despite detailed biophysical characterization and mechanistic studies on the TAT rhodopsin, it has been unknown whether other proteins with similarly unusual features exist. Here, we identified several new rhodopsin genes homologous to the TAT rhodopsin of HIMB114 (TATHIMB) from metagenomic data. Based on the absorption spectra of expressed proteins from these genes with visible and UV peaks similar to that of TATHIMB, they were classified as Twin-peaked Rhodopsin (TwR) family. TwR genes form a gene cluster with a set of 13 ORFs conserved in subclade IIIa of SAR11 bacteria. A glutamic acid in the second transmembrane helix, Glu54, is conserved in all of the TwRs. We investigated E54Q mutants of two TwRs and revealed that Glu54 plays critical roles in regulating the RSB pKa, oligomer formation, and the efficient photoreaction of the UV-absorbing state. The discovery of novel TwRs enables us to study the universality and individuality of the characteristics revealed so far in the original TATHIMB and contributes to further studies on mechanisms of unique properties of TwRs.
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Affiliation(s)
- Kentaro Mannen
- The Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - Takashi Nagata
- The Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - Andrey Rozenberg
- Faculty of Biology, Technion - Israel Institute of Technology, Haifa 3200003, Israel
| | - Masae Konno
- The Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - María Del Carmen Marín
- The Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - Reza Bagherzadeh
- The Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - Oded Béjà
- Faculty of Biology, Technion - Israel Institute of Technology, Haifa 3200003, Israel
| | - Takayuki Uchihashi
- Department of Physics, Nagoya University, Nagoya 464-8602, Japan; Exploratory Research Center on Life and Living Systems, National Institutes of Natural Sciences, Okazaki, Aichi 444-8787, Japan; Institute for Glyco-core Research, Nagoya University, Nagoya 464-8602, Japan
| | - Keiichi Inoue
- The Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan.
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Urui T, Hayashi K, Mizuno M, Inoue K, Kandori H, Mizutani Y. Cis- Trans Reisomerization Preceding Reprotonation of the Retinal Chromophore Is Common to the Schizorhodopsin Family: A Simple and Rational Mechanism for Inward Proton Pumping. J Phys Chem B 2024; 128:744-754. [PMID: 38204413 DOI: 10.1021/acs.jpcb.3c07510] [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: 01/12/2024]
Abstract
The creation of unidirectional ion transporters across membranes represents one of the greatest challenges in chemistry. Proton-pumping rhodopsins are composed of seven transmembrane helices with a retinal chromophore bound to a lysine side chain via a Schiff base linkage and provide valuable insights for designing such transporters. What makes these transporters particularly intriguing is the discovery of both outward and inward proton-pumping rhodopsins. Surprisingly, despite sharing identical overall structures and membrane topologies, these proteins facilitate proton transport in opposite directions, implying an underlying rational mechanism that can transport protons in different directions within similar protein structures. In this study, we unraveled this mechanism by examining the chromophore structures of deprotonated intermediates in schizorhodopsins, a recently discovered subfamily of inward proton-pumping rhodopsins, using time-resolved resonance Raman spectroscopy. The photocycle of schizorhodopsins revealed the cis-trans thermal isomerization that precedes reprotonation at the Schiff base of the retinal chromophore. Notably, this order has not been observed in other proton-pumping rhodopsins, but here, it was observed in all seven schizorhodopsins studied across the archaeal domain, strongly suggesting that cis-trans thermal isomerization preceding reprotonation is a universal feature of the schizorhodopsin family. Based on these findings, we propose a structural basis for the remarkable order of events crucial for facilitating inward proton transport. The mechanism underlying inward proton transport by schizorhodopsins is straightforward and rational. The insights obtained from this study hold great promise for the design of transmembrane unidirectional ion transporters.
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Affiliation(s)
- Taito Urui
- Department of Chemistry, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan
| | - Kouhei Hayashi
- Department of Chemistry, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan
| | - Misao Mizuno
- Department of Chemistry, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan
| | - Keiichi Inoue
- The Institute for Solid State Physics, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581, Japan
| | - Hideki Kandori
- Department of Life Science and Applied Chemistry, Nagoya Institute of Technology, Showa-ku, Nagoya, Aichi 466-8555, Japan
| | - Yasuhisa Mizutani
- Department of Chemistry, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan
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Kawasaki Y, Konno M, Inoue K. Kinetic study on the molecular mechanism of light-driven inward proton transport by schizorhodopsins. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2022; 1864:184016. [PMID: 35931184 DOI: 10.1016/j.bbamem.2022.184016] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/14/2022] [Revised: 06/28/2022] [Accepted: 07/14/2022] [Indexed: 06/15/2023]
Abstract
Schizorhodopsins (SzRs) are light-driven inward proton pumping membrane proteins. A H+ is released to the cytoplasmic solvent from the chromophore, retinal Schiff base (RSB), after light absorption, and then another H+ is bound to the RSB at the end of photocyclic reaction. However, the mechanistic detail of H+ transfers in SzR is almost unknown. Here we studied the deuterium isotope effect and the temperature dependence of the reaction rate constants of elementary steps in the photocycles of SzRs. The former indicated that deprotonation and reprotonation of RSB is mainly accomplished by H+ hopping between heavy atoms with similar H+ affinity. Furthermore, the temperature dependence of the rate constants revealed that most of H+ transfer events have a high entropy barrier. In contrast, the activation enthalpy and entropy of extremely thermostable SzR (MsSzR) are significantly higher than other types of SzRs (SzR1 and MtSzR) suggesting that its highly thermostable structure is optimized with at the cost of slower reaction rates at ambient temperatures.
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Affiliation(s)
- Yuma Kawasaki
- The Institute for Solid State Physics, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581, Japan
| | - Masae Konno
- 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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Abstract
Members of candidate Asgardarchaeota superphylum appear to share numerous eukaryotic-like attributes thus being broadly explored for their relevance to eukaryogenesis. On the contrast, the ecological roles of Asgard archaea remains understudied. Asgard archaea have been frequently associated to low-oxygen aquatic sedimentary environments worldwide spanning a broad but not extreme salinity range. To date, the available information on diversity and potential biogeochemical roles of Asgardarchaeota mostly sourced from marine habitats and to a much lesser extend from true saline environments (i.e., > 3% w/v total salinity). Here, we provide an overview on diversity and ecological implications of Asgard archaea distributed across saline environments and briefly explore their metagenome-resolved potential for osmoadaptation. Loki-, Thor- and Heimdallarchaeota are the dominant Asgard clades in saline habitats where they might employ anaerobic/microaerophilic organic matter degradation and autotrophic carbon fixation. Homologs of primary solute uptake ABC transporters seemingly prevail in Thorarchaeota, whereas those putatively involved in trehalose and ectoine biosynthesis were mostly inferred in Lokiarchaeota. We speculate that Asgardarchaeota might adopt compatible solute-accumulating ('salt-out') strategy as response to salt stress. Our current understanding on the distribution, ecology and salt-adaptive strategies of Asgardarchaeota in saline environments are, however, limited by insufficient sampling and incompleteness of the available metagenome-assembled genomes. Extensive sampling combined with 'omics'- and cultivation-based approaches seem, therefore, crucial to gain deeper knowledge on this particularly intriguing archaeal lineage.
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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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Brown LS. Light-driven proton transfers and proton transport by microbial rhodopsins - A biophysical perspective. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2022; 1864:183867. [PMID: 35051382 DOI: 10.1016/j.bbamem.2022.183867] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/29/2021] [Revised: 12/30/2021] [Accepted: 01/10/2022] [Indexed: 12/31/2022]
Abstract
In the last twenty years, our understanding of the rules and mechanisms for the outward light-driven proton transport (and underlying proton transfers) by microbial rhodopsins has been changing dramatically. It transitioned from a very detailed atomic-level understanding of proton transport by bacteriorhodopsin, the prototypical proton pump, to a confounding variety of sequence motifs, mechanisms, directions, and modes of transport in its newly found homologs. In this review, we will summarize and discuss experimental data obtained on new microbial rhodopsin variants, highlighting their contribution to the refinement and generalization of the ideas crystallized in the previous century. In particular, we will focus on the proton transport (and transfers) vectoriality and their structural determinants, which, in many cases, remain unidentified.
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Affiliation(s)
- Leonid S Brown
- Department of Physics and Biophysics Interdepartmental Group, University of Guelph, Ontario N1G 2W1, Canada.
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Yasuda S, Akiyama T, Kojima K, Ueta T, Hayashi T, Ogasawara S, Nagatoishi S, Tsumoto K, Kunishima N, Sudo Y, Kinoshita M, Murata T. Development of an Outward Proton Pumping Rhodopsin with a New Record in Thermostability by Means of Amino Acid Mutations. J Phys Chem B 2022; 126:1004-1015. [PMID: 35089040 DOI: 10.1021/acs.jpcb.1c08684] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
We have developed a methodology for identifying further thermostabilizing mutations for an intrinsically thermostable membrane protein. The methodology comprises the following steps: (1) identifying thermostabilizing single mutations (TSSMs) for residues in the transmembrane region using our physics-based method; (2) identifying TSSMs for residues in the extracellular and intracellular regions, which are in aqueous environment, using an empirical force field FoldX; and (3) combining the TSSMs identified in steps (1) and (2) to construct multiple mutations. The methodology is illustrated for thermophilic rhodopsin whose apparent midpoint temperature of thermal denaturation Tm is ∼91.8 °C. The TSSMs previously identified in step (1) were F90K, F90R, and Y91I with ΔTm ∼5.6, ∼5.5, and ∼2.9 °C, respectively, and those in step (2) were V79K, T114D, A115P, and A116E with ΔTm ∼2.7, ∼4.2, ∼2.6, and ∼2.3 °C, respectively (ΔTm denotes the increase in Tm). In this study, we construct triple and quadruple mutants, F90K+Y91I+T114D and F90K+Y91I+V79K+T114D. The values of ΔTm for these multiple mutants are ∼11.4 and ∼13.5 °C, respectively. Tm of the quadruple mutant (∼105.3 °C) establishes a new record in a class of outward proton pumping rhodopsins. It is higher than Tm of Rubrobacter xylanophilus rhodopsin (∼100.8 °C) that was the most thermostable in the class before this study.
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Affiliation(s)
- Satoshi Yasuda
- Graduate School of Science, Chiba University, 1-33 Yayoi-cho, Inage, Chiba 263-8522, Japan.,Membrane Protein Research and Molecular Chirality Research Centers, Chiba University, 1-33 Yayoi-cho, Inage, Chiba 263-8522, Japan
| | - Tomoki Akiyama
- Graduate School of Science, Chiba University, 1-33 Yayoi-cho, Inage, Chiba 263-8522, Japan
| | - Keiichi Kojima
- Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, Okayama University, Okayama 700-8530, Japan
| | - Tetsuya Ueta
- Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, Okayama University, Okayama 700-8530, Japan
| | - Tomohiko Hayashi
- Interdisciplinary Program of Biomedical Engineering, Assistive Technology, and Art and Sports Sciences, Faculty of Engineering, Niigata University, 8050 Ikarashi 2-no-cho, Nishi-ku, Niigata 950-2181, Japan.,Institute of Advanced Energy, Kyoto University, Uji, Kyoto 611-0011, Japan
| | - Satoshi Ogasawara
- Graduate School of Science, Chiba University, 1-33 Yayoi-cho, Inage, Chiba 263-8522, Japan.,Membrane Protein Research and Molecular Chirality Research Centers, Chiba University, 1-33 Yayoi-cho, Inage, Chiba 263-8522, Japan
| | - Satoru Nagatoishi
- The Institute of Medical Science, The University of Tokyo, 4-6-1, Shirokanedai, Minato-ku, Tokyo 108-8639, Japan
| | - Kouhei Tsumoto
- The Institute of Medical Science, The University of Tokyo, 4-6-1, Shirokanedai, Minato-ku, Tokyo 108-8639, Japan.,Department of Bioengineering, School of Engineering, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Naoki Kunishima
- RIKEN RSC-Rigaku Collaboration Center, RIKEN SPring-8 Center, Sayo-gun, Hyogo 679-5165, Japan
| | - Yuki Sudo
- Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, Okayama University, Okayama 700-8530, Japan
| | - Masahiro Kinoshita
- Graduate School of Science, Chiba University, 1-33 Yayoi-cho, Inage, Chiba 263-8522, Japan.,Membrane Protein Research and Molecular Chirality Research Centers, Chiba University, 1-33 Yayoi-cho, Inage, Chiba 263-8522, Japan.,Institute of Advanced Energy, Kyoto University, Uji, Kyoto 611-0011, Japan
| | - Takeshi Murata
- Graduate School of Science, Chiba University, 1-33 Yayoi-cho, Inage, Chiba 263-8522, Japan.,Membrane Protein Research and Molecular Chirality Research Centers, Chiba University, 1-33 Yayoi-cho, Inage, Chiba 263-8522, Japan
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