1
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Lucas RJ, Allen AE, Brainard GC, Brown TM, Dauchy RT, Didikoglu A, Do MTH, Gaskill BN, Hattar S, Hawkins P, Hut RA, McDowell RJ, Nelson RJ, Prins JB, Schmidt TM, Takahashi JS, Verma V, Voikar V, Wells S, Peirson SN. Recommendations for measuring and standardizing light for laboratory mammals to improve welfare and reproducibility in animal research. PLoS Biol 2024; 22:e3002535. [PMID: 38470868 DOI: 10.1371/journal.pbio.3002535] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/14/2024] Open
Abstract
Light enables vision and exerts widespread effects on physiology and behavior, including regulating circadian rhythms, sleep, hormone synthesis, affective state, and cognitive processes. Appropriate lighting in animal facilities may support welfare and ensure that animals enter experiments in an appropriate physiological and behavioral state. Furthermore, proper consideration of light during experimentation is important both when it is explicitly employed as an independent variable and as a general feature of the environment. This Consensus View discusses metrics to use for the quantification of light appropriate for nonhuman mammals and their application to improve animal welfare and the quality of animal research. It provides methods for measuring these metrics, practical guidance for their implementation in husbandry and experimentation, and quantitative guidance on appropriate light exposure for laboratory mammals. The guidance provided has the potential to improve data quality and contribute to reduction and refinement, helping to ensure more ethical animal use.
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Affiliation(s)
- Robert J Lucas
- Centre for Biological Timing, School of Biological Sciences, Faculty of Biology Medicine and Health, University of Manchester, Manchester, United Kingdom
| | - Annette E Allen
- Centre for Biological Timing, School of Biological Sciences, Faculty of Biology Medicine and Health, University of Manchester, Manchester, United Kingdom
| | - George C Brainard
- Department of Neurology, Thomas Jefferson University, Philadelphia, Pennsylvania, United States of America
| | - Timothy M Brown
- Centre for Biological Timing, School of Biological Sciences, Faculty of Biology Medicine and Health, University of Manchester, Manchester, United Kingdom
| | - Robert T Dauchy
- Department of Structural and Cellular Biology, Tulane University School of Medicine, Tulane, Louisiana, United States of America
| | - Altug Didikoglu
- Department of Neuroscience, Izmir Institute of Technology, Gülbahçe, Urla, Izmir, Turkey
| | - Michael Tri H Do
- F.M. Kirby Neurobiology Center and Department of Neurology, Boston Children's Hospital and Harvard Medical School, Center for Life Science, Boston, Massachusetts, United States of America
| | - Brianna N Gaskill
- Novartis Institute for Biomedical Research, Cambridge, Massachusetts, United States of America
| | - Samer Hattar
- Section on Light and Circadian Rhythms (SLCR), National Institute of Mental Health, John Edward Porter Neuroscience Research Center, Bethesda, Maryland, United States of America
| | | | - Roelof A Hut
- Chronobiology Unit, Groningen Institute of Evolutionary Life Sciences, University of Groningen, Groningen, the Netherlands
| | - Richard J McDowell
- Centre for Biological Timing, School of Biological Sciences, Faculty of Biology Medicine and Health, University of Manchester, Manchester, United Kingdom
| | - Randy J Nelson
- Department of Neuroscience, Rockefeller Neuroscience Institute, West Virginia University, Morgantown, West Virginia, United States of America
| | - Jan-Bas Prins
- The Francis Crick Institute, London, United Kingdom
- Leiden University Medical Centre, Leiden, the Netherlands
| | - Tiffany M Schmidt
- Department of Neurobiology, Northwestern University, Evanston, Illinois, United States of America
| | - Joseph S Takahashi
- Department of Neuroscience, Peter O'Donnell Jr Brain Institute, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
- Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
| | - Vandana Verma
- NASA Ames Research Center, Space Biosciences Division, Moffett Field, California, United States of America
| | - Vootele Voikar
- Laboratory Animal Center and Neuroscience Center, HiLIFE, University of Helsinki, Helsinki, Finland
| | - Sara Wells
- The Mary Lyon Centre, MRC Harwell, Harwell Campus, Oxfordshire, United Kingdom
| | - Stuart N Peirson
- Sleep and Circadian Neuroscience Institute (SCNi), Kavli Institute for Nanoscience Discovery, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
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2
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Tsukamoto H, Kubo Y. A self-inactivating invertebrate opsin optically drives biased signaling toward Gβγ-dependent ion channel modulation. Proc Natl Acad Sci U S A 2023; 120:e2301269120. [PMID: 37186850 PMCID: PMC10214182 DOI: 10.1073/pnas.2301269120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2023] [Accepted: 04/13/2023] [Indexed: 05/17/2023] Open
Abstract
Animal opsins, light-sensitive G protein-coupled receptors, have been used for optogenetic tools to control G protein-dependent signaling pathways. Upon G protein activation, the Gα and Gβγ subunits drive different intracellular signaling pathways, leading to complex cellular responses. For some purposes, Gα- and Gβγ-dependent signaling needs to be separately modulated, but these responses are simultaneously evoked due to the 1:1 stoichiometry of Gα and Gβγ Nevertheless, we show temporal activation of G protein using a self-inactivating invertebrate opsin, Platynereis c-opsin1, drives biased signaling for Gβγ-dependent GIRK channel activation in a light-dependent manner by utilizing the kinetic difference between Gβγ-dependent and Gα-dependent responses. The opsin-induced transient Gi/o activation preferentially causes activation of the kinetically fast Gβγ-dependent GIRK channels rather than slower Gi/oα-dependent adenylyl cyclase inhibition. Although similar Gβγ-biased signaling properties were observed in a self-inactivating vertebrate visual pigment, Platynereis c-opsin1 requires fewer retinal molecules to evoke cellular responses. Furthermore, the Gβγ-biased signaling properties of Platynereis c-opsin1 are enhanced by genetically fusing with RGS8 protein, which accelerates G protein inactivation. The self-inactivating invertebrate opsin and its RGS8-fusion protein can function as optical control tools biased for Gβγ-dependent ion channel modulation.
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Affiliation(s)
- Hisao Tsukamoto
- Department of Biology, Kobe University, Kobe657-8501, Japan
- Department of Life and Coordination-Complex Molecular Science, Institute for Molecular Science, Okazaki444-8585, Japan
- Japan Science and Technology Agency, Precursory Research for Embryonic Science and Technology, Kawaguchi 332-0012, Japan
| | - Yoshihiro Kubo
- Division of Biophysics and Neurobiology, Department of Molecular Physiology, National Institute for Physiological Sciences, Okazaki444-8585, Japan
- Department of Physiological Sciences, The Graduate University for Advanced Studies, Hayama240-0193, Japan
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3
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Sakai K, Ikeuchi H, Fujiyabu C, Imamoto Y, Yamashita T. Convergent evolutionary counterion displacement of bilaterian opsins in ciliary cells. Cell Mol Life Sci 2022; 79:493. [PMID: 36001156 PMCID: PMC11071972 DOI: 10.1007/s00018-022-04525-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2022] [Revised: 08/10/2022] [Accepted: 08/10/2022] [Indexed: 11/26/2022]
Abstract
Opsins are universal photoreceptive proteins in animals. Vertebrate rhodopsin in ciliary photoreceptor cells photo-converts to a metastable active state to regulate cyclic nucleotide signaling. This active state cannot photo-convert back to the dark state, and thus vertebrate rhodopsin is categorized as a mono-stable opsin. By contrast, mollusk and arthropod rhodopsins in rhabdomeric photoreceptor cells photo-convert to a stable active state to stimulate IP3/calcium signaling. This active state can photo-convert back to the dark state, and thus these rhodopsins are categorized as bistable opsins. Moreover, the negatively charged counterion position crucial for the visible light sensitivity is different between vertebrate rhodopsin (Glu113) and mollusk and arthropod rhodopsins (Glu181). This can be explained by an evolutionary scenario where vertebrate rhodopsin newly acquired Glu113 as a counterion, which is thought to have led to higher signaling efficiency of vertebrate rhodopsin. However, the detailed evolutionary steps which led to the higher efficiency in vertebrate rhodopsin still remain unknown. Here, we analyzed the xenopsin group, which is phylogenetically distinct from vertebrate rhodopsin and functions in protostome ciliary cells. Xenopsins are blue-sensitive bistable opsins that regulate cAMP signaling. We found that a bistable xenopsin of Leptochiton asellus had Glu113 as a counterion but did not exhibit elevated signaling efficiency. Therefore, our results show that vertebrate rhodopsin and L. asellus xenopsin regulate cyclic nucleotide signaling in ciliary cells and displaced the counterion position from Glu181 to Glu113 via convergent evolution, whereas subsequently only vertebrate rhodopsin elevated its signaling efficiency by acquiring the mono-stable property.
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Affiliation(s)
- Kazumi Sakai
- Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto, 606-8502, Japan
| | - Hiroki Ikeuchi
- Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto, 606-8502, Japan
| | - Chihiro Fujiyabu
- Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto, 606-8502, Japan
| | - Yasushi Imamoto
- Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto, 606-8502, Japan
| | - Takahiro Yamashita
- Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto, 606-8502, Japan.
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4
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Sakai K, Shichida Y, Imamoto Y, Yamashita T. Creation of photocyclic vertebrate rhodopsin by single amino acid substitution. eLife 2022; 11:75979. [PMID: 35199641 PMCID: PMC8871353 DOI: 10.7554/elife.75979] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Accepted: 02/14/2022] [Indexed: 01/27/2023] Open
Abstract
Opsins are universal photoreceptive proteins in animals and can be classified into three types based on their photoreaction properties. Upon light irradiation, vertebrate rhodopsin forms a metastable active state, which cannot revert back to the original dark state via either photoreaction or thermal reaction. By contrast, after photoreception, most opsins form a stable active state which can photoconvert back to the dark state. Moreover, we recently found a novel type of opsins whose activity is regulated by photocycling. However, the molecular mechanism underlying this diversification of opsins remains unknown. In this study, we showed that vertebrate rhodopsin acquired the photocyclic and photoreversible properties upon introduction of a single mutation at position 188. This revealed that the residue at position 188 contributes to the diversification of photoreaction properties of opsins by its regulation of the recovery from the active state to the original dark state.
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Affiliation(s)
- Kazumi Sakai
- Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto, Japan
| | - Yoshinori Shichida
- Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto, Japan.,Research Organization for Science and technology, Ritsumeikan University, Kusatsu, Japan
| | - Yasushi Imamoto
- Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto, Japan
| | - Takahiro Yamashita
- Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto, Japan
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5
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Amino acid residue at position 188 determines the UV-sensitive bistable property of vertebrate non-visual opsin Opn5. Commun Biol 2022; 5:63. [PMID: 35042952 PMCID: PMC8766551 DOI: 10.1038/s42003-022-03010-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2021] [Accepted: 12/28/2021] [Indexed: 11/09/2022] Open
Abstract
AbstractOpsins are G protein-coupled receptors specialized for photoreception in animals. Opn5 is categorized in an independent opsin group and functions for various non-visual photoreceptions. Among vertebrate Opn5 subgroups (Opn5m, Opn5L1 and Opn5L2), Opn5m and Opn5L2 bind 11-cis retinal to form a UV-sensitive resting state, which is inter-convertible with the all-trans retinal bound active state by photoreception. Thus, these opsins are characterized as bistable opsins. To assess the molecular basis of the UV-sensitive bistable property, we introduced comprehensive mutations at Thr188, which is well conserved among these opsins. The mutations in Opn5m drastically hampered 11-cis retinal incorporation and the bistable photoreaction. Moreover, T188C mutant Opn5m exclusively bound all-trans retinal and thermally self-regenerated to the original form after photoreception, which is similar to the photocyclic property of Opn5L1 bearing Cys188. Therefore, the residue at position 188 underlies the UV-sensitive bistable property of Opn5m and contributes to the diversification of vertebrate Opn5 subgroups.
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6
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Katayama K, Gulati S, Ortega JT, Alexander NS, Sun W, Shenouda MM, Palczewski K, Jastrzebska B. Specificity of the chromophore-binding site in human cone opsins. J Biol Chem 2019; 294:6082-6093. [PMID: 30770468 DOI: 10.1074/jbc.ra119.007587] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2019] [Revised: 02/13/2019] [Indexed: 01/21/2023] Open
Abstract
The variable composition of the chromophore-binding pocket in visual receptors is essential for vision. The visual phototransduction starts with the cis-trans isomerization of the retinal chromophore upon absorption of photons. Despite sharing the common 11-cis-retinal chromophore, rod and cone photoreceptors possess distinct photochemical properties. Thus, a detailed molecular characterization of the chromophore-binding pocket of these receptors is critical to understanding the differences in the photochemistry of vision between rods and cones. Unlike for rhodopsin (Rh), the crystal structures of cone opsins remain to be determined. To obtain insights into the specific chromophore-protein interactions that govern spectral tuning in human visual pigments, here we harnessed the unique binding properties of 11-cis-6-membered-ring-retinal (11-cis-6mr-retinal) with human blue, green, and red cone opsins. To unravel the specificity of the chromophore-binding pocket of cone opsins, we applied 11-cis-6mr-retinal analog-binding analyses to human blue, green, and red cone opsins. Our results revealed that among the three cone opsins, only blue cone opsin can accommodate the 11-cis-6mr-retinal in its chromophore-binding pocket, resulting in the formation of a synthetic blue pigment (B6mr) that absorbs visible light. A combination of primary sequence alignment, molecular modeling, and mutagenesis experiments revealed the specific amino acid residue 6.48 (Tyr-262 in blue cone opsins and Trp-281 in green and red cone opsins) as a selectivity filter in human cone opsins. Altogether, the results of our study uncover the molecular basis underlying the binding selectivity of 11-cis-6mr-retinal to the cone opsins.
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Affiliation(s)
- Kota Katayama
- From the Department of Pharmacology, Cleveland Center for Membrane and Structural Biology, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106; Department of Life Science and Applied Chemistry, Showa-ku, Nagoya 466-8555, Japan; OptoBio Technology Research Center, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555, Japan
| | - Sahil Gulati
- Gavin Herbert Eye Institute and the Department of Ophthalmology, University of California, Irvine, California 92697
| | - Joseph T Ortega
- From the Department of Pharmacology, Cleveland Center for Membrane and Structural Biology, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106
| | - Nathan S Alexander
- From the Department of Pharmacology, Cleveland Center for Membrane and Structural Biology, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106
| | - Wenyu Sun
- Polgenix Inc., Cleveland, Ohio 44106
| | - Marina M Shenouda
- From the Department of Pharmacology, Cleveland Center for Membrane and Structural Biology, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106
| | - Krzysztof Palczewski
- Gavin Herbert Eye Institute and the Department of Ophthalmology, University of California, Irvine, California 92697; Polgenix Inc., Cleveland, Ohio 44106.
| | - Beata Jastrzebska
- From the Department of Pharmacology, Cleveland Center for Membrane and Structural Biology, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106.
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7
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Opn5L1 is a retinal receptor that behaves as a reverse and self-regenerating photoreceptor. Nat Commun 2018; 9:1255. [PMID: 29593298 PMCID: PMC5871776 DOI: 10.1038/s41467-018-03603-3] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2017] [Accepted: 02/25/2018] [Indexed: 11/09/2022] Open
Abstract
Most opsins are G protein-coupled receptors that utilize retinal both as a ligand and as a chromophore. Opsins' main established mechanism is light-triggered activation through retinal 11-cis-to-all-trans photoisomerization. Here we report a vertebrate non-visual opsin that functions as a Gi-coupled retinal receptor that is deactivated by light and can thermally self-regenerate. This opsin, Opn5L1, binds exclusively to all-trans-retinal. More interestingly, the light-induced deactivation through retinal trans-to-cis isomerization is followed by formation of a covalent adduct between retinal and a nearby cysteine, which breaks the retinal-conjugated double bond system, probably at the C11 position, resulting in thermal re-isomerization to all-trans-retinal. Thus, Opn5L1 acts as a reverse photoreceptor. We conclude that, like vertebrate rhodopsin, Opn5L1 is a unidirectional optical switch optimized from an ancestral bidirectional optical switch, such as invertebrate rhodopsin, to increase the S/N ratio of the signal transduction, although the direction of optimization is opposite to that of vertebrate rhodopsin.
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8
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Sakai K, Tsutsui K, Yamashita T, Iwabe N, Takahashi K, Wada A, Shichida Y. Drosophila melanogaster rhodopsin Rh7 is a UV-to-visible light sensor with an extraordinarily broad absorption spectrum. Sci Rep 2017; 7:7349. [PMID: 28779161 PMCID: PMC5544684 DOI: 10.1038/s41598-017-07461-9] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2017] [Accepted: 06/28/2017] [Indexed: 01/15/2023] Open
Abstract
The genome of Drosophila melanogaster contains seven rhodopsin genes. Rh1-6 proteins are known to have respective absorption spectra and function as visual pigments in ocelli and compound eyes. In contrast, Rh7 protein was recently revealed to function as a circadian photoreceptor in the brain. However, its molecular properties have not been characterized yet. Here we successfully prepared a recombinant protein of Drosophila Rh7 in mammalian cultured cells. Drosophila Rh7 bound both 11-cis-retinal and 11-cis-3-hydroxyretinal to form photo-pigments which can absorb UV light. Irradiation with UV light caused formation of a visible-light absorbing metarhodopsin that activated Gq-type of G protein. This state could be photoconverted back to the original state and, thus Rh7 is a Gq-coupled bistable pigment. Interestingly, Rh7 (lambda max = 350 nm) exhibited an unusual broad spectrum with a longer wavelength tail reaching 500 nm, whose shape is like a composite of spectra of two pigments. In contrast, replacement of lysine at position 90 with glutamic acid caused the formation of a normal-shaped absorption spectrum with maximum at 450 nm. Therefore, Rh7 is a unique photo-sensor that can cover a wide wavelength region by a single pigment to contribute to non-visual photoreception.
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Affiliation(s)
- Kazumi Sakai
- Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto, 606-8502, Japan
| | - Kei Tsutsui
- Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto, 606-8502, Japan
| | - Takahiro Yamashita
- Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto, 606-8502, Japan
| | - Naoyuki Iwabe
- Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto, 606-8502, Japan
| | - Keisuke Takahashi
- Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto, 606-8502, Japan
| | - Akimori Wada
- Department of Organic Chemistry for Life Science, Kobe Pharmaceutical University, Kobe, 658-8558, Japan
| | - Yoshinori Shichida
- Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto, 606-8502, Japan. .,Research Organization for Science and Technology, Ritsumeikan University, Kusatsu, Shiga, 525-8577, Japan.
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9
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Evolutionary steps involving counterion displacement in a tunicate opsin. Proc Natl Acad Sci U S A 2017; 114:6028-6033. [PMID: 28533401 DOI: 10.1073/pnas.1701088114] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Ci-opsin1 is a visible light-sensitive opsin present in the larval ocellus of an ascidian, Ciona intestinalis This invertebrate opsin belongs to the vertebrate visual and nonvisual opsin groups in the opsin phylogenetic tree. Ci-opsin1 contains candidate counterions (glutamic acid residues) at positions 113 and 181; the former is a newly acquired position in the vertebrate visual opsin lineage, whereas the latter is an ancestral position widely conserved among invertebrate opsins. Here, we show that Glu113 and Glu181 in Ci-opsin1 act synergistically as counterions, which imparts molecular properties to Ci-opsin1 intermediate between those of vertebrate- and invertebrate-type opsins. Synergy between the counterions in Ci-opsin1 was demonstrated by E113Q and E181Q mutants that exhibit a pH-dependent spectral shift, whereas only the E113Q mutation in vertebrate rhodopsin yields this spectral shift. On absorbing light, Ci-opsin1 forms an equilibrium between two intermediates with protonated and deprotonated Schiff bases, namely the MI-like and MII-like intermediates, respectively. Adding G protein caused the equilibrium to shift toward the MI-like intermediate, indicating that Ci-opsin1 has a protonated Schiff base in its active state, like invertebrate-type opsins. Ci-opsin1's G protein activation efficiency is between the efficiencies of vertebrate- and invertebrate-type opsins. Interestingly, the E113Y and E181S mutations change the molecular properties of Ci-opsin1 into those resembling invertebrate-type or bistable opsins and vertebrate ancient/vertebrate ancient-long or monostable opsins, respectively. These results strongly suggest that acquisition of counterion Glu113 changed the molecular properties of visual opsin in a vertebrate/tunicate common ancestor as a crucial step in the evolution of vertebrate visual opsins.
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10
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Photocyclic behavior of rhodopsin induced by an atypical isomerization mechanism. Proc Natl Acad Sci U S A 2017; 114:E2608-E2615. [PMID: 28289214 DOI: 10.1073/pnas.1617446114] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Vertebrate rhodopsin (Rh) contains 11-cis-retinal as a chromophore to convert light energy into visual signals. On absorption of light, 11-cis-retinal is isomerized to all-trans-retinal, constituting a one-way reaction that activates transducin (Gt) followed by chromophore release. Here we report that bovine Rh, regenerated instead with a six-carbon-ring retinal chromophore featuring a C11=C12 double bond locked in its cis conformation (Rh6mr), employs an atypical isomerization mechanism by converting 11-cis to an 11,13-dicis configuration for prolonged Gt activation. Time-dependent UV-vis spectroscopy, HPLC, and molecular mechanics analyses revealed an atypical thermal reisomerization of the 11,13-dicis to the 11-cis configuration on a slow timescale, which enables Rh6mr to function in a photocyclic manner similar to that of microbial Rhs. With this photocyclic behavior, Rh6mr repeatedly recruits and activates Gt in response to light stimuli, making it an excellent candidate for optogenetic tools based on retinal analog-bound vertebrate Rhs. Overall, these comprehensive structure-function studies unveil a unique photocyclic mechanism of Rh activation by an 11-cis-to-11,13-dicis isomerization.
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11
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Abstract
Cones are photoreceptor cells used for bright light and color vision. Retinoids are vitamin A derivatives, one of which is the 11-cis aldehyde form that serves as the chromophore for both cone and rod visual pigments. In the visual disease, Type 2 Leber congenital amaurosis (LCA2), 11-cis-retinal generation is inhibited or abolished. Work by others has shown that patients with LCA2 have symptoms consistent with degenerating cones. In mouse models for LCA2, early cone degeneration is readily apparent: cone opsins and other proteins associated with the outer segment are delocalized and cell numbers decline rapidly within the first month. Rods would appear normal morphologically and functionally, if not for the absence of chromophore. Supplementation of mouse models of LCA2 with cis-retinoids has been shown to slow loss of cone photoreceptor cells if mice were maintained in darkness. Thus, 11-cis-retinal appears not only to have a role in the light response reaction but also to promote proper trafficking of the cone opsins and maintain viable cones.
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Affiliation(s)
- Masahiro Kono
- Department of Ophthalmology, Albert Florens Storm Eye Institute, Medical University of South Carolina, Charleston, South Carolina, USA.
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12
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Kubli-Garfias C, Vázquez-Ramírez R, Cabrera-Vivas BM, Gómez-Reyes B, Ramírez JC. Atomic and molecular analysis highlights the biophysics of unprotonated and protonated retinal in UV and scotopic vision. Photochem Photobiol Sci 2015; 14:1660-72. [DOI: 10.1039/c5pp00091b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Unprotonated (UR) and protonated (PR) retinal have marked atomic and molecular differences in cis and trans configurations. In conclusion, UR and PR uphold UV and light vision through their different biophysical properties.
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Affiliation(s)
- Carlos Kubli-Garfias
- Instituto de Investigaciones Biomédicas
- Universidad Nacional Autónoma de México
- México
- Mexico
| | | | | | | | - Juan Carlos Ramírez
- Facultad de Ciencias Químicas
- Benemérita Universidad Autónoma de Puebla
- Puebla 72530
- Mexico
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13
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Mooney V, Sekharan S, Liu J, Guo Y, Batista VS, Yan ECY. Kinetics of thermal activation of an ultraviolet cone pigment. J Am Chem Soc 2014; 137:307-13. [PMID: 25514632 DOI: 10.1021/ja510553f] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Visual pigments can be thermally activated via isomerization of the retinyl chromophore and hydrolysis of the Schiff base (SB) through which the retinyl chromophore is bound to the opsin protein. Here, we present the first combined experimental and theoretical study of the thermal activation of a Siberian hamster ultraviolet (SHUV) pigment. We measured the rates of thermal isomerization and hydrolysis in the SHUV pigment and bovine rhodopsin. We found that these rates were significantly faster in the UV pigment than in rhodopsin due to the difference in the structural and electrostatic effects surrounding the unprotonated Schiff base (USB) retinyl chromophore in the UV pigment. Theoretical (DFT-QM/MM) calculations of the cis-trans thermal isomerization revealed a barrier of ∼23 kcal/mol for the USB retinyl chromophore in SHUV compared to ∼40 kcal/mol for protonated Schiff base (PSB) chromophore in rhodopsin. The lower barrier for thermal isomerization in the SHUV pigment is attributed to the (i) lessening of the steric restraints near the β-ionone ring and SB ends of the chromophore, (ii) displacement of the transmembrane helix 6 (TM6) away from the binding pocket toward TM5 due to absence of the salt bridge between the USB and the protonated E113 residue, and (iii) change in orientation of the hydrogen-bonding networks (HBNs) in the extracellular loop 2 (EII). The results in comparing thermal stability of UV cone pigment and rhodopsin provide insight into molecular evolution of vertebrate visual pigments in achieving low discrete dark noise and high photosensitivity in rod pigments for dim-light vision.
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Affiliation(s)
- Victoria Mooney
- Department of Chemistry, Yale University , New Haven, Connecticut 06520 United States
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14
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Hauser FE, van Hazel I, Chang BSW. Spectral tuning in vertebrate short wavelength-sensitive 1 (SWS1) visual pigments: Can wavelength sensitivity be inferred from sequence data? JOURNAL OF EXPERIMENTAL ZOOLOGY PART B-MOLECULAR AND DEVELOPMENTAL EVOLUTION 2014; 322:529-39. [DOI: 10.1002/jez.b.22576] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/10/2013] [Revised: 03/05/2014] [Accepted: 05/06/2014] [Indexed: 01/12/2023]
Affiliation(s)
- Frances E. Hauser
- Department of Ecology & Evolutionary Biology; University of Toronto; Toronto Ontario Canada
| | - Ilke van Hazel
- Department of Ecology & Evolutionary Biology; University of Toronto; Toronto Ontario Canada
| | - Belinda S. W. Chang
- Department of Ecology & Evolutionary Biology; University of Toronto; Toronto Ontario Canada
- Department of Cell & Systems Biology; University of Toronto; Toronto Ontario Canada
- Centre for the Analysis of Genome Evolution & Function; University of Toronto; Toronto Ontario Canada
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15
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Yamashita T, Ono K, Ohuchi H, Yumoto A, Gotoh H, Tomonari S, Sakai K, Fujita H, Imamoto Y, Noji S, Nakamura K, Shichida Y. Evolution of mammalian Opn5 as a specialized UV-absorbing pigment by a single amino acid mutation. J Biol Chem 2014; 289:3991-4000. [PMID: 24403072 DOI: 10.1074/jbc.m113.514075] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Opn5 is one of the recently identified opsin groups that is responsible for nonvisual photoreception in animals. We previously showed that a chicken homolog of mammalian Opn5 (Opn5m) is a Gi-coupled UV sensor having molecular properties typical of bistable pigments. Here we demonstrated that mammalian Opn5m evolved to be a more specialized photosensor by losing one of the characteristics of bistable pigments, direct binding of all-trans-retinal. We first confirmed that Opn5m proteins in zebrafish, Xenopus tropicalis, mouse, and human are also UV-sensitive pigments. Then we found that only mammalian Opn5m proteins lack the ability to directly bind all-trans-retinal. Mutational analysis showed that these characteristics were acquired by a single amino acid replacement at position 168. By comparing the expression patterns of Opn5m between mammals and chicken, we found that, like chicken Opn5m, mammalian Opn5m was localized in the ganglion cell layer and inner nuclear layer of the retina. However, the mouse and primate (common marmoset) opsins were distributed not in the posterior hypothalamus (including the region along the third ventricle) where chicken Opn5m is localized, but in the preoptic hypothalamus. Interestingly, RPE65, an essential enzyme for forming 11-cis-retinal in the visual cycle is expressed near the preoptic hypothalamus of the mouse and common marmoset brain but not near the region of the chicken brain where chicken Opn5m is expressed. Therefore, mammalian Opn5m may work exclusively as a short wavelength sensor in the brain as well as in the retina with the assistance of an 11-cis-retinal-supplying system.
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Affiliation(s)
- Takahiro Yamashita
- From the Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
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16
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van Hazel I, Sabouhanian A, Day L, Endler JA, Chang BSW. Functional characterization of spectral tuning mechanisms in the great bowerbird short-wavelength sensitive visual pigment (SWS1), and the origins of UV/violet vision in passerines and parrots. BMC Evol Biol 2013; 13:250. [PMID: 24499383 PMCID: PMC4029201 DOI: 10.1186/1471-2148-13-250] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2013] [Accepted: 11/01/2013] [Indexed: 12/18/2022] Open
Abstract
Background One of the most striking features of avian vision is the variation in spectral sensitivity of the short wavelength sensitive (SWS1) opsins, which can be divided into two sub-types: violet- and UV- sensitive (VS & UVS). In birds, UVS has been found in both passerines and parrots, groups that were recently shown to be sister orders. While all parrots are thought to be UVS, recent evidence suggests some passerine lineages may also be VS. The great bowerbird (Chlamydera nuchalis) is a passerine notable for its courtship behaviours in which males build and decorate elaborate bower structures. Results The great bowerbird SWS1 sequence possesses an unusual residue combination at known spectral tuning sites that has not been previously investigated in mutagenesis experiments. In this study, the SWS1 opsin of C. nuchalis was expressed along with a series of spectral tuning mutants and ancestral passerine SWS1 pigments, allowing us to investigate spectral tuning mechanisms and explore the evolution of UV/violet sensitivity in early passerines and parrots. The expressed C. nuchalis SWS1 opsin was found to be a VS pigment, with a λmax of 403 nm. Bowerbird SWS1 mutants C86F, S90C, and C86S/S90C all shifted λmax into the UV, whereas C86S had no effect. Experimentally recreated ancestral passerine and parrot/passerine SWS1 pigments were both found to be VS, indicating that UV sensitivity evolved independently in passerines and parrots from a VS ancestor. Conclusions Our mutagenesis studies indicate that spectral tuning in C. nuchalis is mediated by mechanisms similar to those of other birds. Interestingly, our ancestral sequence reconstructions of SWS1 in landbird evolution suggest multiple transitions from VS to UVS, but no instances of the reverse. Our results not only provide a more precise prediction of where these spectral sensitivity shifts occurred, but also confirm the hypothesis that birds are an unusual exception among vertebrates where some descendants re-evolved UVS from a violet type ancestor. The re-evolution of UVS from a VS type pigment has not previously been predicted elsewhere in the vertebrate phylogeny.
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Affiliation(s)
| | | | | | | | - Belinda S W Chang
- Department of Ecology & Evolutionary, Biology University of Toronto, Toronto, Canada.
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17
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Imamoto Y, Shichida Y. Cone visual pigments. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2013; 1837:664-73. [PMID: 24021171 DOI: 10.1016/j.bbabio.2013.08.009] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/14/2013] [Revised: 08/07/2013] [Accepted: 08/30/2013] [Indexed: 12/16/2022]
Abstract
Cone visual pigments are visual opsins that are present in vertebrate cone photoreceptor cells and act as photoreceptor molecules responsible for photopic vision. Like the rod visual pigment rhodopsin, which is responsible for scotopic vision, cone visual pigments contain the chromophore 11-cis-retinal, which undergoes cis-trans isomerization resulting in the induction of conformational changes of the protein moiety to form a G protein-activating state. There are multiple types of cone visual pigments with different absorption maxima, which are the molecular basis of color discrimination in animals. Cone visual pigments form a phylogenetic sister group with non-visual opsin groups such as pinopsin, VA opsin, parapinopsin and parietopsin groups. Cone visual pigments diverged into four groups with different absorption maxima, and the rhodopsin group diverged from one of the four groups of cone visual pigments. The photochemical behavior of cone visual pigments is similar to that of pinopsin but considerably different from those of other non-visual opsins. G protein activation efficiency of cone visual pigments is also comparable to that of pinopsin but higher than that of the other non-visual opsins. Recent measurements with sufficient time-resolution demonstrated that G protein activation efficiency of cone visual pigments is lower than that of rhodopsin, which is one of the molecular bases for the lower amplification of cones compared to rods. In this review, the uniqueness of cone visual pigments is shown by comparison of their molecular properties with those of non-visual opsins and rhodopsin. 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)
- Yasushi Imamoto
- Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
| | - Yoshinori Shichida
- Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan.
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18
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Kuemmel CM, Sandberg MN, Birge RR, Knox BE. A Conserved Aromatic Residue Regulating Photosensitivity in Short-Wavelength Sensitive Cone Visual Pigments. Biochemistry 2013; 52:5084-91. [DOI: 10.1021/bi400490g] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Colleen M. Kuemmel
- Departments of Neuroscience
and Physiology, Biochemistry and Molecular Biology, and Ophthalmology, SUNY Upstate Medical University, Syracuse, New York
13210, United States
| | - Megan N. Sandberg
- Departments
of Chemistry and
Molecular and Cell Biology, University of Connecticut, Storrs, Connecticut
06269, United States
| | - Robert R. Birge
- Departments
of Chemistry and
Molecular and Cell Biology, University of Connecticut, Storrs, Connecticut
06269, United States
| | - Barry E. Knox
- Departments of Neuroscience
and Physiology, Biochemistry and Molecular Biology, and Ophthalmology, SUNY Upstate Medical University, Syracuse, New York
13210, United States
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19
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Sakai K, Imamoto Y, Su CY, Tsukamoto H, Yamashita T, Terakita A, Yau KW, Shichida Y. Photochemical nature of parietopsin. Biochemistry 2012; 51:1933-41. [PMID: 22303823 DOI: 10.1021/bi2018283] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Parietopsin is a nonvisual green light-sensitive opsin closely related to vertebrate visual opsins and was originally identified in lizard parietal eye photoreceptor cells. To obtain insight into the functional diversity of opsins, we investigated by UV-visible absorption spectroscopy the molecular properties of parietopsin and its mutants exogenously expressed in cultured cells and compared the properties to those of vertebrate and invertebrate visual opsins. Our mutational analysis revealed that the counterion in parietopsin is the glutamic acid (Glu) in the second extracellular loop, corresponding to Glu181 in bovine rhodopsin. This arrangement is characteristic of invertebrate rather than vertebrate visual opsins. The photosensitivity and the molar extinction coefficient of parietopsin were also lower than those of vertebrate visual opsins, features likewise characteristic of invertebrate visual opsins. On the other hand, irradiation of parietopsin yielded meta-I, meta-II, and meta-III intermediates after batho and lumi intermediates, similar to vertebrate visual opsins. The pH-dependent equilibrium profile between meta-I and meta-II intermediates was, however, similar to that between acid and alkaline metarhodopsins in invertebrate visual opsins. Thus, parietopsin behaves as an "evolutionary intermediate" between invertebrate and vertebrate visual opsins.
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Affiliation(s)
- Kazumi Sakai
- Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
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20
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Ohuchi H, Yamashita T, Tomonari S, Fujita-Yanagibayashi S, Sakai K, Noji S, Shichida Y. A non-mammalian type opsin 5 functions dually in the photoreceptive and non-photoreceptive organs of birds. PLoS One 2012; 7:e31534. [PMID: 22348098 PMCID: PMC3279408 DOI: 10.1371/journal.pone.0031534] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2011] [Accepted: 01/09/2012] [Indexed: 11/23/2022] Open
Abstract
A mammalian type opsin 5 (neuropsin) is a recently identified ultraviolet (UV)-sensitive pigment of the retina and other photosensitive organs in birds. Two other opsin 5-related molecules have been found in the genomes of non-mammalian vertebrates. However, their functions have not been examined as yet. Here, we identify the molecular properties of a second avian opsin 5, cOpn5L2 (chicken opsin 5-like 2), and its localization in the post-hatch chicken. Spectrophotometric analysis and radionucleotide-binding assay have revealed that cOpn5L2 is a UV-sensitive bistable pigment that couples with the Gi subtype of guanine nucleotide-binding protein (G protein). As a bistable pigment, it also shows the direct binding ability to agonist all-trans-retinal to activate G protein. The absorption maxima of UV-light-absorbing and visible light-absorbing forms were 350 and 521 nm, respectively. Expression analysis showed relatively high expression of cOpn5L2 mRNA in the adrenal gland, which is not photoreceptive but an endocrine organ, while lower expression was found in the brain and retina. At the protein level, cOpn5L2 immunoreactive cells were present in the chromaffin cells of the adrenal gland. In the brain, cOpn5L2 immunoreactive cells were found in the paraventricular and supraoptic nuclei of the anterior hypothalamus, known for photoreceptive deep brain areas. In the retina, cOpn5L2 protein was localized to subsets of cells in the ganglion cell layer and the inner nuclear layer. These results suggest that the non-mammalian type opsin 5 (Opn5L2) functions as a second UV sensor in the photoreceptive organs, while it might function as chemosensor using its direct binding ability to agonist all-trans-retinal in non-photoreceptive organs such as the adrenal gland of birds.
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Affiliation(s)
- Hideyo Ohuchi
- Department of Life Systems, Institute of Technology and Science, University of Tokushima Graduate School, Tokushima, Japan.
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21
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Hernández-Rodríguez EW, Sánchez-García E, Crespo-Otero R, Montero-Alejo AL, Montero LA, Thiel W. Understanding Rhodopsin Mutations Linked to the Retinitis pigmentosa Disease: a QM/MM and DFT/MRCI Study. J Phys Chem B 2012; 116:1060-76. [DOI: 10.1021/jp2037334] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Affiliation(s)
- Erix Wiliam Hernández-Rodríguez
- Departamento de Bioquímica, Instituto de Ciencias Básicas y Preclínicas “Victoria de Girón”, 11600 Havana City, Cuba, and Charité Centrum für Innere Medizin und Dermatologie, Biomedizinisches Forschungszentrum, Campus Virchow, Charité-Universitätsmedizin, 13353 Berlin, Germany
| | | | | | - Ana Lilian Montero-Alejo
- Laboratorio de Química Computacional y Teórica, Departamento de Química Física, Universidad de La Habana, 10400 Havana City, Cuba
| | - Luis Alberto Montero
- Laboratorio de Química Computacional y Teórica, Departamento de Química Física, Universidad de La Habana, 10400 Havana City, Cuba
| | - Walter Thiel
- Max-Planck-Institut für Kohlenforschung, Mülheim an der Ruhr, 45470 Germany
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22
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Sato K, Yamashita T, Ohuchi H, Shichida Y. Vertebrate Ancient-Long Opsin Has Molecular Properties Intermediate between Those of Vertebrate and Invertebrate Visual Pigments. Biochemistry 2011; 50:10484-90. [DOI: 10.1021/bi201212z] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Keita Sato
- Department of Biophysics, Graduate
School of Science, Kyoto University, Kyoto
606-8502, Japan
| | - Takahiro Yamashita
- Department of Biophysics, Graduate
School of Science, Kyoto University, Kyoto
606-8502, Japan
| | - Hideyo Ohuchi
- Department
of Life Systems,
Institute of Technology and Science, University of Tokushima, Tokushima 770-8506, Japan
| | - Yoshinori Shichida
- Department of Biophysics, Graduate
School of Science, Kyoto University, Kyoto
606-8502, Japan
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23
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Liu J, Liu MY, Fu L, Zhu GA, Yan ECY. Chemical kinetic analysis of thermal decay of rhodopsin reveals unusual energetics of thermal isomerization and hydrolysis of Schiff base. J Biol Chem 2011; 286:38408-38416. [PMID: 21921035 PMCID: PMC3207414 DOI: 10.1074/jbc.m111.280602] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2011] [Revised: 09/07/2011] [Indexed: 11/06/2022] Open
Abstract
The thermal properties of rhodopsin, which set the threshold of our vision, have long been investigated, but the chemical kinetics of the thermal decay of rhodopsin has not been revealed in detail. To understand thermal decay quantitatively, we propose a kinetic model consisting of two pathways: 1) thermal isomerization of 11-cis-retinal followed by hydrolysis of Schiff base (SB) and 2) hydrolysis of SB in dark state rhodopsin followed by opsin-catalyzed isomerization of free 11-cis-retinal. We solve the kinetic model mathematically and use it to analyze kinetic data from four experiments that we designed to assay thermal decay, isomerization, hydrolysis of SB using dark state rhodopsin, and hydrolysis of SB using photoactivated rhodopsin. We apply the model to WT rhodopsin and E181Q and S186A mutants at 55 °C, as well as WT rhodopsin in H(2)O and D(2)O at 59 °C. The results show that the hydrogen-bonding network strongly restrains thermal isomerization but is less important in opsin and activated rhodopsin. Furthermore, the ability to obtain individual rate constants allows comparison of thermal processes under various conditions. Our kinetic model and experiments reveal two unusual energetic properties: the steep temperature dependence of the rates of thermal isomerization and SB hydrolysis in the dark state and a strong deuterium isotope effect on dark state SB hydrolysis. These findings can be applied to study pathogenic rhodopsin mutants and other visual pigments.
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Affiliation(s)
- Jian Liu
- Department of Chemistry, Yale University, New Haven, Connecticut 06520
| | - Monica Yun Liu
- Department of Chemistry, Yale University, New Haven, Connecticut 06520
| | - Li Fu
- Department of Chemistry, Yale University, New Haven, Connecticut 06520
| | - Gefei Alex Zhu
- Department of Chemistry, Yale University, New Haven, Connecticut 06520
| | - Elsa C Y Yan
- Department of Chemistry, Yale University, New Haven, Connecticut 06520.
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24
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Liu J, Liu MY, Nguyen JB, Bhagat A, Mooney V, Yan ECY. Thermal properties of rhodopsin: insight into the molecular mechanism of dim-light vision. J Biol Chem 2011; 286:27622-9. [PMID: 21659526 PMCID: PMC3149353 DOI: 10.1074/jbc.m111.233312] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2011] [Revised: 05/23/2011] [Indexed: 11/06/2022] Open
Abstract
Rhodopsin has developed mechanisms to optimize its sensitivity to light by suppressing dark noise and enhancing quantum yield. We propose that an intramolecular hydrogen-bonding network formed by ∼20 water molecules, the hydrophilic residues, and peptide backbones in the transmembrane region is essential to restrain thermal isomerization, the source of dark noise. We studied the thermal stability of rhodopsin at 55 °C with single point mutations (E181Q and S186A) that perturb the hydrogen-bonding network at the active site. We found that the rate of thermal isomerization increased by 1-2 orders of magnitude in the mutants. Our results illustrate the importance of the intact hydrogen-bonding network for dim-light detection, revealing the functional roles of water molecules in rhodopsin. We also show that thermal isomerization of 11-cis-retinal in solution can be catalyzed by wild-type opsin and that this catalytic property is not affected by the mutations. We characterize the catalytic effect and propose that it is due to steric interactions in the retinal-binding site and increases quantum yield by predetermining the trajectory of photoisomerization. Thus, our studies reveal a balancing act between dark noise and quantum yield, which have opposite effects on the thermal isomerization rate. The acquisition of the hydrogen-bonding network and the tuning of the steric interactions at the retinal-binding site are two important factors in the development of dim-light vision.
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Affiliation(s)
- Jian Liu
- From the Department of Chemistry, Yale University, New Haven, Connecticut 06520
| | - Monica Yun Liu
- From the Department of Chemistry, Yale University, New Haven, Connecticut 06520
| | - Jennifer B. Nguyen
- From the Department of Chemistry, Yale University, New Haven, Connecticut 06520
| | - Aditi Bhagat
- From the Department of Chemistry, Yale University, New Haven, Connecticut 06520
| | - Victoria Mooney
- From the Department of Chemistry, Yale University, New Haven, Connecticut 06520
| | - Elsa C. Y. Yan
- From the Department of Chemistry, Yale University, New Haven, Connecticut 06520
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25
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Opn5 is a UV-sensitive bistable pigment that couples with Gi subtype of G protein. Proc Natl Acad Sci U S A 2010; 107:22084-9. [PMID: 21135214 DOI: 10.1073/pnas.1012498107] [Citation(s) in RCA: 141] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Opn5 (neuropsin) belongs to an independent group separated from the other six groups in the phylogenetic tree of opsins, for which little information of absorption characteristics and molecular properties of the members is available. Here we show that the chicken Opn5 (cOpn5m) is a UV-sensitive bistable pigment that couples with Gi subtype of G protein. The recombinant expression of cOpn5m in HEK 293s cells followed by the addition of 11-cis- and all-trans-retinal produced UV light-absorbing and visible light-absorbing forms, respectively. These forms were interconvertible by UV and visible light irradiations, respectively, indicating that cOpn5m is a bistable pigment. The absorption maxima of these forms were estimated to be 360 and 474 nm, respectively. The GTPγS binding assay clearly showed that the visible light-absorbing form having all-trans-retinal activates Gi type of G protein, whereas no Gt or Gq activation ability was observed. Immunohistochemical studies using an antibody against cOpn5m clearly showed that this pigment is localized within some types of amacrine cells and some cells in the ganglion cell layer of the retinas, the vast majority of cells in the pineal gland and serotonin-positive cells in the paraventricular organ. Because cOpn5m is the only UV-sensitive opsin among the opsins found so far in chicken, this study provides the molecular basis for UV reception in chicken.
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26
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Tsutsui K, Shichida Y. Photosensitivities of Rhodopsin Mutants with a Displaced Counterion. Biochemistry 2010; 49:10089-97. [DOI: 10.1021/bi101020p] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Kei Tsutsui
- Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
| | - Yoshinori Shichida
- Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
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27
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Tsutsui K, Shichida Y. Multiple functions of Schiff base counterion in rhodopsins. Photochem Photobiol Sci 2010; 9:1426-34. [PMID: 20842311 DOI: 10.1039/c0pp00134a] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
In rhodopsins, visible-light absorption is achieved by the protonation of the chromophore Schiff base. The Schiff base proton is stabilized by the negative charge of an amino acid residue called the Schiff base counterion. Since E113 was identified as the counterion in bovine rhodopsin, there has been growing evidence that the counterion has multiple functions besides proton stabilization. Here, we first introduce generally accepted findings as well as some controversial theories about the identity of the Schiff base counterion in the dark and in intermediate states and then review multiple functions of the counterion in vertebrate visual pigments. Special focus is placed on the recently demonstrated role in photoisomerization efficiency. Finally, differences in the position of the counterion between vertebrate visual pigments and other opsins and its relevance to the molecular evolution of opsins are discussed.
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Affiliation(s)
- Kei Tsutsui
- Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto, 606-8502, Japan
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28
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Morrow JM, Chang BSW. The p1D4-hrGFP II expression vector: a tool for expressing and purifying visual pigments and other G protein-coupled receptors. Plasmid 2010; 64:162-9. [PMID: 20627111 DOI: 10.1016/j.plasmid.2010.07.002] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2010] [Revised: 06/29/2010] [Accepted: 07/05/2010] [Indexed: 11/19/2022]
Abstract
The heterologous expression of membrane proteins such as G protein-coupled receptors can be a notoriously difficult task. We have engineered an expression vector, p1D4-hrGFP II, in order to efficiently express visual pigments in mammalian cell culture. This expression vector is based on pIRES-hrGFP II (Stratagene), with the addition of a C-terminal 1D4 epitope tag for immunoblotting and immunoaffinity purification. This vector employs the CMV promoter and hrGFP II, a co-translated reporter gene. We measured the effectiveness of pIRES-hrGFP II in expressing bovine rhodopsin, and showed a 3.9- to 5.7-fold increase in expression as measured by absorbance spectroscopy as compared with the pMT vector, a common choice for visual pigment expression. We then expressed zebrafish RH2-1 using p1D4-hrGFP II in order to assess its utility in expressing cone opsins, known to be less stable and more difficult to express than bovine rhodopsin. We show a λ(280)/λ(MAX) value of 3.3, one third of that reported in previous studies, suggesting increased expression levels and decreased levels of misfolded, non-functional visual pigment. Finally, we monitored HEK293T cell growth following transfection with pIRES-hrGFP II using fluorescence microscopy to illustrate the benefits of having a co-translated reporter during heterologous expression studies.
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Affiliation(s)
- James M Morrow
- Department of Cell & Systems Biology, University of Toronto, Room 501, Toronto, Ontario, Canada
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29
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Ahuja S, Eilers M, Hirshfeld A, Yan ECY, Ziliox M, Sakmar TP, Sheves M, Smith SO. 6-s-cis Conformation and polar binding pocket of the retinal chromophore in the photoactivated state of rhodopsin. J Am Chem Soc 2010; 131:15160-9. [PMID: 19795853 DOI: 10.1021/ja9034768] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The visual pigment rhodopsin is unique among the G protein-coupled receptors in having an 11-cis retinal chromophore covalently bound to the protein through a protonated Schiff base linkage. The chromophore locks the visual receptor in an inactive conformation through specific steric and electrostatic interactions. This efficient inverse agonist is rapidly converted to an agonist, the unprotonated Schiff base of all-trans retinal, upon light activation. Here, we use magic angle spinning NMR spectroscopy to obtain the (13)C chemical shifts (C5-C20) of the all-trans retinylidene chromophore and the (15)N chemical shift of the Schiff base nitrogen in the active metarhodopsin II intermediate. The retinal chemical shifts are sensitive to the conformation of the chromophore and its molecular interactions within the protein-binding site. Comparison of the retinal chemical shifts in metarhodopsin II with those of retinal model compounds reveals that the Schiff base environment is polar. In particular, the (13)C15 and (15)Nepsilon chemical shifts indicate that the C horizontal lineN bond is highly polarized in a manner that would facilitate Schiff base hydrolysis. We show that a strong perturbation of the retinal (13)C12 chemical shift observed in rhodopsin is reduced in wild-type metarhodopsin II and in the E181Q mutant of rhodopsin. On the basis of the T(1) relaxation time of the retinal (13)C18 methyl group and the conjugated retinal (13)C5 and (13)C8 chemical shifts, we have determined that the conformation of the retinal C6-C7 single bond connecting the beta-ionone ring and the retinylidene chain is 6-s-cis in both the inactive and the active states of rhodopsin. These results are discussed within the general framework of ligand-activated G protein-coupled receptors.
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Affiliation(s)
- Shivani Ahuja
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, New York 11794-5215, USA
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30
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In vitro assays of rod and cone opsin activity: retinoid analogs as agonists and inverse agonists. Methods Mol Biol 2010; 652:85-94. [PMID: 20552423 DOI: 10.1007/978-1-60327-325-1_4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Upon absorption of a photon, the bound 11-cis-retinoid isomerizes to the all-trans form resulting in a protein conformational change that enables it to activate its G protein, transducin, to begin the visual signal transduction cascade. The native ligand, 11-cis-retinal, acts as an inverse agonist to both the apoproteins of rod and cone visual pigments (opsins); all-trans-retinal is an agonist. Truncated analogs of retinal have been used to characterize structure-function relationships with rod opsins, but little has been done with cone opsins. Activation of transducin by an opsin is one method to characterize the conformational state of the opsin. This chapter describes an in vitro transducin activation assay that can be used with cone opsins to determine the degree to which different ligands can act as an agonist or an inverse agonist to gain insight into the ligand-binding pocket of cone opsins and differences between the different classes of opsins. The understanding of the effects of ligands on cone opsin activity can potentially be applied to future therapeutic agents targeting opsins.
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Matsuyama T, Yamashita T, Imai H, Shichida Y. Covalent bond between ligand and receptor required for efficient activation in rhodopsin. J Biol Chem 2009; 285:8114-21. [PMID: 20042594 DOI: 10.1074/jbc.m109.063875] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Rhodopsin is an extensively studied member of the G protein-coupled receptors (GPCRs). Although rhodopsin shares many features with the other GPCRs, it exhibits unique features as a photoreceptor molecule. A hallmark in the molecular structure of rhodopsin is the covalently bound chromophore that regulates the activity of the receptor acting as an agonist or inverse agonist. Here we show the pivotal role of the covalent bond between the retinal chromophore and the lysine residue at position 296 in the activation pathway of bovine rhodopsin, by use of a rhodopsin mutant K296G reconstituted with retinylidene Schiff bases. Our results show that photoreceptive functions of rhodopsin, such as regiospecific photoisomerization of the ligand, and its quantum yield were not affected by the absence of the covalent bond, whereas the activation mechanism triggered by photoisomerization of the retinal was severely affected. Furthermore, our results show that an active state similar to the Meta-II intermediate of wild-type rhodopsin did not form in the bleaching process of this mutant, although it exhibited relatively weak G protein activity after light irradiation because of an increased basal activity of the receptor. We propose that the covalent bond is required for transmitting structural changes from the photoisomerized agonist to the receptor and that the covalent bond forcibly keeps the low affinity agonist in the receptor, resulting in a more efficient G protein activation.
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Affiliation(s)
- Take Matsuyama
- Department of Biophysics, Graduate School of Science and CREST-JST, Kyoto University, Kyoto 606-8502, Japan
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Liu J, Liu MY, Nguyen JB, Bhagat A, Mooney V, Yan ECY. Thermal decay of rhodopsin: role of hydrogen bonds in thermal isomerization of 11-cis retinal in the binding site and hydrolysis of protonated Schiff base. J Am Chem Soc 2009; 131:8750-1. [PMID: 19505100 DOI: 10.1021/ja903154u] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Although thermal stability of the G protein-coupled receptor rhodopsin is directly related to its extremely low dark noise level and has recently generated considerable interest, the chemistry behind the thermal decay process of rhodopsin has remained unclear. Using UV-vis spectroscopy and HPLC analysis, we have demonstrated that the thermal decay of rhodopsin involves both hydrolysis of the protonated Schiff base and thermal isomerization of 11-cis to all-trans retinal. Examining the unfolding of rhodopsin by circular dichroism spectroscopy and measuring the rate of thermal isomerization of 11-cis retinal in solution, we conclude that the observed thermal isomerization of 11-cis to all-trans retinal happens when 11-cis retinal is in the binding pocket of rhodopsin. Furthermore, we demonstrate that solvent deuterium isotope effects are involved in the thermal decay process by decreasing the rates of thermal isomerization and hydrolysis, suggesting that the rate-determining step of these processes involves breaking hydrogen bonds. These results provide insight into understanding the critical role of an extensive hydrogen-bonding network on stabilizing the inactive state of rhodopsin and contribute to our current understanding of the low dark noise level of rhodopsin, which enables this specialized protein to function as an extremely sensitive biological light detector. Because similar hydrogen-bonding networks have also been suggested by structural analysis of two other GPCRs, beta1 and beta2 adrenergic receptors, our results could reveal a general role of hydrogen bonds in facilitating GPCR function.
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Affiliation(s)
- Jian Liu
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520, USA
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Tsutsui K, Imai H, Shichida Y. E113 is required for the efficient photoisomerization of the unprotonated chromophore in a UV-absorbing visual pigment. Biochemistry 2008; 47:10829-33. [PMID: 18803408 DOI: 10.1021/bi801377v] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Protonation of the retinal Schiff base chromophore is responsible for the absorption of visible light and is stabilized by the counterion residue E113 in vertebrate visual pigments. However, this residue is also conserved in vertebrate UV-absorbing visual pigments (UV pigments) which have an unprotonated Schiff base chromophore. To elucidate the role played by this residue in the photoisomerization of the unprotonated chromophore in UV pigments, we measured the quantum yield of the E113Q mutant of the mouse UV cone pigment (mouse UV). The quantum yield of the mutant was much lower than that of the wild type, indicating that E113 is required for the efficient photoisomerization of the unprotonated chromophore in mouse UV. Introduction of the E113Q mutation into the chicken violet cone pigment (chicken violet), which has a protonated chromophore, caused deprotonation of the chromophore and a reduction in the quantum yield. On the other hand, the S90C mutation in chicken violet, which deprotonated the chromophore with E113 remaining intact, did not significantly affect the quantum yield. These results suggest that E113 facilitates photoisomerization in both UV-absorbing and visible light-absorbing visual pigments and provide a possible explanation for the complete conservation of E113 among vertebrate UV pigments.
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Affiliation(s)
- Kei Tsutsui
- Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
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