1
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Matsunami-Nakamura R, Tamogami J, Takeguchi M, Ishikawa J, Kikukawa T, Kamo N, Nara T. Key determinants for signaling in the sensory rhodopsin II/transducer complex are different between Halobacterium salinarum and Natronomonas pharaonis. FEBS Lett 2023; 597:2334-2344. [PMID: 37532685 DOI: 10.1002/1873-3468.14711] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2023] [Revised: 07/19/2023] [Accepted: 07/20/2023] [Indexed: 08/04/2023]
Abstract
The cell membrane of Halobacterium salinarum contains a retinal-binding photoreceptor, sensory rhodopsin II (HsSRII), coupled with its cognate transducer (HsHtrII), allowing repellent phototaxis behavior for shorter wavelength light. Previous studies on SRII from Natronomonas pharaonis (NpSRII) pointed out the importance of the hydrogen bonding interaction between Thr204NpSRII and Tyr174NpSRII in signal transfer from SRII to HtrII. Here, we investigated the effect on phototactic function by replacing residues in HsSRII corresponding to Thr204NpSRII and Tyr174NpSRII . Whereas replacement of either residue altered the photocycle kinetics, introduction of any mutations at Ser201HsSRII and Tyr171HsSRII did not eliminate negative phototaxis function. These observations imply the possibility of the presence of an unidentified molecular mechanism for photophobic signal transduction differing from NpSRII-NpHtrII.
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Affiliation(s)
| | - Jun Tamogami
- College of Pharmaceutical Sciences, Matsuyama University, Japan
| | - Miki Takeguchi
- College of Pharmaceutical Sciences, Matsuyama University, Japan
| | - Junya Ishikawa
- College of Pharmaceutical Sciences, Matsuyama University, Japan
| | - Takashi Kikukawa
- Faculty of Advanced Life Science, Hokkaido University, Sapporo, Japan
| | - Naoki Kamo
- College of Pharmaceutical Sciences, Matsuyama University, Japan
- Faculty of Advanced Life Science, Hokkaido University, Sapporo, Japan
| | - Toshifumi Nara
- College of Pharmaceutical Sciences, Matsuyama University, Japan
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2
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Abstract
The first stage in biological signaling is based on changes in the functional state of a receptor protein triggered by interaction of the receptor with its ligand(s). The light-triggered nature of photoreceptors allows studies on the mechanism of such changes in receptor proteins using a wide range of biophysical methods and with superb time resolution. Here, we critically evaluate current understanding of proton and electron transfer in photosensory proteins and their involvement both in primary photochemistry and subsequent processes that lead to the formation of the signaling state. An insight emerging from multiple families of photoreceptors is that ultrafast primary photochemistry is followed by slower proton transfer steps that contribute to triggering large protein conformational changes during signaling state formation. We discuss themes and principles for light sensing shared by the six photoreceptor families: rhodopsins, phytochromes, photoactive yellow proteins, light-oxygen-voltage proteins, blue-light sensors using flavin, and cryptochromes.
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Affiliation(s)
- Tilman Kottke
- Department of Chemistry, Bielefeld University, 33615 Bielefeld, Germany
| | - Aihua Xie
- Department of Physics, Oklahoma State University, Stillwater, Oklahoma 74078, USA
| | - Delmar S. Larsen
- Department of Chemistry, University of California, Davis, California 95616, USA
| | - Wouter D. Hoff
- Department of Microbiology and Molecular Genetics, Oklahoma State University, Stillwater, Oklahoma 74078, USA
- Department of Chemistry, Oklahoma State University, Stillwater, Oklahoma 74078, USA
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3
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Abstract
Microbial rhodopsins (MRs) are a large family of photoactive membrane proteins, found in microorganisms belonging to all kingdoms of life, with new members being constantly discovered. Among the MRs are light-driven proton, cation and anion pumps, light-gated cation and anion channels, and various photoreceptors. Due to their abundance and amenability to studies, MRs served as model systems for a great variety of biophysical techniques, and recently found a great application as optogenetic tools. While the basic aspects of microbial rhodopsins functioning have been known for some time, there is still a plenty of unanswered questions. This chapter presents and summarizes the available knowledge, focusing on the functional and structural studies.
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Affiliation(s)
- Ivan Gushchin
- Moscow Institute of Physics and Technology, Dolgoprudniy, Russia.
| | - Valentin Gordeliy
- Moscow Institute of Physics and Technology, Dolgoprudniy, Russia.
- University of Grenoble Alpes, CEA, CNRS, IBS, Grenoble, France.
- Institute of Complex Systems (ICS), ICS-6: Structural Biochemistry, Research Centre Jülich, Jülich, Germany.
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4
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Ishchenko A, Round E, Borshchevskiy V, Grudinin S, Gushchin I, Klare JP, Remeeva A, Polovinkin V, Utrobin P, Balandin T, Engelhard M, Büldt G, Gordeliy V. New Insights on Signal Propagation by Sensory Rhodopsin II/Transducer Complex. Sci Rep 2017; 7:41811. [PMID: 28165484 PMCID: PMC5292967 DOI: 10.1038/srep41811] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2016] [Accepted: 12/01/2016] [Indexed: 01/29/2023] Open
Abstract
The complex of two membrane proteins, sensory rhodopsin II (NpSRII) with its cognate transducer (NpHtrII), mediates negative phototaxis in halobacteria N. pharaonis. Upon light activation NpSRII triggers a signal transduction chain homologous to the two-component system in eubacterial chemotaxis. Here we report on crystal structures of the ground and active M-state of the complex in the space group I212121. We demonstrate that the relative orientation of symmetrical parts of the dimer is parallel (“U”-shaped) contrary to the gusset-like (“V”-shaped) form of the previously reported structures of the NpSRII/NpHtrII complex in the space group P21212, although the structures of the monomers taken individually are nearly the same. Computer modeling of the HAMP domain in the obtained “V”- and “U”-shaped structures revealed that only the “U”-shaped conformation allows for tight interactions of the receptor with the HAMP domain. This is in line with existing data and supports biological relevance of the “U” shape in the ground state. We suggest that the “V”-shaped structure may correspond to the active state of the complex and transition from the “U” to the “V”-shape of the receptor-transducer complex can be involved in signal transduction from the receptor to the signaling domain of NpHtrII.
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Affiliation(s)
- A Ishchenko
- Institute of Complex Systems (ICS), ICS-6: Structural Biochemistry, Research Centre Jülich, 52425 Jülich, Germany.,Institute of Crystallography, University of Aachen (RWTH), Jägerstraße 17-19, 52056 Aachen, Germany
| | - E Round
- Institute of Complex Systems (ICS), ICS-6: Structural Biochemistry, Research Centre Jülich, 52425 Jülich, Germany.,Institut de Biologie Structurale J.-P. Ebel, Université Grenoble Alpes-CEA-CNRS, F-38000 Grenoble, France
| | - V Borshchevskiy
- Institute of Complex Systems (ICS), ICS-6: Structural Biochemistry, Research Centre Jülich, 52425 Jülich, Germany.,Moscow Institute of Physics and Technology, 141700 Dolgoprudniy, Russia
| | - S Grudinin
- CNRS, Laboratoire Jean Kuntzmann, BP 53, Grenoble Cedex 9, France.,NANO-D, INRIA Grenoble-Rhone-Alpes Research Center, 38334 Saint Ismier Cedex, Montbonnot, France
| | - I Gushchin
- Institute of Complex Systems (ICS), ICS-6: Structural Biochemistry, Research Centre Jülich, 52425 Jülich, Germany.,Institut de Biologie Structurale J.-P. Ebel, Université Grenoble Alpes-CEA-CNRS, F-38000 Grenoble, France.,Moscow Institute of Physics and Technology, 141700 Dolgoprudniy, Russia
| | - J P Klare
- Max-Planck Institute of Molecular Physiology, 44227 Dortmund, Germany.,Department of Physics, University of Osnabrück, Barbarastrasse 7, D-49069 Osnabrück, Germany
| | - A Remeeva
- Institute of Complex Systems (ICS), ICS-6: Structural Biochemistry, Research Centre Jülich, 52425 Jülich, Germany
| | - V Polovinkin
- Institute of Complex Systems (ICS), ICS-6: Structural Biochemistry, Research Centre Jülich, 52425 Jülich, Germany.,Institut de Biologie Structurale J.-P. Ebel, Université Grenoble Alpes-CEA-CNRS, F-38000 Grenoble, France
| | - P Utrobin
- Moscow Institute of Physics and Technology, 141700 Dolgoprudniy, Russia
| | - T Balandin
- Institute of Complex Systems (ICS), ICS-6: Structural Biochemistry, Research Centre Jülich, 52425 Jülich, Germany
| | - M Engelhard
- Max-Planck Institute of Molecular Physiology, 44227 Dortmund, Germany
| | - G Büldt
- Institute of Complex Systems (ICS), ICS-6: Structural Biochemistry, Research Centre Jülich, 52425 Jülich, Germany.,Moscow Institute of Physics and Technology, 141700 Dolgoprudniy, Russia
| | - V Gordeliy
- Institute of Complex Systems (ICS), ICS-6: Structural Biochemistry, Research Centre Jülich, 52425 Jülich, Germany.,Institute of Crystallography, University of Aachen (RWTH), Jägerstraße 17-19, 52056 Aachen, Germany.,Institut de Biologie Structurale J.-P. Ebel, Université Grenoble Alpes-CEA-CNRS, F-38000 Grenoble, France.,Moscow Institute of Physics and Technology, 141700 Dolgoprudniy, Russia
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5
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Intramolecular proton transfer in channelrhodopsins. Biophys J 2013; 104:807-17. [PMID: 23442959 DOI: 10.1016/j.bpj.2013.01.002] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2012] [Revised: 12/19/2012] [Accepted: 01/02/2013] [Indexed: 10/27/2022] Open
Abstract
Channelrhodopsins serve as photoreceptors that control the motility behavior of green flagellate algae and act as light-gated ion channels when heterologously expressed in animal cells. Here, we report direct measurements of proton transfer from the retinylidene Schiff base in several channelrhodopsin variants expressed in HEK293 cells. A fast outward-directed current precedes the passive channel current that has the opposite direction at physiological holding potentials. This rapid charge movement occurs on the timescale of the M intermediate formation in microbial rhodopsins, including that for channelrhodopsin from Chlamydomonas augustae and its mutants, reported in this study. Mutant analysis showed that the glutamate residue corresponding to Asp(85) in bacteriorhodopsin acts as the primary acceptor of the Schiff-base proton in low-efficiency channelrhodopsins. Another photoactive-site residue corresponding to Asp(212) in bacteriorhodopsin serves as an alternative proton acceptor and plays a more important role in channel opening than the primary acceptor. In more efficient channelrhodopsins from Chlamydomonas reinhardtii, Mesostigma viride, and Platymonas (Tetraselmis) subcordiformis, the fast current was apparently absent. The inverse correlation of the outward proton transfer and channel activity is consistent with channel function evolving in channelrhodopsins at the expense of their capacity for active proton transport.
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6
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Inoue K, Tsukamoto T, Sudo Y. Molecular and evolutionary aspects of microbial sensory rhodopsins. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2013; 1837:562-77. [PMID: 23732219 DOI: 10.1016/j.bbabio.2013.05.005] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2013] [Revised: 05/14/2013] [Accepted: 05/16/2013] [Indexed: 02/03/2023]
Abstract
Retinal proteins (~rhodopsins) are photochemically reactive membrane-embedded proteins, with seven transmembrane α-helices which bind the chromophore retinal (vitamin A aldehyde). They are widely distributed through all three biological kingdoms, eukarya, bacteria and archaea, indicating the biological significance of the retinal proteins. Light absorption by the retinal proteins triggers a photoisomerization of the chromophore, leading to the biological function, light-energy conversion or light-signal transduction. This article reviews molecular and evolutionary aspects of the light-signal transduction by microbial sensory receptors and their related proteins. This article is part of a Special Issue entitled: Retinal Proteins - You can teach an old dog new tricks.
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Affiliation(s)
- Keiichi Inoue
- Department of Frontier Materials, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555, Japan; Japan Science and Technology Agency (JST), PRESTO, 4-1-8 Honcho Kawaguchi, Saitama 332-0012, Japan
| | - Takashi Tsukamoto
- Division of Biological Science, Graduate School of Science, Nagoya University, Nagoya, 464-8602, Japan
| | - Yuki Sudo
- Japan Science and Technology Agency (JST), PRESTO, 4-1-8 Honcho Kawaguchi, Saitama 332-0012, Japan; Division of Biological Science, Graduate School of Science, Nagoya University, Nagoya, 464-8602, Japan; Department of Life and Coordination-Complex Molecular Science, Institute for Molecular Science, 38 Nishigo-Naka, Myodaiji, Okazaki, Japan.
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7
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Ishchenko A, Round E, Borshchevskiy V, Grudinin S, Gushchin I, Klare J, Balandin T, Remeeva A, Engelhard M, Büldt G, Gordeliy V. Ground state structure of D75N mutant of sensory rhodopsin II in complex with its cognate transducer. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY 2013; 123:55-8. [DOI: 10.1016/j.jphotobiol.2013.03.008] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2012] [Revised: 02/27/2013] [Accepted: 03/19/2013] [Indexed: 11/15/2022]
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8
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Salt bridge in the conserved His-Asp cluster inGloeobacterrhodopsin contributes to trimer formation. FEBS Lett 2013; 587:322-7. [DOI: 10.1016/j.febslet.2012.12.022] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2012] [Revised: 12/12/2012] [Accepted: 12/13/2012] [Indexed: 12/18/2022]
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9
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Wang J, Sasaki J, Tsai AL, Spudich JL. HAMP domain signal relay mechanism in a sensory rhodopsin-transducer complex. J Biol Chem 2012; 287:21316-25. [PMID: 22511775 DOI: 10.1074/jbc.m112.344622] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The phototaxis receptor complex composed of sensory rhodopsin II (SRII) and the transducer subunit HtrII mediates photorepellent responses in haloarchaea. Light-activated SRII transmits a signal through two HAMP switch domains (HAMP1 and HAMP2) in HtrII that bridge the photoreceptive membrane domain of the complex and the cytoplasmic output kinase-modulating domain. HAMP domains, widespread signal relay modules in prokaryotic sensors, consist of four-helix bundles composed of two helices, AS1 and AS2, from each of two dimerized transducer subunits. To examine their molecular motion during signal transmission, we incorporated SRII-HtrII dimeric complexes in nanodiscs to allow unrestricted probe access to the cytoplasmic side HAMP domains. Spin-spin dipolar coupling measurements confirmed that in the nanodiscs, SRII photoactivation induces helix movement in the HtrII membrane domain diagnostic of transducer activation. Labeling kinetics of a fluorescein probe in monocysteine-substituted HAMP1 mutants revealed a light-induced shift of AS2 against AS1 by one-half α-helix turn with minimal other changes. An opposite shift of AS2 against AS1 in HAMP2 at the corresponding positions supports the proposal from x-ray crystal structures by Airola et al. (Airola, M. V., Watts, K. J., Bilwes, A. M., and Crane, B. R. (2010) Structure 18, 436-448) that poly-HAMP chains undergo alternating opposite interconversions to relay the signal. Moreover, we found that haloarchaeal cells expressing a HAMP2-deleted SRII-HtrII exhibit attractant phototaxis, opposite from the repellent phototaxis mediated by the wild-type di-HAMP SRII-HtrII complex. The opposite conformational changes and corresponding opposite output signals of HAMP1 and HAMP2 imply a signal transmission mechanism entailing small shifts in helical register between AS1 and AS2 alternately in opposite directions in adjacent HAMPs.
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Affiliation(s)
- Jihong Wang
- Center for Membrane Biology, Department of Biochemistry and Molecular Biology, Houston, Texas 77030, USA
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10
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Klare JP, Bordignon E, Engelhard M, Steinhoff HJ. Transmembrane signal transduction in archaeal phototaxis: the sensory rhodopsin II-transducer complex studied by electron paramagnetic resonance spectroscopy. Eur J Cell Biol 2012; 90:731-9. [PMID: 21684631 DOI: 10.1016/j.ejcb.2011.04.013] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Archaeal photoreceptors, together with their cognate transducer proteins, mediate phototaxis by regulating cell motility through two-component signal transduction pathways. This sensory pathway is closely related to the bacterial chemotactic system, which has been studied in detail during the past 40 years. Structural and functional studies applying site-directed spin labelling and electron paramagnetic resonance spectroscopy on the sensory rhodopsin II/transducer (NpSRII/NpHtrII) complex of Natronomonas pharaonis have yielded insights into the structure, the mechanisms of signal perception, the signal transduction across the membrane and provided information about the subsequent information transfer within the transducer protein towards the components of the intracellular signalling pathway. Here, we provide an overview about the findings of the last decade, which, combined with the wealth of data from research on the Escherichia coli chemotaxis system, served to understand the basic principles microorganisms use to adapt to their environment. We document the time course of a signal being perceived at the membrane, transferred across the membrane and, for the first time, how this signal modulates the dynamic properties of a HAMP domain, a ubiquitous signal transduction module found in various protein classes.
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Affiliation(s)
- Johann P Klare
- Faculty of Physics, University of Osnabrück, Barbarastrasse 7, 49076 Osnabrück, Germany
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11
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Miura K, Sato A, Ohta M, Furukawa J. Increased tolerance to salt stress in the phosphate-accumulating Arabidopsis mutants siz1 and pho2. PLANTA 2011; 234:1191-9. [PMID: 21748325 DOI: 10.1007/s00425-011-1476-y] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/28/2011] [Accepted: 06/28/2011] [Indexed: 05/23/2023]
Abstract
High salinity is an environmental factor that inhibits plant growth and development, leading to large losses in crop yields. We report here that mutations in SIZ1 or PHO2, which cause more accumulation of phosphate compared with the wild type, enhance tolerance to salt stress. The siz1 and pho2 mutations reduce the uptake and accumulation of Na(+). These mutations are also able to suppress the Na(+) hypersensitivity of the sos3-1 mutant, and genetic analyses suggest that SIZ1 and SOS3 or PHO2 and SOS3 have an additive effect on the response to salt stress. Furthermore, the siz1 mutation cannot suppress the Li(+) hypersensitivity of the sos3-1 mutant. These results indicate that the phosphate-accumulating mutants siz1 and pho2 reduce the uptake and accumulation of Na(+), leading to enhanced salt tolerance, and that, genetically, SIZ1 and PHO2 are likely independent of SOS3-dependent salt signaling.
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Affiliation(s)
- Kenji Miura
- Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, 305-8572, Japan.
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12
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Holterhues J, Bordignon E, Klose D, Rickert C, Klare JP, Martell S, Li L, Engelhard M, Steinhoff HJ. The signal transfer from the receptor NpSRII to the transducer NpHtrII is not hampered by the D75N mutation. Biophys J 2011; 100:2275-82. [PMID: 21539797 DOI: 10.1016/j.bpj.2011.03.017] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2010] [Revised: 02/17/2011] [Accepted: 03/16/2011] [Indexed: 11/28/2022] Open
Abstract
Sensory rhodopsin II (NpSRII) is a phototaxis receptor of Natronomonas pharaonis that performs its function in complex with its cognate transducer (NpHtrII). Upon light activation NpSRII triggers by means of NpHtrII a signal transduction chain homologous to the two component system in eubacterial chemotaxis. The D75N mutant of NpSRII, which lacks the blue-shifted M intermediate and therefore exhibits a significantly faster photocycle compared to the wild-type, mediates normal phototaxis responses demonstrating that deprotonation of the Schiff base is not a prerequisite for transducer activation. Using site-directed spin labeling and time resolved electron paramagnetic-resonance spectroscopy, we show that the mechanism revealed for activation of the wild-type complex, namely an outward tilt motion of the cytoplasmic part of the receptor helix F and a concomitant rotation of the transmembrane transducer helix TM2, is also valid for the D75N variant. Apparently, the D75N mutation shifts the ground state conformation of NpSRII-D75N and its cognate transducer into the direction of the signaling state.
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13
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Sasaki J, Tsai AL, Spudich JL. Opposite displacement of helix F in attractant and repellent signaling by sensory rhodopsin-Htr complexes. J Biol Chem 2011; 286:18868-77. [PMID: 21454480 DOI: 10.1074/jbc.m110.200345] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Two forms of the phototaxis receptor sensory rhodopsin I distinguished by differences in its photoactive site have been shown to be directly correlated with attractant and repellent signaling by the dual-signaling protein. In prior studies, differences in the photoactive site defined the two forms, namely the direction of light-induced proton transfer from the chromophore and the pK(a) of an Asp counterion to the protonated chromophore. Here, we show by both in vivo and in vitro measurements that the two forms are distinct protein conformers with structural similarities to two conformers seen in the light-driven proton transport cycle of the related protein bacteriorhodopsin. Measurements of spontaneous cell motility reversal frequencies, an in vivo measure of histidine kinase activity in the phototaxis system, indicate that the two forms are a photointerconvertible pair, with one conformer activating and the other inhibiting the kinase. Protein conformational changes in these photoconversions monitored by site-directed spin labeling show that opposite structural changes in helix F, distant from the photoactive site, correspond to the opposite phototaxis signals. The results provide the first direct evidence that displacements of helix F are directly correlated with signaling and impact our understanding of the sensory rhodopsin I signaling mechanism and the evolution of diverse functionality in this protein family.
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Affiliation(s)
- Jun Sasaki
- Center for Membrane Biology, Department of Biochemistry and Molecular Biology, University of Texas Medical School, Houston, Texas 77030, USA
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14
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Sineshchekov OA, Sasaki J, Wang J, Spudich JL. Attractant and repellent signaling conformers of sensory rhodopsin-transducer complexes. Biochemistry 2010; 49:6696-704. [PMID: 20590098 PMCID: PMC2914491 DOI: 10.1021/bi100798w] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
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Attractant and repellent signaling conformers of the dual-signaling phototaxis receptor sensory rhodopsin I and its transducer subunit (SRI−HtrI) have recently been distinguished experimentally by the opposite connection of their retinylidene protonated Schiff bases to the outwardly located periplasmic side and inwardly located cytoplasmic side. Here we show that the pKa of the outwardly located Asp76 counterion in the outwardly connected conformer is lowered by ∼1.5 units from that of the inwardly connected conformer. The pKa difference enables quantitative determination of the relative amounts of the two conformers in wild-type cells and behavioral mutants prior to photoexcitation, comparison of their absorption spectra, and determination of their relative signaling efficiency. We have shown that the one-photon excitation of the SRI−HtrI attractant conformer causes a Schiff base connectivity switch from inwardly connected to outwardly connected states in the attractant signaling photoreaction. Conversely, a second near-UV photon drives the complex back to the inwardly connected conformer in the repellent signaling photoreaction. The results suggest a model of the color-discriminating dual-signaling mechanism in which phototaxis responses (his-kinase modulation) result from the photointerconversion of the two oppositely connected SRI−HtrI conformers by one-photon and two-photon activation. Furthermore, we find that the related repellent phototaxis SRII−HtrII receptor complex has an outwardly connected retinylidene Schiff base like the repellent signaling forms of the SRI−HtrI complex, indicating the general applicability of macro conformational changes, which can be detected by the connectivity switch, to phototaxis signaling by sensory rhodopsin−transducer complexes.
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Affiliation(s)
- Oleg A Sineshchekov
- Center for Membrane Biology, Department of Biochemistry and Molecular Biology, University of Texas Medical School, Houston, Texas 77030, USA
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15
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Sasaki J, Spudich JL. Signal Transfer in Haloarchaeal Sensory Rhodopsin Transducer Complexes. Photochem Photobiol 2008; 84:863-8. [DOI: 10.1111/j.1751-1097.2008.00314.x] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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16
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Kawamura I, Yoshida H, Ikeda Y, Yamaguchi S, Tuzi S, Saitô H, Kamo N, Naito A. Dynamics change of phoborhodopsin and transducer by activation: study using D75N mutant of the receptor by site-directed solid-state 13C NMR. Photochem Photobiol 2008; 84:921-30. [PMID: 18363620 DOI: 10.1111/j.1751-1097.2008.00326.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Pharaonis phoborhodopsin (ppR or sensory rhodopsin II) is a negative phototaxis receptor of Natronomonas pharaonis, and forms a complex, which transmits the photosignal into cytoplasm, with its cognate transducer (pHtrII). We examined a possible local dynamics change of ppR and its D75N mutant complexed with pHtrII, using solid-state (13)C NMR of [3-(13)C]Ala- and [1-(13)C]Val-labeled preparations. We distinguished Ala C(beta) (13)C signals of relatively static stem (Ala221) in the C-terminus of the receptors from those of flexible tip (Ala228, 234, 236 and 238), utilizing a mutant with truncated C-terminus. The local fluctuation frequency at the C-terminal tip was appreciably decreased when ppR was bound to pHtrII, while it was increased when D75N, that mimics the signaling state because of disrupted salt bridge between C and G helices prerequisite for the signal transfer, was bound to pHtrII. This signal change may be considered with the larger dissociation constant of the complex between pHtrII and M-state of ppR. At the same time, it turned out that fluctuation frequency of cytoplasmic portion of pHtrII is lowered when ppR is replaced by D75N in the complex with pHtrII. This means that the C-terminal tip partly participates in binding with the linker region of pHtrII in the dark, but this portion might be released at the signaling state leading to mutual association of the two transducers in the cytoplasmic regions within the ppR/pHtrII complex.
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Affiliation(s)
- Izuru Kawamura
- Graduate School of Engineering, Yokohama National University, Hodogaya-ku, Yokohama, Japan
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17
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Furutani Y, Takahashi H, Sasaki J, Sudo Y, Spudich JL, Kandori H. Structural Changes of Sensory Rhodopsin I and Its Transducer Protein Are Dependent on the Protonated State of Asp76. Biochemistry 2008; 47:2875-83. [DOI: 10.1021/bi702050c] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Yuji Furutani
- Department of Materials Science and Engineering, Nagoya Institute of Technology, Showa-ku, Nagoya, 466-8555, Japan, and Center for Membrane Biology, Department of Biochemistry and Molecular Biology, University of Texas Health Science Center, Houston, Texas 77030
| | - Hazuki Takahashi
- Department of Materials Science and Engineering, Nagoya Institute of Technology, Showa-ku, Nagoya, 466-8555, Japan, and Center for Membrane Biology, Department of Biochemistry and Molecular Biology, University of Texas Health Science Center, Houston, Texas 77030
| | - Jun Sasaki
- Department of Materials Science and Engineering, Nagoya Institute of Technology, Showa-ku, Nagoya, 466-8555, Japan, and Center for Membrane Biology, Department of Biochemistry and Molecular Biology, University of Texas Health Science Center, Houston, Texas 77030
| | - Yuki Sudo
- Department of Materials Science and Engineering, Nagoya Institute of Technology, Showa-ku, Nagoya, 466-8555, Japan, and Center for Membrane Biology, Department of Biochemistry and Molecular Biology, University of Texas Health Science Center, Houston, Texas 77030
| | - John L. Spudich
- Department of Materials Science and Engineering, Nagoya Institute of Technology, Showa-ku, Nagoya, 466-8555, Japan, and Center for Membrane Biology, Department of Biochemistry and Molecular Biology, University of Texas Health Science Center, Houston, Texas 77030
| | - Hideki Kandori
- Department of Materials Science and Engineering, Nagoya Institute of Technology, Showa-ku, Nagoya, 466-8555, Japan, and Center for Membrane Biology, Department of Biochemistry and Molecular Biology, University of Texas Health Science Center, Houston, Texas 77030
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18
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Sasaki J, Nara T, Spudich EN, Spudich JL. Constitutive activity in chimeras and deletions localize sensory rhodopsin II/HtrII signal relay to the membrane-inserted domain. Mol Microbiol 2007; 66:1321-30. [PMID: 17986191 DOI: 10.1111/j.1365-2958.2007.05983.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Halobacterium salinarum sensory rhodopsin II (HsSRII) is a phototaxis receptor for blue-light avoidance that relays signals to its tightly bound transducer HsHtrII (H. salinarum haloarchaeal transducer for SRII). We found that disruption of the salt bridge between the protonated Schiff base of the receptor's retinylidene chromophore and its counterion Asp73 by residue substitutions D73A, N or Q constitutively activates HsSRII, whereas the corresponding Asp75 counterion substitutions do not constitutively activate Natronomonas pharaonis SRII (NpSRII) when complexed with N. pharaonis haloarchaeal transducer for SRII (NpHtrII). However, NpSRII(D75Q) in complex with HsHtrII is fully constitutively active, showing that transducer sensitivity to the receptor signal contributes to the phenotype. The swimming behaviour of cells expressing chimeras exchanging portions of the two homologous transducers localizes their differing sensitivities to the HtrII transmembrane domains. Furthermore, deletion constructs show that the known contact region in the cytoplasmic domain of the NpSRII-NpHtrII complex is not required for phototaxis, excluding the domain as a site for signal transmission. These results distinguish between the prevailing models for SRII-HtrII signal relay, strongly supporting the 'steric trigger-transmembrane relay model', which proposes that retinal isomerization directly signals HtrII through the mid-membrane SRII-HtrII interface, and refuting alternative models that propose signal relay in the cytoplasmic membrane-proximal domain.
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Affiliation(s)
- Jun Sasaki
- Center for Membrane Biology, Department of Biochemistry and Molecular Biology, University of Texas Medical School, 6431 Fannin Street, Houston, TX 77030, USA
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19
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Zhu J, Fu X, Koo YD, Zhu JK, Jenney FE, Adams MWW, Zhu Y, Shi H, Yun DJ, Hasegawa PM, Bressan RA. An enhancer mutant of Arabidopsis salt overly sensitive 3 mediates both ion homeostasis and the oxidative stress response. Mol Cell Biol 2007; 27:5214-24. [PMID: 17485445 PMCID: PMC1951954 DOI: 10.1128/mcb.01989-06] [Citation(s) in RCA: 113] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2006] [Revised: 12/20/2006] [Accepted: 04/04/2007] [Indexed: 11/20/2022] Open
Abstract
The myristoylated calcium sensor SOS3 and its interacting protein kinase, SOS2, play critical regulatory roles in salt tolerance. Mutations in either of these proteins render Arabidopsis thaliana plants hypersensitive to salt stress. We report here the isolation and characterization of a mutant called enh1-1 that enhances the salt sensitivity of sos3-1 and also causes increased salt sensitivity by itself. ENH1 encodes a chloroplast-localized protein with a PDZ domain at the N-terminal region and a rubredoxin domain in the C-terminal part. Rubredoxins are known to be involved in the reduction of superoxide in some anaerobic bacteria. The enh1-1 mutation causes enhanced accumulation of reactive oxygen species (ROS), particularly under salt stress. ROS also accumulate to higher levels in sos2-1 but not in sos3-1 mutants. The enh1-1 mutation does not enhance sos2-1 phenotypes. Also, enh1-1 and sos2-1 mutants, but not sos3-1 mutants, show increased sensitivity to oxidative stress. These results indicate that ENH1 functions in the detoxification of reactive oxygen species resulting from salt stress by participating in a new salt tolerance pathway that may involve SOS2 but not SOS3.
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Affiliation(s)
- Jianhua Zhu
- Horticulture and Landscape Architecture Department, Purdue University, West Lafayette, IN 47907, USA
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20
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Sasaki J, Phillips BJ, Chen X, Van Eps N, Tsai AL, Hubbell WL, Spudich JL. Different dark conformations function in color-sensitive photosignaling by the sensory rhodopsin I-HtrI complex. Biophys J 2007; 92:4045-53. [PMID: 17351006 PMCID: PMC1868990 DOI: 10.1529/biophysj.106.101121] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The haloarchaeal phototaxis receptor sensory rhodopsin I (SRI) in complex with its transducer HtrI delivers an attractant signal from excitation with an orange photon and a repellent signal from a second near-UV photon excitation. Using a proteoliposome system with purified SRI in complex with its transducer HtrI, we identified by site-directed fluorescence labeling a site (Ser(155)) on SRI that is conformationally active in signal relay to HtrI. Using site-directed spin labeling of Ser(155)Cys with a nitroxide side chain, we detected a change in conformation following one-photon excitation such that the spin probe exhibits a splitting of the outer hyperfine extrema (2A'(zz)) significantly smaller than that of the electron paramagnetic resonance spectrum in the dark state. The dark conformations of five mutant complexes that do not discriminate between orange and near-UV excitation show shifts to lower or higher 2A'(zz) values correlated with the alterations in their motility behavior to one- and two-photon stimuli. These data are interpreted in terms of a model in which the dark complex is populated by two conformers in the wild type, one that inhibits the CheA kinase (A) and the other that activates it (R), shifted in the dark by mutations and shifted in the wild-type SRI-HtrI complex in opposite directions by one-photon and two-photon reactions.
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Affiliation(s)
- Jun Sasaki
- Center for Membrane Biology, Department of Biochemistry & Molecular Biology, University of Texas Medical School, Houston, Texas 77030, USA
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21
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Sudo Y, Spudich JL. Three strategically placed hydrogen-bonding residues convert a proton pump into a sensory receptor. Proc Natl Acad Sci U S A 2006; 103:16129-34. [PMID: 17050685 PMCID: PMC1637548 DOI: 10.1073/pnas.0607467103] [Citation(s) in RCA: 93] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2006] [Indexed: 11/18/2022] Open
Abstract
In haloarchaea, light-driven ion transporters have been modified by evolution to produce sensory receptors that relay light signals to transducer proteins controlling motility behavior. The proton pump bacteriorhodopsin and the phototaxis receptor sensory rhodopsin II (SRII) differ by 74% of their residues, with nearly all conserved residues within the photoreactive retinal-binding pocket in the membrane-embedded center of the proteins. Here, we show that three residues in bacteriorhodopsin replaced by the corresponding residues in SRII enable bacteriorhodopsin to efficiently relay the retinal photoisomerization signal to the SRII integral membrane transducer (HtrII) and induce robust phototaxis responses. A single replacement (Ala-215-Thr), bridging the retinal and the membrane-embedded surface, confers weak phototaxis signaling activity, and the additional two (surface substitutions Pro-200-Thr and Val-210-Tyr), expected to align bacteriorhodopsin and HtrII in similar juxtaposition as SRII and HtrII, greatly enhance the signaling. In SRII, the three residues form a chain of hydrogen bonds from the retinal's photoisomerized C(13)=C(14) double bond to residues in the membrane-embedded alpha-helices of HtrII. The results suggest a chemical mechanism for signaling that entails initial storage of energy of photoisomerization in SRII's hydrogen bond between Tyr-174, which is in contact with the retinal, and Thr-204, which borders residues on the SRII surface in contact with HtrII, followed by transfer of this chemical energy to drive structural transitions in the transducer helices. The results demonstrate that evolution accomplished an elegant but simple conversion: The essential differences between transport and signaling proteins in the rhodopsin family are far less than previously imagined.
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Affiliation(s)
- Yuki Sudo
- Center for Membrane Biology, Department of Biochemistry and Molecular Biology, University of Texas Medical School, Houston, TX 77030
| | - John L. Spudich
- Center for Membrane Biology, Department of Biochemistry and Molecular Biology, University of Texas Medical School, Houston, TX 77030
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22
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Bergo VB, Spudich EN, Rothschild KJ, Spudich JL. Photoactivation perturbs the membrane-embedded contacts between sensory rhodopsin II and its transducer. J Biol Chem 2005; 280:28365-9. [PMID: 15951432 DOI: 10.1074/jbc.m505555200] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The photoactivation mechanism of the sensory rho-dopsin II (SRII)-HtrII receptor-transducer complex of Natronomonas pharaonis was investigated by time-resolved Fourier transform infrared difference spectroscopy to identify structural changes associated with early events in the signal relay mechanism from the receptor to the transducer. Several prominent bands in the wild-type SRII-HtrII spectra are affected by amino acid substitutions at the receptor Tyr(199) and transducer Asn(74) residues, which form a hydrogen bond between the two proteins near the middle of the bilayer. Our results indicate disappearance of this hydrogen bond in the M and O photointermediates, the likely signaling states of the complex. This event represents one of the largest light-induced alterations in the binding contacts between the receptor and transducer. The vibrational frequency changes suggest that Asn(74) and Tyr(199) form other stronger hydrogen bonds in the M state. The light-induced disruption of the Tyr(199)-Asn(74) bond also occurs when the Schiff base counterion Asp(75) is replaced with a neutral asparagine. We compared the decrease in intensity of difference bands assigned to the Tyr(199)-Asn(74) pair and to chromophore and protein groups of the receptor at various time points during the recovery of the initial state. All difference bands exhibit similar decay kinetics indicating that reformation of the Tyr(199)-Asn(74) hydrogen bond occurs concomitantly with the decay of the M and O photointermediates. This work demonstrates that the signal relay from SRII to HtrII involves early structural alterations in the deeply membrane-embedded domain of the complex and provides a spectroscopic signal useful for correlation with the downstream events in signal transduction.
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Affiliation(s)
- Vladislav B Bergo
- Center for Membrane Biology, Department of Biochemistry and Molecular Biology, University of Texas Medical School, Houston, Texas 77030, USA
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23
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Nakabayashi T, Wahadoszamen M, Ohta N. External Electric Field Effects on State Energy and Photoexcitation Dynamics of Diphenylpolyenes. J Am Chem Soc 2005; 127:7041-52. [PMID: 15884948 DOI: 10.1021/ja0401444] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
External electric field effects on state energy and photoexcitation dynamics have been examined for para-substituted and unsubstituted all-trans-diphenylpolyenes doped in a film, based on the steady-state and picosecond time-resolved measurements of the field effects on absorption and fluorescence. The substitution dependence of the electroabsorption spectra shows that the dipole moment of the substituted stilbene in the Franck-Condon excited state becomes larger with increasing difference between the Hammet constants of the substituents. Fluorescence quantum yields of 4-(dimethylamino)-4'-nitrostilbene and 4-(dimethylamino)-4'-nitrodiphenylbutadiene are markedly reduced by an electric field, suggesting that the rates of the intramolecular charge transfer (CT) from the fluorescent state to the nonradiative CT state are accelerated by an external electric field. The magnitude of the field-induced decrease in fluorescence lifetime has been evaluated. The isomerization of the unsubstituted all-trans-diphenylpolyenes to the cis forms is shown to be a significant nonradiative pathway even in a film. Field-induced quenching of their fluorescence as well as field-induced decrease in fluorescence lifetime suggests that the trans to cis photoisomerization is enhanced by an electric field.
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Affiliation(s)
- Takakazu Nakabayashi
- Research Institute for Electronic Science (RIES), Hokkaido University, Sapporo 060-0812, Japan.
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24
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Sato Y, Hata M, Neya S, Hoshino T. Computational analysis of the transient movement of helices in sensory rhodopsin II. Protein Sci 2004; 14:183-92. [PMID: 15576566 PMCID: PMC2253333 DOI: 10.1110/ps.04973805] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
MD simulation of sensory rhodopsin II was executed for three intermediates (ground-state, K-state, M-state) appearing in its photocycle. We observed a large displacement of the cytoplasmic side of helixF only in M-state among the three intermediates. This displacement was transmitted to TM2, and the cytoplasmic side of TM2 rotated clockwise. These transient movements are in agreement with the results of an EPR experiment. That is, the early stage of signal transduction in a sRII-HtrII complex was successfully reproduced by the in silico MD simulation. By analyzing the structure of the sRII-HtrII complex, the following findings about the photocycle of sRII were obtained: (1) The hydrogen bonds between helixF and other helices determine the direction of the movement of helixF; (2) three amino acids (Arg162, Thr189, Tyr199) are essential for sRII-HtrII binding and contribute to the motion transfer from sRII to HtrII; (3) after the isomerization of retinal, a major conformational change of retinal was caused by proton transfer from Schiff base to Asp75, which, in turn, triggers the steric collision of retinal with Trp171. This is the main reason for the movement of the cytoplasmic side of helixF.
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Affiliation(s)
- Y Sato
- Graduate School of Pharmaceutical Sciences, Chiba University, Chiba 263-8522, Japan
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25
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Klare JP, Gordeliy VI, Labahn J, Büldt G, Steinhoff HJ, Engelhard M. The archaeal sensory rhodopsin II/transducer complex: a model for transmembrane signal transfer. FEBS Lett 2004; 564:219-24. [PMID: 15111099 DOI: 10.1016/s0014-5793(04)00193-0] [Citation(s) in RCA: 93] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2004] [Accepted: 02/04/2004] [Indexed: 11/24/2022]
Abstract
Archaebacterial photoreceptors mediate phototaxis by regulating cell motility through two-component signalling cascades. Homologs of this sensory pathway occur in all three kingdoms of life, most notably in enteric bacteria in which the chemotaxis has been extensively studied. Recent structural and functional studies on the sensory rhodopsin II/transducer complex mediating the photophobic response of Natronomonas pharaonis have yielded new insights into the mechanisms of signal transfer across the membrane. Electron paramagnetic resonance data and the atomic resolution structure of the receptor molecule in complex with the transmembrane segment of its cognate transducer provided a model for signal transfer from the receptor to the cytoplasmic side of the transducer. This mechanism might also be relevant for eubacterial chemoreceptor signalling.
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Affiliation(s)
- Johann P Klare
- Max-Planck-Institut für molekulare Physiologie, Otto-Hahn-Str. 11, D-44227 Dortmund, Germany
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26
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Wahadoszamen M, Nakabayashi T, Ohta N. Electric field effects on photoisomerization process of diphenylpolyenes doped in a polymer film as revealed by a field-induced change in fluorescence spectrum. Chem Phys Lett 2004. [DOI: 10.1016/j.cplett.2004.01.107] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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27
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Pebay-Peyroula E, Royant A, Landau EM, Navarro J. Structural basis for sensory rhodopsin function. BIOCHIMICA ET BIOPHYSICA ACTA 2002; 1565:196-205. [PMID: 12409195 DOI: 10.1016/s0005-2736(02)00569-2] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The crystal structure of sensory rhodopsin II from Natronobacterium pharaonis was recently solved at 2.1 A resolution from lipidic cubic phase-grown crystals. A critical analysis of previous structure-function studies is possible within the framework of the high-resolution structure of this photoreceptor. Based on the structure, a molecular understanding emerges of the efficiency and selectivity of the photoisomerization reaction, of the interaction of the sensory receptor and its cognate transducer protein HtrII, and of the mechanism of spectral tuning in photoreceptors. The architecture of the retinal binding pocket is compact, representing a major determinant for the selective binding of the chromophore, all-trans retinal to the apoprotein, opsin. Several chromophore-protein interactions revealed by the structure were not predicted by previous mutagenesis and spectroscopic analyses. The structure suggests likely mechanisms by which photoisomerization triggers the activation of sensory rhodopsin II, and highlights the possibility of a unified mechanism of signaling mediated by sensory receptors, including visual rhodopsins. Future investigations using time-resolved crystallography, structural dynamics, and computational studies will provide the basis to unveil the molecular mechanisms of sensory receptors-mediated transmembrane signaling.
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Affiliation(s)
- Eva Pebay-Peyroula
- Institut de Biologie Structurale, UMR5075, CEA-CNRS-Université Joseph Fourier, 41 rue Jules Horowitz, Grenoble, France
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28
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Abstract
Atomic resolution structures of a sensory rhodopsin phototaxis receptor in haloarchaea (the first sensory member of the widespread microbial rhodopsin family) have yielded insights into the interaction face with its membrane-embedded transducer and into the mechanism of spectral tuning. Spectral differences between sensory rhodopsin and the light-driven proton pump bacteriorhodopsin depend largely upon the repositioning of a conserved arginine residue in the chromophore-binding pocket. Information derived from the structures, combined with biophysical and biochemical analysis, has established a model for receptor activation and signal relay, in which light-induced helix tilting in the receptor is transmitted to the transducer by lateral transmembrane helix-helix interactions.
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Affiliation(s)
- John L Spudich
- Department of Biochemistry and Molecular Biology, University of Texas Medical School, Houston 77030, USA.
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29
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Sudo Y, Iwamoto M, Shimono K, Kamo N. Association between a photo-intermediate of a M-lacking mutant D75N of pharaonis phoborhodopsin and its cognate transducer. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY. B, BIOLOGY 2002; 67:171-6. [PMID: 12167316 DOI: 10.1016/s1011-1344(02)00322-6] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Pharaonis phoborhodopsin (ppR or pharaonis sensory rhodopsin II) is a receptor of the negative phototaxis of Natronobacterium pharaonis and forms a complex with its transducer pHtrII in membranes. Flash-photolyis of a D75N mutant did not yield the M-intermediate, but an O-like intermediate is observed in a ms time range. We examined the interaction between the D75N of ppR and t-Htr (truncated pHtrII). These formed a complex in the presence of 0.1% n-dodecyl-beta-maltoside, and the association accelerated the decay of the O of D75N from 15 to 56 s(-1). From the decay time constants under varying ratios of D75N and t-Htr, n, the molar ratio of D75N/t-Htr in the complex, and K(D), the dissociation constant, were estimated. The value of n was unity and K(D) was estimated to 146 nM. This K(D) value can be considered to be the association between the photo-intermediate and t-Htr, which is deduced by the method of estimation. Previously we (Photochem. Photobiol. 74 (2001) 489) reported a K(D) of 15 microM for the interaction between the wild-type and t-Htr by means of the change in M-decay rates. Therefore, this value should be the K(D) value for the interaction between M of the wild-type and t-Htr.
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Affiliation(s)
- Yuki Sudo
- Laboratory of Biophysical Chemistry, Graduate School of Pharmaceutical Sciences, Hokkaido University, Sapporo 060-0812, Japan
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30
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Sudo Y, Iwamoto M, Shimono K, Kamo N. Tyr-199 and charged residues of pharaonis Phoborhodopsin are important for the interaction with its transducer. Biophys J 2002; 83:427-32. [PMID: 12080131 PMCID: PMC1302158 DOI: 10.1016/s0006-3495(02)75180-1] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
pharaonis Phoborhodopsin (ppR; also pharaonis sensory rhodopsin II, psRII) is a retinal protein in Natronobacterium pharaonis and is a receptor of negative phototaxis. It forms a complex with its transducer, pHtrII, in membranes and transmits light signals by protein-protein interaction. Tyr-199 is conserved completely in phoborhodopsins among a variety of archaea, but it is replaced by Val (for bacteriorhodopsin) and Phe (for sensory rhodopsin I). Previously, we (Sudo, Y., M. Iwamoto, K. Shimono, and N. Kamo, submitted for publication) showed that analysis of flash-photolysis data of a complex between D75N and the truncated pHtrII (t-Htr) give a good estimate of the dissociation constant K(D) in the dark. To investigate the importance of Tyr-199, K(D) of double mutants of D75N/Y199F or D75N/Y199V with t-Htr was estimated by flash-photolysis and was approximately 10-fold larger than that of D75N, showing the significant contribution of Tyr-199 to binding. The K(D) of the D75N/t-Htr complex increased with decreasing pH, and the data fitted well with the Henderson-Hasselbach equation with a single pK(a) of 3.86 +/- 0.02. This suggests that certain deprotonated carboxyls at the surface of the transducer (possibly Asp-102, Asp-104, and Asp-106) are needed for the binding.
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Affiliation(s)
- Yuki Sudo
- Laboratory of Biophysical Chemistry, Graduate School of Pharmaceutical Sciences, Hokkaido University, Sapporo 060-0812, Japan
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31
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Edman K, Royant A, Nollert P, Maxwell CA, Pebay-Peyroula E, Navarro J, Neutze R, Landau EM. Early structural rearrangements in the photocycle of an integral membrane sensory receptor. Structure 2002; 10:473-82. [PMID: 11937052 DOI: 10.1016/s0969-2126(02)00736-0] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Sensory rhodopsins are the primary receptors of vision in animals and phototaxis in microorganisms. Light triggers the rapid isomerization of a buried retinal chromophore, which the protein both accommodates and amplifies into the larger structural rearrangements required for signaling. We trapped an early intermediate of the photocycle of sensory rhodopsin II from Natronobacterium pharaonis (pSRII) in 3D crystals and determined its X-ray structure to 2.3 A resolution. The observed structural rearrangements were localized near the retinal chromophore, with a key water molecule becoming disordered and the retinal's beta-ionone ring undergoing a prominent movement. Comparison with the early structural rearrangements of bacteriorhodopsin illustrates how modifications in the retinal binding pocket of pSRII allow subtle differences in the early relaxation of photoisomerized retinal.
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Affiliation(s)
- Karl Edman
- Department of Molecular Biotechnology, Chalmers University of Technology, Box 462, S-40530 Gothenburg, Sweden
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32
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Kunji ER, Spudich EN, Grisshammer R, Henderson R, Spudich JL. Electron crystallographic analysis of two-dimensional crystals of sensory rhodopsin II: a 6.9 A projection structure. J Mol Biol 2001; 308:279-93. [PMID: 11327767 DOI: 10.1006/jmbi.2001.4565] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Sensory rhodopsins, phototaxis receptors in Haloarchaea, were purified and reconstituted into halobacterial lipids to form photoactive two-dimensional crystals. Images of vitreous ice-embedded, flattened, tubular crystals of sensory rhodopsin II (SRII) of Natronobacterium pharaonis were recorded using a field emission gun electron cryo-microscope. Fourier components for the SRII structure were determined either from the separated image transforms from single layers that formed each side of flattened tubes, or by a deconvolution procedure when two layers were stacked in register so that they generated a single crystal lattice by superposition. Most micrographs showed significant diffraction to 6.9 A after computer processing, and the results provide the first intermediate- resolution information obtained for an archaeal sensory rhodopsin. The projection structure of SRII indicates that the helix positions match the seven-helix arrangement of the archaeal transport rhodopsins rather than that of the eukaryotic visual pigments. The structural similarity of SRII to the transport rhodopsins supports models in which the transport and signalling mechanisms of archaeal rhodopsins derive from the same retinal-driven changes in protein conformation.
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Affiliation(s)
- E R Kunji
- MRC Laboratory of Molecular Biology, Hills Road, Cambridge, CB2 2QH, England
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33
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Spudich JL, Yang CS, Jung KH, Spudich EN. Retinylidene proteins: structures and functions from archaea to humans. Annu Rev Cell Dev Biol 2001; 16:365-92. [PMID: 11031241 DOI: 10.1146/annurev.cellbio.16.1.365] [Citation(s) in RCA: 440] [Impact Index Per Article: 19.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Retinylidene proteins, containing seven membrane-embedded alpha-helices that form an internal pocket in which the chromophore retinal is bound, are ubiquitous in photoreceptor cells in eyes throughout the animal kingdom. They are also present in a diverse range of other organisms and locations, such as archaeal prokaryotes, unicellular eukaryotic microbes, the dermal tissue of frogs, the pineal glands of lizards and birds, the hypothalamus of toads, and the human brain. Their functions include light-driven ion transport and phototaxis signaling in microorganisms, and retinal isomerization and various types of photosignal transduction in higher animals. The aims of this review are to examine this group of photoactive proteins as a whole, to summarize our current understanding of structure/function relationships in the best-studied examples, and to report recent new developments.
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Affiliation(s)
- J L Spudich
- Department of Microbiology and Molecular Genetics, University of Texas Medical School, Houston, Texas 77030, USA.
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34
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Shimono K, Kitami M, Iwamoto M, Kamo N. Involvement of two groups in reversal of the bathochromic shift of pharaonis phoborhodopsin by chloride at low pH. Biophys Chem 2000; 87:225-30. [PMID: 11099184 DOI: 10.1016/s0301-4622(00)00195-2] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Pharaonis phoborhodopsin (ppR; or pharaonis sensory rhodopsin II, psRII) is a photophobic receptor of the halobacterium Natronobacterium pharaonis. Its lambdamax is at 496 nm, but upon acidification in the absence of chloride, lambdamax shifted to 522 nm. This bathochromic shift is thought to be caused by the protonation of Asp75, which corresponds to Asp85 of bacteriorhodopsin (bR). The D75N mutant, in which Asp75 was replaced by Asn, had its lambdamax at approximately 520 nm, supporting this mechanism for the bathochromic shift. A titration of the shift yielded a pKa of 3.5 for Asp75. In the presence of chloride, the spectral shifts were different: with a decrease in pH, a bathochromic shift was first observed, followed by a hypsochromic shift on further acidification. This was interpreted as: the disappearance of a negative charge by the protonation of Asp75 was compensated by the binding of chloride, but it is worthy to note that the binding requires the protonation of another proton-associable group other than Asp75. This is supported by the observation that in the presence of chloride, upon acidification, the lambdamax of D75N even showed a blue shift, showing that the protonation of a proton-associable group (pKa = 1.2) leads to the chloride binding that gives rise to a blue shift.
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Affiliation(s)
- K Shimono
- Laboratory of Biophysical Chemistry, Graduate School of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan
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35
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Sasaki J, Spudich JL. Proton transport by sensory rhodopsins and its modulation by transducer-binding. BIOCHIMICA ET BIOPHYSICA ACTA 2000; 1460:230-9. [PMID: 10984603 DOI: 10.1016/s0005-2728(00)00142-0] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The study of light-induced proton transfers in the archaeal sensory rhodopsins (SR), phototaxis receptors in Halobacterium salinarum, has contributed important insights into their mechanism of signaling to their cognate transducer subunits in the signaling complex. Essential features of the bacteriorhodopsin (BR) pumping mechanism have been conserved in the evolution of the sensors, which carry out light-driven electrogenic proton transport when their transducers are removed. The interaction of SRI with its transducer blocks proton-conducting channels in the receptor thereby inhibiting its proton pumping, indicating that the pump machinery, rather than the transport activity itself, is functionally important for signaling. Analysis of SRII mutants has shown that the salt bridge between the protonated Schiff base and its counterion Asp73 constrains the receptor in its inactive conformation. Similarly, in BR, the corresponding salt bridge between the protonated Schiff base and Asp85 contributes to constraining the protein in a conformation in which its cytoplasmic channel is closed. Transducer chimera studies further indicate that the receptor conformational changes are transmitted from the sensors to their cognate transducers through transmembrane helix-helix interaction. These and other results reviewed here support a signaling mechanism in which tilting of helices on the cytoplasmic side (primarily outward tilting of helix F), similar to that which occurs in BR in its open cytoplasmic channel conformation, causes structural alterations in the transducer transmembrane helices.
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Affiliation(s)
- J Sasaki
- Department of Space and Earth Science, Osaka University, Osaka 560-0043, Japan
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36
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Abstract
The retinal protein phoborhodopsin (pR) (also called sensory rhodopsin II) is a specialized photoreceptor pigment used for negative phototaxis in halobacteria. Upon absorption of light, the pigment is transformed into a short-wavelength intermediate, M, that most likely is the signaling state (or its precursor) that triggers the motility response of the cell. The M intermediate thermally decays into the initial pigment, completing the cycle of transformations. In this study we attempted to determine whether M can be converted into the initial state by light. The M intermediate was trapped by the illumination of a water glycerol suspension of phoborhodopsin from Natronobacterium pharaonis called pharaonis phoborhodopsin (ppR) with yellow light (>450 nm) at -50 degrees C. The M intermediate absorbing at 390 nm is stable in the dark at this temperature. We found, however, that M is converted into the initial (or spectrally similar) state with an absorption maximum at 501 nm upon illumination with 380-nm light at -60 degrees C. The reversible transformations ppR if M are accompanied by the perturbation of tryptophan(s) and probably tyrosine(s) residues, as reflected by changes in the UV absorption band. Illumination at lower temperature (-160 degrees C) reveals two intermediates in the photoconversion of M, which we termed M' (or M'(404)) and ppR' (or ppR'(496)). A third photoproduct, ppR'(504), is formed at -110 degrees C during thermal transformations of M'(404) and ppR'(496). The absorption spectrum of M'(404) (maximum at 404 nm) consists of distinct vibronic bands at 362, 382, 404, and 420 nm that are different from the vibronic bands of M at 348, 368, 390, and 415 nm. ppR'(496) has an absorption band that is shifted to shorter wavelengths by 5 nm compared to the initial ppR, whereas ppR'(504) is redshifted by at least 3 nm. As in bacteriorhodopsin, photoexcitation of the M intermediate of ppR and, presumably, photoisomerization of the chromophore during the M --> M' transition result in a dramatic increase in the proton affinity of the Schiff base, followed by its reprotonation during the M' --> ppR' transition. Because the latter reaction occurs at very low temperature, the proton is most likely taken from the counterion (Asp(75)) rather than from the bulk. The phototransformation of M reveals a certain heterogeneity of the pigment, which probably reflects different populations of M or its photoproduct M'. Photoconversion of the M intermediate provides a possible pathway for photoreception in halobacteria and a useful tool for studying the mechanisms of signal transduction by phoborhodopsin (sensory rhodopsin II).
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Affiliation(s)
- S P Balashov
- Center for Biophysics and Computational Biology, Department of Cell and Structural Biology, University of Illinois at Urbana-Champaign, 61801, USA.
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37
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Losi A, Wegener AA, Engelhard M, Gärtner W, Braslavsky SE. Aspartate 75 mutation in sensory rhodopsin II from Natronobacterium pharaonis does not influence the production of the K-like intermediate, but strongly affects its relaxation pathway. Biophys J 2000; 78:2581-9. [PMID: 10777754 PMCID: PMC1300847 DOI: 10.1016/s0006-3495(00)76802-0] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The early steps in the photocycle of the aspartate 75-mutated sensory rhodopsin II from Natrobacterium pharaonis (pSRII-D75N) were studied by time-resolved laser-induced optoacoustic spectroscopy combined with quantum yield determinations by flash photolysis with optical detection. Similar to the case of pSRII-WT, excitation of pSRII-D75N produces in subnanosecond time a K-like intermediate. Different to the case of K in pSRII-WT, in pSRII-D75N there are two K states. K(E) decays into K(L) with a lifetime of 400 ns (independent of temperature in the range 6.5-52 degrees C) which is optically silent under the experimental conditions of our transient absorption experiments. This decay is concomitant with an expansion of 6.5 ml/mol of produced intermediate. This indicates a protein relaxation not affecting the chromophore absorption. For pSRII-D75N reconstituted into polar lipids from purple membrane, the mutation of Asp-75 by the neutral residue Asn affects neither the K(E) production yield (PhiK(e) 0.51 +/- 0.05) nor the energy stored by this intermediate (E(E)K(E) = 91 +/- 11 kJ/mol), nor the expansion upon its production (DeltaV(R,1) = 10 +/- 0.3 ml/mol). All these values are very similar to those previously determined for K with pSRII-WT in the same medium. The millisecond transient species is attributed to K(L) with a lifetime corresponding to that determined by electronic absorption spectroscopy for K(565). The determined energy content of the intermediates as well as the structural volume changes for the various steps afford the calculation of the free energy profile of the phototransformation during the pSRII-D75N photocycle. These data offer insights regarding the photocycle in pSRII-WT. Detergent solubilization of pSRII-D75N affects the sample properties to a larger extent than in the case of pSRII-WT.
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Affiliation(s)
- A Losi
- Max-Planck-Institut für Strahlenchemie, Postfach 10-13-65, D-45413 Mülheim an der Ruhr, Germany
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38
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Schmies G, Lüttenberg B, Chizhov I, Engelhard M, Becker A, Bamberg E. Sensory rhodopsin II from the haloalkaliphilic natronobacterium pharaonis: light-activated proton transfer reactions. Biophys J 2000; 78:967-76. [PMID: 10653809 PMCID: PMC1300699 DOI: 10.1016/s0006-3495(00)76654-9] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
In the present work the light-activated proton transfer reactions of sensory rhodopsin II from Natronobacterium pharaonis (pSRII) and those of the channel-mutants D75N-pSRII and F86D-pSRII are investigated using flash photolysis and black lipid membrane (BLM) techniques. Whereas the photocycle of the F86D-pSRII mutant is quite similar to that of the wild-type protein, the photocycle of D75N-pSRII consists of only two intermediates. The addition of external proton donors such as azide, or in the case of F86D-pSRII, imidazole, accelerates the reprotonation of the Schiff base, but not the turnover. The electrical measurements prove that pSRII and F86D-pSRII can function as outwardly directed proton pumps, whereas the mutation in the extracellular channel (D75N-pSRII) leads to an inwardly directed transient current. The almost negligible size of the photostationary current is explained by the long-lasting photocycle of about a second. Although the M decay, but not the photocycle turnover, of pSRII and F86D-pSRII is accelerated by the addition of azide, the photostationary current is considerably increased. It is discussed that in a two-photon process a late intermediate (N- and/or O-like species) is photoconverted back to the original resting state; thereby the long photocycle is cut short, giving rise to the large increase of the photostationary current. The results presented in this work indicate that the function to generate ion gradients across membranes is a general property of archaeal rhodopsins.
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Affiliation(s)
- G Schmies
- Max-Planck-Institut für Molekulare Physiologie, D-44227 Dortmund, Germany
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39
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Losi A, Wegener AA, Engelhard M, Gärtner W, Braslavsky SE. Time-resolved absorption and photothermal measurements with recombinant sensory rhodopsin II from Natronobacterium pharaonis. Biophys J 1999; 77:3277-86. [PMID: 10585949 PMCID: PMC1300598 DOI: 10.1016/s0006-3495(99)77158-4] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
Purified wild-type sensory rhodopsin II from Natronobacterium pharaonis (pSRII-WT) and its histidine-tagged analog (pSRII-His) were studied by laser-induced optoacoustic spectroscopy (LIOAS) and flash photolysis with optical detection. The samples were either dissolved in detergent or reconstituted into polar lipids from purple membrane (PML). The quantum yield for the formation of the long-lived state M(400) was determined as Phi(M) = 0.5 +/- 0.06 for both proteins. The structural volume change accompanying the production of K(510) as determined with LIOAS was DeltaV(R,1) </= 10 ml for both proteins, assuming Phi(K) >/= Phi(M), indicating that the His tag does not influence this early step of the photocycle. The medium has no influence on DeltaV(R,1), which is the largest so far measured for a retinal protein in this time range (<10 ns). This confirms the occurrence of conformational movements in pSRII for this step, as previously suggested by Fourier transform infrared spectroscopy. On the contrary, the decay of K(510) is an expansion in the detergent-dissolved sample and a contraction in PML. Assuming an efficiency of 1.0, DeltaV(R,2) = -3 ml/mol for pSRII-WT and -4.6 ml/mol for pSRII-His were calculated in PML, indicative of a small structural difference between the two proteins. The energy content of K(510) is also affected by the tag. It is E(K) = (88 +/- 13) for pSRII-WT and (134 +/- 11) kJ/mol for pSRII-His. A slight difference in the activation parameters for K(510) decay confirms an influence of the C-terminal His on this step. At variance with DeltaV(R,1), the opposite sign of DeltaV(R,2) in detergent and PML suggests the occurrence of solvation effects on the decay of K(510), which are probably due to a different interaction of the active site with the two dissolving media.
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Affiliation(s)
- A Losi
- Max-Planck-Institut für Strahlenchemie, D-45413 Mülheim an der Ruhr, Germany
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40
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Abstract
Sensory rhodopsin II (SRII) in Halobacterium salinarum membranes is a phototaxis receptor that signals through its bound transducer HtrII for avoidance of blue-green light. In the present study we investigated the proton movements during the photocycle of SRII in the HtrII-free and HtrII-complexed form. We monitored sustained light-induced pH changes with a pH electrode, and laser flash-induced pH changes with the pH indicator pyranine using sealed membrane vesicles and open sheets containing the free or the complexed receptor. The results demonstrated that SRII takes up a proton in M-to-O conversion and releases it during O-decay. The uptake and release are from and to the extracellular side, and therefore SRII does not transport the proton across the membrane. The pH dependence of the SRII photocycle indicated the presence of a protonatable group (pK(a) approximately 7.5) in the extracellular proton-conducting path, which plays a role in proton uptake by the Schiff base in the M-to-O conversion. The extracellular proton circulation produced by SRII was not blocked by HtrII complexation, unlike the cytoplasmic proton conduction in SRI that was found in the same series of measurements to be blocked by its transducer, HtrI. The implications of this finding for current models of SRI and SRII signaling are discussed.
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Affiliation(s)
- J Sasaki
- Department of Microbiology & Molecular Genetics, University of Texas Medical School, Houston, Texas 77030 USA
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41
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Perazzona B, Spudich JL. Identification of methylation sites and effects of phototaxis stimuli on transducer methylation in Halobacterium salinarum. J Bacteriol 1999; 181:5676-83. [PMID: 10482508 PMCID: PMC94087 DOI: 10.1128/jb.181.18.5676-5683.1999] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The two transducers in the phototaxis system of the archaeon Halobacterium salinarum, HtrI and HtrII, are methyl-accepting proteins homologous to the chemotaxis transducers in eubacteria. Consensus sequences predict three glutamate pairs containing potential methylation sites in HtrI and one in HtrII. Mutagenic substitution of an alanine pair for one of these, Glu265-Glu266, in HtrI and for the homologous Glu513-Glu514 in HtrII eliminated methylation of these two transducers, as demonstrated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis autofluorography. Photostimulation of the repellent receptor sensory rhodopsin II (SRII) induced reversible demethylation of HtrII, while no detectable change in the extent of methylation of HtrI was observed in response to stimulation of its cognate sensory rhodopsin, the attractant receptor SRI. Cells containing HtrI or HtrII with all consensus sites replaced by alanine still exhibited phototaxis responses and behavioral adaptation, and methanol release assays showed that methyl group turnover was still induced in response to photostimulation of SRI or SRII. By pulse-chase experiments with in vivo L-[methyl-(3)H]methionine-labeled cells, we found that repetitive photostimulation of SRI complexed with wild-type (or nonmethylatable) HtrI induced methyl group turnover in transducers other than HtrI to the same extent as in wild-type HtrI. Both attractant and repellent stimuli cause a transient increase in the turnover rate of methyl groups in wild-type H. salinarum cells. This result is unlike that obtained with Escherichia coli, in which attractant stimuli decrease and repellent stimuli increase turnover rate, and is similar to that obtained with Bacillus subtilis, which also shows turnover rate increases regardless of the nature of the stimulus. We found that a CheY deletion mutant of H. salinarum exhibited the E. coli-like asymmetric pattern, as has recently also been observed in B. subtilis. Further, we demonstrate that the CheY-dependent feedback effect does not require the stimulated transducer to be methylatable and operates globally on other transducers present in the cell.
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Affiliation(s)
- B Perazzona
- Department of Microbiology and Molecular Genetics, The University of Texas Medical School, Houston, Texas 77030, USA
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42
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Luecke H, Schobert B, Richter HT, Cartailler JP, Lanyi JK. Structure of bacteriorhodopsin at 1.55 A resolution. J Mol Biol 1999; 291:899-911. [PMID: 10452895 DOI: 10.1006/jmbi.1999.3027] [Citation(s) in RCA: 1155] [Impact Index Per Article: 46.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Th?e atomic structure of the light-driven ion pump bacteriorhodopsin and the surrounding lipid matrix was determined by X-ray diffraction of crystals grown in cubic lipid phase. In the extracellular region, an extensive three-dimensional hydrogen-bonded network of protein residues and seven water molecules leads from the buried retinal Schiff base and the proton acceptor Asp85 to the membrane surface. Near Lys216 where the retinal binds, transmembrane helix G contains a pi-bulge that causes a non-proline? kink. The bulge is stabilized by hydrogen-bonding of the main-chain carbonyl groups of Ala215 and Lys216 with two buried water molecules located between the Schiff base and the proton donor Asp96 in the cytoplasmic region. The results indicate extensive involvement of bound water molecules in both the structure and the function of this seven-helical membrane protein. A bilayer of 18 tightly bound lipid chains forms an annulus around the protein in the crystal. Contacts between the trimers in the membrane plane are mediated almost exclusively by lipids.
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Affiliation(s)
- H Luecke
- Department of Molecular Biology and Biochemistry, University of California, Irvine, CA, 92697, USA
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43
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Zhang XN, Zhu J, Spudich JL. The specificity of interaction of archaeal transducers with their cognate sensory rhodopsins is determined by their transmembrane helices. Proc Natl Acad Sci U S A 1999; 96:857-62. [PMID: 9927658 PMCID: PMC15315 DOI: 10.1073/pnas.96.3.857] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Chimeras of the Halobacterium salinarum transducers HtrI and HtrII were constructed to study the structural determinants for their specific interaction with the phototaxis receptors sensory rhodopsins I and II (SRI and SRII), respectively. Interaction of receptors and transducers was assessed by two criteria: phototaxis responses by the cells and transducer-modulation of receptor photochemical reaction kinetics in membranes. Coexpression of HtrI with SRII or HtrII with SRI did not result in interaction by either criterion. Each receptor was coexpressed with chimeric transducers in which various domains of the two transducers were interchanged. The results show that the presence of the two transmembrane helices of HtrI in a chimera is necessary and sufficient for functional transducer complexation with SRI, i.e., for wild-type SRI photoreactions and attractant and 2-photon repellent phototaxis responses. Additionally, a previously demonstrated chaperone-like facilitation of SRI folding or stability by HtrI was shown to depend only on the two transmembrane helices of HtrI in chimeric transducers. Similarly, the two transmembrane helices of HtrII specify interaction with the repellent receptor SRII according to motility analysis and laser-flash spectroscopy. The results support a model in which the membrane domains of the receptor/transducer complexes, consisting of the seven helices of the receptor interacting with the four-helix bundle of the transducer dimer, produce SRI- and SRII-specific signals to the flagellar motor by means of interchangeable cytoplasmic domains.
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Affiliation(s)
- X N Zhang
- Department of Microbiology and Molecular Genetics, The University of Texas Medical School, Houston, TX 77030, USA
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44
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Sasaki J, Spudich JL. The transducer protein HtrII modulates the lifetimes of sensory rhodopsin II photointermediates. Biophys J 1998; 75:2435-40. [PMID: 9788938 PMCID: PMC1299917 DOI: 10.1016/s0006-3495(98)77687-8] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We studied the photochemical reaction cycle of sensory rhodopsin II (SRII) by flash photolysis of Halobacterium salinarum membranes genetically engineered to contain or to lack its transducer protein HtrII. Flash photolysis data from membranes containing HtrII were fit well in the 10 micros-10 s range by three rate constants and a linear unbranched pathway from the unphotolyzed state with 487 nm absorption maximum to a species with absorption maximum near 350 nm (M) followed by a species with maximum near 520 nm (O), as has been found in previous studies of wild-type membranes. Data from membranes devoid of HtrII exhibited similar M and O intermediates but with altered kinetics, and a third intermediate absorbing maximally near 470 nm (N) was present in an equilibrium mixture with O. The modulation of SRII photoreactions by HtrII indicates that SRII and HtrII are physically associated in a molecular complex. Arrhenius analysis shows that the largest effect of HtrII, the acceleration of O decay, is attributable to a large decrease in activation enthalpy. Based on comparison of SRII photoreactions to those of sensory rhodopsin I and bacteriorhodopsin, we interpret this kinetic effect to indicate that HtrII interacts with SRII so that it alters the reaction process involving deprotonation of Asp73, the proton acceptor from the Schiff base.
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Affiliation(s)
- J Sasaki
- Department of Microbiology and Molecular Genetics, University of Texas Medical School, Houston, Texas 77030, USA
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45
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Cercignani G, Lucia S, Petracchi D. Photoresponses of Halobacterium salinarum to repetitive pulse stimuli. Biophys J 1998; 75:1466-72. [PMID: 9726948 PMCID: PMC1299821 DOI: 10.1016/s0006-3495(98)74065-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Halobacterium salinarum cells from 3-day-old cultures have been stimulated with different patterns of repetitive pulse stimuli. A short train of 0.6-s orange light pulses with a 4-s period resulted in reversal peaks of increasing intensity. The reverse occurred when blue light pulses were delivered as a finite train: with a 3-s period, the response declined in sequence from the first to the last pulse. To evaluate the response of the system under steady-state conditions of stimulation, continuous trains of pulses were also applied; whereas blue light always produced a sharply peaked response immediately after each pulse, orange pulses resulted in a declining peak of reversals that lasted until the subsequent pulse. An attempt to account for these results in terms of current excitation/adaptation models shows that additional mechanisms appear to be at work in this transduction chain.
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Affiliation(s)
- G Cercignani
- Dipartimento di Fisiologia e Biochimica, Università di Pisa, Italy
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46
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Chizhov I, Schmies G, Seidel R, Sydor JR, Lüttenberg B, Engelhard M. The photophobic receptor from Natronobacterium pharaonis: temperature and pH dependencies of the photocycle of sensory rhodopsin II. Biophys J 1998; 75:999-1009. [PMID: 9675200 PMCID: PMC1299773 DOI: 10.1016/s0006-3495(98)77588-5] [Citation(s) in RCA: 161] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
The photocycle of the photophobic receptor sensory rhodopsin II from N. pharaonis was analyzed by varying measuring wavelengths, temperature, and pH, and by exchanging H2O with D2O. The data can be satisfactorily modeled by eight exponents over the whole range of modified parameters. The kinetic data support a model similar to that of bacteriorhodopsin (BR) if a scheme of irreversible first-order reactions is assumed. Eight kinetically distinct protein states can then be identified. These states are formed from five spectrally distinct species. The chromophore states Si correspond in their spectral properties to those of the BR photocycle, namely pSRII510 (K), pSRII495 (L), pSRII400 (M), pSRII485 (N), and pSRII535 (O). In comparison to BR, pSRII400 is formed approximately 10 times faster than the M state; however, the back-reaction is almost 100 times slower. Comparison of the temperature dependence of the rate constants with those from the BR photocycle suggests that the differences are caused by changes of DeltaS. The rate constants of the pSRII photocycle are almost insensitive to the pH variation from 9.0 to 5.5, and show only a small H2O/D2O effect. This analysis supports the idea that the conformational dynamics of pSRII controls the kinetics of the photocycle of pSRII.
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Affiliation(s)
- I Chizhov
- Max-Planck-Institut für Molekulare Physiologie, 44139 Dortmund, Germany
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47
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Oesterhelt D. The structure and mechanism of the family of retinal proteins from halophilic archaea. Curr Opin Struct Biol 1998; 8:489-500. [PMID: 9729742 DOI: 10.1016/s0959-440x(98)80128-0] [Citation(s) in RCA: 177] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Retinal proteins from halophilic archaea provide a unique opportunity to analyze vectorial ion translocation. Studies on its structure, conformational changes, proton conduction and electrogenic steps have helped to elucidate the catalytic cycle of bacteriorhodopsin in increasing detail. Experimental modulation of the vectoriality and ion specificity by altering the substrate availability, point mutations and light conditions for the different retinal proteins allows the proposal of a general model of ion transport for this protein family.
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Affiliation(s)
- D Oesterhelt
- Max-Planck-Institut für Biochemie, Martinsried, Germany.
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48
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Abstract
The archaeal rhodopsins are a family of seven-transmembrane-helix, visual pigment-like proteins found in Halobacterium salinarum and related halophilic Archaea. Two, bacteriorhodopsin (BR) and halorhodopsin (HR), are transport rhodopsins that carry out light-driven electrogenic translocation of protons and chloride, respectively, across the cell membrane. The other two, sensory rhodopsins I and II (SRI and SRII), are phototaxis receptors that send signals to tightly bound transducer proteins that in turn control a phosphorylation cascade modulating the cell's flagellar motors. Recent progress has cast light on how nature has modified the common design of these proteins to carry out their distinctly different functions: electrogenic ion transport and non-electrogenic signal transduction. A key shared mechanism between BR and SRII appears to be an interhelical salt bridge locked conformational switch that is released by photoisomerization of retinal. In BR disruption of the lock opens a cytoplasmic half-channel that ensures uptake of the transported proton from the cytoplasmic side of the membrane at a critical time in the pumping cycle. Transducer-free SRI uses the same mechanism to carry out light-driven proton transport, but interaction with its transducer blocks the cytoplasmic half-channel thereby interrupting the transport cycle. In SRI, transducer interaction also disrupts the salt bridge in the dark, poising the receptor in an intermediate conformation able to produce opposite signals depending on the colour of the stimulus light. A model for signalling is proposed in which the salt bridge-controlled half-channel is used to modulate interaction with the Htr proteins when the receptor signalling states are formed.
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Affiliation(s)
- J L Spudich
- Department of Microbiology and Molecular Genetics, University of Texas Medical School, Houston 77030, USA.
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49
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Jung KH, Spudich JL. Suppressor mutation analysis of the sensory rhodopsin I-transducer complex: insights into the color-sensing mechanism. J Bacteriol 1998; 180:2033-42. [PMID: 9555883 PMCID: PMC107127 DOI: 10.1128/jb.180.8.2033-2042.1998] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The molecular complex containing the phototaxis receptor sensory rhodopsin I (SRI) and transducer protein HtrI (halobacterial transducer for SRI) mediates color-sensitive phototaxis responses in the archaeon Halobacterium salinarum. One-photon excitation of the complex by orange light elicits attractant responses, while two-photon excitation (orange followed by near-UV light) elicits repellent responses in swimming cells. Several mutations in SRI and HtrI cause an unusual mutant phenotype, called orange-light-inverted signaling, in which the cell produces a repellent response to normally attractant light. We applied a selection procedure for intragenic and extragenic suppressors of orange-light-inverted mutants and identified 15 distinct second-site mutations that restore the attractant response. Two of the 3 suppressor mutations in SRI are positioned at the cytoplasmic ends of helices F and G, and 12 suppressor mutations in HtrI cluster at the cytoplasmic end of the second HtrI transmembrane helix (TM2). Nearly all suppressors invert the normally repellent response to two-photon stimulation to an attractant response when they are expressed with their suppressible mutant alleles or in an otherwise wild-type strain. The results lead to a model for control of flagellar reversal by the SRI-HtrI complex. The model invokes an equilibrium between the A (reversal-inhibiting) and R (reversal-stimulating) conformers of the signaling complex. Attractant light and repellent light shift the equilibrium toward the A and R conformers, respectively, and mutations are proposed to cause intrinsic shifts in the equilibrium in the dark form of the complex. Differences in the strength of the two-photon signal inversion and in the allele specificity of suppression are correlated, and this correlation can be explained in terms of different values of the equilibrium constant (Keq) for the conformational transition in different mutants and mutant-suppressor pairs.
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Affiliation(s)
- K H Jung
- Department of Microbiology and Molecular Genetics, University of Texas-Houston Medical School, 77030, USA
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Affiliation(s)
- M D Manson
- Department of Biology, Texas A&M University, College Station 77843, USA.
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