1
|
Nikolaev D, Mironov VN, Metelkina EM, Shtyrov AA, Mereshchenko AS, Demidov NA, Vyazmin SY, Tennikova TB, Moskalenko SE, Bondarev SA, Zhouravleva GA, Vasin AV, Panov MS, Ryazantsev MN. Rational Design of Far-Red Archaerhodopsin-3-Based Fluorescent Genetically Encoded Voltage Indicators: from Elucidation of the Fluorescence Mechanism in Archers to Novel Red-Shifted Variants. ACS PHYSICAL CHEMISTRY AU 2024; 4:347-362. [PMID: 39069984 PMCID: PMC11274289 DOI: 10.1021/acsphyschemau.3c00073] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/25/2023] [Revised: 04/07/2024] [Accepted: 04/08/2024] [Indexed: 07/30/2024]
Abstract
Genetically encoded voltage indicators (GEVIs) have found wide applications as molecular tools for visualization of changes in cell membrane potential. Among others, several classes of archaerhodopsin-3-based GEVIs have been developed and have proved themselves promising in various molecular imaging studies. To expand the application range for this type of GEVIs, new variants with absorption band maxima shifted toward the first biological window and enhanced fluorescence signal are required. Here, we integrate computational and experimental strategies to reveal structural factors that distinguish far-red bright archaerhodopsin-3-based GEVIs, Archers, obtained by directed evolution in a previous study (McIsaac et al., PNAS, 2014) and the wild-type archaerhodopsin-3 with an extremely dim fluorescence signal, aiming to use the obtained information in subsequent rational design. We found that the fluorescence can be enhanced by stabilization of a certain conformation of the protein, which, in turn, can be achieved by tuning the pK a value of two titratable residues. These findings were supported further by introducing mutations into wild-type archeorhodopsin-3 and detecting the enhancement of the fluorescence signal. Finally, we came up with a rational design and proposed previously unknown Archers variants with red-shifted absorption bands (λmax up to 640 nm) and potential-dependent bright fluorescence (quantum yield up to 0.97%).
Collapse
Affiliation(s)
- Dmitrii
M. Nikolaev
- Institute
of Chemistry, Saint Petersburg State University, 26 Universitetskii pr, St. Petersburg 198504, Russia
- Institute
of Biomedical Systems and Biotechnologies, Peter the Great St. Petersburg Polytechnic University, 29 Polytechnicheskaya Str., St. Petersburg 195251, Russia
| | - Vladimir N. Mironov
- Saint
Petersburg Academic University, 8/3 Khlopina Street, St.
Petersburg 194021, Russia
| | - Ekaterina M. Metelkina
- Institute
of Chemistry, Saint Petersburg State University, 26 Universitetskii pr, St. Petersburg 198504, Russia
| | - Andrey A. Shtyrov
- Institute
of Chemistry, Saint Petersburg State University, 26 Universitetskii pr, St. Petersburg 198504, Russia
| | - Andrey S. Mereshchenko
- Institute
of Chemistry, Saint Petersburg State University, 26 Universitetskii pr, St. Petersburg 198504, Russia
| | - Nikita A. Demidov
- Saint
Petersburg Academic University, 8/3 Khlopina Street, St.
Petersburg 194021, Russia
| | - Sergey Yu. Vyazmin
- Saint
Petersburg Academic University, 8/3 Khlopina Street, St.
Petersburg 194021, Russia
| | - Tatiana B. Tennikova
- Institute
of Chemistry, Saint Petersburg State University, 26 Universitetskii pr, St. Petersburg 198504, Russia
| | - Svetlana E. Moskalenko
- Department
of Genetics and Biotechnology, Saint Petersburg
State University, 7/9
Universitetskaya emb, St. Petersburg 199034, Russia
- Vavilov
Institute of General Genetics, St. Petersburg
Branch, Russian Academy of Sciences, St. Petersburg 199034, Russia
| | - Stanislav A. Bondarev
- Department
of Genetics and Biotechnology, Saint Petersburg
State University, 7/9
Universitetskaya emb, St. Petersburg 199034, Russia
- Laboratory
of Amyloid Biology, Saint Petersburg State
University, St. Petersburg 199034, Russia
| | - Galina A. Zhouravleva
- Department
of Genetics and Biotechnology, Saint Petersburg
State University, 7/9
Universitetskaya emb, St. Petersburg 199034, Russia
- Laboratory
of Amyloid Biology, Saint Petersburg State
University, St. Petersburg 199034, Russia
| | - Andrey V. Vasin
- Institute
of Biomedical Systems and Biotechnologies, Peter the Great St. Petersburg Polytechnic University, 29 Polytechnicheskaya Str., St. Petersburg 195251, Russia
| | - Maxim S. Panov
- Institute
of Chemistry, Saint Petersburg State University, 26 Universitetskii pr, St. Petersburg 198504, Russia
- St.
Petersburg State Chemical Pharmaceutical University, Professor Popov str., 14, lit. A, St. Petersburg 197022, Russia
| | - Mikhail N. Ryazantsev
- Institute
of Chemistry, Saint Petersburg State University, 26 Universitetskii pr, St. Petersburg 198504, Russia
| |
Collapse
|
2
|
Shigeta A, Otani Y, Miyasa R, Makino Y, Kawamura I, Okitsu T, Wada A, Naito A. Photoreaction Pathways of Bacteriorhodopsin and Its D96N Mutant as Revealed by in Situ Photoirradiation Solid-State NMR. MEMBRANES 2022; 12:membranes12030279. [PMID: 35323754 PMCID: PMC8949607 DOI: 10.3390/membranes12030279] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/28/2021] [Revised: 02/25/2022] [Accepted: 02/26/2022] [Indexed: 11/18/2022]
Abstract
Bacteriorhodopsin (BR) functions as a light-driven proton pump that transitions between different states during the photocycle, such as all-trans (AT; BR568) and 13-cis, 15-syn (CS; BR548) state and K, L, M1, M2, N, and O intermediates. In this study, we used in situ photoirradiation 13C solid-state NMR to observe a variety of photo-intermediates and photoreaction pathways in [20-13C]retinal-WT-BR and its mutant [20-13C, 14-13C]retinal-D96N-BR. In WT-BR, the CS state converted to the CS* intermediate under photoirradiation with green light at −20 °C and consequently converted to the AT state in the dark. The AT state converted to the N intermediate under irradiation with green light. In D96N-BR, the CS state was converted to the CS* intermediate at −30 °C and consequently converted to the AT state. Simultaneously, the AT state converted to the M and L intermediates under green light illumination at −30 °C and subsequently converted to the AT state in the dark. The M intermediate was directly excited to the AT state by UV light illumination. We demonstrated that short-lived photo-intermediates could be observed in a stationary state using in situ photoirradiation solid-state NMR spectroscopy for WT-BR and D96N-BR, enabling insight into the light-driven proton pump activity of BR.
Collapse
Affiliation(s)
- Arisu Shigeta
- Graduate School of Engineering, Yokohama National University, 79-5 Tokiwadai, Hodogaya-ku, Yokohama 240-8501, Japan; (A.S.); (Y.O.); (R.M.); (Y.M.)
| | - Yuto Otani
- Graduate School of Engineering, Yokohama National University, 79-5 Tokiwadai, Hodogaya-ku, Yokohama 240-8501, Japan; (A.S.); (Y.O.); (R.M.); (Y.M.)
| | - Ryota Miyasa
- Graduate School of Engineering, Yokohama National University, 79-5 Tokiwadai, Hodogaya-ku, Yokohama 240-8501, Japan; (A.S.); (Y.O.); (R.M.); (Y.M.)
| | - Yoshiteru Makino
- Graduate School of Engineering, Yokohama National University, 79-5 Tokiwadai, Hodogaya-ku, Yokohama 240-8501, Japan; (A.S.); (Y.O.); (R.M.); (Y.M.)
| | - Izuru Kawamura
- Graduate School of Engineering, Yokohama National University, 79-5 Tokiwadai, Hodogaya-ku, Yokohama 240-8501, Japan; (A.S.); (Y.O.); (R.M.); (Y.M.)
- Correspondence: (I.K.); (A.N.)
| | - Takashi Okitsu
- Laboratory of Organic Chemistry for Life Science, Kobe Pharmaceutical University, 4-19-1 Motoyamakitamachi, Higashinada-ku, Kobe 658-8558, Japan; (T.O.); (A.W.)
| | - Akimori Wada
- Laboratory of Organic Chemistry for Life Science, Kobe Pharmaceutical University, 4-19-1 Motoyamakitamachi, Higashinada-ku, Kobe 658-8558, Japan; (T.O.); (A.W.)
| | - Akira Naito
- Graduate School of Engineering, Yokohama National University, 79-5 Tokiwadai, Hodogaya-ku, Yokohama 240-8501, Japan; (A.S.); (Y.O.); (R.M.); (Y.M.)
- Correspondence: (I.K.); (A.N.)
| |
Collapse
|
3
|
Naito A, Makino Y, Shigeta A, Kawamura I. Photoreaction pathways and photointermediates of retinal-binding photoreceptor proteins as revealed by in situ photoirradiation solid-state NMR spectroscopy. Biophys Rev 2019; 11:167-181. [PMID: 30811009 DOI: 10.1007/s12551-019-00501-w] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2018] [Accepted: 01/28/2019] [Indexed: 12/20/2022] Open
Abstract
Photoirradiation solid-state NMR spectroscopy is a powerful means to study photoreceptor retinal-binding proteins by the detection of short-lived photointermediates to elucidate the photoreaction cycle and photoactivated structural changes. An in situ photoirradiation solid-state NMR apparatus has been developed for the irradiation of samples with extremely high efficiency to enable observation of photointermediates which are stationary trapped states. Such observation enables elucidation of the photoreaction processes of photoreceptor membrane proteins. Therefore, in situ photoirradiation is particularly useful study the photocycle of retinal-binding proteins such as sensory rhodopsin I (SRI) and sensory rhodopsin II (SRII) because functional photointermediates have relatively longer half-lives than other photointermediates. As a result, several photointermediates have been trapped as stationary state and their detailed structures and photoreaction cycles have been revealed using photoirradiation solid-state NMR spectroscopy at low temperature. Photoreaction intermediates of bacteriorhodopsin, which functions to provide light-driven proton pump activity, were difficult to trap because the half-lives of the photointermediates were shorter than those of sensory rhodopsin. Therefore, these photointermediates are trapped in a freeze-trapped state at a very low temperature and the NMR signals were observed using a combination of photoirradiation and dynamic nuclear polarization (DNP) experiments.
Collapse
Affiliation(s)
- Akira Naito
- Graduate School of Engineering, Yokohama National University, Yokohama, 240-8501, Japan.
| | - Yoshiteru Makino
- Graduate School of Engineering, Yokohama National University, Yokohama, 240-8501, Japan
| | - Arisu Shigeta
- Graduate School of Engineering, Yokohama National University, Yokohama, 240-8501, Japan
| | - Izuru Kawamura
- Graduate School of Engineering, Yokohama National University, Yokohama, 240-8501, Japan
| |
Collapse
|
4
|
Mei G, Mamaeva N, Ganapathy S, Wang P, DeGrip WJ, Rothschild KJ. Raman spectroscopy of a near infrared absorbing proteorhodopsin: Similarities to the bacteriorhodopsin O photointermediate. PLoS One 2018; 13:e0209506. [PMID: 30586409 PMCID: PMC6306260 DOI: 10.1371/journal.pone.0209506] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2018] [Accepted: 12/06/2018] [Indexed: 02/07/2023] Open
Abstract
Microbial rhodopsins have become an important tool in the field of optogenetics. However, effective in vivo optogenetics is in many cases severely limited due to the strong absorption and scattering of visible light by biological tissues. Recently, a combination of opsin site-directed mutagenesis and analog retinal substitution has produced variants of proteorhodopsin which absorb maximally in the near-infrared (NIR). In this study, UV-Visible-NIR absorption and resonance Raman spectroscopy were used to study the double mutant, D212N/F234S, of green absorbing proteorhodopsin (GPR) regenerated with MMAR, a retinal analog containing a methylamino modified β-ionone ring. Four distinct subcomponent absorption bands with peak maxima near 560, 620, 710 and 780 nm are detected with the NIR bands dominant at pH <7.3, and the visible bands dominant at pH 9.5. FT-Raman using 1064-nm excitation reveal two strong ethylenic bands at 1482 and 1498 cm-1 corresponding to the NIR subcomponent absorption bands based on an extended linear correlation between λmax and γC = C. This spectrum exhibits two intense bands in the fingerprint and HOOP mode regions that are highly characteristic of the O640 photointermediate from the light-adapted bacteriorhodopsin photocycle. In contrast, 532-nm excitation enhances the 560-nm component, which exhibits bands very similar to light-adapted bacteriorhodopsin and/or the acid-purple form of bacteriorhodopsin. Native GPR and its mutant D97N when regenerated with MMAR also exhibit similar absorption and Raman bands but with weaker contributions from the NIR absorbing components. Based on these results it is proposed that the NIR absorption in GPR-D212N/F234S with MMAR arises from an O-like chromophore, where the Schiff base counterion D97 is protonated and the MMAR adopts an all-trans configuration with a non-planar geometry due to twists in the conjugated polyene segment. This configuration is characterized by extensive charge delocalization, most likely involving nitrogens atoms in the MMAR chromophore.
Collapse
Affiliation(s)
- Gaoxiang Mei
- Molecular Biophysics Laboratory, Photonics Center and Department of Physics, Boston University, Boston, Massachusetts, United States of America
| | - Natalia Mamaeva
- Molecular Biophysics Laboratory, Photonics Center and Department of Physics, Boston University, Boston, Massachusetts, United States of America
| | - Srividya Ganapathy
- Department of Biophysical Organic Chemistry, Leiden Institute of Chemistry, Leiden UniversityAR Leiden, The Netherlands
| | - Peng Wang
- Bruker Corporation, Billerica, MA, United States of America
| | - Willem J. DeGrip
- Department of Biophysical Organic Chemistry, Leiden Institute of Chemistry, Leiden UniversityAR Leiden, The Netherlands
| | - Kenneth J. Rothschild
- Molecular Biophysics Laboratory, Photonics Center and Department of Physics, Boston University, Boston, Massachusetts, United States of America
- * E-mail:
| |
Collapse
|
5
|
Ding X, Sun C, Cui H, Chen S, Gao Y, Yang Y, Wang J, He X, Iuga D, Tian F, Watts A, Zhao X. Functional roles of tyrosine 185 during the bacteriorhodopsin photocycle as revealed by in situ spectroscopic studies. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2018; 1859:1006-1014. [PMID: 29800547 DOI: 10.1016/j.bbabio.2018.05.011] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2017] [Revised: 04/15/2018] [Accepted: 05/20/2018] [Indexed: 01/22/2023]
Abstract
Tyrosine 185 (Y185), one of the aromatic residues within the retinal (Ret) chromophore binding pocket in helix F of bacteriorhodopsin (bR), is highly conserved among the microbial rhodopsin family proteins. Many studies have investigated the functions of Y185, but its underlying mechanism during the bR photocycle remains unclear. To address this research gap, in situ two-dimensional (2D) magic-angle spinning (MAS) solid-state NMR (ssNMR) of specifically labelled bR, combined with light-induced transient absorption change measurements, dynamic light scattering (DLS) measurements, titration analysis and site-directed mutagenesis, was used to elucidate the functional roles of Y185 during the bR photocycle in the native membrane environment. Different interaction modes were identified between Y185 and the Ret chromophore in the dark-adapted (inactive) state and M (active) state, indicating that Y185 may serve as a rotamer switch maintaining the protein dynamics, and plays an important role in the efficient proton-pumping mechanism in the bR purple membrane.
Collapse
Affiliation(s)
- Xiaoyan Ding
- Shanghai Key Laboratory of Magnetic Resonance, School of Physics and Materials Science, East China Normal University, Shanghai 200062, PR China; Department of Biochemistry and Molecular Biology, Penn State College of Medicine, PA 17033-0850, USA
| | - Chao Sun
- Shanghai Key Laboratory of Magnetic Resonance, School of Physics and Materials Science, East China Normal University, Shanghai 200062, PR China
| | - Haolin Cui
- Shanghai Key Laboratory of Magnetic Resonance, School of Physics and Materials Science, East China Normal University, Shanghai 200062, PR China
| | - Sijin Chen
- Shanghai Key Laboratory of Magnetic Resonance, School of Physics and Materials Science, East China Normal University, Shanghai 200062, PR China
| | - Yujiao Gao
- Shanghai Key Laboratory of Magnetic Resonance, School of Physics and Materials Science, East China Normal University, Shanghai 200062, PR China
| | - Yanan Yang
- Shanghai Key Laboratory of Magnetic Resonance, School of Physics and Materials Science, East China Normal University, Shanghai 200062, PR China
| | - Juan Wang
- Shanghai Key Laboratory of Magnetic Resonance, School of Physics and Materials Science, East China Normal University, Shanghai 200062, PR China
| | - Xiao He
- Shang Engineering Research Center of Molecular Therapeutics and New Drug Development, School of Chemistry and Molecular Engineering, East China Normal University, Shanghai 200062, PR China
| | - Dinu Iuga
- The UK 850 MHz Solid-State NMR Facility, Department of Physics, University of Warwick, Coventry CV4 7AL, UK
| | - Fang Tian
- Department of Biochemistry and Molecular Biology, Penn State College of Medicine, PA 17033-0850, USA.
| | - Anthony Watts
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK.
| | - Xin Zhao
- Shanghai Key Laboratory of Magnetic Resonance, School of Physics and Materials Science, East China Normal University, Shanghai 200062, PR China.
| |
Collapse
|
6
|
Oshima K, Shigeta A, Makino Y, Kawamura I, Okitsu T, Wada A, Tuzi S, Iwasa T, Naito A. Characterization of photo-intermediates in the photo-reaction pathways of a bacteriorhodopsin Y185F mutant using in situ photo-irradiation solid-state NMR spectroscopy. Photochem Photobiol Sci 2015; 14:1694-702. [PMID: 26169449 DOI: 10.1039/c5pp00154d] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Photo-reaction pathways of a bacteriorhodopsin Y185F mutant were examined using in situ photo-irradiation solid-state NMR spectroscopy. (13)C CP MAS NMR spectra were recorded at -40 °C in the dark (D1), under irradiation with 520 nm light (L1), subsequently in the dark (D2), and again under irradiation with 520 nm light (L2). In the process from D1 to L1, the 13-cis, 15-syn (CS; bR548) state changed to a CS*- (13-cis, 15-syn) intermediate, which was highly stable at -40 °C, and the all-trans (AT; bR568) state transformed to an N-intermediate. Under the D2 conditions, the N-intermediate transformed to an O-intermediate, which was highly stable at -40 °C in the dark. During subsequent irradiation with 520 nm light (L2), the O-intermediate transformed to the N-intermediate through the AT state, whereas the CS*-intermediate did not change. The CS*-intermediate was converted to the AT state (or O-intermediate) after the temperature was increased to -20 °C. Upon subsequent increase of the temperature to 20 °C, the AT state (or O-intermediate) was converted to the CS state until reaching equilibrium. In this experiment, the chemical shift values of [20-(13)C, 14-(13)C]retinal provided the 13C[double bond, length as m-dash]C and 15C[double bond, length as m-dash]N configurations, respectively. From these data, the configurations of the AT and CS states and the CS*-, N-, and O-intermediates were determined to be (13-trans, 15-anti), (13-cis, 15-syn), (13-cis, 15-syn), (13-cis, 15-anti), and (13-trans, 15-anti), respectively. (13)C NMR signals of the CS*- and O-intermediates were observed for the first time for the Y185F bR mutant by in situ photo-irradiation solid-state NMR spectroscopy and the configuration of the CS*-intermediate was revealed to be significantly twisted from that of the CS state although both were assigned as (13-cis, 15-syn) configurations.
Collapse
Affiliation(s)
- Kyosuke Oshima
- Graduate School of Engineering, Yokohama National University, 79-5 Tokiwadai, Hodogaya-ku, Yokohama 240-8501, Japan.
| | | | | | | | | | | | | | | | | |
Collapse
|
7
|
Maeda A. Application of FTIR Spectroscopy to the Structural Study on the Function of Bacteriorhodopsin. Isr J Chem 2013. [DOI: 10.1002/ijch.199500038] [Citation(s) in RCA: 124] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
|
8
|
|
9
|
Mizuno M, Sudo Y, Homma M, Mizutani Y. Direct Observation of the Structural Change of Tyr174 in the Primary Reaction of Sensory Rhodopsin II. Biochemistry 2011; 50:3170-80. [DOI: 10.1021/bi101817y] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Affiliation(s)
- Misao Mizuno
- Department of Chemistry, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan
| | - Yuki Sudo
- Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan
- PRESTO, Japan Science and Technology Agency (JST), 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan
| | - Michio Homma
- Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan
| | - Yasuhisa Mizutani
- Department of Chemistry, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan
| |
Collapse
|
10
|
Lazarova T, Querol E, Padrós E. Coupling between the retinal thermal isomerization and the Glu194 residue of bacteriorhodopsin. Photochem Photobiol 2009; 85:617-23. [PMID: 19267876 DOI: 10.1111/j.1751-1097.2008.00534.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: 11/29/2022]
Abstract
Glu194 is a residue located at the end of F helix on the extracellular side of the light-induced proton pump bacteriorhodopsin (BR). Currently, it is well recognized that Glu194 and Glu204 residues, along with water clusters, constitute the proton release group of BR. Here we report that the replacement of Glu194 for Gln affects not only the photocycle of the protein but also has tremendous effect on the all-trans to 13-cis thermal isomerization. We studied the pH dependence of the dark adaptation of the E194Q mutant and performed HPLC analysis of the isomer compositions of the light- and partially dark-adapted states of the mutant at several pH values. Our data confirmed that E194Q exhibits extremely slow dark adaptation over a wide range of pH. HPLC data showed that a significantly larger concentration of all-trans isomer was present in the samples of the E194Q mutant even after prolonged dark adaptation. After 14 days in the dark the 13-cis to all-trans ratio was 1:3 in the mutant, compared to 2:1 in the wild type. These data clearly indicate the involvement of Glu194 in control of the rate of all-trans to 13-cis thermal isomerization.
Collapse
Affiliation(s)
- Tzvetana Lazarova
- Departament de Bioquímica i de Biologia Molecular, Universitat Autònoma de Barcelona, Bellaterra, Spain.
| | | | | |
Collapse
|
11
|
Bergo V, Spudich EN, Spudich JL, Rothschild KJ. A Fourier Transform Infrared Study of Neurospora Rhodopsin: Similarities with Archaeal Rhodopsins¶†. Photochem Photobiol 2007. [DOI: 10.1562/0031-8655(2002)0760341aftiso2.0.co2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
|
12
|
Sudo Y, Furutani Y, Kandori H, Spudich JL. Functional importance of the interhelical hydrogen bond between Thr204 and Tyr174 of sensory rhodopsin II and its alteration during the signaling process. J Biol Chem 2006; 281:34239-45. [PMID: 16968701 DOI: 10.1074/jbc.m605907200] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Sensory rhodopsin II (SRII), a receptor for negative phototaxis in haloarchaea, transmits light signals through changes in protein-protein interaction with its transducer HtrII. Light-induced structural changes throughout the SRII-HtrII interface, which spans the periplasmic region, membrane-embedded domains, and cytoplasmic domains near the membrane, have been identified by several studies. Here we demonstrate by site-specific mutagenesis and analysis of phototaxis behavior that two residues in SRII near the membrane-embedded interface (Tyr174 on helix F and Thr204 on helix G) are essential for signaling by the SRII-HtrII complex. These residues, which are the first in SRII shown to be required for phototaxis function, provide biological significance to the previous observation that the hydrogen bond between them is strengthened upon the formation of the earliest SRII photointermediate (SRII(K)) only when SRII is complexed with HtrII. Here we report frequency changes of the S-H stretch of a cysteine substituted for SRII Thr204 in the signaling state intermediates of the SRII photocycle, as well as an influence of HtrII on the hydrogen bond strength, supporting a direct role of the hydrogen bond in SRII-HtrII signal relay chemistry. Our results suggest that the light signal is transmitted to HtrII from the energized interhelical hydrogen bond between Thr204 and Tyr174, which is located at both the retinal chromophore pocket and in helices F and G that form the membrane-embedded interaction surface to the signal-bearing second transmembrane helix of HtrII. The results argue for a critical process in signal relay occurring at this membrane interfacial region of the complex.
Collapse
Affiliation(s)
- Yuki Sudo
- Center for Membrane Biology, Department of Biochemistry and Molecular Biology, University of Texas Health Science Center, Houston, Texas 77030, USA
| | | | | | | |
Collapse
|
13
|
Gillespie NB, Ren L, Ramos L, Daniel H, Dews D, Utzat KA, Stuart JA, Buck CH, Birge RR. Characterization and Photochemistry of 13-Desmethyl Bacteriorhodopsin. J Phys Chem B 2005; 109:16142-52. [PMID: 16853051 PMCID: PMC1513633 DOI: 10.1021/jp052124+] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The photochemistry of the 13-desmethyl (DM) analogue of bacteriorhodopsin (BR) is examined by using spectroscopy, molecular orbital theory, and chromophore extraction followed by conformational analysis. The removal of the 13-methyl group permits the direct photochemical formation of a thermally stable, photochemically reversible state, P1(DM) (lambda(max) = 525 nm), which can be generated efficiently by exciting the resting state, bR(DM) with yellow or red light (lambda > 590 nm). Chromophore extraction analysis reveals that the retinal configuration in P1(DM) is 9-cis, identical to that of the retinal configuration in the native BR P1 state. Fourier transform infrared and Raman experiments on P1(DM) indicate an anti configuration around the C15=N bond, as would be expected of an O-state photoproduct. However, low-temperature spectroscopy and ambient, time-resolved studies indicate that the P1(DM) state forms primarily via thermal relaxation from the L(D)(DM) state. Theoretical studies on the BR binding site show that 13-dm retinal is capable of isomerizing into a 9-cis configuration with minimal steric hindrance from surrounding residues, in contrast to the native chromophore in which surrounding residues significantly obstruct the corresponding motion. Analysis of the photokinetic experiments indicates that the Arrhenius activation energy of the bR(DM) --> P1(DM) transition in 13-dm-BR is less than 0.6 kcal/mol (vs 22 +/-5 kcal/mol measured for the bR --> P (P1 and P2) reaction in 85:15 glycerol:water suspensions of wild type). Consequently, the P1(DM) state in 13-dm-BR can form directly from all-trans, 15-anti intermediates (bR(DM) and O(DM)) or all-trans, 15-syn (K(D)(DM)/L(D)(DM)) intermediates. This study demonstrates that the 13-methyl group, and its interactions with nearby binding site residues, is primarily responsible for channeling one-photon photochemical and thermal reactions and is limited to the all-trans and 13-cis species interconversions in the native protein.
Collapse
Affiliation(s)
- Nathan B. Gillespie
- Departments of Chemistry and of Molecular and Cell Biology, University of Connecticut, 55 North Eagleville Road, Storrs, Connecticut 06269-3060
- W. M. Keck Center for Molecular Electronics and Department of Chemistry, Syracuse University, 111 College Place, Syracuse, New York 13244-4100
| | - Lei Ren
- Departments of Chemistry and of Molecular and Cell Biology, University of Connecticut, 55 North Eagleville Road, Storrs, Connecticut 06269-3060
- W. M. Keck Center for Molecular Electronics and Department of Chemistry, Syracuse University, 111 College Place, Syracuse, New York 13244-4100
| | - Lavoisier Ramos
- Departments of Chemistry and of Molecular and Cell Biology, University of Connecticut, 55 North Eagleville Road, Storrs, Connecticut 06269-3060
| | - Heather Daniel
- Departments of Chemistry and of Molecular and Cell Biology, University of Connecticut, 55 North Eagleville Road, Storrs, Connecticut 06269-3060
| | - Deborah Dews
- Departments of Chemistry and of Molecular and Cell Biology, University of Connecticut, 55 North Eagleville Road, Storrs, Connecticut 06269-3060
| | - Karissa A. Utzat
- Departments of Chemistry and of Molecular and Cell Biology, University of Connecticut, 55 North Eagleville Road, Storrs, Connecticut 06269-3060
| | - Jeffrey A. Stuart
- W. M. Keck Center for Molecular Electronics and Department of Chemistry, Syracuse University, 111 College Place, Syracuse, New York 13244-4100
| | - Charles H. Buck
- W. M. Keck Center for Molecular Electronics and Department of Chemistry, Syracuse University, 111 College Place, Syracuse, New York 13244-4100
| | - Robert R. Birge
- Departments of Chemistry and of Molecular and Cell Biology, University of Connecticut, 55 North Eagleville Road, Storrs, Connecticut 06269-3060
- *Address correspondence to this author (
) corresponding author: Robert R. Birge, Department of Chemistry, University of Connecticut, 55 North Eagleville Road, Storrs, Connecticut 06269-3060: 860-486-6720; Fax(860-486-2981);
| |
Collapse
|
14
|
Perálvarez-Marín A, Márquez M, Bourdelande JL, Querol E, Padrós E. Thr-90 plays a vital role in the structure and function of bacteriorhodopsin. J Biol Chem 2004; 279:16403-9. [PMID: 14757760 DOI: 10.1074/jbc.m313988200] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The role of Thr-90 in the bacteriorhodopsin structure and function was investigated by its replacement with Ala and Val. The mutant D115A was also studied because Asp-115 in helix D forms a hydrogen bond with Thr-90 in helix C. Differential scanning calorimetry showed a decreased thermal stability of all three mutants, with T90A being the least stable. Light-dark adaptation of T90A was found to be abnormal and salt-dependent. Proton transport monitored using pyranine signals was approximately 10% of wild type for T90A, 20% for T90V, and 50% for D115A. At neutral or alkaline pH, the M rise of these mutants was faster than that of wild type, whereas M decay was slower in T90A. Overall, Fourier transform infrared (FTIR) difference spectra of T90A were strongly pH-dependent. Spectra recorded on films adjusted at the same pH at 243 or 277 K, dry or wet, showed similar features. The D115A and T90V FTIR spectra were closer to WT, showing minor structural differences. The band at 1734 cm(-1) of the deconvoluted FTIR spectrum, corresponding to the carboxylate of Asp-115, was absent in all mutants. In conclusion, Thr-90 plays a critical role in maintaining the operative location and structure of helix C through three complementary interactions, namely an interhelical hydrogen bond with Asp-115, an intrahelical hydrogen bond with the peptide carbonyl oxygen of Trp-86, and a steric contact with the retinal. The interactions established by Thr-90 emerge as a general feature of archaeal rhodopsin proteins.
Collapse
Affiliation(s)
- Alex Perálvarez-Marín
- Unitat de Biofísica, Departament de Bioquímica i de Biologia Molecular, Facultat de Medicina, Universitat Autònoma de Barcelona, Bellaterra (Cerdanyola del Vallès), Barcelona, Spain
| | | | | | | | | |
Collapse
|
15
|
Bergo V, Spudich EN, Spudich JL, Rothschild KJ. A Fourier transform infrared study of Neurospora rhodopsin: similarities with archaeal rhodopsins. Photochem Photobiol 2002; 76:341-9. [PMID: 12403457 DOI: 10.1562/0031-8655(2002)076<0341:aftiso>2.0.co;2] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The NOP-1 gene from the eukaryote Neurospora crassa, a filamentous fungus, has recently been shown to encode an archaeal rhodopsin-like protein NOP-1. To explore the functional mechanism of NOP-1 and its possible similarities to archaeal and visual rhodopsins, static and time-resolved Fourier transform infrared difference spectra were measured from wild-type NOP-1 and from a mutant containing an Asp-->Glu substitution in the Schiff base (SB) counterion, Asp131 (D131E). Several conclusions could be drawn about the molecular mechanism of NOP-1: (1) the NOP-1 retinylidene chromophore undergoes an all-trans to 13-cis isomerization, which is typical of archaeal rhodopsins, and closely resembles structural changes of the chromophore in sensory rhodopsin II; (2) the NOP-1 SB counterion, Asp131, has a very similar environment and behavior compared with the SB counterions in bacteriorhodopsin (BR) and sensory rhodopsin II; (3) the O-H stretching of a structurally active water molecule(s) in NOP-1 is similar to water detected in BR and is most likely located near the SB and SB counterion in these proteins; and (4) one or more cysteine residues undergo structural changes during the NOP-1 photocycle. Overall, these results indicate that many features of the active sites of the archaeal rhodopsins are conserved in NOP-1, despite its eukaryotic origin.
Collapse
Affiliation(s)
- Vladislav Bergo
- Department of Physics, Molecular Biophysics Laboratory, Boston University, Boston, MA 02215, USA
| | | | | | | |
Collapse
|
16
|
Hackmann C, Guijarro J, Chizhov I, Engelhard M, Rödig C, Siebert F. Static and time-resolved step-scan Fourier transform infrared investigations of the photoreaction of halorhodopsin from Natronobacterium pharaonis: consequences for models of the anion translocation mechanism. Biophys J 2001; 81:394-406. [PMID: 11423423 PMCID: PMC1301520 DOI: 10.1016/s0006-3495(01)75708-6] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The molecular changes during the photoreaction of halorhodopsin from Natronobacterium pharaonis have been monitored by low-temperature static and by time-resolved step-scan Fourier transform infrared difference spectroscopy. In the low-temperature L spectrum anions only influence a band around 1650 cm(-1), tentatively assigned to the C=N stretch of the protonated Schiff base of L. The analysis of the time-resolved spectra allows to identify the four states: K, L(1), L(2), and O. Between L(1) and L(2), only the apoprotein undergoes alterations. The O state is characterized by an all-trans chromophore and by rather large amide I spectral changes. Because in our analysis the intermediate containing O is in equilibrium with a state indistinguishable from L(2), we are unable to identify an N-like state. At very high chloride concentrations (>5 M), we observe a branching of the photocycle from L(2) directly back to the dark state, and we provide evidence for direct back-isomerization from L(2). This branching leads to the reported reduction of transport activity at such high chloride concentrations. We interpret the L(1) to L(2) transition as an accessibility change of the anion from the extracellular to the cytosolic side, and the large amide I bands in O as an indication for opening of the cytosolic channel from the Schiff base toward the cytosolic surface and/or as indication for changes of the binding constant of the release site.
Collapse
Affiliation(s)
- C Hackmann
- Sektion Biophysik, Institut für Molekulare Medizin und Zellforschung, Albert-Ludwigs-Universität, D-79104 Freiburg, Germany
| | | | | | | | | | | |
Collapse
|
17
|
Richter HT, Needleman R, Lanyi JK. Perturbed interaction between residues 85 and 204 in Tyr-185-->Phe and Asp-85-->Glu bacteriorhodopsins. Biophys J 1996; 71:3392-8. [PMID: 8968608 PMCID: PMC1233826 DOI: 10.1016/s0006-3495(96)79532-2] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
According to earlier reports, residue 85 in the bacteriorhodopsin mutants D85E and Y185F deprotonates with two apparent pKa values. Additionally, in Y185F, Asp-85 becomes significantly more protonated during light adaptation. We provide a new explanation for these findings. It is based on the scheme that links the protonation state of residue 85 to the protonation state of residue 204 (S.P. Balashov, E.S. Imasheva, R. Govindjee, and T.G. Ebrey. 1996. Biophys. J. 70:473-481; H.T. Richter, L.S. Brown, R. Needleman, and J.K. Lanyi. 1996. Biochemistry. 35:4054-4062) and justified by the observation that the biphasic titration curves of D85E and Y185F are converted to monophasic when the E204Q residue change is introduced as a second mutation. Accordingly, the D85E and Y 185F mutations are not the cause of the biphasic titration, as that is a property of the wild-type protein. By perturbing the extracellular region of the protein, the mutations increase the pKa of residue 85. This increases the amplitude of the second titration component and makes the biphasic character of the curves more obvious. Likewise, a small rise in the pKa of Asp-85 when the retinal isomerizes from 13-cis, 15-syn to all-trans accounts for the changed titration behavior of Y185F after light adaptation. This mechanism simplifies and unites the interpretation of what had appeared to be complex and unrelated phenomena.
Collapse
Affiliation(s)
- H T Richter
- Department of Physiology and Biophysics, University of California, Irvine 92717, USA
| | | | | |
Collapse
|
18
|
Balashov SP, Imasheva ES, Govindjee R, Sheves M, Ebrey TG. Evidence that aspartate-85 has a higher pK(a) in all-trans than in 13-cisbacteriorhodopsin. Biophys J 1996; 71:1973-84. [PMID: 8889171 PMCID: PMC1233663 DOI: 10.1016/s0006-3495(96)79395-5] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Three experimental observations indicate that the pK(a) of the purple-to-blue transition (the pK(a) of Asp-85) is higher for all-trans-bR(1) than for 13-cis-bR. First, light adaptation of bacteriorhodopsin (bR) at pHs near the pK(a) of Asp-85 causes an increase in the fraction of the blue membrane present. This transformation is reversible in the dark. Second, the pK(a) of the purple-to-blue transition in the dark is lower than that in the light-adapted bR (pK(a)(DA) = 3.5, pK(a)(LA) = 3.8 in 10 microM K(2)SO(4)). Third, the equilibrium fractions of 13-cis and all-trans isomers are pH dependent; the fraction of all-trans-bR increases upon formation of the blue membrane. Based on the conclusion that thermal all-trans <=> 13-cis isomerization occurs in the blue membrane rather than in the purple, we have developed a simple model that accounts for all three observations. From the fit of experimental data we estimate that the pK(a) of Asp-85 in 13-cis-bR is 0.5 +/- 0.1 pK(a) unit less than the pK(a) of all-trans-bR. Thus in 10 microM K(2)SO(4), pK(a)(c) = 3.3, whereas pK(a)(t) = 3.8.
Collapse
Affiliation(s)
- S P Balashov
- Department of Cell and Structural Biology, University of Illinois at Urbana-Champaign 61801, USA
| | | | | | | | | |
Collapse
|
19
|
Nilsson A, Rath P, Olejnik J, Coleman M, Rothschild KJ. Protein conformational changes during the bacteriorhodopsin photocycle. A Fourier transform infrared/resonance Raman study of the alkaline form of the mutant Asp-85-->Asn. J Biol Chem 1995; 270:29746-51. [PMID: 8530365 DOI: 10.1074/jbc.270.50.29746] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Bacteriorhodopsin is a light-driven proton pump, which undergoes a photocycle consisting of several distinct intermediates. Previous studies have established that the M-->N step of this photocycle involves a major conformational change of membrane embedded alpha-helices. In order to further investigate this conformational change, we have studied the photocycle of the high pH form of the mutant Asp-85-->Asn (D85Nalk). In contrast to wild type bacteriorhodopsin, D85Nalk has a deprotonated Schiff base and a blue-shifted absorption near 410 nm, yet it still transports protons in the same direction as wild type bacteriorhodopsin (Tittor, J., Schweiger, U., Oesterhelt, D. and Bamberg, E. (1994) Biophys. J., 67, 1682-1690). Resonance Raman spectroscopy of D85Nalk and D85Nalk regenerated with retinal labeled at the C-15 position with deuterium reveals the existence of an all-trans configuration of the chromophore. Fourier transform infrared difference spectroscopy shows that the photocycle of this light-adapted form involves similar events as the wild type bacteriorhodopsin photocycle including the M-->N protein conformational change. These results help to explain the ability of D85Nalk to transport protons and demonstrate that the M-->N conformational change can occur even in the photocycle of an unprotonated Schiff base form of bacteriorhodopsin.
Collapse
Affiliation(s)
- A Nilsson
- Physics Department, Boston University, Massachusetts 02215, USA
| | | | | | | | | |
Collapse
|
20
|
Liu XM, Sonar S, Lee CP, Coleman M, RajBhandary UL, Rothschild KJ. Site-directed isotope labeling and FTIR spectroscopy: assignment of tyrosine bands in the bR-->M difference spectrum of bacteriorhodopsin. Biophys Chem 1995; 56:63-70. [PMID: 7662870 DOI: 10.1016/0301-4622(95)00016-q] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Fourier transform infrared difference spectroscopy has been used extensively to probe structural changes in bacteriorthodopsin and other retinal proteins. However, the absence of a general method to assign bands to individual chemical groups in a protein has limited the application of this technique. While site-directed mutagenesis has been successful in special cases for such assignments, in general, this approach induces perturbations in the structure and function of the protein, thereby preventing unambiguous band assignments. A new approach has recently been reported (Sonar et al., Nature Struct. Biol. 1 (1994) 512-517) which involves cell-free expression of bacteriorhodopsin and site-directed isotope labeling (SDIL). We have now used this method to re-examine bands assigned in the bR-->M difference spectrum to tyrosine residues. Our results show that out of 11 tyrosines in bR, only Tyr 185 is structurally active. This work further demonstrates the power of SDIL and FTIR to probe conformational changes at the level of individual amino acid residues in proteins.
Collapse
Affiliation(s)
- X M Liu
- Physics Department and Molecular Biophysics Laboratory, Boston University, MA 02215, USA
| | | | | | | | | | | |
Collapse
|
21
|
Sonar S, Lee CP, Coleman M, Patel N, Liu X, Marti T, Khorana HG, RajBhandary UL, Rothschild KJ. Site-directed isotope labelling and FTIR spectroscopy of bacteriorhodopsin. NATURE STRUCTURAL BIOLOGY 1994; 1:512-7. [PMID: 7664078 DOI: 10.1038/nsb0894-512] [Citation(s) in RCA: 57] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Insight into integral membrane proteins function is presently limited by the difficulty of producing three-dimensional crystals. In addition, X-ray structures of proteins normally do not provide information about the protonation state and structural changes of individual residues. We report here the first use of site-directed isotope labelling and Fourier transform infrared (FTIR) difference spectroscopy to detect structural changes at the level of single residues in an integral membrane protein. Two site-directed isotope labeled (SDIL) tyrosine analogues of bacteriorhodopsin were produced which exhibit normal activity. FTIR spectroscopy shows that out of 11 tyrosines, only Tyr 185 is structurally active during the early photocycle and may be part of a proton wire.
Collapse
Affiliation(s)
- S Sonar
- Physics Department, Boston University, Massachusetts 02215, USA
| | | | | | | | | | | | | | | | | |
Collapse
|
22
|
Maeda A, Sasaki J, Yamazaki Y, Needleman R, Lanyi JK. Interaction of aspartate-85 with a water molecule and the protonated Schiff base in the L intermediate of bacteriorhodopsin: a Fourier-transform infrared spectroscopic study. Biochemistry 1994; 33:1713-7. [PMID: 8110773 DOI: 10.1021/bi00173a013] [Citation(s) in RCA: 78] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Fourier-transform infrared spectra were recorded at 170 K before and after irradiating the Asp85-->Asn mutant of bacteriorhodopsin. The difference spectrum exhibits protein bands such as those due to the perturbations of Asp96 and Asp115 and the N-H stretching vibration of tryptophan, characteristic of the L minus all-trans-bacteriorhodopsin spectrum of the wild-type protein. However, some vibrational bands of the peptide backbone and the chromophore are different from L and more characteristic of N of the wild-type protein. Remarkably, the shift observed for the vibrational band due to an internal water molecule upon L formation [Maeda, Sasaki, Shichida, and Yoshizawa (1992) Biochemistry 31, 462-467] is absent. These changes in the spectrum of the mutant could originate from the destruction of a hydrogen-bonding system consisting of Asp85, the water molecule, and the Schiff base, upon replacement of Asp85 with asparagine. These observations constitute direct evidence for the interaction of water with Asp85 at the time when it is protonated by the Schiff base.
Collapse
Affiliation(s)
- A Maeda
- Department of Biophysics, Faculty of Science, Kyoto University, Japan
| | | | | | | | | |
Collapse
|
23
|
Lanyi JK. Proton translocation mechanism and energetics in the light-driven pump bacteriorhodopsin. BIOCHIMICA ET BIOPHYSICA ACTA 1993; 1183:241-61. [PMID: 8268193 DOI: 10.1016/0005-2728(93)90226-6] [Citation(s) in RCA: 301] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
In spite of many still unsolved problems, the mechanism and energetics of the light-driven proton transport are now basically understood. Energy captured during photoexcitation, and retained in the form of bond rotations and strains of the retinal, is transformed into directed changes in the pKa values of vectorially arranged proton transfer groups. The framework for the spatial and temporal organization of these changes is provided by the protein near the retinal Schiff base. The transport is completed by proton transfer among three essential groups in three domains lying roughly parallel with the membrane plane (Fig. 1): (a) the anionic D85 that is included in a complex of residues on the extracellular side containing also R82, D212, Y57 and bound water; (b) the protonated Schiff base; and (c) the protonated D96 that is included in a complex of residues on the cytoplasmic side containing also R227, T46, S226, and bound water. Other neighboring polar groups and water bound elsewhere which play a role in the transport do so either by further influencing the pKa values of the three protonable groups, or by providing passive pathways for proton transfer. The Schiff base proton, destabilized after photoexcitation, is transferred to the low pKa group D85 located on the extracellular side. The access of the deprotonated Schiff base then changes to the cytoplasmic side (the 'reprotonation switch') and its proton affinity increases. Finally, the proton of the high pKa group D96, with access to the cytoplasmic side, is destabilized by a protein conformational change through rearrangement of R227, T46, S226 and bound water, and becomes transferred to the Schiff base. As shown schematically in Fig. 3, these internal events are coupled to proton release and uptake at the two aqueous surfaces. The charge of the extracellular hydrogen-bonded complex is redistributed upon protonation of D85, and if the pH is above the pKa of the complex a proton is released to the bulk. After reprotonation of the Schiff base the pKa of the cytoplasmic hydrogen-bonded complex is raised well above the pH, and D96 regains a proton from the bulk. If the pH is lower than the pKa of the extracellular complex the proton release is delayed until the end of the photocycle. In either sequence there is net transfer of a proton from the cytoplasmic to the extracellular phase. The transfer of excess free energy from the chromophore to the protein, and finally to the transported proton, is described by a characteristic thermodynamic cycle.(ABSTRACT TRUNCATED AT 400 WORDS)
Collapse
Affiliation(s)
- J K Lanyi
- Department of Physiology and Biophysics, University of California, Irvine 92717
| |
Collapse
|
24
|
Rothschild KJ, Marti T, Sonar S, He YW, Rath P, Fischer W, Khorana HG. Asp96 deprotonation and transmembrane alpha-helical structural changes in bacteriorhodopsin. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(19)74216-1] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
|
25
|
Gerwert K. Molecular reaction mechanisms of proteins as monitored by time-resolved FTIR spectroscopy. Curr Opin Struct Biol 1993. [DOI: 10.1016/0959-440x(93)90062-p] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
|
26
|
Rath P, Marti T, Sonar S, Khorana H, Rothschild K. Hydrogen bonding interactions with the Schiff base of bacteriorhodopsin. Resonance Raman spectroscopy of the mutants D85N and D85A. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(17)46767-6] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
|