1
|
Mackintosh MJ, Hoischen D, Martin HD, Schapiro I, Gärtner W. Merocyanines form bacteriorhodopsins with strongly bathochromic absorption maxima. Photochem Photobiol Sci 2024; 23:31-53. [PMID: 38070056 DOI: 10.1007/s43630-023-00496-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2023] [Accepted: 10/13/2023] [Indexed: 02/02/2024]
Abstract
There is a need to shift the absorbance of biomolecules to the optical transparency window of tissue for applications in optogenetics and photo-pharmacology. There are a few strategies to achieve the so-called red shift of the absorption maxima. Herein, a series of 11 merocyanine dyes were synthesized and employed as chromophores in place of retinal in bacteriorhodopsin (bR) to achieve a bathochromic shift of the absorption maxima relative to bR's [Formula: see text] of 568 nm. Assembly with the apoprotein bacterioopsin (bO) led to stable, covalently bound chromoproteins with strongly bathochromic absorbance bands, except for three compounds. Maximal red shifts were observed for molecules 9, 2, and 8 in bR where the [Formula: see text] was 766, 755, and 736 nm, respectively. While these three merocyanines have different end groups, they share a similar structural feature, namely, a methyl group which is located at the retinal equivalent position 13 of the polyene chain. The absorption and fluorescence data are also presented for the retinal derivatives in their aldehyde, Schiff base (SB), and protonated SB (PSB) forms in solution. According to their hemicyanine character, the PSBs and their analogue bRs exhibited fluorescence quantum yields (Φf) several orders of magnitude greater than native bR (Φf 0.02 to 0.18 versus 1.5 × 10-5 in bR) while also exhibiting much smaller Stokes shifts than bR (400 to 1000 cm-1 versus 4030 cm-1 in bR). The experimental results are complemented by quantum chemical calculations where excellent agreement between the experimental [Formula: see text] and the calculated [Formula: see text] was achieved with the second-order algebraic-diagrammatic construction [ADC(2)] method. In addition, quantum mechanics/molecular mechanics (QM/MM) calculations were employed to shed light on the origin of the bathochromic shift of merocyanine 2 in bR compared with native bR.
Collapse
Affiliation(s)
- Megan J Mackintosh
- Fritz Haber Center for Molecular Dynamics, Institute of Chemistry, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Dorothee Hoischen
- Institute for Organic Chemistry and Macromolecular Chemistry, University of Düsseldorf, 40225, Düsseldorf, Germany
- ISK Biosciences Europe N.V., 1831, Diegem, Belgium
| | - Hans-Dieter Martin
- Institute for Organic Chemistry and Macromolecular Chemistry, University of Düsseldorf, 40225, Düsseldorf, Germany
| | - Igor Schapiro
- Fritz Haber Center for Molecular Dynamics, Institute of Chemistry, The Hebrew University of Jerusalem, Jerusalem, Israel.
| | | |
Collapse
|
2
|
Cárdenas G, Ledentu V, Huix-Rotllant M, Olivucci M, Ferré N. Automatic Rhodopsin Modeling with Multiple Protonation Microstates. J Phys Chem A 2023; 127:9365-9380. [PMID: 37877699 DOI: 10.1021/acs.jpca.3c05413] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2023]
Abstract
Automatic Rhodopsin Modeling (ARM) is a simulation protocol providing QM/MM models of rhodopsins capable of reproducing experimental electronic absorption and emission trends. Currently, ARM is restricted to a single protonation microstate for each rhodopsin model. Herein, we incorporate an extension of the minimal electrostatic model (MEM) into the ARM protocol to account for all relevant protonation microstates at a given pH. The new ARM+MEM protocol determines the most important microstates contributing to the description of the absorption spectrum. As a test case, we have applied this methodology to simulate the pH-dependent absorption spectrum of a toy model, showing that the single-microstate picture breaks down at certain pH values. Subsequently, we applied ARM+MEM toAnabaenasensory rhodopsin, confirming an improved description of its absorption spectrum when the titration of several key residues is considered.
Collapse
Affiliation(s)
| | | | | | - Massimo Olivucci
- Department of Chemistry, Bowling Green State University, Bowling Green, Ohio 43403, United States
- Dipartimento di Biotecnologie, Chimica e Farmacia, Università degli Studi di Siena, 53100 Siena, Italy
| | - Nicolas Ferré
- Aix-Marseille Univ, CNRS, ICR, 13013 Marseille, France
| |
Collapse
|
3
|
Li G, Hu Y, Pei S, Meng J, Wang J, Wang J, Yue S, Wang Z, Wang S, Liu X, Weng Y, Peng X, Zhao Q. Excited-state dynamics of all-trans protonated retinal Schiff base in CRABPII-based rhodopsin mimics. Biophys J 2022; 121:4109-4118. [PMID: 36181266 PMCID: PMC9675042 DOI: 10.1016/j.bpj.2022.09.032] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2022] [Revised: 09/06/2022] [Accepted: 09/26/2022] [Indexed: 11/20/2022] Open
Abstract
The rhodopsin mimic is a chemically synthetized complex with retinyl Schiff base (RSB) formed between protein and the retinal chromophore that can mimic the natural rhodopsin-like protein. The artificial rhodopsin mimic is more stable and designable than the natural protein and hence has wider uses in photon detection devices. The mimic structure RSB, like the case in the actual rhodopsin-like protein, undergoes isomerization and protonation throughout the photoreaction process. As a result, understanding the dynamics of the RSB in the photoreaction process is critical. In this study, the ultrafast transient absorption spectra of three mutants of the cellular retinoic acid-binding protein II-based rhodopsin mimic at acidic environment were recorded, from which the related excited-state dynamics of the all-trans protonated RSB (AT-PRSB) were investigated. The transient fluorescence spectra measurements are used to validate some of the dynamic features. We find that the excited-state dynamics of AT-PRSB in three mutants share a similar pattern that differs significantly from the dynamics of 15-cis PRSB of the rhodopsin mimic in neutral solution. By comparing the dynamics across the three mutants, we discovered that the aromatic residues near the β-ionone ring structure of the retinal may help stabilize the AT-PRSB and hence slow down its isomerization rate. The experimental results provide implications on designing a rhodopsin-like protein with significant infrared fluorescence, which can be particularly useful in the applications in biosensing or bioimaging in deeper tissues.
Collapse
Affiliation(s)
- Gaoshang Li
- Center for Quantum Technology Research, Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurements (MOE), School of Physics, Beijing Institute of Technology, Beijing, China
| | - Yongnan Hu
- Center for Quantum Technology Research, Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurements (MOE), School of Physics, Beijing Institute of Technology, Beijing, China
| | - Sizhu Pei
- Center for Quantum Technology Research, Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurements (MOE), School of Physics, Beijing Institute of Technology, Beijing, China
| | - Jiajia Meng
- Center for Quantum Technology Research, Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurements (MOE), School of Physics, Beijing Institute of Technology, Beijing, China
| | - Jiayu Wang
- Beijing National Laboratory for Condensed Matter Physics, Laboratory of Soft Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, China; University of Chinese Academy of Sciences, Beijing, China
| | - Ju Wang
- State Key Laboratory for Artificial Microstructure and Mesoscopic Physics, Department of Physics, Peking University, Beijing, China
| | - Shuai Yue
- National Center for Nanoscience and Nanotechnology, Beijing, China
| | - Zhuan Wang
- Beijing National Laboratory for Condensed Matter Physics, Laboratory of Soft Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, China
| | - Shufeng Wang
- State Key Laboratory for Artificial Microstructure and Mesoscopic Physics, Department of Physics, Peking University, Beijing, China
| | - Xinfeng Liu
- National Center for Nanoscience and Nanotechnology, Beijing, China; University of Chinese Academy of Sciences, Beijing, China
| | - Yuxiang Weng
- Beijing National Laboratory for Condensed Matter Physics, Laboratory of Soft Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, China; University of Chinese Academy of Sciences, Beijing, China
| | - Xubiao Peng
- Center for Quantum Technology Research, Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurements (MOE), School of Physics, Beijing Institute of Technology, Beijing, China; Beijing Academy of Quantum Information Sciences, Beijing, China.
| | - Qing Zhao
- Center for Quantum Technology Research, Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurements (MOE), School of Physics, Beijing Institute of Technology, Beijing, China; Beijing Academy of Quantum Information Sciences, Beijing, China.
| |
Collapse
|
4
|
Buhrke D, Hildebrandt P. Probing Structure and Reaction Dynamics of Proteins Using Time-Resolved Resonance Raman Spectroscopy. Chem Rev 2019; 120:3577-3630. [PMID: 31814387 DOI: 10.1021/acs.chemrev.9b00429] [Citation(s) in RCA: 46] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The mechanistic understanding of protein functions requires insight into the structural and reaction dynamics. To elucidate these processes, a variety of experimental approaches are employed. Among them, time-resolved (TR) resonance Raman (RR) is a particularly versatile tool to probe processes of proteins harboring cofactors with electronic transitions in the visible range, such as retinal or heme proteins. TR RR spectroscopy offers the advantage of simultaneously providing molecular structure and kinetic information. The various TR RR spectroscopic methods can cover a wide dynamic range down to the femtosecond time regime and have been employed in monitoring photoinduced reaction cascades, ligand binding and dissociation, electron transfer, enzymatic reactions, and protein un- and refolding. In this account, we review the achievements of TR RR spectroscopy of nearly 50 years of research in this field, which also illustrates how the role of TR RR spectroscopy in molecular life science has changed from the beginning until now. We outline the various methodological approaches and developments and point out current limitations and potential perspectives.
Collapse
Affiliation(s)
- David Buhrke
- Technische Universität Berlin, Institut für Chemie, Sekr. PC14, Straße des 17, Juni 135, D-10623 Berlin, Germany
| | - Peter Hildebrandt
- Technische Universität Berlin, Institut für Chemie, Sekr. PC14, Straße des 17, Juni 135, D-10623 Berlin, Germany
| |
Collapse
|
5
|
Ferenczi EA, Tan X, Huang CLH. Principles of Optogenetic Methods and Their Application to Cardiac Experimental Systems. Front Physiol 2019; 10:1096. [PMID: 31572204 PMCID: PMC6749684 DOI: 10.3389/fphys.2019.01096] [Citation(s) in RCA: 40] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2019] [Accepted: 08/08/2019] [Indexed: 12/12/2022] Open
Abstract
Optogenetic techniques permit studies of excitable tissue through genetically expressed light-gated microbial channels or pumps permitting transmembrane ion movement. Light activation of these proteins modulates cellular excitability with millisecond precision. This review summarizes optogenetic approaches, using examples from neurobiological applications, and then explores their application in cardiac electrophysiology. We review the available opsins, including depolarizing and hyperpolarizing variants, as well as modulators of G-protein coupled intracellular signaling. We discuss the biophysical properties that determine the ability of microbial opsins to evoke reliable, precise stimulation or silencing of electrophysiological activity. We also review spectrally shifted variants offering possibilities for enhanced depth of tissue penetration, combinatorial stimulation for targeting different cell subpopulations, or all-optical read-in and read-out studies. Expression of the chosen optogenetic tool in the cardiac cell of interest then requires, at the single-cell level, introduction of opsin-encoding genes by viral transduction, or coupling "spark cells" to primary cardiomyocytes or a stem-cell derived counterpart. At the system-level, this requires construction of transgenic mice expressing ChR2 in their cardiomyocytes, or in vivo injection (myocardial or systemic) of adenoviral expression systems. Light delivery, by laser or LED, with widespread or multipoint illumination, although relatively straightforward in vitro may be technically challenged by cardiac motion and light-scattering in biological tissue. Physiological read outs from cardiac optogenetic stimulation include single cell patch clamp recordings, multi-unit microarray recordings from cell monolayers or slices, and electrical recordings from isolated Langendorff perfused hearts. Optical readouts of specific cellular events, including ion transients, voltage changes or activity in biochemical signaling cascades, using small detecting molecules or genetically encoded sensors now offer powerful opportunities for all-optical control and monitoring of cellular activity. Use of optogenetics has expanded in cardiac physiology, mainly using optically controlled depolarizing ion channels to control heart rate and for optogenetic defibrillation. ChR2-expressing cardiomyocytes show normal baseline and active excitable membrane and Ca2+ signaling properties and are sensitive even to ~1 ms light pulses. They have been employed in studies of the intrinsic cardiac adrenergic system and of cardiac arrhythmic properties.
Collapse
Affiliation(s)
- Emily A. Ferenczi
- Department of Neurology, Massachusetts General Hospital and Brigham and Women’s Hospital, Harvard Medical School, Boston, MA, United States
| | - Xiaoqiu Tan
- Key Laboratory of Medical Electrophysiology, Ministry of Education and Medical Electrophysiological Key Laboratory of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, China
| | - Christopher L.-H. Huang
- Physiological Laboratory, University of Cambridge, Cambridge, United Kingdom
- Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
| |
Collapse
|
6
|
Soto-Rodríguez J, Hemmatian Z, Black J, Rolandi M, Baneyx F. Two-Channel Bioprotonic Photodetector. ACS APPLIED BIO MATERIALS 2019; 2:930-935. [DOI: 10.1021/acsabm.8b00789] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Affiliation(s)
- Jessica Soto-Rodríguez
- Department of Chemical Engineering, University of Washington, Box 351750, Seattle, Washington 98195, United States
| | - Zahra Hemmatian
- Department of Electrical and Computer Engineering, University of California, Santa Cruz, California 95064, United States
| | - Jennifer Black
- Department of Electrical and Computer Engineering, University of California, Santa Cruz, California 95064, United States
| | - Marco Rolandi
- Department of Electrical and Computer Engineering, University of California, Santa Cruz, California 95064, United States
| | - François Baneyx
- Department of Chemical Engineering, University of Washington, Box 351750, Seattle, Washington 98195, United States
| |
Collapse
|
7
|
Collette F, Renger T, Müh F, Schmidt am Busch M. Red/Green Color Tuning of Visual Rhodopsins: Electrostatic Theory Provides a Quantitative Explanation. J Phys Chem B 2018; 122:4828-4837. [DOI: 10.1021/acs.jpcb.8b02702] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Florimond Collette
- Institut für Theoretische Physik, Johannes Kepler University Linz, Altenberger Strasse 69, 4040 Linz, Austria
| | - Thomas Renger
- Institut für Theoretische Physik, Johannes Kepler University Linz, Altenberger Strasse 69, 4040 Linz, Austria
| | - Frank Müh
- Institut für Theoretische Physik, Johannes Kepler University Linz, Altenberger Strasse 69, 4040 Linz, Austria
| | - Marcel Schmidt am Busch
- Institut für Theoretische Physik, Johannes Kepler University Linz, Altenberger Strasse 69, 4040 Linz, Austria
| |
Collapse
|
8
|
Characterization of an Unconventional Rhodopsin from the Freshwater Actinobacterium Rhodoluna lacicola. J Bacteriol 2015; 197:2704-12. [PMID: 26055118 DOI: 10.1128/jb.00386-15] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2015] [Accepted: 06/04/2015] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED Rhodopsin-encoding microorganisms are common in many environments. However, knowing that rhodopsin genes are present provides little insight into how the host cells utilize light. The genome of the freshwater actinobacterium Rhodoluna lacicola encodes a rhodopsin of the uncharacterized actinorhodopsin family. We hypothesized that actinorhodopsin was a light-activated proton pump and confirmed this by heterologously expressing R. lacicola actinorhodopsin in retinal-producing Escherichia coli. However, cultures of R. lacicola did not pump protons, even though actinorhodopsin mRNA and protein were both detected. Proton pumping in R. lacicola was induced by providing exogenous retinal, suggesting that the cells lacked the retinal cofactor. We used high-performance liquid chromatography (HPLC) and oxidation of accessory pigments to confirm that R. lacicola does not synthesize retinal. These results suggest that in some organisms, the actinorhodopsin gene is constitutively expressed, but rhodopsin-based light capture may require cofactors obtained from the environment. IMPORTANCE Up to 70% of microbial genomes in some environments are predicted to encode rhodopsins. Because most microbial rhodopsins are light-activated proton pumps, the prevalence of this gene suggests that in some environments, most microorganisms respond to or utilize light energy. Actinorhodopsins were discovered in an analysis of freshwater metagenomic data and subsequently identified in freshwater actinobacterial cultures. We hypothesized that actinorhodopsin from the freshwater actinobacterium Rhodoluna lacicola was a light-activated proton pump and confirmed this by expressing actinorhodopsin in retinal-producing Escherichia coli. Proton pumping in R. lacicola was induced only after both light and retinal were provided, suggesting that the cells lacked the retinal cofactor. These results indicate that photoheterotrophy in this organism and others may require cofactors obtained from the environment.
Collapse
|
9
|
Mao J, Do NN, Scholz F, Reggie L, Mehler M, Lakatos A, Ong YS, Ullrich SJ, Brown LJ, Brown RCD, Becker-Baldus J, Wachtveitl J, Glaubitz C. Structural basis of the green-blue color switching in proteorhodopsin as determined by NMR spectroscopy. J Am Chem Soc 2014; 136:17578-90. [PMID: 25415762 DOI: 10.1021/ja5097946] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Proteorhodopsins (PRs) found in marine microbes are the most abundant retinal-based photoreceptors on this planet. PR variants show high levels of environmental adaptation, as their colors are tuned to the optimal wavelength of available light. The two major green and blue subfamilies can be interconverted through a L/Q point mutation at position 105. Here we reveal the structural basis behind this intriguing color-tuning effect. High-field solid-state NMR spectroscopy was used to visualize structural changes within green PR directly within the lipid bilayer upon introduction of the green-blue L105Q mutation. The observed effects are localized within the binding pocket and close to retinal carbons C14 and C15. Subsequently, magic-angle spinning (MAS) NMR spectroscopy with sensitivity enhancement by dynamic nuclear polarization (DNP) was applied to determine precisely the retinal structure around C14-C15. Upon mutation, a significantly stretched C14-C15 bond, deshielding of C15, and a slight alteration of the retinal chain's out-of-plane twist was observed. The L105Q blue switch therefore acts locally on the retinal itself and induces a conjugation defect between the isomerization region and the imine linkage. Consequently, the S0-S1 energy gap increases, resulting in the observed blue shift. The distortion of the chromophore structure also offers an explanation for the elongated primary reaction detected by pump-probe spectroscopy, while chemical shift perturbations within the protein can be linked to the elongation of late-photocycle intermediates studied by flash photolysis. Besides resolving a long-standing problem, this study also demonstrates that the combination of data obtained from high-field and DNP-enhanced MAS NMR spectroscopy together with time-resolved optical spectroscopy enables powerful synergies for in-depth functional studies of membrane proteins.
Collapse
Affiliation(s)
- Jiafei Mao
- Institute of Biophysical Chemistry and Centre for Biomolecular Magnetic Resonance, Goethe University Frankfurt , 60438 Frankfurt am Main, Germany
| | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
10
|
Donor-Acceptor Conjugated Linear Polyenes: A Study of Excited State Intramolecular Charge Transfer, Photoisomerization and Fluorescence Probe Properties. J Fluoresc 2014; 28:21-28. [DOI: 10.1007/s10895-014-1430-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2014] [Accepted: 07/14/2014] [Indexed: 01/05/2023]
|
11
|
Mehler M, Scholz F, Ullrich SJ, Mao J, Braun M, Brown LJ, Brown RCD, Fiedler SA, Becker-Baldus J, Wachtveitl J, Glaubitz C. The EF loop in green proteorhodopsin affects conformation and photocycle dynamics. Biophys J 2014; 105:385-97. [PMID: 23870260 DOI: 10.1016/j.bpj.2013.06.014] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2013] [Revised: 06/10/2013] [Accepted: 06/11/2013] [Indexed: 11/20/2022] Open
Abstract
The proteorhodopsin family consists of retinal proteins of marine bacterial origin with optical properties adjusted to their local environments. For green proteorhodopsin, a highly specific mutation in the EF loop, A178R, has been found to cause a surprisingly large redshift of 20 nm despite its distance from the chromophore. Here, we analyze structural and functional consequences of this EF loop mutation by time-resolved optical spectroscopy and solid-state NMR. We found that the primary photoreaction and the formation of the K-like photo intermediate is almost pH-independent and slower compared to the wild-type, whereas the decay of the K-intermediate is accelerated, suggesting structural changes within the counterion complex upon mutation. The photocycle is significantly elongated mainly due to an enlarged lifetime of late photo intermediates. Multidimensional MAS-NMR reveals mutation-induced chemical shift changes propagating from the EF loop to the chromophore binding pocket, whereas dynamic nuclear polarization-enhanced (13)C-double quantum MAS-NMR has been used to probe directly the retinylidene conformation. Our data show a modified interaction network between chromophore, Schiff base, and counterion complex explaining the altered optical and kinetic properties. In particular, the mutation-induced distorted structure in the EF loop weakens interactions, which help reorienting helix F during the reprotonation step explaining the slower photocycle. These data lead to the conclusion that the EF loop plays an important role in proton uptake from the cytoplasm but our data also reveal a clear interaction pathway between the EF loop and retinal binding pocket, which might be an evolutionary conserved communication pathway in retinal proteins.
Collapse
Affiliation(s)
- Michaela Mehler
- Institute of Biophysical Chemistry and Centre for Biomolecular Magnetic Resonance, Goethe-University Frankfurt, Germany
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
12
|
Bassolino G, Sovdat T, Liebel M, Schnedermann C, Odell B, Claridge TD, Kukura P, Fletcher SP. Synthetic Control of Retinal Photochemistry and Photophysics in Solution. J Am Chem Soc 2014; 136:2650-8. [DOI: 10.1021/ja4121814] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Giovanni Bassolino
- Department
of Chemistry, Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QZ, U.K
| | - Tina Sovdat
- Department
of Chemistry, Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford OX1 3TA, U.K
| | - Matz Liebel
- Department
of Chemistry, Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QZ, U.K
| | - Christoph Schnedermann
- Department
of Chemistry, Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QZ, U.K
| | - Barbara Odell
- Department
of Chemistry, Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford OX1 3TA, U.K
| | - Timothy D.W. Claridge
- Department
of Chemistry, Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford OX1 3TA, U.K
| | - Philipp Kukura
- Department
of Chemistry, Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QZ, U.K
| | - Stephen P. Fletcher
- Department
of Chemistry, Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford OX1 3TA, U.K
| |
Collapse
|
13
|
Affiliation(s)
| | - Salim Al-Babili
- BESE Division, King Abdullah University of Science and Technology (KAUST), Thuwal, Kingdom of Saudi Arabia
| | - Eleanore T. Wurtzel
- The Graduate School and University Center, The City University of New York, New York, New York, USA
- Department of Biological Sciences, Lehman College, The City University of New York, Bronx, New York, USA
| |
Collapse
|
14
|
Ernst OP, Lodowski DT, Elstner M, Hegemann P, Brown L, Kandori H. Microbial and animal rhodopsins: structures, functions, and molecular mechanisms. Chem Rev 2014; 114:126-63. [PMID: 24364740 PMCID: PMC3979449 DOI: 10.1021/cr4003769] [Citation(s) in RCA: 777] [Impact Index Per Article: 77.7] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2013] [Indexed: 12/31/2022]
Affiliation(s)
- Oliver P. Ernst
- Departments
of Biochemistry and Molecular Genetics, University of Toronto, 1 King’s College Circle, Medical Sciences Building, Toronto, Ontario M5S 1A8, Canada
| | - David T. Lodowski
- Center
for Proteomics and Bioinformatics, Case
Western Reserve University School of Medicine, 10900 Euclid Avenue, Cleveland, Ohio 44106, United States
| | - Marcus Elstner
- Institute
for Physical Chemistry, Karlsruhe Institute
of Technology, Kaiserstrasse
12, 76131 Karlsruhe, Germany
| | - Peter Hegemann
- Institute
of Biology, Experimental Biophysics, Humboldt-Universität
zu Berlin, Invalidenstrasse
42, 10115 Berlin, Germany
| | - Leonid
S. Brown
- Department
of Physics and Biophysics Interdepartmental Group, University of Guelph, 50 Stone Road East, Guelph, Ontario N1G 2W1, Canada
| | - Hideki Kandori
- Department
of Frontier Materials, Nagoya Institute
of Technology, Showa-ku, Nagoya 466-8555, Japan
| |
Collapse
|
15
|
Wang W, Geiger JH, Borhan B. The photochemical determinants of color vision: revealing how opsins tune their chromophore's absorption wavelength. Bioessays 2013; 36:65-74. [PMID: 24323922 DOI: 10.1002/bies.201300094] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The evolution of a variety of important chromophore-dependent biological processes, including microbial light sensing and mammalian color vision, relies on protein modifications that alter the spectral characteristics of a bound chromophore. Three different color opsins share the same chromophore, but have three distinct absorptions that together cover the entire visible spectrum, giving rise to trichromatic vision. The influence of opsins on the absorbance of the chromophore has been studied through methods such as model compounds, opsin mutagenesis, and computational modeling. The recent development of rhodopsin mimic that uses small soluble proteins to recapitulate the binding and wavelength tuning of the native opsins provides a new platform for studying protein-regulated spectral tuning. The ability to achieve far-red shifted absorption in the rhodopsin mimic system was attributed to a combination of the lack of a counteranion proximal to the iminium, and a uniformly neutral electrostatic environment surrounding the chromophore.
Collapse
Affiliation(s)
- Wenjing Wang
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA, USA
| | | | | |
Collapse
|
16
|
Abstract
Rhodopsins are photochemically reactive membrane proteins that covalently bind retinal chromophores. Type I rhodopsins are found in both prokaryotes and eukaryotic microbes, whereas type II rhodopsins function as photoactivated G-protein coupled receptors (GPCRs) in animal vision. Both rhodopsin families share the seven transmembrane α-helix GPCR fold and a Schiff base linkage from a conserved lysine to retinal in helix G. Nevertheless, rhodopsins are widely cited as a striking example of evolutionary convergence, largely because the two families lack detectable sequence similarity and differ in many structural and mechanistic details. Convergence entails that the shared rhodopsin fold is so especially suited to photosensitive function that proteins from separate origins were selected for this architecture twice. Here we show, however, that the rhodopsin fold is not required for photosensitive activity. We engineered functional bacteriorhodopsin variants with novel folds, including radical noncircular permutations of the α-helices, circular permutations of an eight-helix construct, and retinal linkages relocated to other helices. These results contradict a key prediction of convergence and thereby provide an experimental attack on one of the most intractable problems in molecular evolution: how to establish structural homology for proteins devoid of discernible sequence similarity.
Collapse
|
17
|
Sudo Y, Okazaki A, Ono H, Yagasaki J, Sugo S, Kamiya M, Reissig L, Inoue K, Ihara K, Kandori H, Takagi S, Hayashi S. A blue-shifted light-driven proton pump for neural silencing. J Biol Chem 2013; 288:20624-32. [PMID: 23720753 DOI: 10.1074/jbc.m113.475533] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Ion-transporting rhodopsins are widely utilized as optogenetic tools both for light-induced neural activation and silencing. The most studied representative is Bacteriorhodopsin (BR), which absorbs green/red light (∼570 nm) and functions as a proton pump. Upon photoexcitation, BR induces a hyperpolarization across the membrane, which, if incorporated into a nerve cell, results in its neural silencing. In this study, we show that several residues around the retinal chromophore, which are completely conserved among BR homologs from the archaea, are involved in the spectral tuning in a BR homolog (HwBR) and that the combination mutation causes a large spectral blue shift (λmax = 498 nm) while preserving the robust pumping activity. Quantum mechanics/molecular mechanics calculations revealed that, compared with the wild type, the β-ionone ring of the chromophore in the mutant is rotated ∼130° because of the lack of steric hindrance between the methyl groups of the retinal and the mutated residues, resulting in the breakage of the π conjugation system on the polyene chain of the retinal. By the same mutations, similar spectral blue shifts are also observed in another BR homolog, archearhodopsin-3 (also called Arch). The color variant of archearhodopsin-3 could be successfully expressed in the neural cells of Caenorhabditis elegans, and illumination with blue light (500 nm) led to the effective locomotory paralysis of the worms. Thus, we successfully produced a blue-shifted proton pump for neural silencing.
Collapse
Affiliation(s)
- Yuki Sudo
- Division of Biological Science, Graduate School of Science, Nagoya University, Nagoya 464-8602, Japan.
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
18
|
Maiti TK, Yamada K, Inoue K, Kandori H. L105K Mutant of Proteorhodopsin. Biochemistry 2012; 51:3198-204. [DOI: 10.1021/bi201916a] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Tushar Kanti Maiti
- Department
of Frontier Materials, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555,
Japan
| | - Keisuke Yamada
- Department
of Frontier Materials, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555,
Japan
| | - Keiichi Inoue
- Department
of Frontier Materials, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555,
Japan
| | - Hideki Kandori
- Department
of Frontier Materials, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555,
Japan
| |
Collapse
|
19
|
Patil AV, Premaraban T, Berthoumieu O, Watts A, Davis JJ. Engineered Bacteriorhodopsin: A Molecular Scale Potential Switch. Chemistry 2012; 18:5632-6. [DOI: 10.1002/chem.201103597] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2011] [Revised: 02/24/2012] [Indexed: 11/10/2022]
|
20
|
Rajamani R, Lin YL, Gao J. The opsin shift and mechanism of spectral tuning in rhodopsin. J Comput Chem 2011; 32:854-65. [PMID: 20941732 PMCID: PMC3021771 DOI: 10.1002/jcc.21663] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2010] [Accepted: 08/07/2010] [Indexed: 01/12/2023]
Abstract
Molecular dynamics simulations and combined quantum mechanical and molecular mechanical calculations have been performed to investigate the mechanism of the opsin shift and spectral tuning in rhodopsin. A red shift of -980 cm(-1) was estimated in the transfer of the chromophore from methanol solution environment to the protonated Schiff base (PSB)-binding site of the opsin. The conformational change from a 6-s-cis-all-trans configuration in solution to the 6-s-cis-11-cis conformer contributes additional -200 cm(-1), and the remaining effects were attributed to dispersion interactions with the aromatic residues in the binding site. An opsin shift of 2100 cm(-1) was obtained, in reasonable accord with experiment (2730 cm(-1)). Dynamics simulations revealed that the 6-s-cis bond can occupy two main conformations for the β-ionone ring, resulting in a weighted average dihedral angle of about -50°, which may be compared with the experimental estimate of -28° from solid-state NMR and Raman data. We investigated a series of four single mutations, including E113D, A292S, T118A, and A269T, which are located near the PSB, along the polyene chain of retinal and close to the ionone ring. The computational results on absorption energy shift provided insights into the mechanism of spectral tuning, which involves all means of electronic structural effects, including the stabilization or destabilization of either the ground or the electronically excited state of the retinal PSB.
Collapse
Affiliation(s)
| | - Yen-lin Lin
- Department of Chemistry, Digital Technology Center, and Supercomputing Institute, University of Minnesota, Minneapolis, MN 55455
| | - Jiali Gao
- Department of Chemistry, Digital Technology Center, and Supercomputing Institute, University of Minnesota, Minneapolis, MN 55455
| |
Collapse
|
21
|
Sudo Y, Yuasa Y, Shibata J, Suzuki D, Homma M. Spectral tuning in sensory rhodopsin I from Salinibacter ruber. J Biol Chem 2011; 286:11328-36. [PMID: 21288897 DOI: 10.1074/jbc.m110.187948] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Organisms utilize light as energy sources and as signals. Rhodopsins, which have seven transmembrane α-helices with retinal covalently linked to a conserved Lys residue, are found in various organisms as distant in evolution as bacteria, archaea, and eukarya. One of the most notable properties of rhodopsin molecules is the large variation in their absorption spectrum. Sensory rhodopsin I (SRI) and sensory rhodopsin II (SRII) function as photosensors and have similar properties (retinal composition, photocycle, structure, and function) except for their λ(max) (SRI, ∼560 nm; SRII, ∼500 nm). An expression system utilizing Escherichia coli and the high protein stability of a newly found SRI-like protein, SrSRI, enables studies of mutant proteins. To determine the residue contributing to the spectral shift from SRI to SRII, we constructed various SRI mutants, in which individual residues were substituted with the corresponding residues of SRII. Three such mutants of SrSRI showed a large spectral blue-shift (>14 nm) without a large alteration of their retinal composition. Two of them, A136Y and A200T, are newly discovered color tuning residues. In the triple mutant, the λ(max) was 525 nm. The inverse mutation of SRII (F134H/Y139A/T204A) generated a spectral-shifted SRII toward longer wavelengths, although the effect is smaller than in the case of SRI, which is probably due to the lack of anion binding in the SRII mutant. Thus, half of the spectral shift from SRI to SRII could be explained by only those three residues taking into account the effect of Cl(-) binding.
Collapse
Affiliation(s)
- Yuki Sudo
- Division of Biological Science, Graduate School of Science, Nagoya University, Nagoya, Japan.
| | | | | | | | | |
Collapse
|
22
|
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
![]()
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.
Collapse
Affiliation(s)
- Oleg A Sineshchekov
- Center for Membrane Biology, Department of Biochemistry and Molecular Biology, University of Texas Medical School, Houston, Texas 77030, USA
| | | | | | | |
Collapse
|
23
|
Spectral tuning in photoactive yellow protein by modulation of the shape of the excited state energy surface. Proc Natl Acad Sci U S A 2010; 107:5821-6. [PMID: 20220103 DOI: 10.1073/pnas.0903092107] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Protein-chromophore interactions in photoreceptors often shift the chromophore absorbance maximum to a biologically relevant spectral region. A fundamental question regarding such spectral tuning effects is how the electronic ground state S(0) and excited state S(1) are modified by the protein. It is widely assumed that changes in energy gap between S(0) and S(1) are the main factor in biological spectral tuning. We report a generally applicable approach to determine if a specific residue modulates the energy gap, or if it alters the equilibrium nuclear geometry or width of the energy surfaces. This approach uses the effects that changes in these three parameters have on the absorbance and fluorescence emission spectra of mutants. We apply this strategy to a set of mutants of photoactive yellow protein (PYP) containing all 20 side chains at active site residue 46. While the mutants exhibit significant variation in both the position and width of their absorbance spectra, the fluorescence emission spectra are largely unchanged. This provides strong evidence against a major role for changes in energy gap in the spectral tuning of these mutants and reveals a change in the width of the S(1) energy surface. We determined the excited state lifetime of selected mutants and the observed correlation between the fluorescence quantum yield and lifetime shows that the fluorescence spectra are representative of the energy surfaces of the mutants. These results reveal that residue 46 tunes the absorbance spectrum of PYP largely by modulating the width of the S(1) energy surface.
Collapse
|
24
|
Rajput J, Rahbek D, Andersen L, Hirshfeld A, Sheves M, Altoè P, Orlandi G, Garavelli M. Probing and Modeling the Absorption of Retinal Protein Chromophores in Vacuo. Angew Chem Int Ed Engl 2010. [DOI: 10.1002/ange.200905061] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
|
25
|
Rajput J, Rahbek D, Andersen L, Hirshfeld A, Sheves M, Altoè P, Orlandi G, Garavelli M. Probing and Modeling the Absorption of Retinal Protein Chromophores in Vacuo. Angew Chem Int Ed Engl 2010; 49:1790-3. [DOI: 10.1002/anie.200905061] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
|
26
|
Suzuki D, Furutani Y, Inoue K, Kikukawa T, Sakai M, Fujii M, Kandori H, Homma M, Sudo Y. Effects of chloride ion binding on the photochemical properties of salinibacter sensory rhodopsin I. J Mol Biol 2009; 392:48-62. [PMID: 19560470 DOI: 10.1016/j.jmb.2009.06.050] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2009] [Revised: 05/31/2009] [Accepted: 06/18/2009] [Indexed: 10/20/2022]
Abstract
Microbial organisms utilize light not only as energy sources but also as signals by which rhodopsins (containing retinal as a chromophore) work as photoreceptors. Sensory rhodopsin I (SRI) is a dual photoreceptor that regulates both negative and positive phototaxis in microbial organisms, such as the archaeon Halobacterium salinarum and the eubacterium Salinibacter ruber. These organisms live in highly halophilic environments, suggesting the possibility of the effects of salts on the function of SRI. However, such effects remain unclear because SRI proteins from H. salinarum (HsSRI) are unstable in dilute salt solutions. Recently, we characterized a new SRI protein (SrSRI) that is stable even in the absence of salts, thus allowing us to investigate the effects of salts on the photochemical properties of SRI. In this study, we report that the absorption maximum of SrSRI is shifted from 542 to 556 nm in a Cl(-)-dependent manner with a K(m) of 307+/-56 mM, showing that Cl(-)-binding sites exist in SRI. The bathochromic shift was caused not only by NaCl but also by other salts (NaI, NaBr, and NaNO(3)), implying that I(-), Br(-), and NO(3)(-) can also bind to SrSRI. In addition, the photochemical properties during the photocycle are also affected by chloride ion binding. Mutagenesis studies strongly suggested that a conserved residue, His131, is involved in the Cl(-)-binding site. In light of these results, we discuss the effects of the Cl(-) binding to SRI and the roles of Cl(-) binding in its function.
Collapse
|
27
|
Kim SY, Waschuk SA, Brown LS, Jung KH. Screening and characterization of proteorhodopsin color-tuning mutations in Escherichia coli with endogenous retinal synthesis. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2008; 1777:504-13. [PMID: 18433714 DOI: 10.1016/j.bbabio.2008.03.010] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/07/2008] [Revised: 03/08/2008] [Accepted: 03/13/2008] [Indexed: 11/18/2022]
Abstract
Proteorhodopsin is photoactive 7-transmembrane protein, which uses all-trans retinal as a chromophore. Proteorhodopsin subfamilies are spectrally tuned in accordance with the depth of habitat of the host organisms, numerous species of marine picoplankton. We try to find residues critical for the spectral tuning through the use of random PCR mutagenesis and endogenous retinal biosynthesis. We obtained 16 isolates with changed color by screening in Escherichia coli with internal retinal biosynthesis system containing genes for beta-carotene biosynthesis and retinal synthase. Some isolates contained multiple substitutions, which could be separated to give 20 single mutations influencing the spectral properties. The color-changing residues are distributed through the protein except for the helix A, and about a half of the mutations is localized on the helices C and D, implying their importance for color tuning. In the pumping form of the pigment, absorption maxima in 8 mutants are red-shifted and in 12 mutants are blue-shifted compared to the wild-type. The results of flash-photolysis showed that most of the low pumping activity mutants possess slower rates of M decay and O decay. These results suggest that the color-tuning residues are not restricted to the retinal binding pocket, in accord with a recent evolutionary analysis.
Collapse
Affiliation(s)
- So Young Kim
- Department of Life Science and Interdisciplinary Program of Integrated Biotechnology, Sogang University, Mapo-Gu, Seoul, Korea
| | | | | | | |
Collapse
|
28
|
Singh AK, Hota PK. Development of Bacteriorhodopsin Analogues and Studies of Charge Separated Excited States in the Photoprocesses of Linear Polyenes†. Photochem Photobiol 2007; 83:50-62. [PMID: 16872254 DOI: 10.1562/2006-03-11-ir-844] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Development of bacteriorhodopsin (bR) analogues employing chromophore substitution technique for the purpose of characterizing the binding site of bR and generating bR analogues with novel opto-electronic properties for applications as photoactive element in nanotechnical devices are described. Additionally, the photophysical and photochemical properties of variously substituted diarylpolyenes as models of photobiologically relevant linear polyenes are discussed. The role of charge separated dipolar excited states in the photoprocesses of linear polyenes is highlighted.
Collapse
Affiliation(s)
- Anil K Singh
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, India.
| | | |
Collapse
|
29
|
Moise AR, Kuksa V, Imanishi Y, Palczewski K. Identification of all-trans-retinol:all-trans-13,14-dihydroretinol saturase. J Biol Chem 2004; 279:50230-42. [PMID: 15358783 PMCID: PMC2665716 DOI: 10.1074/jbc.m409130200] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Retinoids carry out essential functions in vertebrate development and vision. Many of the retinoid processing enzymes remain to be identified at the molecular level. To expand the knowledge of retinoid biochemistry in vertebrates, we studied the enzymes involved in plant metabolism of carotenoids, a related group of compounds. We identified a family of vertebrate enzymes that share significant similarity and a putative phytoene desaturase domain with a recently described plant carotenoid isomerase (CRTISO), which isomerizes prolycopene to all-trans-lycopene. Comparison of heterologously expressed mouse and plant enzymes indicates that unlike plant CRTISO, the CRTISO-related mouse enzyme is inactive toward prolycopene. Instead, the CRTISO-related mouse enzyme is a retinol saturase carrying out the saturation of the 13-14 double bond of all-trans-retinol to produce all-trans-13,14-dihydroretinol. The product of mouse retinol saturase (RetSat) has a shifted UV absorbance maximum, lambda(max) = 290 nm, compared with the parent compound, all-trans-retinol (lambda(max) = 325 nm), and its MS analysis (m/z = 288) indicates saturation of a double bond. The product was further identified as all-trans-13,14-dihydroretinol, since its characteristics were identical to those of a synthetic standard. Mouse RetSat is membrane-associated and expressed in many tissues, with the highest levels in liver, kidney, and intestine. All-trans-13,14-dihydroretinol was also detected in several tissues of animals maintained on a normal diet. Thus, saturation of all-trans-retinol to all-trans-13,14-dihydroretinol by RetSat produces a new metabolite of yet unknown biological function.
Collapse
Affiliation(s)
- Alexander R. Moise
- Department of Ophthalmology, University of Washington, Seattle, Washington 98195
- To whom correspondence may be addressed: Dept. of Ophthalmology, University of Washington, Box 356485, Seattle, WA 98195-6485. Tel.: 206-543-9074; Fax: 206-221-6784; E-mail:
| | - Vladimir Kuksa
- Department of Ophthalmology, University of Washington, Seattle, Washington 98195
| | - Yoshikazu Imanishi
- Department of Ophthalmology, University of Washington, Seattle, Washington 98195
| | - Krzysztof Palczewski
- Department of Ophthalmology, University of Washington, Seattle, Washington 98195
- Department of Pharmacology, University of Washington, Seattle, Washington 98195
- Department of Chemistry, University of Washington, Seattle, Washington 98195
- To whom correspondence may be addressed: Dept. of Ophthalmology, University of Washington, Box 356485, Seattle, WA 98195-6485. Tel.: 206-543-9074; Fax: 206-221-6784; E-mail:
| |
Collapse
|
30
|
Wang WW, Sineshchekov OA, Spudich EN, Spudich JL. Spectroscopic and photochemical characterization of a deep ocean proteorhodopsin. J Biol Chem 2003; 278:33985-91. [PMID: 12821661 DOI: 10.1074/jbc.m305716200] [Citation(s) in RCA: 124] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A second group of proteorhodopsin-encoding genes (blue-absorbing proteorhodopsin, BPR) differing by 20-30% in predicted primary structure from the first-discovered green-absorbing (GPR) group has been detected in picoplankton from Hawaiian deep sea water. Here we compare BPR and GPR absorption spectra, photochemical reactions, and proton transport activity. The photochemical reaction cycle of Hawaiian deep ocean BPR in cells is 10-fold slower than that of GPR with very low accumulation of a deprotonated Schiff base intermediate in cells and exhibits mechanistic differences, some of which are due to its glutamine residue rather than leucine at position 105. In contrast to GPR and other characterized microbial rhodopsins, spectral titrations of BPR indicate that a second titratable group, in addition to the retinylidene Schiff base counterion Asp-97, modulates the absorption spectrum near neutral pH. Mutant analysis confirms that Asp-97 and Glu-108 are proton acceptor and proton donor, respectively, in retinylidene Schiff base proton transfer reactions during the BPR photocycle as previously shown for GPR, but BPR contains an alternative acceptor evident in its D97N mutant, possibly the same as the second titratable group modulating the absorption spectrum. BPR, similar to GPR, carries out outward light-driven proton transport in Escherichia coli vesicles but with a reduced translocation rate attributable to its slower photocycle. In energized E. coli cells at physiological pH, the net effect of BPR photocycling is to generate proton currents dominated by a triggered proton influx, rather than efflux as observed with GPR-containing cells. Reversal of the proton current with the K+-ionophore valinomycin supports that the influx is because of voltage-gated channels in the E. coli cell membrane. These observations demonstrate diversity in photochemistry and mechanism among proteorhodopsins. Calculations of photon fluence rates at different ocean depths show that the difference in photocycle rates between GPR and BPR as well as their different absorption maxima may be explained as an adaptation to the different light intensities available in their respective marine environments. Finally, the results raise the possibility of regulatory (i.e. sensory) rather than energy harvesting functions of some members of the proteorhodopsin family.
Collapse
Affiliation(s)
- Wei-Wu Wang
- Center for Membrane Biology, Department of Biochemistry and Molecular Biology, University of Texas Medical School, Houston, Texas 77030, USA
| | | | | | | |
Collapse
|
31
|
Shimono K, Hayashi T, Ikeura Y, Sudo Y, Iwamoto M, Kamo N. Importance of the broad regional interaction for spectral tuning in Natronobacterium pharaonis phoborhodopsin (sensory rhodopsin II). J Biol Chem 2003; 278:23882-9. [PMID: 12690098 DOI: 10.1074/jbc.m301200200] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Natronobacterium pharaonis phoborhodopsin (ppR; also called N. pharaonis sensory rhodopsin II, NpsRII) is a photophobic sensor in N. pharaonis, and has a shorter absorption maximum (lambdamax, 500 nm) than those of other archaeal retinal proteins (lambdamax, 560-590 nm) such as bacteriorhodopsin (bR). We constructed chimeric proteins between bR and ppR to investigate the long range interactions effecting the color regulation among archaeal retinal proteins. The lambdamax of B-DEFG/P-ABC was 545 nm, similar to that of bR expressed in Escherichia coli (lambdamax, 550 nm). B-DEFG/P-ABC means a chimera composed of helices D, E, F, and G of bR and helices A, B, and C of ppR. This indicates that the major factor(s) determining the difference in lambdamax between bR and ppR exist in helices DEFG. To specify the more minute regions for the color determination between bR and ppR, we constructed 15 chimeric proteins containing helices D, E, F, and G of bR. According to the absorption spectra of the various chimeric proteins, the interaction between helices D and E as well as the effect of the hydroxyl group around protonated Schiff base on helix G (Thr-204 for ppR and Ala-215 for bR) are the main factors for spectral tuning between bR and ppR.
Collapse
Affiliation(s)
- Kazumi Shimono
- Laboratory of Biophysical Chemistry, Graduate School of Pharmaceutical Sciences, Hokkaido University, Sapporo 060-0812, Japan.
| | | | | | | | | | | |
Collapse
|
32
|
Aharoni A, Khatchatouriants A, Manevitch A, Lewis A, Sheves M. Protein−β-Ionone Ring Interactions Enhance the Light-Induced Dipole of the Chromophore in Bacteriorhodopsin. J Phys Chem B 2003. [DOI: 10.1021/jp027702q] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Amir Aharoni
- Department of Organic Chemistry, Weizmann Institute of Science, Rehovot, Israel, and Department of Applied Physics, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
| | - Artium Khatchatouriants
- Department of Organic Chemistry, Weizmann Institute of Science, Rehovot, Israel, and Department of Applied Physics, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
| | - Alexandra Manevitch
- Department of Organic Chemistry, Weizmann Institute of Science, Rehovot, Israel, and Department of Applied Physics, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
| | - Aaron Lewis
- Department of Organic Chemistry, Weizmann Institute of Science, Rehovot, Israel, and Department of Applied Physics, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
| | - Mordechai Sheves
- Department of Organic Chemistry, Weizmann Institute of Science, Rehovot, Israel, and Department of Applied Physics, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
| |
Collapse
|
33
|
Man D, Wang W, Sabehi G, Aravind L, Post AF, Massana R, Spudich EN, Spudich JL, Béjà O. Diversification and spectral tuning in marine proteorhodopsins. EMBO J 2003; 22:1725-31. [PMID: 12682005 PMCID: PMC154475 DOI: 10.1093/emboj/cdg183] [Citation(s) in RCA: 222] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2002] [Revised: 02/06/2003] [Accepted: 02/25/2003] [Indexed: 11/14/2022] Open
Abstract
Proteorhodopsins, ubiquitous retinylidene photoactive proton pumps, were recently discovered in the cosmopolitan uncultured SAR86 bacterial group in oceanic surface waters. Two related proteorhodopsin families were found that absorb light with different absorption maxima, 525 nm (green) and 490 nm (blue), and their distribution was shown to be stratified with depth. Using structural modeling comparisons and mutagenesis, we report here on a single amino acid residue at position 105 that functions as a spectral tuning switch and accounts for most of the spectral difference between the two pigment families. Furthermore, looking at natural environments, we found novel proteorhodopsin gene clusters spanning the range of 540-505 nm and containing changes in the same identified key switch residue leading to changes in their absorption maxima. The results suggest a simultaneous diversification of green proteorhodopsin and the new key switch variant pigments. Our observations demonstrate that this single-residue switch mechanism is the major determinant of proteorhodopsin wavelength regulation in natural marine environments.
Collapse
Affiliation(s)
- Dikla Man
- Department of Biology, Technion-Israel Institute of Technology, Haifa 32000, Israel
| | | | | | | | | | | | | | | | | |
Collapse
|
34
|
Torii H. Vibrational polarization and opsin shift of retinal schiff bases: theoretical study. J Am Chem Soc 2002; 124:9272-7. [PMID: 12149034 DOI: 10.1021/ja017279j] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The changes in the electronic excitation energy arising from molecular structural displacement induced by external electric field (so-called vibrational polarization) are examined theoretically for the protonated and neutral 11-cis retinal Schiff bases. It is shown that the magnitude of the field-induced structural displacement is significantly large for the protonated species, so that the change in the electronic excitation energy arising from this structural displacement is of the same order of magnitude as that arising from the direct effect of electric field on the electronic wave function. These two effects contribute additively to the field-induced spectral shift. The intensity-carrying mode (ICM) theory is employed to extract a single vibrational mode (called primary infrared ICM) that is most important for the field-induced structural displacement. A simple one-dimensional model is constructed, and the extent to which we can interpret the field-induced spectral shift by such a model is examined. In the case of the neutral species, only a small change in the electronic excitation energy is induced by external electric field, mainly because the vibrational polarizability of this species is small. The meaning of these results in the spectral tuning of visual pigments is discussed.
Collapse
Affiliation(s)
- Hajime Torii
- Department of Chemistry, School of Education, Shizuoka University, 836 Ohya, Shizuoka 422-8529, Japan.
| |
Collapse
|
35
|
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.
Collapse
Affiliation(s)
- John L Spudich
- Department of Biochemistry and Molecular Biology, University of Texas Medical School, Houston 77030, USA.
| | | |
Collapse
|
36
|
Zsila F, Bikádi Z, Simonyi M. Further insight into the molecular basis of carotenoid–albumin interactions: circular dichroism and electronic absorption study on different crocetin–albumin complexes. ACTA ACUST UNITED AC 2002. [DOI: 10.1016/s0957-4166(02)00097-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
|
37
|
Abstract
Combined quantum mechanical and molecular mechanical (QM/MM) calculations and molecular dynamics simulations of bacteriorhodopsin (bR) in the membrane matrix have been carried out to determine the factors that make significant contributions to the opsin shift. We found that both solvation and interactions with the protein significantly shifts the absorption maximum of the retinal protonated Schiff base, but the effects are much more pronounced in polar solvents such as methanol, acetonitrile, and water than in the protein environment. The differential solvatochromic shifts of PSB in methanol and in bR leads to a bathochromic shift of about 1800 cm(-1). Because the combined QM/MM configuration interaction calculation is essentially a point charge model, this contribution is attributed to the extended point-charge model of Honig and Nakanishi. The incorporation of retinal in bR is accompanied by a change in retinal conformation from the 6-s-cis form in solution to the 6-s-trans configuration in bR. The extension of the pi-conjugated system further increases the red-shift by 2400 cm(-1). The remaining factors are due to the change in dispersion interactions. Using an estimate of about 1000 cm(-1) in the dispersion contribution by Houjou et al., we obtained a theoretical opsin shift of 5200 cm(-1) in bR, which is in excellent agreement with the experimental value of 5100 cm(-1). Structural analysis of the PSB binding site revealed the specific interactions that make contributions to the observed opsin shift. The combined QM/MM method used in the present study provides an opportunity to accurately model the photoisomerization and proton transfer reactions in bR.
Collapse
Affiliation(s)
- Ramkumar Rajamani
- Department of Chemistry and Minnesota Supercomputing Institute, University of Minnesota, Minneapolis 55455, USA
| | | |
Collapse
|
38
|
Luecke H, Schobert B, Lanyi JK, Spudich EN, Spudich JL. Crystal structure of sensory rhodopsin II at 2.4 angstroms: insights into color tuning and transducer interaction. Science 2001; 293:1499-503. [PMID: 11452084 PMCID: PMC4996266 DOI: 10.1126/science.1062977] [Citation(s) in RCA: 298] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
We report an atomic-resolution structure for a sensory member of the microbial rhodopsin family, the phototaxis receptor sensory rhodopsin II (NpSRII), which mediates blue-light avoidance by the haloarchaeon Natronobacterium pharaonis. The 2.4 angstrom structure reveals features responsible for the 70- to 80-nanometer blue shift of its absorption maximum relative to those of haloarchaeal transport rhodopsins, as well as structural differences due to its sensory, as opposed to transport, function. Multiple factors appear to account for the spectral tuning difference with respect to bacteriorhodopsin: (i) repositioning of the guanidinium group of arginine 72, a residue that interacts with the counterion to the retinylidene protonated Schiff base; (ii) rearrangement of the protein near the retinal ring; and (iii) changes in tilt and slant of the retinal polyene chain. Inspection of the surface topography reveals an exposed polar residue, tyrosine 199, not present in bacteriorhodopsin, in the middle of the membrane bilayer. We propose that this residue interacts with the adjacent helices of the cognate NpSRII transducer NpHtrII.
Collapse
Affiliation(s)
- Hartmut Luecke
- Department of Molecular Biology and Biochemistry, University of California, Irvine, CA 92697, USA
- Department of Physiology and Biophysics, University of California, Irvine, CA 92697, USA
| | - Brigitte Schobert
- Department of Physiology and Biophysics, University of California, Irvine, CA 92697, USA
| | - Janos K. Lanyi
- Department of Physiology and Biophysics, University of California, Irvine, CA 92697, USA
| | - Elena N. Spudich
- Department of Microbiology and Molecular Genetics and Structural Biology Center, University of Texas Medical School, Houston, TX 77030, USA
| | - John L. Spudich
- Department of Microbiology and Molecular Genetics and Structural Biology Center, University of Texas Medical School, Houston, TX 77030, USA
| |
Collapse
|
39
|
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.
Collapse
Affiliation(s)
- J L Spudich
- Department of Microbiology and Molecular Genetics, University of Texas Medical School, Houston, Texas 77030, USA.
| | | | | | | |
Collapse
|
40
|
|
41
|
Houjou H, Inoue Y, Sakurai M. Physical Origin of the Opsin Shift of Bacteriorhodopsin. Comprehensive Analysis Based on Medium Effect Theory of Absorption Spectra. J Am Chem Soc 1998. [DOI: 10.1021/ja973941t] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Hirohiko Houjou
- Contribution from the Department of Biomolecular Engineering, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama 2268501, Japan
| | - Yoshio Inoue
- Contribution from the Department of Biomolecular Engineering, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama 2268501, Japan
| | - Minoru Sakurai
- Contribution from the Department of Biomolecular Engineering, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama 2268501, Japan
| |
Collapse
|
42
|
Sasaki M, Fukuhara T. Spectroscopic mimicry for the protonated retinal Schiff base in vivo with modified amphiphilic clay interlayers as a possible model of opsin environment. Photochem Photobiol 1997; 66:716-8. [PMID: 9383996 DOI: 10.1111/j.1751-1097.1997.tb03212.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
We have found that clay acts as a novel model matrix for the amphiphilic protein-opsin to mimic the visible absorption spectrum of a protonated retinal Schiff base (RSB) in vivo. Without strong acids at ambient temperature, a visible broad absorption spectrum with a lambda max at 530 nm covering the range from 400 to 680 nm was achieved for the protonated RSB with cationic surfactant-modified montmorillonite clay. The interlayers of the dimethyloctadecylamine (DOA) modified clay were found to provide amphiphilic space allowing the amphiphilic RSB to be intercalated easily and sequentially and protonated by the DOA. It is proposed that the visible absorption spectrum at lambda max 530 nm was attributable to electrostatic effects, permitting the appropriate distance between the nitrogen of the protonated RSB and the negatively charged clay interlayers and also to the anisotropic orientation of the RSB molecules in the interlayers.
Collapse
Affiliation(s)
- M Sasaki
- Research Institute of Science and Technology, Tokai University, Kanagawa, Japan.
| | | |
Collapse
|
43
|
Sakar K, Vacek G, Luthi HP, Nagashima U. The Importance of Charge Transfer between the Retinal Chromophore and the Protein Environment in Bacteriorhodopsin: A Theoretical Analysis on Reduced and Oxidized Chromophores. Photochem Photobiol 1997. [DOI: 10.1111/j.1751-1097.1997.tb03185.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
|
44
|
Francesch A, Alvarez R, López S, de Lera AR. Synthesis of Retinals Fluorinated at Odd-Numbered Side-Chain Positions and of the Corresponding Fluorobacteriorhodopsins. J Org Chem 1997; 62:310-319. [PMID: 11671404 DOI: 10.1021/jo961355x] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Conventional Horner-Wadsworth-Emmons and Wittig condensations were used to fluorinate the odd-numbered positions of the retinal side chain past C(7). The stereochemically labile cis-fluororetinals were easily converted into the most stable trans-fluororetinals, which were incubated with bacterio-opsin. Contrary to expectations, the fluorinated retinals provided artificial pigments with near normal absorption properties, showing that any electrostatic interactions between the fluorine atoms and protein groups were insufficient to prevent normal binding. The new artificial pigments had smaller opsin shifts than did native bacteriorhodopsin, which is interpreted as due either to greater electrostatic interaction between the protonated imine and its counterion, or to local interactions between the fluorine substituents and nearby polar protein groups.
Collapse
Affiliation(s)
- Andrés Francesch
- Departamento de Química Orgánica, Universidade de Santiago de Compostela, 15706 Santiago de Compostela, Spain
| | | | | | | |
Collapse
|
45
|
Hoff WD, Jung KH, Spudich JL. Molecular mechanism of photosignaling by archaeal sensory rhodopsins. ANNUAL REVIEW OF BIOPHYSICS AND BIOMOLECULAR STRUCTURE 1997; 26:223-58. [PMID: 9241419 DOI: 10.1146/annurev.biophys.26.1.223] [Citation(s) in RCA: 244] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Two sensory rhodopsins (SRI and SRII) mediate color-sensitive phototaxis responses in halobacteria. These seven-helix receptor proteins, structurally and functionally similar to animal visual pigments, couple retinal photoisomerization to receptor activation and are complexed with membrane-embedded transducer proteins (HtrI and HtrII) that modulate a cytoplasmic phosphorylation cascade controlling the flagellar motor. The Htr proteins resemble the chemotaxis transducers from Escherichia coli. The SR-Htr signaling complexes allow studies of the biophysical chemistry of signal generation and relay, from the photobiophysics of initial excitation of the receptors to the final output at the level of the flagellar motor switch, revealing fundamental principles of sensory transduction and more broadly the nature of dynamic interactions between membrane proteins. We review here recent advances that have led to new insights into the molecular mechanism of signaling by these membrane complexes.
Collapse
Affiliation(s)
- W D Hoff
- Department of Microbiology and Molecular Genetics, University of Texas Medical School, Houston 77030-1501, USA
| | | | | |
Collapse
|
46
|
Kroon AR, Hoff WD, Fennema HP, Gijzen J, Koomen GJ, Verhoeven JW, Crielaard W, Hellingwerf KJ. Spectral tuning, fluorescence, and photoactivity in hybrids of photoactive yellow protein, reconstituted with native or modified chromophores. J Biol Chem 1996; 271:31949-56. [PMID: 8943241 DOI: 10.1074/jbc.271.50.31949] [Citation(s) in RCA: 90] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Photoactive yellow proteins (PYPs) constitute a new class of eubacterial photoreceptors, containing a deprotonated thiol ester-linked 4-hydroxycinnamic acid chromophore. Interactions with the protein dramatically change the (photo)chemical properties of this cofactor. Here we describe the reconstitution of apoPYP with anhydrides of various chromophore analogues. The resulting hybrid PYPs, their acid-denatured states, and corresponding model compounds were characterized with respect to their absorption spectrum, pK for chromophore deprotonation, fluorescence quantum yield, and Stokes shift. Three factors contributing to the tuning of the absorption of the hybrid PYPs were quantified: (i) thiol ester bond formation, (ii) chromophore deprotonation, and (iii) specific chromophore-protein interactions. Analogues lacking the 4-hydroxy substituent lack both contributions (chromophore deprotonation and specific chromophore-protein interactions), confirming the importance of this substituent in optical tuning of PYP. Hydroxy and methoxy substituents in the 3- and/or 5-position do not disrupt strong interactions with the protein but increase their pK for protonation and the fluorescence quantum yield. Both deprotonation and binding to apoPYP strongly decrease the Stokes shift of chromophore fluorescence. Therefore, coupling of the chromophore to the apoprotein not only reduces the energy gap between its ground and excited state but also the extent of reorganization between these two states. Two of the PYP hybrids show photoactivity comparable with native PYP, although with retarded recovery of the initial state.
Collapse
Affiliation(s)
- A R Kroon
- Laboratory for Microbiology, E. C. Slater Institute, BioCentrum Amsterdam, Nieuwe Achtergracht 127, 1018 WS, Amsterdam, The Netherlands.
| | | | | | | | | | | | | | | |
Collapse
|