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Urui T, Mizuno M, Otomo A, Kandori H, Mizutani Y. Resonance Raman Determination of Chromophore Structures of Heliorhodopsin Photointermediates. J Phys Chem B 2021; 125:7155-7162. [PMID: 34167296 DOI: 10.1021/acs.jpcb.1c04010] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Light is utilized as energy or information by rhodopsins (membrane proteins that contain a retinal chromophore). Heliorhodopsins (HeRs) are a new class of rhodopsins with low sequence identity (<15%) to microbial and animal rhodopsins. Their physiological roles remain unknown, although the involvement of a long-lived intermediate in the photocycle suggests a light-sensor function. Characterization of the molecular structures of the intermediates is essential to an understanding of the roles and mechanisms of HeRs. We determined the chromophore structures of the intermediates in HeR 48C12 by time-resolved resonance Raman spectroscopy and observed that the hydrogen bond of the protonated Schiff base strengthened prior to deprotonation. The chromophore is photoisomerized from the all-trans to the 13-cis form and is reisomerized in the transition from the O intermediate to the unphotolyzed state. Our results demonstrate that the chromophore structure evolves similarly to microbial rhodopsins, despite the dissimilarity in amino acid residues surrounding the chromophore.
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Affiliation(s)
- Taito Urui
- Department of Chemistry, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan
| | - Misao Mizuno
- Department of Chemistry, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan
| | - Akihiro Otomo
- Department of Chemistry, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan
| | - Hideki Kandori
- Department of Life Science and Applied Chemistry, Nagoya Institute of Technology, Showa-ku, Nagoya, Aichi 466-8555, Japan
| | - Yasuhisa Mizutani
- Department of Chemistry, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan
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2
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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: 45] [Impact Index Per Article: 9.0] [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.
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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
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Schulten K, Humphrey W, Logunov I, Sheves M, Xu D. Molecular Dynamics Studies of Bacteriorhodopsin's Photocycles. Isr J Chem 2013. [DOI: 10.1002/ijch.199500042] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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6
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Honig B, Ottolenghi M, Sheves M. Acid-Base Equilibria and the Proton Pump in Bacteriorhodopsin. Isr J Chem 2013. [DOI: 10.1002/ijch.199500041] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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7
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Althaus T, Eisfeld W, Lohrmann R, Stockburger M. Application of Raman Spectroscopy to Retinal Proteins. Isr J Chem 2013. [DOI: 10.1002/ijch.199500029] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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8
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Morgan JE, Vakkasoglu AS, Lanyi JK, Lugtenburg J, Gennis RB, Maeda A. Structure changes upon deprotonation of the proton release group in the bacteriorhodopsin photocycle. Biophys J 2013; 103:444-452. [PMID: 22947860 DOI: 10.1016/j.bpj.2012.06.022] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2012] [Revised: 05/19/2012] [Accepted: 06/04/2012] [Indexed: 11/18/2022] Open
Abstract
In the photocycle of bacteriorhodopsin at pH 7, a proton is ejected to the extracellular medium during the protonation of Asp-85 upon formation of the M intermediate. The group that releases the ejected proton does not become reprotonated until the prephotolysis state is restored from the N and O intermediates. In contrast, at acidic pH, this proton release group remains protonated to the end of the cycle. Time-resolved Fourier transform infrared measurements obtained at pH 5 and 7 were fitted to obtain spectra of kinetic intermediates, from which the spectra of M and N/O versus unphotolyzed state were calculated. Vibrational features that appear in both M and N/O spectra at pH 7, but not at pH 5, are attributable to deprotonation from the proton release group and resulting structural alterations. Our results agree with the earlier conclusion that this group is a protonated internal water cluster, and provide a stronger experimental basis for this assignment. A decrease in local polarity at the N-C bond of the side chain of Lys-216 resulting from deprotonation of this water cluster may be responsible for the increase in the proton affinity of Asp-85 through M and N/O, which is crucial for maintaining the directionality of proton pumping.
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Affiliation(s)
- Joel E Morgan
- Department of Biology, Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, New York
| | - Ahmet S Vakkasoglu
- Center for Biophysics and Computational Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois
| | - Janos K Lanyi
- Department of Physiology and Biophysics, University of California, Irvine, California
| | - Johan Lugtenburg
- Department of Chemistry, University of Leiden, Leiden, The Netherlands
| | - Robert B Gennis
- Center for Biophysics and Computational Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois; Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois
| | - Akio Maeda
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois.
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9
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Babitzki G, Denschlag R, Tavan P. Polarization Effects Stabilize Bacteriorhodopsin’s Chromophore Binding Pocket: A Molecular Dynamics Study. J Phys Chem B 2009; 113:10483-95. [DOI: 10.1021/jp902428x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- G. Babitzki
- Theoretische Biophysik, Lehrstuhl für Biomolekulare Optik, Ludwig-Maximilians-Universität, Oettingenstr. 67, 80538 München, Germany
| | - R. Denschlag
- Theoretische Biophysik, Lehrstuhl für Biomolekulare Optik, Ludwig-Maximilians-Universität, Oettingenstr. 67, 80538 München, Germany
| | - P. Tavan
- Theoretische Biophysik, Lehrstuhl für Biomolekulare Optik, Ludwig-Maximilians-Universität, Oettingenstr. 67, 80538 München, Germany
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Hendler RW. An apparent general solution for the kinetic models of the bacteriorhodopsin photocycles. J Phys Chem B 2007; 109:16515-28. [PMID: 16853100 DOI: 10.1021/jp052733h] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
For the past decade, the field of Bacteriorhodopsin (BR) research has been influenced by a kinetic view of the photocycle as a reversible, homogeneous, model (RHM) with a linear sequence of intermediates. More recently, we proposed a much different model which consists of essentially unidirectional, parallel (i.e., heterogeneous) cycles (UPM) (Hendler, R. W.; Shrager, R. I.; Bose, S. J. Phys. Chem. B 2001, 105, 3319-3328). It is important to try to resolve which of the two models is more likely to be correct, because models influence and provide a basis for further experimentation. Therefore, in this communication, we reexamine the basis for the RHM with a focus on the most recent and complete description of this model (van Stokkum, I., H., M.; Lozier, R. J. Phys. Chem. B 2002, 106, 3477-3485) vis a vis the UPM in an in-depth study. We show that (i) the tested RHM does not really work for the data of van Stokkum and Lozier nor ours; (ii) no previously published RHM model has been shown to work for data under any conditions; (iii) there are many published observations that are difficult if not impossible to explain by RHM, but are readily explained by parallel cycles. It is also shown that either a UPM or a parallel cycle model with limited reversibility correctly describes photocycle data collected at pH 5, 7, and 9 and at 10, 20, and 30 degrees and is consistent with all known experimental observations.
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Affiliation(s)
- Richard W Hendler
- Laboratory of Cell Biology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
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Eisfeld W, Althaus T, Stockburger M. Evidence for parallel photocycles and implications for the proton pump in bacteriorhodopsin. Biophys Chem 2007; 56:105-12. [PMID: 17023317 DOI: 10.1016/0301-4622(95)00021-o] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
In order to account for the large variety of kinetic phenomena in the light-induced reactions of bacteriorhodopsin's retinal chromophore (BR), a scheme of parallel photocycles has been proposed [W. Eisfeld, C. Pusch, R. Diller, R. Lohrmann and M. Stockburger, Biochemistry, 32 (1993) 7196-7215]. In the present study an experimental test for the validity of this model is described which is based on the fact that in the alkaline region the longest-living intermediates M(f), M(S) or N in each of the proposed cycles have significantly different lifetimes. A condition for the existence of parallel cycles would be that the population of M(f), M(S) or N is accompanied by a respective depletion of BR in each individual cycle. Dual-beam laser experiments were performed which showed that this condition is fulfilled. It is concluded that those proton transfer steps which are important for the function as a proton pump are the same for all cycles.
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Affiliation(s)
- W Eisfeld
- Max-Planck-Institut für biophysikalische Chemie, Abteilung Spektroskopie, Am Fassberg Postfach 2841, D-37018 Göttingen, Germany
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12
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Shrager RI, Hendler RW. Critical Evaluation of Kinetic Models for Bacteriorhodopsin Photocycles. J Phys Chem B 2003. [DOI: 10.1021/jp0273070] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Richard I. Shrager
- Mathematical and Statistical Computing Laboratory, Center for Information Technology, National Institutes of Health, Bethesda, Maryland 20892
| | - Richard W. Hendler
- Laboratory of Cell Biology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892
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Balashov SP. Protonation reactions and their coupling in bacteriorhodopsin. BIOCHIMICA ET BIOPHYSICA ACTA 2000; 1460:75-94. [PMID: 10984592 DOI: 10.1016/s0005-2728(00)00131-6] [Citation(s) in RCA: 130] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Light-induced changes of the proton affinities of amino acid side groups are the driving force for proton translocation in bacteriorhodopsin. Recent progress in obtaining structures of bacteriorhodopsin and its intermediates with an increasingly higher resolution, together with functional studies utilizing mutant pigments and spectroscopic methods, have provided important information on the molecular architecture of the proton transfer pathways and the key groups involved in proton transport. In the present paper I consider mechanisms of light-induced proton release and uptake and intramolecular proton transport and mechanisms of modulation of proton affinities of key groups in the framework of these data. Special attention is given to some important aspects that have surfaced recently. These are the coupling of protonation states of groups involved in proton transport, the complex titration of the counterion to the Schiff base and its origin, the role of the transient protonation of buried groups in catalysis of the chromophore's thermal isomerization, and the relationship between proton affinities of the groups and the pH dependencies of the rate constants of the photocycle and proton transfer reactions.
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Affiliation(s)
- S P Balashov
- Center for Biophysics and Computational Biology, Department of Cell and Structural Biology, University of Illinois at Urbana-Champaign, B107 CLSL, 601 S. Goodwin Ave., 61801, Urbana, IL, USA.
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14
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Betancourt FM, Glaeser RM. Chemical and physical evidence for multiple functional steps comprising the M state of the bacteriorhodopsin photocycle. BIOCHIMICA ET BIOPHYSICA ACTA 2000; 1460:106-18. [PMID: 10984594 DOI: 10.1016/s0005-2728(00)00133-x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
In the photocycle of bacteriorhodopsin (bR), light-induced transfer of a proton from the Schiff base to an acceptor group located in the extracellular half of the protein, followed by reprotonation from the cytoplasmic side, are key steps in vectorial proton pumping. Between the deprotonation and reprotonation events, bR is in the M state. Diverse experiments undertaken to characterize the M state support a model in which the M state is not a static entity, but rather a progression of two or more functional substates. Structural changes occurring in the M state and in the entire photocycle of wild-type bR can be understood in the context of a model which reconciles the chloride ion-pumping phenotype of mutants D85S and D85T with the fact that bR creates a transmembrane proton-motive force.
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Affiliation(s)
- F M Betancourt
- Life Sciences Division, Donner Laboratory, Lawrence Berkeley, National Laboratory, University of California, Berkeley, CA 94720, USA.
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Delaney JK, Schmidt PK, Brack TL, Atkinson GH. Photochemistry of K-590 in the Room-Temperature Bacteriorhodopsin Photocycle. J Phys Chem B 2000. [DOI: 10.1021/jp000374e] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- J. K. Delaney
- Department of Chemistry and Optical Science Center, University of Arizona, Tucson, Arizona 85721, and Department of Chemistry, Hofstra University, Hempstead, New York 11549
| | - P. K. Schmidt
- Department of Chemistry and Optical Science Center, University of Arizona, Tucson, Arizona 85721, and Department of Chemistry, Hofstra University, Hempstead, New York 11549
| | - T. L. Brack
- Department of Chemistry and Optical Science Center, University of Arizona, Tucson, Arizona 85721, and Department of Chemistry, Hofstra University, Hempstead, New York 11549
| | - G. H. Atkinson
- Department of Chemistry and Optical Science Center, University of Arizona, Tucson, Arizona 85721, and Department of Chemistry, Hofstra University, Hempstead, New York 11549
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16
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Seitz A, Hampp N. Kinetic Optimization of Bacteriorhodopsin Films for Holographic Interferometry. J Phys Chem B 2000. [DOI: 10.1021/jp993949k] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- A. Seitz
- Institute for Physical Chemistry, University of Marburg, Hans Meerwein-Strasse, Geb. H, D-35032 Marburg, Germany
| | - N. Hampp
- Institute for Physical Chemistry, University of Marburg, Hans Meerwein-Strasse, Geb. H, D-35032 Marburg, Germany
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Li Q, Sun Q, Zhao W, Wang H, Xu D. Newly isolated archaerhodopsin from a strain of Chinese halobacteria and its proton pumping behavior. BIOCHIMICA ET BIOPHYSICA ACTA 2000; 1466:260-6. [PMID: 10825447 DOI: 10.1016/s0005-2736(00)00188-7] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
A strain of extremely salt-loving halobacteria Halobacterium species xz515 from a salt lake in Tibet was isolated. SDS-polyacrylamide gel electrophoresis shows that there is only one protein on claret membrane, which is the same membrane fraction as purple membrane from Halobacterium salinarum, with a molecular weight close to bacteriorhodopsin (br). The purified retinal containing protein from xz515 has an absorption peak at around 550 nm. These facts indicate that it is a br-like protein. The partial sequence determination [H. Wang et al., Chin. Sci. Bull., 45 (2000)] shows that this br-like protein belongs to the archaerhodopsin family. The measurements of light-induced medium pH change in intact cells and cell envelope vesicles of xz515 suggest that this type of archaerhodopsin has a proton pumping function. However, the study about the dynamics of pumped protons across the membrane reveal that the proton release and proton uptake is in reverse order compared to br. The probable reason, attributing to regulating the rate of proton release is discussed.
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Affiliation(s)
- Q Li
- Department of Physiology and Biophysics, School of life Science, Fudan University, 200433, Shanghai, China.
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Li Q, Bressler S, Ovrutsky D, Ottolenghi M, Friedman N, Sheves M. On the protein residues that control the yield and kinetics of O(630) in the photocycle of bacteriorhodopsin. Biophys J 2000; 78:354-62. [PMID: 10620299 PMCID: PMC1300643 DOI: 10.1016/s0006-3495(00)76598-2] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The effects of pH on the yield (phi(r)), and on the apparent rise and decay constants (k(r), k(d)), of the O(630) intermediate are important features of the bacteriorhodopsin (bR) photocycle. The effects are associated with three titration-like transitions: 1) A drop in k(r), k(d), and phi(r) at high pH [pK(a)(1) approximately 8]; 2) A rise in phi(r) at low pH [pK(a)(2) approximately 4.5]; and 3) A drop in k(r) and k(d) at low pH [pK(a)(3) approximately 4. 5]. (pK(a) values are for native bR in 100 mM NaCl). Clarification of these effects is approached by studying the pH dependence of phi(r), k(r), and k(d) in native and acetylated bR, and in its D96N and R82Q mutants. The D96N experiments were carried out in the presence of small amounts of the weak acids, azide, nitrite, and thiocyanate. Analysis of the mutant's data leads to the identification of the protein residue (R(1)) whose state of protonation controls the magnitude of phi(r), k(r), and k(d) at high pH, as Asp-96. Acetylation of bR modifies the Lys-129 residue, which is known to affect the pK(a) of the group (XH), which releases the proton to the membrane exterior during the photocycle. The effects of acetylation on the O(630) parameters reveal that the low-pH titrations should be ascribed to two additional protein residues R(2) and R(3). R(2) affects the rise of phi(r) at low pH, whereas the state of protonation of R(3) affects both k(r) and k(d). Our data confirm a previous suggestion that R(3) should be identified as the proton release moiety (XH). A clear identification of R(2), including its possible identity with R(3), remains open.
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Affiliation(s)
- Q Li
- Department of Physical Chemistry, The Hebrew University, Jerusalem 91904, Israel
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Zscherp C, Schlesinger R, Tittor J, Oesterhelt D, Heberle J. In situ determination of transient pKa changes of internal amino acids of bacteriorhodopsin by using time-resolved attenuated total reflection Fourier-transform infrared spectroscopy. Proc Natl Acad Sci U S A 1999; 96:5498-503. [PMID: 10318912 PMCID: PMC21888 DOI: 10.1073/pnas.96.10.5498] [Citation(s) in RCA: 134] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Active proton transfer through membrane proteins is accomplished by shifts in the acidity of internal amino acids, prosthetic groups, and water molecules. The recently introduced step-scan attenuated total reflection Fourier-transform infrared (ATR/FT-IR) spectroscopy was employed to determine transient pKa changes of single amino acid side chains of the proton pump bacteriorhodopsin. The high pKa of D96 (>12 in the ground state) drops to 7.1 +/- 0.2 (in 1 M KCl) during the lifetime of the N intermediate, quantitating the role of D96 as the internal proton donor of the retinal Schiff base. We conclude from experiments on the pH dependence of the proton release reaction and on point mutants where each of the glutamates on the extracellular surface has been exchanged that besides D85 no other carboxylic group changes its protonation state during proton release. However, E194 and E204 interact with D85, the primary proton acceptor of the Schiff base proton. The C==O stretching vibration of D85 undergoes a characteristic pH-dependent shift in frequency during the M state of wild-type bacteriorhodopsin with a pKa of 5.2 (+/-0.3) which is abolished in the single-site mutants E194Q and E204Q and the quadruple mutant E9Q/E74Q/E194Q/E204Q. The double mutation E9Q/E74Q does not affect the lifetime of the intermediates, ruling out any participation of these residues in the proton transfer chain of bacteriorhodopsin. This study demonstrates that transient changes in acidity of single amino acid residues can be quantified in situ with infrared spectroscopy.
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Affiliation(s)
- C Zscherp
- Forschungszentrum Jülich GmbH, IBI-2: Structural Biology, 52425 Jülich, Germany
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Rödig C, Chizhov I, Weidlich O, Siebert F. Time-resolved step-scan Fourier transform infrared spectroscopy reveals differences between early and late M intermediates of bacteriorhodopsin. Biophys J 1999; 76:2687-701. [PMID: 10233083 PMCID: PMC1300238 DOI: 10.1016/s0006-3495(99)77421-7] [Citation(s) in RCA: 84] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
In this report, from time-resolved step-scan Fourier transform infrared investigations from 15 ns to 160 ms, we provide evidence for the subsequent rise of three different M states that differ in their structures. The first state rises with approximately 3 microseconds to only a small percentage. Its structure as judged from amide I/II bands differs in small but well-defined aspects from the L state. The next M state, which appears in approximately 40 microseconds, has almost all of the characteristics of the "late" M state, i.e., it differs considerably from the first one. Here, the L left arrow over right arrow M equilibrium is shifted toward M, although some percentage of L still persists. In the last M state (rise time approximately 130 microseconds), the equilibrium is shifted toward full deprotonation of the Schiff base, and only small additional structural changes take place. In addition to these results obtained for unbuffered conditions or at pH 7, experiments performed at lower and higher pH are presented. These results are discussed in terms of the molecular changes postulated to occur in the M intermediate to allow the shift of the L/M equilibrium toward M and possibly to regulate the change of the accessibility of the Schiff base necessary for effective proton pumping.
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Affiliation(s)
- C Rödig
- Institut für Biophysik und Strahlenbiologie der Universität Freiburg, 79104 Freiburg, Germany
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The effect of chemical additives on the bacteriorhodopsin photocycle. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY 1999. [DOI: 10.1016/s1011-1344(99)00058-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Ludmann K, Gergely C, Váró G. Kinetic and thermodynamic study of the bacteriorhodopsin photocycle over a wide pH range. Biophys J 1998; 75:3110-9. [PMID: 9826631 PMCID: PMC1299982 DOI: 10.1016/s0006-3495(98)77752-5] [Citation(s) in RCA: 80] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The photocycle of bacteriorhodopsin and its thermodynamic parameters were studied in the pH range of 4.5-9. Measurements were performed at five different wavelengths (410, 500, 570, 610, and 650 nm), in the time interval 300 ns to 0.5 s, at six temperatures between 5 and 30 degreesC. Data were fitted to different photocycle models. The sequential model with reversible reactions gave a good fit, and the linear character of the Eyring plots was fulfilled. The parallel model with unidirectional reactions gave a poor fit, and the Eyring plot of the rate constants did not follow the expected linear behavior. When a parallel model with reversible reactions, which has twice as many free parameters as the sequential model, was considered, the quality of the fit did not improve and the Eyring plots were not linear. The sequential model was used to determine the thermodynamic activation parameters (activation enthalpy, entropy, and free energy) of the transitions and the free energy levels of the intermediates. pH dependence of the parameters revealed details of the transitions between the intermediates: the transitions M1 to M2 and N to O disclosed a large entropy increase, which could be interpreted as a loosening of the protein structure. The pH dependence of the energy levels explains the disappearance of intermediate O at high pH. A hypothesis is proposed to interpret the relation between the observed pKa of the photocycle energetics and the role of several amino acids in the protein.
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Affiliation(s)
- K Ludmann
- Institute of Biophysics, Biological Research Centre of the Hungarian Academy of Sciences, Szeged H-6701, Hungary
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Ludmann K, Gergely C, Dér A, Váró G. Electric signals during the bacteriorhodopsin photocycle, determined over a wide pH range. Biophys J 1998; 75:3120-6. [PMID: 9826632 PMCID: PMC1299983 DOI: 10.1016/s0006-3495(98)77753-7] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
From the electric signals measured after photoexcitation, the electrogenicity of the photocycle intermediates of bacteriorhodopsin were determined in a pH range of 4.5-9. Current measurements and absorption kinetic signals at five wavelengths were recorded in the time interval from 300 ns to 0.5 s. To fit the data, the model containing sequential intermediates connected by reversible first-order reactions was used. The electrogenicities were calculated from the integral of the current signal, by using the time-dependent concentrations of the intermediates, obtained from the fits. Almost all of the calculated electrogenicities were pH independent, suggesting that the charge motions occur inside the protein. Only the N intermediate exhibited pH-dependent electrogenicity, implying that the protonation of Asp96, from the intracellular part of the protein, is not from a well-determined proton donor. The calculated electrogenicities gave good approximations of all of the details of the measured electric signals.
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Affiliation(s)
- K Ludmann
- Institute of Biophysics, Biological Research Centre of the Hungarian Academy of Sciences, Szeged H-6701, Hungary
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24
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Gergely C, Zimányi L, Váró G. Bacteriorhodopsin Intermediate Spectra Determined over a Wide pH Range. J Phys Chem B 1997. [DOI: 10.1021/jp971381e] [Citation(s) in RCA: 73] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Csilla Gergely
- Institute of Biophysics, Biological Research Centre of the Hungarian Academy of Sciences, H-6701 Szeged, Hungary
| | - László Zimányi
- Institute of Biophysics, Biological Research Centre of the Hungarian Academy of Sciences, H-6701 Szeged, Hungary
| | - György Váró
- Institute of Biophysics, Biological Research Centre of the Hungarian Academy of Sciences, H-6701 Szeged, Hungary
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25
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Hessling B, Herbst J, Rammelsberg R, Gerwert K. Fourier transform infrared double-flash experiments resolve bacteriorhodopsin's M1 to M2 transition. Biophys J 1997; 73:2071-80. [PMID: 9336202 PMCID: PMC1181107 DOI: 10.1016/s0006-3495(97)78237-7] [Citation(s) in RCA: 76] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The orientation of the central proton-binding site, the protonated Schiff base, away from the proton release side to the proton uptake side is crucial for the directionality of the proton pump bacteriorhodopsin. It has been proposed that this movement, called the reprotonation switch, takes place in the M1 to M2 transition. To resolve the molecular events in this M1 to M2 transition, we performed double-flash experiments. In these experiments a first pulse initiates the photocycle and a second pulse selectively drives bR molecules in the M intermediate back into the BR ground state. For short delay times between initiating and resetting pulses, most of the M molecules being reset are in the M1 intermediate, and for longer delay times most of the reset M molecules are in the M2 intermediate. The BR-M1 and BR-M2 difference spectra are monitored with nanosecond step-scan Fourier transform infrared spectroscopy. Because the Schiff base reprotonation rate is kM1 = 0.8 x 10(7) s(-1) in the light-induced M1 back-reaction and kM2 = 0.36 x 10(7) s(-1) in the M2 back-reaction, the two different M intermediates represent two different proton accessibility configurations of the Schiff base. The results show only a minute movement of one or two peptide bonds in the M1 to M2 transition that changes the interaction of the Schiff base with Y185. This backbone movement is distinct from the larger one in the subsequent M to N transition. No evidence of a chromophore isomerization is seen in the M1 to M2 transition. Furthermore, the results show time-resolved reprotonation of the Schiff base from D85 in the M photo-back-reaction, instead of from D96, as in the conventional cycle.
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Affiliation(s)
- B Hessling
- Lehrstuhl für Biophysik, Fakultät Biologie, Ruhr Universität Bochum, Germany
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26
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Radionov AN, Kaulen AD. Inhibition of the M1-->M2 (M(closed) --> M(open)) transition in the D96N mutant photocycle and its relation to the corresponding transition in wild-type bacteriorhodopsin. FEBS Lett 1997; 409:137-40. [PMID: 9202133 DOI: 10.1016/s0014-5793(97)00474-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Glutaraldehyde, lutetium ions and glycerol inhibit the blue shift of the difference spectra maximum of the M intermediate in the D96N mutant. The M formed has a spectrum indistinguishable from the M intermediate in wild-type bacteriorhodopsin. It has been concluded that the M(open) form previously described by us is identical to the M2 and Mn intermediates postulated by Zimanyi et al. (Photochem. Photobiol. (1992) 56, 1049-1055) and Sasaki et al. (J. Biol. Chem. (1992) 267, 20782-20786), respectively. It is supposed that its formation is accompanied by the appearance of the cytoplasmic proton half-channel. M(open) in the wild-type protein is present in a very low amount due to the shift of the M(closed) <--> M(open) equilibrium towards the M(closed). The inhibitors used do not prevent the multiphase pattern of the M formation in either mutant or wild-type proteins.
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Affiliation(s)
- A N Radionov
- Department of Photobiochemistry, A.N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, Russia
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27
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Weidlich O, Ujj L, Jäger F, Atkinson GH. Nanosecond retinal structure changes in K-590 during the room-temperature bacteriorhodopsin photocycle: picosecond time-resolved coherent anti-stokes Raman spectroscopy. Biophys J 1997; 72:2329-41. [PMID: 9129836 PMCID: PMC1184428 DOI: 10.1016/s0006-3495(97)78877-5] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Time-resolved vibrational spectra are used to elucidate the structural changes in the retinal chromophore within the K-590 intermediate that precedes the formation of the L-550 intermediate in the room-temperature (RT) bacteriorhodopsin (BR) photocycle. Measured by picosecond time-resolved coherent anti-Stokes Raman scattering (PTR/CARS), these vibrational data are recorded within the 750 cm-1 to 1720 cm-1 spectral region and with time delays of 50-260 ns after the RT/BR photocycle is optically initiated by pulsed (< 3 ps, 1.75 nJ) excitation. Although K-590 remains structurally unchanged throughout the 50-ps to 1-ns time interval, distinct structural changes do appear over the 1-ns to 260-ns period. Specifically, comparisons of the 50-ps PTR/CARS spectra with those recorded with time delays of 1 ns to 260 ns reveal 1) three types of changes in the hydrogen-out-of-plane (HOOP) region: the appearance of a strong, new feature at 984 cm-1; intensity decreases for the bands at 957 cm-1, 952 cm-1, and 939 cm-1; and small changes intensity and/or frequency of bands at 855 cm-1 and 805 cm-1; and 2) two types of changes in the C-C stretching region: the intensity increase in the band at 1196 cm-1 and small intensity changes and/or frequency shifts for bands at 1300 cm-1 and 1362 cm-1. No changes are observed in the C = C stretching region, and no bands assignable to the Schiff base stretching mode (C = NH+) mode are found in any of the PTR/CARS spectra assignable to K-590. These PTR/CARS data are used, together with vibrational mode assignments derived from previous work, to characterize the retinal structural changes in K-590 as it evolves from its 3.5-ps formation (ps/K-590) through the nanosecond time regime (ns/K-590) that precedes the formation of L-550. The PTR/CARS data suggest that changes in the torsional modes near the C14-C15 = N bonds are directly associated with the appearance of ns/K-590, and perhaps with the KL intermediate proposed in earlier studies. These vibrational data can be primarily interpreted in terms of the degree of twisting of the C14-C15 retinal bond. Such twisting may be accompanied by changes in the adjacent protein. Other smaller, but nonetheless clear, spectral changes indicate that alterations along the retinal polyene chain also occur. The changes in the retinal structure are preliminary to the deprotonation of the Schiff base nitrogen during the formation of M-412. The time constant for the ps/ns K-590 transformation is estimated from the amplitude change of four vibrational bands in the HOOP region to be 40-70 ns.
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Affiliation(s)
- O Weidlich
- Department of Chemistry, University of Arizona, Tucson 85721, USA
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28
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Tokaji Z, Dancsházy Z. Cooperativity-induced optical anisotropy changes during the photocycle of bacteriorhodopsin. Biochem Biophys Res Commun 1997; 233:532-6. [PMID: 9144572 DOI: 10.1006/bbrc.1997.6494] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Previous photoselection measurements showed that if the excitation is weak no optical anisotropy changes appear in immobilized purple membranes during the photocycle. The present study demonstrates that surprisingly at stronger excitations the anisotropy changes versus time. At 412 nm the dichroic ratio decreases after a few milliseconds, while at 570 nm the similar decrease is followed by an increase. The phenomenon cannot be described by tiltings of the retinal chromophore. It is the consequence of the cooperative interaction among the photocycling bacteriorhodopsin molecules that regulates the yields of more than one (expectedly two main) parallel pathways existing in the millisecond time domain of the photocycle.
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Affiliation(s)
- Z Tokaji
- Institute of Biophysics, Biological Research Center, Szeged, Hungary
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29
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Conformational flexibility of arginine-82 as source for the heterogeneous and pH-dependent kinetics of the primary proton transfer step in the bacteriorhodopsin photocycle: An electrostatic model. Chem Phys 1996. [DOI: 10.1016/s0301-0104(96)00192-9] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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30
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Jäger F, Ujj L, Atkinson GH, Sheves M, Livnah N, Ottolenghi M. Vibrational Spectrum of K-590 Containing 13C14,15 Retinal: Picosecond Time-Resolved Coherent Anti-Stokes Raman Spectroscopy of the Room Temperature Bacteriorhodopsin Photocycle. ACTA ACUST UNITED AC 1996. [DOI: 10.1021/jp961131i] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
| | | | | | | | | | - M. Ottolenghi
- Department of Chemistry, Hebrew University, Jerusalem, Israel
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31
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Dracheva S, Bose S, Hendler RW. Chemical and functional studies on the importance of purple membrane lipids in bacteriorhodopsin photocycle behavior. FEBS Lett 1996; 382:209-12. [PMID: 8612754 DOI: 10.1016/0014-5793(96)00181-0] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
In native purple membrane (PM), there are approximately 1 squalene, 2 glycolipid sulfate (GLS), and 6 phospholipid (PL) molecules per bacteriorhodopsin (BR) monomer. Brief (approximately 2 min) exposure to 0.1% Triton X-100 removes about 25%, 20%, and 6% of squalenes, GLS, and PL, respectively (this paper) while causing profound changes in the BR photocycle, including the loss of 'photocooperativity'. The BR photocycle in Triton-treated PM can be restored to near normal behavior by reconstitution with native PM lipids. Isolated squalenes are not effective whereas PL alone partially restores normal photocycle characteristics.
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Affiliation(s)
- S Dracheva
- Laboratory of Cell Biology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA
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32
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Komrakov AY, Kaulen AD. M-decay in the bacteriorhodopsin photocycle: effect of cooperativity and pH. Biophys Chem 1995; 56:113-9. [PMID: 17023318 DOI: 10.1016/0301-4622(95)00022-p] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The dependence of the bacteriorhodopsin (bR) photocycle on the intensity of the exciting flash was investigated in purple membranes. The dependence was most pronounced at slightly alkaline pH values. A comparison study of the kinetics of the photocycle and proton uptake at different intensities of the flash suggested that there exist two parallel photocycles in purple membranes at a high intensity of the flash. The photocycle of excited bR in a trimer with the two other bR molecules nonexcited is characterized by an almost irreversible M --> N transition. Excitation of two or three bR in a trimer induces the N --> M back reaction and accelerates the N --> bR transition. Based on the qualitative similarity of the pH dependencies of the photocycles of solubilized bR and excited dimers and trimers we proposed that the interaction of nonexcited bR in trimers alters the photocycle of the excited monomer as compared to solubilized bR and the changes in the photocycles in excited dimers and trimers are the result of decoupling of this interaction.
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Affiliation(s)
- A Y Komrakov
- A.N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, Moscow 119899, Russia
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33
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Shrager RI, Hendler RW, Bose S. The ability of actinic light to modify the bacteriorhodopsin photocycle. Heterogeneity and/or photocooperativity? EUROPEAN JOURNAL OF BIOCHEMISTRY 1995; 229:589-95. [PMID: 7758451 DOI: 10.1111/j.1432-1033.1995.tb20502.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The focus of this paper is on the established observation that the bacteriorhodopsin (BR) photocycle responds to the level of actinic light by altering the proportions of two forms of the M intermediate. The first form of M, called M-fast or MF, decays to the O intermediate. In contrast, the second form of M, called M-slow or MS, decays directly to the ground state, and its decay rate is slower than that of MF. Any proposed scheme for the BR photocycle must account for this light-dependent phenomenon. Several papers have attempted to explain the observation on the basis of photocooperativity, or on the basis of heterogeneous populations. In this paper, we test previously proposed cooperative models with experimental data, and find those models to be inadequate. We show that two new models, one purely cooperative, the other purely heterogeneous, can both fit the data, hence such modelling will not resolve the mechanism. Taking into account the demonstration of heterogeneity, the trimer structure of BR, and certain experimental evidence in favor of cooperativity, it appears likely that both heterogeneity and cooperativity are involved in the adaptation of the BR photocycle to different levels of actinic light.
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Affiliation(s)
- R I Shrager
- Physical Sciences Laboratory, National Institutes of Health, Bethesda, MD 20892, USA
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34
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Cao Y, Brown LS, Sasaki J, Maeda A, Needleman R, Lanyi JK. Relationship of proton release at the extracellular surface to deprotonation of the schiff base in the bacteriorhodopsin photocycle. Biophys J 1995; 68:1518-30. [PMID: 7787037 PMCID: PMC1282046 DOI: 10.1016/s0006-3495(95)80324-3] [Citation(s) in RCA: 54] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
The surface potential of purple membranes and the release of protons during the bacteriorhodopsin photocycle have been studied with the covalently linked pH indicator dye, fluorescein. The titration of acidic lipids appears to cause the surface potential to be pH-dependent and causes other deviations from ideal behavior. If these anomalies are neglected, the appearance of protons can be followed by measuring the absorption change of fluorescein bound to various residues at the extracellular surface. Contrary to widely held assumption, the activation enthalpies of kinetic components, deuterium isotope effects in the time constants, and the consequences of the D85E, F208R, and D212N mutations demonstrate a lack of direct correlation between proton transfer from the buried retinal Schiff base to D85 and proton release at the surface. Depending on conditions and residue replacements, the proton release can occur at any time between the protonation of D85 and the recovery of the initial state. We conclude that once D85 is protonated the proton release at the extracellular protein surface is essentially independent of the chromophore reactions that follow. This finding is consistent with the recently suggested version of the alternating access mechanism of bacteriorhodopsin, in which the change of the accessibility of the Schiff base is to and away from D85 rather than to and away from the extracellular membrane surface.
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Affiliation(s)
- Y Cao
- Department of Physiology and Biophysics, University of California, Irvine 92717, USA
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35
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Haupts U, Eisfeld W, Stockburger M, Oesterhelt D. Sensory rhodopsin I photocycle intermediate SRI380 contains 13-cis retinal bound via an unprotonated Schiff base. FEBS Lett 1994; 356:25-9. [PMID: 7988713 DOI: 10.1016/0014-5793(94)01226-1] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Sensory rhodopsin I (SRI), the mutated derivative SRI-D76N and the complex of SRI with its transducer HtrI were overexpressed in Halobacterium salinarium and analyzed by resonance Raman spectroscopy. In the initial state SRI contains all-trans retinal bound via a protonated Schiff base as confirmed by retinal extraction which yields 95 +/- 3% all-trans retinal. The photocycle intermediate absorbing maximally at 380 nm (SRI380) contains a Schiff base linkage between the protein and 13-cis retinal. Extraction of illuminated SRI yields up to 93% 13-cis retinal. Neither the mutation D76N nor HtrI changed the vibrational pattern of the chromophore.
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Affiliation(s)
- U Haupts
- Max-Planck Institut für Biochemie, Martinsried, Germany
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36
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Brown LS, Gat Y, Sheves M, Yamazaki Y, Maeda A, Needleman R, Lanyi JK. The retinal Schiff base-counterion complex of bacteriorhodopsin: changed geometry during the photocycle is a cause of proton transfer to aspartate 85. Biochemistry 1994; 33:12001-11. [PMID: 7918419 DOI: 10.1021/bi00206a001] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Bacteriorhodopsin contains all-trans-retinal linked via a protonated Schiff base to K216. The proton transport in this pump is initiated by all-trans to 13-cis photoisomerization of the retinal and the ensuing transfer of the Schiff base proton to D85. Changed geometrical relationship of the Schiff base and D85 after the photoisomerization is a possible reason for the proton transfer. We introduced small volume/shape changes with site-specific mutagenesis of residues V49 and A53 that contact the side chain of K216, in order to force the Schiff base into somewhat different positions relative to D85. Earlier [Zimányi, L., Váró, G., Chang, M., Ni, B., Needleman, R., & Lanyi, J. K. (1992) Biochemistry 31, 8535-8543] we had described the kinetics of absorbance changes in the microsecond to millisecond time range after photoexcitation with the scheme L<-->M1<-->M2 + H+ (where the first equilibrium is the internal proton transfer and the second is proton release on the extracellular surface). Testing it at various pH values with mutants, where selected rate constants are changed, now confirms the validity of this scheme. The kinetics of the M state thus allowed examination of the transient equilibrium that develops in the L<-->M1 reaction and represents the redistribution of the proton between the Schiff base and D85. From the structure of the protein, the V49A and V49M residue replacements were both predicted to cause decreased alignment of the Schiff base and D85, and indeed we found that they both changed the equilibrium toward the protonated Schiff base. In contrast, the residue replacements A53V and A53G were predicted to move the Schiff base in opposite directions, away from and closer to alignment with D85, respectively. The former indeed changed the equilibrium toward the protonated Schiff base and the latter toward the deprotonated Schiff base. In addition, the hydroxyl stretch band of a bound water in the L state was affected by all mutations that disfavor proton transfer to D85. We conclude that the geometry of the proton donor and acceptor in the Schiff base-D85 pair, mediated by bound water, is a determinant of the proton transfer equilibrium.
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Affiliation(s)
- L S Brown
- Department of Physiology and Biophysics, University of California, Irvine 92717
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37
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Hoff WD, van Stokkum IH, van Ramesdonk HJ, van Brederode ME, Brouwer AM, Fitch JC, Meyer TE, van Grondelle R, Hellingwerf KJ. Measurement and global analysis of the absorbance changes in the photocycle of the photoactive yellow protein from Ectothiorhodospira halophila. Biophys J 1994; 67:1691-705. [PMID: 7819501 PMCID: PMC1225531 DOI: 10.1016/s0006-3495(94)80643-5] [Citation(s) in RCA: 199] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
The photocycle of the photoactive yellow protein (PYP) from Ectothiorhodospira halophila was examined by time-resolved difference absorption spectroscopy in the wavelength range of 300-600 nm. Both time-gated spectra and single wavelength traces were measured. Global analysis of the data established that in the time domain between 5 ns and 2 s only two intermediates are involved in the room temperature photocycle of PYP, as has been proposed before (Meyer T.E., E. Yakali, M. A. Cusanovich, and G. Tollin. 1987. Biochemistry. 26:418-423; Meyer, T. E., G. Tollin, T. P. Causgrove, P. Cheng, and R. E. Blankenship. 1991. Biophys. J. 59:988-991). The first, red-shifted intermediate decays biexponentially (60% with tau = 0.25 ms and 40% with tau = 1.2 ms) to a blue-shifted intermediate. The last step of the photocycle is the biexponential (93% with tau = 0.15 s and 7% with tau = 2.0 s) recovery to the ground state of the protein. Reconstruction of the absolute spectra of these photointermediates yielded absorbance maxima of about 465 and 355 nm for the red- and blue-shifted intermediate with an epsilon max at about 50% and 40% relative to the epsilon max of the ground state. The quantitative analysis of the photocycle in PYP described here paves the way to a detailed biophysical analysis of the processes occurring in this photoreceptor molecule.
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Affiliation(s)
- W D Hoff
- Department of Microbiology, E.C. Slater Institute, BioCentrum Amsterdam, University of Amsterdam, The Netherlands
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38
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Mukhopadhyay AK, Bose S, Hendler RW. Membrane-mediated control of the bacteriorhodopsin photocycle. Biochemistry 1994; 33:10889-95. [PMID: 8086405 DOI: 10.1021/bi00202a007] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The ability of actinic light to modify the proportion of fast and slow forms of the M intermediate (i.e., Mf and M(s)) in the bacteriorhodopsin (BR) photocycle is lost by exposure of the purple membrane (PM) to 0.05% Triton for 1-2 min. The decay path of Mf through the O intermediate is also lost, and new, much slower kinetic forms of M appear. In this brief exposure, the trimer structure for BR, as measured by circular dichroism (CD) exciton coupling and sedimentability, is unaffected. The optical properties of the treated PM are affected within seconds of exposure to the detergent as indicated by an increase in transmittance and a blue shift in the wavelength of maximum absorbance for the ground state. Different concentrations of Triton cause reproducibly different changes in the kinetics of the system. These observations support the view that the BR trimer-membrane interaction is important in controlling the BR photocycle.
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Affiliation(s)
- A K Mukhopadhyay
- Laboratory of Cell Biology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892
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39
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Hendler RW, Dancsházy Z, Bose S, Shrager RI, Tokaji Z. Influence of excitation energy on the bacteriorhodopsin photocycle. Biochemistry 1994; 33:4604-10. [PMID: 8161516 DOI: 10.1021/bi00181a022] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Kinetic curves for the bacteriorhodopsin (BR) photocycle were obtained both at 570 and at 412 nm at a series of increasing levels of intensity of the exciting laser. Singular value decomposition (SVD) of these curves showed two transitions in the kinetic profiles that occurred at specific levels of actinic light. This means that the photocycle was influenced by photon density in two ways. In a separate application of SVD, time-resolved optical spectra were analyzed at each of many levels of exciting laser intensities. The studies showed that the transition at the low level of laser intensity was due principally to an increase in the amount of BR that was turning over. The transition at the higher level of laser intensity showed a fundamental change in kinetics of the photocycle. At low intensity levels, the fast form of M (Mf) predominated, whereas at high levels the slow form of M (Ms) predominated. A distinction was found between Mf and Ms, in that the former decayed directly to the O intermediate whereas the latter decayed directly to BR.
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Affiliation(s)
- R W Hendler
- Laboratory of Cell Biology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892
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40
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Schulenberg PJ, Gärtner W, Braslavsky SE. A possible protein motion during the bacteriorhodopsin photocycle detected by combined photothermal beam deflection and optical detection. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1994. [DOI: 10.1016/0005-2728(94)90198-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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41
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Gergely C, Ganea C, Groma G, Váró G. Study of the photocycle and charge motions of the bacteriorhodopsin mutant D96N. Biophys J 1993; 65:2478-83. [PMID: 8312486 PMCID: PMC1225989 DOI: 10.1016/s0006-3495(93)81308-0] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Absorption kinetic and electric measurements were performed on oriented purple membranes of D96N bacteriorhodopsin mutant embedded in polyacrylamide gel and the kinetic parameters of the photointermediates determined. The rate constants, obtained from fits to time-dependent concentrations, were used to calculate the relative electrogenicity of the intermediates. The signals were analyzed on the basis of different photocycle models. The preferred model is the sequential one with reversible reaction. To improve the quality of the fits the necessity of introducing a second L intermediate arose. We also attempted to interpret our data in the view of reversible reactions containing two parallel photocycles, but the pH dependencies of the rate constants and electrogenicities favored the model containing sequential reversible transitions. A fast equilibrium for the L2<==>M1 transition and a strong pH dependence of the M2 electrogenicity was found, indicating that the M1 to M2 transition involves complex charge motions, as is expected in a conformational change of the protein.
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Affiliation(s)
- C Gergely
- Institute of Biophysics, Biological Research Centre of the Hungarian Academy of Science, Szeged
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