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Noji T, Ishikita H. Mechanism of Absorption Wavelength Shift of Bacteriorhodopsin During Photocycle. J Phys Chem B 2022; 126:9945-9955. [PMID: 36413506 DOI: 10.1021/acs.jpcb.2c04359] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Bacteriorhodopsin, a light-driven proton pump, alters the absorption wavelengths in the range of 410-617 nm during the photocycle. Here, we report the absorption wavelengths, calculated using 12 bacteriorhodopsin crystal structures (including the BR, BR13-cis, J, K0, KE, KL, L, M, N, and O state structures) and a combined quantum mechanical/molecular mechanical/polarizable continuum model (QM/MM/PCM) approach. The QM/MM/PCM calculations reproduced the experimentally measured absorption wavelengths with a standard deviation of 4 nm. The shifts in the absorption wavelengths can be explained mainly by the following four factors: (i) retinal Schiff base deformation/twist induced by the protein environment, leading to a decrease in the electrostatic interaction between the protein environment and the retinal Schiff base; (ii) changes in the protonation state of the protein environment, directly altering the electrostatic interaction between the protein environment and the retinal Schiff base; (iii) changes in the protonation state; or (iv) isomerization of the retinal Schiff base, where the absorption wavelengths of the isomers originally differ.
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Affiliation(s)
- Tomoyasu Noji
- Research Center for Advanced Science and Technology, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo153-8904, Japan
| | - Hiroshi Ishikita
- Research Center for Advanced Science and Technology, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo153-8904, Japan.,Department of Applied Chemistry, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo113-8654, Japan
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Punwong C, Hannongbua S, Martínez TJ. Electrostatic Influence on Photoisomerization in Bacteriorhodopsin and Halorhodopsin. J Phys Chem B 2019; 123:4850-4857. [DOI: 10.1021/acs.jpcb.9b01837] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Affiliation(s)
- C. Punwong
- Department of Physics, Faculty of Science, Prince of Songkla University, Songkhla 90112 Thailand
| | - S. Hannongbua
- Department of Chemistry, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand
| | - T. J. Martínez
- Department of Chemistry and the PULSE Institute, Stanford University, Stanford, California 94305, United States
- SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States
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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.
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Affiliation(s)
- Michaela Mehler
- Institute of Biophysical Chemistry and Centre for Biomolecular Magnetic Resonance, Goethe-University Frankfurt, Germany
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Affiliation(s)
- Colin D. Heyes
- Laser Dynamics Laboratory, School of Chemistry & Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332-0400
| | - Mostafa A. El-Sayed
- Laser Dynamics Laboratory, School of Chemistry & Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332-0400
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Wang J, Link S, Heyes CD, El-Sayed MA. Comparison of the dynamics of the primary events of bacteriorhodopsin in its trimeric and monomeric states. Biophys J 2002; 83:1557-66. [PMID: 12202380 PMCID: PMC1302253 DOI: 10.1016/s0006-3495(02)73925-8] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
In this paper, femtosecond pump-probe spectroscopy in the visible region of the spectrum has been used to examine the ultrafast dynamics of the retinal excited state in both the native trimeric state and the monomeric state of bacteriorhodopsin (bR). It is found that the excited state lifetime (probed at 490 nm) increases only slightly upon the monomerization of bR. No significant kinetic difference is observed in the recovery process of the bR ground state probed at 570 nm nor in the fluorescent state observed at 850 nm. However, an increase in the relative amplitude of the slow component of bR excited state decay is observed in the monomer, which is due to the increase in the concentration of the 13-cis retinal isomer in the ground state of the light-adapted bR monomer. Our data indicate that when the protein packing around the retinal is changed upon bR monomerization, there is only a subtle change in the retinal potential surface, which is dependent on the charge distribution and the dipoles within the retinal-binding cavity. In addition, our results show that 40% of the excited state bR molecules return to the ground state on three different time scales: one-half-picosecond component during the relaxation of the excited state and the formation of the J intermediate, a 3-ps component as the J changes to the K intermediate where retinal photoisomerization occurs, and a subnanosecond component during the photocycle.
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Affiliation(s)
- Jianping Wang
- Laser Dynamics Laboratory, School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332-0400 USA
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Lee HM, Kim J, Kim CJ, Kim KS. Ab initio study of the isomerization of retinal chromophore and its derivatives. J Chem Phys 2002. [DOI: 10.1063/1.1459705] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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Hatcher ME, Hu JG, Belenky M, Verdegem P, Lugtenburg J, Griffin RG, Herzfeld J. Control of the pump cycle in bacteriorhodopsin: mechanisms elucidated by solid-state NMR of the D85N mutant. Biophys J 2002; 82:1017-29. [PMID: 11806941 PMCID: PMC1301908 DOI: 10.1016/s0006-3495(02)75461-1] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
By varying the pH, the D85N mutant of bacteriorhodopsin provides models for several photocycle intermediates of the wild-type protein in which D85 is protonated. At pH 10.8, NMR spectra of [zeta-(15)N]lys-, [12-(13)C]retinal-, and [14,15-(13)C]retinal-labeled D85N samples indicate a deprotonated, 13-cis,15-anti chromophore. On the other hand, at neutral pH, the NMR spectra of D85N show a mixture of protonated Schiff base species similar to that seen in the wild-type protein at low pH, and more complex than the two-state mixture of 13-cis,15-syn, and all-trans isomers found in the dark-adapted wild-type protein. These results lead to several conclusions. First, the reversible titration of order in the D85N chromophore indicates that electrostatic interactions have a major influence on events in the active site. More specifically, whereas a straight chromophore is preferred when the Schiff base and residue 85 are oppositely charged, a bent chromophore is found when both the Schiff base and residue 85 are electrically neutral, even in the dark. Thus a "bent" binding pocket is formed without photoisomerization of the chromophore. On the other hand, when photoisomerization from the straight all-trans,15-anti configuration to the bent 13-cis,15-anti does occur, reciprocal thermodynamic linkage dictates that neutralization of the SB and D85 (by proton transfer from the former to the latter) will result. Second, the similarity between the chromophore chemical shifts in D85N at alkaline pH and those found previously in the M(n) intermediate of the wild-type protein indicate that the latter has a thoroughly relaxed chromophore like the subsequent N intermediate. By comparison, indications of L-like distortion are found for the chromophore of the M(o) state. Thus, chromophore strain is released in the M(o)-->M(n) transition, probably coincident with, and perhaps instrumental to, the change in the connectivity of the Schiff base from the extracellular side of the membrane to the cytoplasmic side. Because the nitrogen chemical shifts of the Schiff base indicate interaction with a hydrogen-bond donor in both M states, it is possible that a water molecule travels with the Schiff base as it switches connectivity. If so, the protein is acting as an inward-driven hydroxyl pump (analogous to halorhodopsin) rather than an outward-driven proton pump. Third, the presence of a significant C [double bond] N syn component in D85N at neutral pH suggests that rapid deprotonation of D85 is necessary at the end of the wild-type photocycle to avoid the generation of nonfunctional C [double bond] N syn species.
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Affiliation(s)
- Mary E Hatcher
- Department of Chemistry, Brandeis University, Waltham Massachusetts 02454, USA
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Baudry J, Tajkhorshid E, Molnar F, Phillips J, Schulten K. Molecular Dynamics Study of Bacteriorhodopsin and the Purple Membrane. J Phys Chem B 2001. [DOI: 10.1021/jp000898e] [Citation(s) in RCA: 80] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Jérôme Baudry
- Beckman Institute and Department of Physics, University of Illinois at Urbana−Champaign, Urbana, Illinois 61801
| | - Emad Tajkhorshid
- Beckman Institute and Department of Physics, University of Illinois at Urbana−Champaign, Urbana, Illinois 61801
| | - Ferenc Molnar
- Beckman Institute and Department of Physics, University of Illinois at Urbana−Champaign, Urbana, Illinois 61801
| | - James Phillips
- Beckman Institute and Department of Physics, University of Illinois at Urbana−Champaign, Urbana, Illinois 61801
| | - Klaus Schulten
- Beckman Institute and Department of Physics, University of Illinois at Urbana−Champaign, Urbana, Illinois 61801
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The dielectric effect of the environment on the p K a of the retinal Schiff base and on the stabilization of the ion pair in bacteriorhodopsin. ACTA ACUST UNITED AC 2000. [DOI: 10.1016/s0166-1280(99)00441-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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Tajkhorshid E, Baudry J, Schulten K, Suhai S. Molecular dynamics study of the nature and origin of retinal's twisted structure in bacteriorhodopsin. Biophys J 2000; 78:683-93. [PMID: 10653781 PMCID: PMC1300671 DOI: 10.1016/s0006-3495(00)76626-4] [Citation(s) in RCA: 94] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
The planarity of the polyene chain of the retinal chromophore in bacteriorhodopsin is studied using molecular dynamics simulation techniques and applying different force-field parameters and starting crystal structures. The largest deviations from a planar structure are observed for the C(13)==C(14) and C(15)==N(16) double bonds in the retinal Schiff base structure. The other dihedral angles along the polyene chain of the chromophore, although having lower torsional barriers in some cases, do not significantly deviate from the planar structure. The results of the simulations of different mutants of the pigment show that, among the studied amino acids of the binding pocket, the side chain of Trp-86 has the largest impact on the planarity of retinal, and the mutation of this amino acid to alanine leads to chromophore planarity. Deletion of the methyl C(20), removal of a water molecule hydrogen-bonded to H(15), or mutation of other amino acids to alanine did not show any significant influence on the distortion of the chromophore. The results from the present study suggest the importance of the bulky residue of Trp-86 in the isomerization process, in both ground and excited states of the chromophore, and in fine-tuning of the pK(a) of the retinal protonated Schiff base in bacteriorhodopsin. The dark adaptation of the pigment and the last step of the bacteriorhodopsin photocycle imply low barriers against the rotation of the double bonds in the Schiff base region. The twisted double bonds found in the present study are consistent with the proposed mechanism of these ground state isomerization events.
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Affiliation(s)
- E Tajkhorshid
- Theoretical Biophysics Group, Beckman Institute, University of Illinois at Urbana-Champaign 61801, USA
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Radding W, Romo T, Phillips GN. Protein-assisted pericyclic reactions: an alternate hypothesis for the action of quantal receptors. Biophys J 1999; 77:2920-9. [PMID: 10585916 PMCID: PMC1300565 DOI: 10.1016/s0006-3495(99)77125-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
The rules for allowable pericyclic reactions indicate that the photoisomerizations of retinals in rhodopsins can be formally analogous to thermally promoted Diels-Alder condensations of monoenes with retinols. With little change in the seven-transmembrane helical environment these latter reactions could mimic the retinal isomerization while providing highly sensitive chemical reception. In this way archaic progenitors of G-protein-coupled chemical quantal receptors such as those for pheromones might have been evolutionarily plagiarized from the photon quantal receptor, rhodopsin, or vice versa. We investigated whether the known structure of bacteriorhodopsin exhibited any similarity in its active site with those of the two known antibody catalysts of Diels-Alder reactions and that of the photoactive yellow protein. A remarkable three-dimensional motif of aromatic side chains emerged in all four proteins despite the drastic differences in backbone structure. Molecular orbital calculations supported the possibility of transient pericyclic reactions as part of the isomerization-signal transduction mechanisms in both bacteriorhodopsin and the photoactive yellow protein. It appears that reactions in all four of the proteins investigated may be biological analogs of the organic chemists' chiral auxiliary-aided Diels-Alder reactions. Thus the light receptor and the chemical receptor subfamilies of the heptahelical receptor family may have been unified at one time by underlying pericyclic chemistry.
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Affiliation(s)
- W Radding
- Department of Biochemistry and Cell Biology, Rice University, Houston, Texas 77005, USA.
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Abstract
The topic of femtochemistry is surveyed from both theoretical and experimental points of view. A time-dependent wave packet description of the photodissociation of the O---C---S molecule reveals vibrational motion in the transition-state region and suggests targets for direct experimental observation. Theoretical approaches for treating femtosecond chemical phenomena in condensed phases are featured along with prospects for laser-controlled chemical reactions by using tailored ultrashort chirped pulses. An experimental study of the photoisomerization of retinal in the protein bacteriorhodopsin is discussed with an aim to gain insight into the potential energy surfaces on which this remarkably efficient and selective reactions proceeds. Finally, a prospective view of new frontiers in femtochemistry is given.
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Affiliation(s)
- Y Tanimura
- Institute for Molecular Science, Myodaiji, Okazaki, Aichi 444-8585, Japan.
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Tajkhorshid E, Suhai S. Influence of the Methyl Groups on the Structure, Charge Distribution, and Proton Affinity of the Retinal Schiff Base. J Phys Chem B 1999. [DOI: 10.1021/jp983742b] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Emadeddin Tajkhorshid
- Department of Molecular Biophysics, German Cancer Research Center, Im Neuenheimer Feld 280, D-69120 Heidelberg, Germany
| | - Sándor Suhai
- Department of Molecular Biophysics, German Cancer Research Center, Im Neuenheimer Feld 280, D-69120 Heidelberg, Germany
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Tajkhorshid E, Paizs B, Suhai S. Role of Isomerization Barriers in the pKa Control of the Retinal Schiff Base: A Density Functional Study. J Phys Chem B 1999. [DOI: 10.1021/jp982625d] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Emadeddin Tajkhorshid
- Department of Molecular Biophysics, German Cancer Research Center, Im Neuenheimer Feld 280, D-69120 Heidelberg, Germany
| | - Béla Paizs
- Department of Molecular Biophysics, German Cancer Research Center, Im Neuenheimer Feld 280, D-69120 Heidelberg, Germany
| | - Sándor Suhai
- Department of Molecular Biophysics, German Cancer Research Center, Im Neuenheimer Feld 280, D-69120 Heidelberg, Germany
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Affiliation(s)
- M H Vos
- INSERM U451, Laboratoire d'Optique Appliquée, Ecole Polytechnique-ENSTA, 91761, Palaiseau Cedex, France.
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Tajkhorshid E, Paizs B, Suhai S. Conformational Effects on the Proton Affinity of the Schiff Base in Bacteriorhodopsin: A Density Functional Study. J Phys Chem B 1997. [DOI: 10.1021/jp971283t] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Emadeddin Tajkhorshid
- Department of Molecular Biophysics, German Cancer Research Center, Im Neuenheimer Feld 280, D-69120 Heidelberg, FRG
| | - Béla Paizs
- Department of Molecular Biophysics, German Cancer Research Center, Im Neuenheimer Feld 280, D-69120 Heidelberg, FRG
| | - Sándor Suhai
- Department of Molecular Biophysics, German Cancer Research Center, Im Neuenheimer Feld 280, D-69120 Heidelberg, FRG
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Hasson KC, Gai F, Anfinrud PA. The photoisomerization of retinal in bacteriorhodospin: experimental evidence for a three-state model. Proc Natl Acad Sci U S A 1996; 93:15124-9. [PMID: 8986774 PMCID: PMC26367 DOI: 10.1073/pnas.93.26.15124] [Citation(s) in RCA: 151] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
The primary events in the all-trans to 13-cis photoisomerization of retinal in bacteriorhodopsin have been investigated with femtosecond time-resolved absorbance spectroscopy. Spectra measured over a broad range extending from 7000 to 22,400 cm-1 reveal features whose dynamics are inconsistent with a model proposed earlier to account for the highly efficient photoisomerization process. Emerging from this work is a new three-state model. Photoexcitation of retinal with visible light accesses a shallow well on the excited state potential energy surface. This well is bounded by a small barrier, arising from an avoided crossing that separates the Franck-Condon region from the nearby reactive region of the photoisomerization coordinate. At ambient temperatures, the reactive region is accessed with a time constant of approximately 500 fs, whereupon the retinal rapidly twists and encounters a second avoided crossing region. The protein mediates the passage into the second avoided crossing region and thereby exerts control over the quantum yield for forming 13-cis retinal. The driving force for photoisomerization resides in the retinal, not in the surrounding protein. This view contrasts with an earlier model where photoexcitation was thought to access directly a reactive region of the excited-state potential and thereby drive the retinal to a twisted conformation within 100-200 fs.
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Affiliation(s)
- K C Hasson
- Department of Physics, Harvard University, Cambridge, MA 02138, USA
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