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Misra R, Das I, Dér A, Steinbach G, Shim JG, Busse W, Jung KH, Zimányi L, Sheves M. Impact of protein-chromophore interaction on the retinal excited state and photocycle of Gloeobacter rhodopsin: role of conserved tryptophan residues. Chem Sci 2023; 14:9951-9958. [PMID: 37736621 PMCID: PMC10510653 DOI: 10.1039/d3sc02961a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2023] [Accepted: 08/25/2023] [Indexed: 09/23/2023] Open
Abstract
The function of microbial as well as mammalian retinal proteins (aka rhodopsins) is associated with a photocycle initiated by light excitation of the retinal chromophore of the protein, covalently bound through a protonated Schiff base linkage. Although electrostatics controls chemical reactions of many organic molecules, attempt to understand its role in controlling excited state reactivity of rhodopsins and, thereby, their photocycle is scarce. Here, we investigate the effect of highly conserved tryptophan residues, between which the all-trans retinal chromophore of the protein is sandwiched in microbial rhodopsins, on the charge distribution along the retinal excited state, quantum yield and nature of the light-induced photocycle and absorption properties of Gloeobacter rhodopsin (GR). Replacement of these tryptophan residues by non-aromatic leucine (W222L and W122L) or phenylalanine (W222F) does not significantly affect the absorption maximum of the protein, while all the mutants showed higher sensitivity to photobleaching, compared to wild-type GR. Flash photolysis studies revealed lower quantum yield of trans-cis photoisomerization in W222L as well as W222F mutants relative to wild-type. The photocycle kinetics are also controlled by these tryptophan residues, resulting in altered accumulation and lifetime of the intermediates in the W222L and W222F mutants. We propose that protein-retinal interactions facilitated by conserved tryptophan residues are crucial for achieving high quantum yield of the light-induced retinal isomerization, and affect the thermal retinal re-isomerization to the resting state.
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Affiliation(s)
- Ramprasad Misra
- Department of Molecular Chemistry and Materials Science, Weizmann Institute of Science Rehovot 76100 Israel
| | - Ishita Das
- Department of Molecular Chemistry and Materials Science, Weizmann Institute of Science Rehovot 76100 Israel
| | - András Dér
- Institute of Biophysics, Biological Research Centre, Eötvös Loránd Research Network Szeged H-6726 Hungary
| | - Gábor Steinbach
- Institute of Biophysics, Biological Research Centre, Eötvös Loránd Research Network Szeged H-6726 Hungary
- Cellular Imaging Laboratory, Biological Research Centre, Eötvös Loránd Research Network Szeged H-6726 Hungary
| | - Jin-Gon Shim
- Department of Life Science and Institute of Biological Interfaces, Sogang University Seoul 04107 South Korea
| | - Wayne Busse
- Institute for Biology, Experimental Biophysics, Humboldt-Universität zu Berlin Berlin 10115 Germany
| | - Kwang-Hwan Jung
- Department of Life Science and Institute of Biological Interfaces, Sogang University Seoul 04107 South Korea
| | - László Zimányi
- Institute of Biophysics, Biological Research Centre, Eötvös Loránd Research Network Szeged H-6726 Hungary
| | - Mordechai Sheves
- Department of Molecular Chemistry and Materials Science, Weizmann Institute of Science Rehovot 76100 Israel
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2
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Das I, Pushkarev A, Sheves M. Light-Induced Conformational Alterations in Heliorhodopsin Triggered by the Retinal Excited State. J Phys Chem B 2021; 125:8797-8804. [PMID: 34342994 PMCID: PMC8389987 DOI: 10.1021/acs.jpcb.1c04551] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
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Heliorhodopsins are a recently discovered
diverse retinal protein
family with an inverted topology of the opsin where the retinal protonated
Schiff base proton is facing the cell cytoplasmic side in contrast
to type 1 rhodopsins. To explore whether light-induced retinal double-bond
isomerization is a prerequisite for triggering protein conformational
alterations, we utilized the retinal oxime formation reaction and
thermal denaturation of a native heliorhodopsin of Thermoplasmatales archaeon SG8-52-1 (TaHeR) as well
as a trans-locked retinal analogue (TaHeRL) in which the critical C13=C14 double-bond
isomerization is prevented. We found that both reactions are light-accelerated
not only in the native but also in the “locked” pigment
despite lacking any isomerization. It is suggested that light-induced
charge redistribution in the retinal excited state polarizes the protein
and triggers protein conformational perturbations that thermally decay
in microseconds. The extracted activation energy and the frequency
factor for both the reactions reveal that the light enhancement of
TaHeR differs distinctly from the earlier studied type 1 microbial
rhodopsins.
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Affiliation(s)
- Ishita Das
- Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Alina Pushkarev
- Faculty of Biology, Technion-Israel Institute of Technology, Haifa 3200003, Israel
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3
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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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4
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Ghosh M, Jung KH, Sheves M. Protein conformational alterations induced by the retinal excited state in proton and sodium pumping rhodopsins. Phys Chem Chem Phys 2019; 21:9450-9455. [PMID: 31012470 DOI: 10.1039/c9cp00681h] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Retinal proteins' biological activity is triggered by the retinal chromophore's light absorption, which initiates a photocycle. However, the mechanism by which retinal light excitation induces the protein's response is not completely understood. Recently, two new retinal proteins were discovered, namely, King Sejong 1-2 (KS1-2) and Nonlabens (Donghaeana) dokdonensis (DDR2), which exhibit H+ and Na+ pumping activities, respectively. To pinpoint whether protein conformation alterations can be achieved without light-induced retinal C13[double bond, length as m-dash]C14 double-bond isomerization, we utilized the hydroxylamine reaction, which cleaves the protonated Schiff base bond through which the retinal chromophore is covalently bound to the protein. The reaction is accelerated by light even though the cleavage is not a photochemical reaction. Therefore, the cleavage reaction may serve as a tool to detect protein conformation alterations. We discovered that in both KS1-2 and DDR2, the hydroxylamine reaction is light accelerated, even in artificial pigments derived from synthetic retinal in which the crucial C13[double bond, length as m-dash]C14 double-bond isomerization is prevented. Therefore, we propose that in both proteins the light-induced retinal charge redistribution taking place in the retinal excited state polarizes the protein, which, in turn, triggers protein conformation alterations. A further general possible application of the present finding is associated with other photoreceptor proteins having retinal or other non-retinal chromophores whose light excitation may affect the protein conformation.
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Affiliation(s)
- Mihir Ghosh
- Department of Organic Chemistry, Weizmann Institute of Science Rehovot, Israel.
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5
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Wang Y, Liu Y, Bersuker IB. Sudden polarization and zwitterion formation as a pseudo-Jahn–Teller effect: a new insight into the photochemistry of alkenes. Phys Chem Chem Phys 2019; 21:10677-10692. [DOI: 10.1039/c9cp01023h] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We show that the intermediates of photochemical reactions—sudden polarization and zwitterion formations—are consequences of the pseudo-Jahn–Teller effect (PJTE), which facilitates a better understanding, rationalization, prediction, and manipulation of the corresponding chemical and biological processes.
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Affiliation(s)
- Ya Wang
- State Key Laboratory of Advanced Welding and Joining, MIIT Key Laboratory of Critical Materials Technology for New Energy Conversion and Storage, School of Chemistry and Chemical Engineering, Harbin Institute of Technology
- Harbin
- People's Republic of China
| | - Yang Liu
- State Key Laboratory of Advanced Welding and Joining, MIIT Key Laboratory of Critical Materials Technology for New Energy Conversion and Storage, School of Chemistry and Chemical Engineering, Harbin Institute of Technology
- Harbin
- People's Republic of China
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6
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The role of retinal light induced dipole in halorhodopsin structural alteration. FEBS Lett 2015; 589:3576-80. [PMID: 26467279 DOI: 10.1016/j.febslet.2015.10.005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2015] [Revised: 08/05/2015] [Accepted: 10/02/2015] [Indexed: 11/20/2022]
Abstract
The present work studies the mechanism of light induced protein conformational changes in the over-expressed mutant of halorhodopsin (phR) from Natronomonas pharaonis. The catalytic effect of light is reflected in accelerating hydroxyl amine reaction rate of light adapted phR. Light catalysis was detected in native phR but also in artificial pigments derived from tailored retinal analogs locked at the crucial C13=C14 double bond. It is proposed that the photoexcited retinal chromophore induces protein concerted motion that decreases the energy gap between reactants ground and transition states. This energy gap is overcome by coupling to specific protein vibrations. Surprisingly, the rate constants show unusual decreasing trend following temperature increase both for native and artificial pigments.
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7
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Ground-state properties of the retinal molecule: from quantum mechanical to classical mechanical computations of retinal proteins. Theor Chem Acc 2011. [DOI: 10.1007/s00214-011-1054-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/15/2022]
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Zgrablić G, Ricci M, Novello AM, Parmigiani F. Dependence of Photochemical Reactivity of the All-trans Retinal Protonated Schiff Base on the Solvent and the Excitation Wavelength. Photochem Photobiol 2010; 86:507-12. [DOI: 10.1111/j.1751-1097.2009.00697.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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9
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Gross R, Wolf MMN, Schumann C, Friedman N, Sheves M, Li L, Engelhard M, Trentmann O, Neuhaus HE, Diller R. Primary photoinduced protein response in bacteriorhodopsin and sensory rhodopsin II. J Am Chem Soc 2010; 131:14868-78. [PMID: 19778046 DOI: 10.1021/ja904218n] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Essential for the biological function of the light-driven proton pump, bacteriorhodopsin (BR), and the light sensor, sensory rhodopsin II (SRII), is the coupling of the activated retinal chromophore to the hosting protein moiety. In order to explore the dynamics of this process we have performed ultrafast transient mid-infrared spectroscopy on isotopically labeled BR and SRII samples. These include SRII in D(2)O buffer, BR in H(2)(18)O medium, SRII with (15)N-labeled protein, and BR with (13)C(14)(13)C(15)-labeled retinal chromophore. Via observed shifts of infrared difference bands after photoexcitation and their kinetics we provide evidence for nonchromophore bands in the amide I and the amide II region of BR and SRII. A band around 1550 cm(-1) is very likely due to an amide II vibration. In the amide I region, contributions of modes involving exchangeable protons and modes not involving exchangeable protons can be discerned. Observed bands in the amide I region of BR are not due to bending vibrations of protein-bound water molecules. The observed protein bands appear in the amide I region within the system response of ca. 0.3 ps and in the amide II region within 3 ps, and decay partially in both regions on a slower time scale of 9-18 ps. Similar observations have been presented earlier for BR5.12, containing a nonisomerizable chromophore (R. Gross et al. J. Phys. Chem. B 2009, 113, 7851-7860). Thus, the results suggest a common mechanism for ultrafast protein response in the artificial and the native system besides isomerization, which could be induced by initial chromophore polarization.
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Affiliation(s)
- Ruth Gross
- University of Kaiserslautern, Department of Physics, Erwin-Schrodinger-Strasse, 67663 Kaiserslautern, Germany
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10
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Gross R, Schumann C, Wolf MMN, Herbst J, Diller R, Friedman N, Sheves M. Ultrafast Protein Conformational Alterations in Bacteriorhodopsin and Its Locked Analogue BR5.12. J Phys Chem B 2009; 113:7851-60. [PMID: 19422251 DOI: 10.1021/jp810042f] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Ruth Gross
- Department of Physics, University of Kaiserslautern, D-67663 Kaiserslautern, Germany, and Department of Organic Chemistry, Weizmann Institute of Science, Rehovot, Israel
| | - Christian Schumann
- Department of Physics, University of Kaiserslautern, D-67663 Kaiserslautern, Germany, and Department of Organic Chemistry, Weizmann Institute of Science, Rehovot, Israel
| | - Matthias M. N. Wolf
- Department of Physics, University of Kaiserslautern, D-67663 Kaiserslautern, Germany, and Department of Organic Chemistry, Weizmann Institute of Science, Rehovot, Israel
| | - Johannes Herbst
- Department of Physics, University of Kaiserslautern, D-67663 Kaiserslautern, Germany, and Department of Organic Chemistry, Weizmann Institute of Science, Rehovot, Israel
| | - Rolf Diller
- Department of Physics, University of Kaiserslautern, D-67663 Kaiserslautern, Germany, and Department of Organic Chemistry, Weizmann Institute of Science, Rehovot, Israel
| | - Noga Friedman
- Department of Physics, University of Kaiserslautern, D-67663 Kaiserslautern, Germany, and Department of Organic Chemistry, Weizmann Institute of Science, Rehovot, Israel
| | - Mordechai Sheves
- Department of Physics, University of Kaiserslautern, D-67663 Kaiserslautern, Germany, and Department of Organic Chemistry, Weizmann Institute of Science, Rehovot, Israel
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11
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Functional electric field changes in photoactivated proteins revealed by ultrafast Stark spectroscopy of the Trp residues. Proc Natl Acad Sci U S A 2009; 106:7718-23. [PMID: 19416877 DOI: 10.1073/pnas.0812877106] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Ultrafast transient absorption spectroscopy of wild-type bacteriorhodopsin (WT bR) and 2 tryptophan mutants (W86F and W182F) is performed with visible light excitation (pump) and UV probe. The aim is to investigate the photoinduced change in the charge distribution with 50-fs time resolution by probing the effects on the tryptophan absorption bands. A systematic, quantitative comparison of the transient absorption of the 3 samples is carried out. The main result is the absence in the W86F mutant of a transient induced absorption band observed at approximately 300-310 nm in WT bR and W182F. A simple model describing the dipolar interaction of the retinal moiety with the 2 tryptophan residues of interest allows us to reproduce the dominant features of the transient signals observed in the 3 samples at ultrashort pump-probe delays. In particular, we show that Trp(86) undergoes a significant Stark shift induced by the transient retinal dipole moment. The corresponding transient signal can be isolated by direct subtraction of experimental data obtained for WT bR and W86F. It shows an instantaneous rise, followed by a decay over approximately 500 fs corresponding to the isomerization time. Interestingly, it does not decay back to zero, thus revealing a change in the local electrostatic environment that remains long after isomerization, in the K intermediate state of the protein cycle. The comparison of WT bR and W86F also leads to a revised interpretation of the overall transient UV absorption of bR.
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12
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13
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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.
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Affiliation(s)
- Anil K Singh
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, India.
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14
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Li C, Li JJ, Montgomery MG, Wood SP, Bugg TDH. Catalytic Role for Arginine 188 in the C−C Hydrolase Catalytic Mechanism for Escherichia coli MhpC and Burkholderia xenovorans LB400 BphD. Biochemistry 2006; 45:12470-9. [PMID: 17029402 DOI: 10.1021/bi061253t] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The alpha/beta-hydrolase superfamily, comprised mainly of esterase and lipase enzymes, contains a family of bacterial C-C hydrolases, including MhpC and BphD which catalyze the hydrolytic C-C cleavage of meta-ring fission intermediates on the Escherichia coli phenylpropionic acid pathway and Burkholderia xenovorans LB400 biphenyl degradation pathway, respectively. Five active site amino acid residues (Arg-188, Asn-109, Phe-173, Cys-261, and Trp-264) were identified from sequence alignments that are conserved in C-C hydrolases, but not in enzymes of different function. Replacement of Arg-188 in MhpC with Gln and Lys led to 200- and 40-fold decreases, respectively, in k(cat); the same replacements for Arg-190 of BphD led to 400- and 700-fold decreases, respectively, in k(cat). Pre-steady-state kinetic analysis of the R188Q MhpC mutant revealed that the first step of the reaction, keto-enol tautomerization, had become rate-limiting, indicating that Arg-188 has a catalytic role in ketonization of the dienol substrate, which we propose is via substrate destabilization. Mutation of nearby residues Phe-173 and Trp-264 to Gly gave 4-10-fold reductions in k(cat) but 10-20-fold increases in K(m), indicating that these residues are primarily involved in substrate binding. The X-ray structure of a succinate-H263A MhpC complex shows concerted movements in the positions of both Phe-173 and Trp-264 that line the approach to Arg-188. Mutation of Asn-109 to Ala and His yielded 200- and 350-fold reductions, respectively, in k(cat) and pre-steady-state kinetic behavior similar to that of a previous S110A mutant, indicating a role for Asn-109 is positioning the active site loop containing Ser-110. The catalytic role of Arg-188 is rationalized by a hydrogen bond network close to the C-1 carboxylate of the substrate, which positions the substrate and promotes substrate ketonization, probably via destabilization of the bound substrate.
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Affiliation(s)
- Chen Li
- Department of Chemistry, University of Warwick, Coventry CV4 7AL, UK
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15
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Schenkl S, van Mourik F, Friedman N, Sheves M, Schlesinger R, Haacke S, Chergui M. Insights into excited-state and isomerization dynamics of bacteriorhodopsin from ultrafast transient UV absorption. Proc Natl Acad Sci U S A 2006; 103:4101-6. [PMID: 16537491 PMCID: PMC1449653 DOI: 10.1073/pnas.0506303103] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
A visible-pump/UV-probe transient absorption is used to characterize the ultrafast dynamics of bacteriorhodopsin with 80-fs time resolution. We identify three spectral components in the 265- to 310-nm region, related to the all-trans retinal, tryptophan (Trp)-86 and the isomerized photoproduct, allowing us to map the dynamics from reactants to products, along with the response of Trp amino acids. The signal of the photoproduct appears with a time delay of approximately 250 fs and is characterized by a steep rise ( approximately 150 fs), followed by additional rise and decay components, with time scales characteristic of the J intermediate. The delayed onset and the steep rise point to an impulsive formation of a transition state on the way to isomerization. We argue that this impulsive formation results from a splitting of a wave packet of torsional modes on the potential surface at the branching between the all-trans and the cis forms. Parallel to these dynamics, the signal caused by Trp response rises in approximately 200 fs, because of the translocation of charge along the conjugate chain, and possible mechanisms are presented, which trigger isomerization.
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Affiliation(s)
- S. Schenkl
- *Laboratoire de Spectroscopie Ultrarapide, Institut des Sciences et Ingeniérie Chimiques, Faculté des Sciences de Base, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne-Dorigny, Switzerland
| | - F. van Mourik
- *Laboratoire de Spectroscopie Ultrarapide, Institut des Sciences et Ingeniérie Chimiques, Faculté des Sciences de Base, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne-Dorigny, Switzerland
| | - N. Friedman
- Departments of Organic Chemistry and Chemical Services, The Weizmann Institute of Sciences, Rehovot 76100, Israel; and
| | - M. Sheves
- Departments of Organic Chemistry and Chemical Services, The Weizmann Institute of Sciences, Rehovot 76100, Israel; and
| | - R. Schlesinger
- Institute for Structural Biology, Forschungszentrum Jülich, 52425 Jülich, Germany
| | - S. Haacke
- *Laboratoire de Spectroscopie Ultrarapide, Institut des Sciences et Ingeniérie Chimiques, Faculté des Sciences de Base, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne-Dorigny, Switzerland
| | - M. Chergui
- *Laboratoire de Spectroscopie Ultrarapide, Institut des Sciences et Ingeniérie Chimiques, Faculté des Sciences de Base, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne-Dorigny, Switzerland
- To whom correspondence should be addressed. E-mail:
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Crocker E, Eilers M, Ahuja S, Hornak V, Hirshfeld A, Sheves M, Smith SO. Location of Trp265 in metarhodopsin II: implications for the activation mechanism of the visual receptor rhodopsin. J Mol Biol 2006; 357:163-72. [PMID: 16414074 DOI: 10.1016/j.jmb.2005.12.046] [Citation(s) in RCA: 102] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2005] [Revised: 12/06/2005] [Accepted: 12/13/2005] [Indexed: 10/25/2022]
Abstract
Isomerization of the 11-cis retinal chromophore in the visual pigment rhodopsin is coupled to motion of transmembrane helix H6 and receptor activation. We present solid-state magic angle spinning NMR measurements of rhodopsin and the metarhodopsin II intermediate that support the proposal that interaction of Trp265(6.48) with the retinal chromophore is responsible for stabilizing an inactive conformation in the dark, and that motion of the beta-ionone ring allows Trp265(6.48) and transmembrane helix H6 to adopt active conformations in the light. Two-dimensional dipolar-assisted rotational resonance NMR measurements are made between the C19 and C20-methyl groups of the retinal and uniformly 13C-labeled Trp265(6.48). The retinal C20-Trp265(6.48) contact present in the dark-state of rhodopsin is lost in metarhodopsin II, and a new contact is formed with the C19 methyl group. We have previously shown that the retinal translates 4-5 A toward H5 in metarhodopsin II. This motion, in conjunction with the Trp-C19 contact, implies that the Trp265(6.48) side-chain moves significantly upon rhodopsin activation. NMR measurements also show that a packing interaction in rhodopsin between Trp265(6.48) and Gly121(3.36) is lost in metarhodopsin II, consistent with H6 motion away from H3. However, a close contact between Gly120(3.35) on H3 and Met86(2.53) on H2 is observed in both rhodopsin and metarhodopsin II, suggesting that H3 does not change orientation significantly upon receptor activation.
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Affiliation(s)
- Evan Crocker
- Departments of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794-5115, USA
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17
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Zadok U, Klare JP, Engelhard M, Sheves M. The hydroxylamine reaction of sensory rhodopsin II: light-induced conformational alterations with C13=C14 nonisomerizable pigment. Biophys J 2005; 89:2610-7. [PMID: 16085771 PMCID: PMC1366761 DOI: 10.1529/biophysj.105.065631] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Sensory rhodopsin II, a repellent phototaxis receptor from Natronomonas (Natronobacterium) pharaonis (NpSRII), forms a complex with its cognate transducer (NpHtrII). In micelles the two proteins form a 1:1 heterodimer, whereas in membranes they assemble to a 2:2 complex. Similarly to other retinal proteins, sensory rhodopsin II undergoes a bleaching reaction with hydroxylamine in the dark which is markedly catalyzed by light. The reaction involves cleavage of the protonated Schiff base bond which covalently connects the retinal chromophore to the protein. The light acceleration reflects protein conformation alterations, at least in the retinal binding site, and thus allows for detection of these changes in various conditions. In this work we have followed the hydroxylamine reaction at different temperatures with and without the cognate transducer. We have found that light irradiation reduces the activation energy of the hydroxylamine reaction as well as the frequency factor. A similar effect was found previously for bacteriorhodopsin. The interaction with the transducer altered the light effect both in detergent and membranes. The transducer interaction decreased the apparent light effect on the energy of activation and the frequency factor in detergent but increased it in membranes. In addition, we have employed an artificial pigment derived from a retinal analog in which the critical C13=C14 double bond is locked by a rigid ring structure preventing its isomerization. We have observed light enhancement of the reaction rate and reduction of the energy of activation as well as the frequency factor, despite the fact that this pigment does not experience C13=C14 double bond isomerization. It is suggested that retinal excited state polarization caused by light absorption of the "locked" pigment polarizes the protein and triggers relatively long-lived protein conformational alterations.
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Affiliation(s)
- U Zadok
- Department of Organic Chemistry, The Weizmann Institute of Science, Rehovot, Israel
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