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Umegawa Y, Kawatake S, Murata M, Matsuoka S. Combined effect of the head groups and alkyl chains of archaea lipids when interacting with bacteriorhodopsin. Biophys Chem 2023; 294:106959. [PMID: 36709544 DOI: 10.1016/j.bpc.2023.106959] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2022] [Revised: 01/12/2023] [Accepted: 01/16/2023] [Indexed: 01/21/2023]
Abstract
Bacteriorhodopsin (bR), a transmembrane protein with seven α-helices, is highly expressed in the purple membrane (PM) of archaea such as Halobacterium salinarum. It is well known that bR forms two-dimensional crystals with acidic lipids such as phosphatidylglycerol phosphate methyl ester (PGP-Me)-a major component of PM lipids bearing unique chemical structures-methyl-branched alkyl chains, ether linkages, and divalent anionic head groups with two phosphodiester groups. Therefore, we aimed to determine which functional groups of PGP-Me are essential for the boundary lipids of bR and how these functionalities interact with bR. To this end, we compared various well-known phospholipids (PLs) that carry one of the structural features of PGP-Me, and evaluated the affinity of PLs to bR using the centerband-only analysis of rotor-unsynchronized spin echo (COARSE) method in solid-state NMR measurements and thermal shift assays. The results clearly showed that the branched methyl groups of alkyl chains and double negative charges in the head groups are important for PL interactions with bR. We then examined the effect of phospholipids on the monomer-trimer exchange of bR using circular dichroism (CD) spectra. The results indicated that the divalent negative charge in a head group stabilizes the trimer structure, while the branched methyl chains significantly enhance the PLs' affinity for bR, thus dispersing bR trimers in the PM even at high concentrations. Finally, we investigated the effects of PL on the proton-pumping activity of bR based on the decay rate constant of the M intermediate of a bR photocycle. The findings showed that bR activities decreased to 20% in 1,2-dimyristoyl-sn-glycero-3-phosphate (DMPA), and in 1,2-diphytanoyl-sn-glycero-3-phosphocholine (DPhPC) bilayers as compared to that in PM. Meanwhile, 1,2-Diphytanoyl-sn-glycero-3-phosphate (DPhPA) bilayers bearing both negative charges and branched methyl groups preserved over 80% of the activity. These results strongly suggest that the head groups and alkyl chains of phospholipids are essential for boundary lipids and greatly influence the biological function of bR.
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Affiliation(s)
- Yuichi Umegawa
- JST ERATO, Lipid Active Structure Project, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan; Department of Chemistry, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan; Forefront Research Center, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan.
| | - Satoshi Kawatake
- JST ERATO, Lipid Active Structure Project, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan; Department of Chemistry, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan; Forefront Research Center, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan
| | - Michio Murata
- JST ERATO, Lipid Active Structure Project, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan; Department of Chemistry, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan
| | - Shigeru Matsuoka
- JST ERATO, Lipid Active Structure Project, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan; Department of Chemistry, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan; Forefront Research Center, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan
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Hu R, Ding X, Yu P, He X, Watts A, Zhao X, Wang J. Ultrafast Two-Dimensional Infrared Spectroscopy Resolved a Structured Lysine 159 on the Cytoplasmic Surface of the Microbial Photoreceptor Bacteriorhodopsin. J Am Chem Soc 2022; 144:22083-22092. [PMID: 36399663 DOI: 10.1021/jacs.2c09435] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Bacteriorhodopsin (bR) is a light-driven microbial receptor, and lysine 159 (K159) is a charged residue on the cytoplasmic (CP) side of its E-F loop. However, its conformation and function remain unknown due to fast surface dynamics. By utilizing a 13C, 15N-labeled lysine (K) as an isotope probe, we created a network of site-specific amide-I vibrational signatures (backbone carbonyl stretch) to identify the frequency contribution of the labeled residues to the amide-I excitonic band structure. Thus, the red-shifted amide-I frequency in the 13C, 15N-lysine-labeled bR (uK-bR) to the unlabeled bR (WT-bR) could be differentiated and examined by ultrafast two-dimensional vibrational echo infrared (2D IR) spectroscopy. Our results showed that the backbone carbonyl of K159 is located at a high frequency of ca. 1693 cm-1 and has a vibrational excited-state relaxation time shorter than the bulk helical amide-I mode at the same frequency, suggesting that K159 may possess a hydrogen-bonded γ-turn structure with E161, one of the carboxylate residues on the CP surface of bR. The 2D solid-state NMR study of uK-bR also revealed conformational dependent lysine residues, from which K159 was found to involve the turn motif. This γ-turn structure maintained by K159 may help to stabilize the E-F loop and support E161 in attracting protons from the bulk during the late stage of the bR photocycle. The combined spectroscopic approach illustrated in this work may be applied to map residue-specific local structures and dynamics of other receptors and large proteins.
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Affiliation(s)
- Rong Hu
- Molecular Reaction Dynamics Laboratory, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P.R. China.,University of Chinese Academy of Sciences, Beijing 100049, P.R. China
| | - Xiaoyan Ding
- Department of Physics, School of Physics and Electronic Science, East China Normal University, 500 Dongchuan Road, Minhang District, Shanghai 200241, P.R. China.,Department of Biochemistry, University of Oxford, South Park Road, Oxford OX1 3QU, U.K
| | - Pengyun Yu
- Molecular Reaction Dynamics Laboratory, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P.R. China.,University of Chinese Academy of Sciences, Beijing 100049, P.R. China
| | - Xuemei He
- Molecular Reaction Dynamics Laboratory, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P.R. China
| | - Anthony Watts
- Department of Biochemistry, University of Oxford, South Park Road, Oxford OX1 3QU, U.K
| | - Xin Zhao
- Department of Physics, School of Physics and Electronic Science, East China Normal University, 500 Dongchuan Road, Minhang District, Shanghai 200241, P.R. China
| | - Jianping Wang
- Molecular Reaction Dynamics Laboratory, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P.R. China.,University of Chinese Academy of Sciences, Beijing 100049, P.R. China
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3
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Excitonic Model and Circular Dichroism Spectrum of Bacteriorhodopsin. Chem Phys 2022. [DOI: 10.1016/j.chemphys.2022.111642] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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4
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The chirality origin of retinal-carotenoid complex in gloeobacter rhodopsin: a temperature-dependent excitonic coupling. Sci Rep 2020; 10:13992. [PMID: 32814821 PMCID: PMC7438509 DOI: 10.1038/s41598-020-70697-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2020] [Accepted: 07/29/2020] [Indexed: 11/08/2022] Open
Abstract
Retinal proteins play significant roles in light-induced protons/ions transport across the cell membrane. A recent studied retinal protein, gloeobacter rhodopsin (gR), functions as a proton pump, and binds the carotenoid salinixanthin (sal) in addition to the retinal chromophore. We have studied the interactions between the two chromophores as reflected in the circular dichroism (CD) spectrum of gR complex. gR exhibits a weak CD spectrum but following binding of sal, it exhibits a significant enhancement of the CD bands. To examine the CD origin, we have substituted the retinal chromophore of gR by synthetic retinal analogues, and have concluded that the CD bands originated from excitonic interaction between sal and the retinal chromophore as well as the sal chirality induced by binding to the protein. Temperature increase significantly affected the CD spectra, due to vanishing of excitonic coupling. A similar phenomenon of excitonic interaction lose between chromophores was recently reported for a photosynthetic pigment-protein complex (Nature Commmun, 9, 2018, 99). We propose that the excitonic interaction in gR is weaker due to protein conformational alterations. The excitonic interaction is further diminished following reduction of the retinal protonated Schiff base double bond. Furthermore, the intact structure of the retinal ring is necessary for obtaining the excitonic interaction.
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Misra R, Eliash T, Sudo Y, Sheves M. Retinal-Salinixanthin Interactions in a Thermophilic Rhodopsin. J Phys Chem B 2018; 123:10-20. [PMID: 30525616 DOI: 10.1021/acs.jpcb.8b06795] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
In microbial rhodopsins (also called retinal proteins), the retinal chromophore is used for harvesting light. A carotenoid molecule has been reported to complement the retinal as light harvesting antenna in bacterial retinal proteins, although examples are scarce. In this paper, we present the formation of a novel antenna complex between thermophilic rhodopsin (TR) and the carotenoid salinixanthin (Sal). The complex formation and its structure were studied using UV-visible absorption as well as circular dichroism (CD) spectroscopies. Our studies indicate that the complex is formed in both the trimeric and monomeric forms of TR. CD spectroscopy suggests that excitonic coupling takes place between retinal and Sal. The binding of Sal with artificial TR pigments derived from synthetic retinal analogues further supports the contribution of the retinal chromophore to the CD spectrum. These studies further support the possibility of interaction between the 4-keto ring of the Sal and the retinal in TR-Sal complexes. Temperature-dependent CD spectra indicate that the positive band (ca. 482 nm) of the bisignate CD spectra of the studied complexes originates from the contribution of excitonic coupling and induced chirality of Sal in the protein binding site. The presence of a relatively smaller glycine residue in the vicinity of the retinal chromophore in TR is proposed to be crucial for binding with Sal. The results are expected to shed light on the mechanism of retinal-carotenoid interactions in other biological systems.
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Affiliation(s)
- Ramprasad Misra
- Department of Organic Chemistry , Weizmann Institute of Science , Rehovot 76100 , Israel
| | - Tamar Eliash
- Department of Organic Chemistry , Weizmann Institute of Science , Rehovot 76100 , Israel
| | - Yuki Sudo
- Graduate School of Medicine, Dentistry and Pharmaceutical sciences , Okayama University , Kita-Ku, Okayama 700-8530 , Japan
| | - Mordechai Sheves
- Department of Organic Chemistry , Weizmann Institute of Science , Rehovot 76100 , Israel
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6
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Gdor I, Mani-Hazan M, Friedman N, Sheves M, Ruhman S. Membrane Independence of Ultrafast Photochemistry in Pharaonis Halorhodopsin: Testing the Role of Bacterioruberin. J Phys Chem B 2017; 121:2319-2325. [PMID: 28230358 DOI: 10.1021/acs.jpcb.6b12698] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Ultrafast photochemistry of pharaonis halorhodopsin (p-HR) in the intact membrane of Natronomonas pharaonis has been studied by photoselective femtosecond pump-hyperspectral probe spectroscopy with high time resolution. Two variants of this sample were studied, one with wild-type retinal prosthetic groups and another after shifting the retinal absorption deep into the blue range by reducing the Schiff base linkage, and the results were compared to a previous study on detergent-solubilized p-HR. This comparison shows that retinal photoisomerization dynamics is identical in the membrane and in the solubilized sample. Selective photoexcitation of bacterioruberin, which is associated with the protein in the native membrane, in wild-type and reduced samples, demonstrates conclusively that unlike the carotenoids associated with some bacterial retinal proteins the carrotenoid in p-HR does not act as a light-harvesting antenna.
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Affiliation(s)
- Itay Gdor
- Institute of Chemistry, the Hebrew University , Jerusalem 91904, Israel
| | - Maya Mani-Hazan
- Department of Organic Chemistry, Weizmann Institute of Science , Rehovot 76100, Israel
| | - Noga Friedman
- Department of Organic Chemistry, Weizmann Institute of Science , Rehovot 76100, Israel
| | - Mordechai Sheves
- Department of Organic Chemistry, Weizmann Institute of Science , Rehovot 76100, Israel
| | - Sanford Ruhman
- Institute of Chemistry, the Hebrew University , Jerusalem 91904, Israel
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7
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Structural analysis of bacteriorhodopsin solubilized by lipid-like phosphocholine biosurfactants with varying micelle concentrations. J Colloid Interface Sci 2015; 437:170-180. [DOI: 10.1016/j.jcis.2014.09.007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2014] [Revised: 09/05/2014] [Accepted: 09/08/2014] [Indexed: 12/18/2022]
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8
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Smolensky Koganov E, Brumfeld V, Friedman N, Sheves M. Origin of Circular Dichroism of Xanthorhodopsin. A Study with Artificial Pigments. J Phys Chem B 2014; 119:456-64. [DOI: 10.1021/jp510534s] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
| | - Vlad Brumfeld
- Department
of Chemical Research Support, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Noga Friedman
- Department
of Organic Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Mordechai Sheves
- Department
of Organic Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel
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9
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Pescitelli G, Kato HE, Oishi S, Ito J, Maturana AD, Nureki O, Woody RW. Exciton circular dichroism in channelrhodopsin. J Phys Chem B 2014; 118:11873-85. [PMID: 25247388 DOI: 10.1021/jp505917p] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Channelrhodopsins (ChRs) are of great interest currently because of their important applications in optogenetics, the photostimulation of neurons. The absorption and circular dichroism (CD) spectra of C1C2, a chimera of ChR1 and ChR2 of Chlamydomonas reinhardtii, have been studied experimentally and theoretically. The visible absorption spectrum of C1C2 shows vibronic fine structure in the 470 nm band, consistent with the relatively nonpolar binding site. The CD spectrum has a negative band at 492 nm (Δε(max) = -6.17 M(-1) cm(-1)) and a positive band at 434 nm (Δε(max) = +6.65 M(-1) cm(-1)), indicating exciton coupling within the C1C2 dimer. Time-dependent density functional theory (TDDFT) calculations are reported for three models of the C1C2 chromophore: (1) the isolated protonated retinal Schiff base (retPSB); (2) an ion pair, including the retPSB chromophore, two carboxylate side chains (Asp 292, Glu 162), modeled by acetate, and a water molecule; and (3) a hybrid quantum mechanical/molecular mechanical (QM/MM) model depicting the binding pocket, in which the QM part consists of the same ion pair as that in (2) and the MM part consists of the protein residues surrounding the ion pair within 10 Å. For each of these models, the CD of both the monomer and the dimer was calculated with TDDFT. For the dimer, DeVoe polarizability theory and exciton calculations were also performed. The exciton calculations were supplemented by calculations of the coupling of the retinal transition with aromatic and peptide group transitions. For the dimer, all three methods and three models give a long-wavelength C2-axis-polarized band, negative in CD, and a short-wavelength band polarized perpendicular to the C2 axis with positive CD, differing in wavelength by 1-5 nm. Only the retPSB model gives an exciton couplet that agrees qualitatively with experiment. The other two models give a predominantly or solely positive band. We further analyze an N-terminal truncated mutant because it was assumed that the N-terminal domain has a crucial role in the dimerization of ChRs. However, the CD spectrum of this mutant has an exciton couplet comparable to that of the wild-type, demonstrating that it is dimeric. Patch-clamp experiments suggest that the N-terminal domain is involved in protein stabilization and channel kinetics rather than dimerization or channel activity.
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Affiliation(s)
- Gennaro Pescitelli
- Dipartimento di Chimica e Chimica Industriale, Università di Pisa , via Moruzzi 3, I-56124 Pisa, Italy
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10
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Effects of Triton X-100 on Proton Transfer and in the Photocycle of Archaerhodopsin 4. Biosci Biotechnol Biochem 2014; 76:250-6. [DOI: 10.1271/bbb.110508] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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11
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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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13
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14
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Imhof M, Pudewills J, Rhinow D, Chizhik I, Hampp N. Stability of Purple Membranes from Halobacterium salinarum toward Surfactants: Inkjet Printing of a Retinal Protein. J Phys Chem B 2012; 116:9727-31. [DOI: 10.1021/jp3057459] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Martin Imhof
- Department of Chemistry, Philipps-University of Marburg, Hans-Meerwein-Str.
Bldg. H, D-35032 Marburg, Germany
| | - Jens Pudewills
- Department of Chemistry, Philipps-University of Marburg, Hans-Meerwein-Str.
Bldg. H, D-35032 Marburg, Germany
| | - Daniel Rhinow
- Department of Structural Biology, Max Planck Institute of Biophysics, Max-von-Laue-Str. 3, D-60438 Frankfurt,
Germany
| | - Ivan Chizhik
- Department of Chemistry, Philipps-University of Marburg, Hans-Meerwein-Str.
Bldg. H, D-35032 Marburg, Germany
| | - Norbert Hampp
- Department of Chemistry, Philipps-University of Marburg, Hans-Meerwein-Str.
Bldg. H, D-35032 Marburg, Germany
- Material Sciences Center, Hans-Meerwein-Str. Bldg. H, D-35032
Marburg, Germany
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15
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Rhinow D, Imhof M, Chizhik I, Baumann RP, Hampp N. Structural Changes in Bacteriorhodopsin Caused by Two-Photon-Induced Photobleaching. J Phys Chem B 2012; 116:7455-62. [DOI: 10.1021/jp2112846] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Daniel Rhinow
- Department of Structural
Biology, Max-Planck-Institute of Biophysics, Max-von-Laue-Str. 3, D-60438 Frankfurt, Germany
| | - Martin Imhof
- Department of Chemistry, Philipps-University of Marburg, Hans-Meerwein-Str. Bldg. H, D-35032 Marburg,
Germany
| | - Ivan Chizhik
- Department of Chemistry, Philipps-University of Marburg, Hans-Meerwein-Str. Bldg. H, D-35032 Marburg,
Germany
| | - Roelf-Peter Baumann
- Department of Chemistry, Philipps-University of Marburg, Hans-Meerwein-Str. Bldg. H, D-35032 Marburg,
Germany
| | - Norbert Hampp
- Department of Chemistry, Philipps-University of Marburg, Hans-Meerwein-Str. Bldg. H, D-35032 Marburg,
Germany
- Material Sciences Center, D-35032 Marburg, Germany
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16
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Pescitelli G, Woody RW. The Exciton Origin of the Visible Circular Dichroism Spectrum of Bacteriorhodopsin. J Phys Chem B 2012; 116:6751-63. [DOI: 10.1021/jp212166k] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Gennaro Pescitelli
- Dipartimento
di Chimica e Chimica
Industriale, Università degli Studi di Pisa, via Risorgimento 35, I-56126 Pisa, Italy
| | - Robert W. Woody
- Department of Biochemistry and
Molecular Biology, Colorado State University, Fort Collins, Colorado 80523, United States
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Negishi L, Mitaku S. Electrostatic effects influence the formation of two-dimensional crystals of bacteriorhodopsin reconstituted into dimyristoylphosphatidylcholine membranes. J Biochem 2011; 150:113-9. [DOI: 10.1093/jb/mvr043] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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18
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Imasheva ES, Balashov SP, Wang JM, Lanyi JK. Removal and reconstitution of the carotenoid antenna of xanthorhodopsin. J Membr Biol 2010; 239:95-104. [PMID: 21104180 PMCID: PMC3030941 DOI: 10.1007/s00232-010-9322-x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2010] [Accepted: 11/05/2010] [Indexed: 11/24/2022]
Abstract
Salinixanthin, a C40-carotenoid acyl glycoside, serves as a light-harvesting antenna in the retinal-based proton pump xanthorhodopsin of Salinibacter ruber. In the crystallographic structure of this protein, the conjugated chain of salinixanthin is located at the protein–lipid boundary and interacts with residues of helices E and F. Its ring, with a 4-keto group, is rotated relative to the plane of the π-system of the carotenoid polyene chain and immobilized in a binding site near the β-ionone retinal ring. We show here that the carotenoid can be removed by oxidation with ammonium persulfate, with little effect on the other chromophore, retinal. The characteristic CD bands attributed to bound salinixanthin are now absent. The kinetics of the photocycle is only slightly perturbed, showing a 1.5-fold decrease in the overall turnover rate. The carotenoid-free protein can be reconstituted with salinixanthin extracted from the cell membrane of S. ruber. Reconstitution is accompanied by restoration of the characteristic vibronic structure of the absorption spectrum of the antenna carotenoid, its chirality, and the excited-state energy transfer to the retinal. Minor modification of salinixanthin, by reducing the carbonyl C=O double bond in the ring to a C-OH, suppresses its binding to the protein and eliminates the antenna function. This indicates that the presence of the 4-keto group is critical for carotenoid binding and efficient energy transfer.
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Affiliation(s)
- Eleonora S Imasheva
- Department of Physiology and Biophysics, University of California, Irvine, CA 92697-4560, USA
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19
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Beebe ET, Makino SI, Nozawa A, Matsubara Y, Frederick RO, Primm JG, Goren MA, Fox BG. Robotic large-scale application of wheat cell-free translation to structural studies including membrane proteins. N Biotechnol 2010; 28:239-49. [PMID: 20637905 DOI: 10.1016/j.nbt.2010.07.003] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2010] [Accepted: 07/03/2010] [Indexed: 10/19/2022]
Abstract
The use of the Protemist XE, an automated discontinuous-batch protein synthesis robot, in cell-free translation is reported. The soluble Galdieria sulphuraria protein DCN1 was obtained in greater than 2mg total synthesis yield per mL of reaction mixture from the Protemist XE, and the structure was subsequently solved by X-ray crystallography using material from one 10 mL synthesis (PDB ID: 3KEV). The Protemist XE was also capable of membrane protein translation. Thus human sigma-1 receptor was translated in the presence of unilamellar liposomes and bacteriorhodopsin was translated directly into detergent micelles in the presence of all-trans-retinal. The versatility, ease of use, and compact size of the Protemist XE robot demonstrate its suitability for large-scale synthesis of many classes of proteins.
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Affiliation(s)
- Emily T Beebe
- Center for Eukaryotic Structural Genomics, Department of Biochemistry, University of Wisconsin-Madison, 445 Henry Mall, Madison, WI 53706, USA
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Unique biphasic band shape of the visible circular dichroism of bacteriorhodopsin in purple membrane: Excitons, multiple transitions or protein heterogeneity? Biophys J 2010; 63:1432-42. [PMID: 19431860 DOI: 10.1016/s0006-3495(92)81701-0] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
OVER A DECADE AND A HALF AGO, WHEN THE FIRST VISIBLE MEMBRANE SUSPENSION CIRCULAR DICHROIC (CD) SPECTRUM OF THE PURPLE MEMBRANE (PM) WAS PRESENTED, TWO MECHANISMS WERE PROPOSED TO ACCOUNT FOR THE OBSERVED BIPHASIC SHAPED CD BAND: (a) excitonic interactions among the retinals of the sole protein bacteriorhodopsin (bR) in the crystalline structure of the PM, and (b) combination of CD bands with opposite rotational strengths due to a retinal-apoprotein heterogeneity of the bR molecules or due to two possible close-lying long-wavelength transitions of the retinal of the bR with opposite rotational strengths. Since that time, an impressive body of experimental and theoretical evidence has been accumulated, mostly consistent with an exciton model but many at serious odds with any heterogeneity or multiple transition model. Recently, a number of articles have appeared reporting analyses of new experimental observations which are proposed to cast serious doubts on the viability of the exciton model, and therefore, may revive the heterogeneity or multiple transition model as an explanation for the unique shape of the CD band of the PM. The intent of this article is to demonstrate that if all observations found in literature baring on this question are considered in toto and in a consistent manner, they can be interpreted without exception by excitons, and furthermore, that there is no plausible evidence available to warrant the revival of the heterogeneity or multiple transition model as an explanation for the unique shape of the biphasic CD band of the PM.
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21
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Phatak P, Frähmcke JS, Wanko M, Hoffmann M, Strodel P, Smith J, Suhai S, Bondar AN, Elstner M. Long-distance proton transfer with a break in the bacteriorhodopsin active site. J Am Chem Soc 2009; 131:7064-78. [PMID: 19405533 PMCID: PMC2746972 DOI: 10.1021/ja809767v] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Bacteriorhodopsin is a proton-pumping membrane protein found in the plasma membrane of the archaeon Halobacterium salinarium. Light-induced isomerization of the retinal chromophore from all-trans to 13-cis leads to a sequence of five conformation-coupled proton transfer steps and the net transport of one proton from the cytoplasmic to the extracellular side of the membrane. The mechanism of the long-distance proton transfer from the primary acceptor Asp85 to the extracellular proton release group during the O --> bR is poorly understood. Experiments suggest that this long-distance transfer could involve a transient state [O] in which the proton resides on the intermediate carrier Asp212. To assess whether the transient protonation of Asp212 participates in the deprotonation of Asp85, we performed hybrid Quantum Mechanics/Molecular Mechanics proton transfer calculations using different protein structures and with different retinal geometries and active site water molecules. The structural models were assessed by computing UV-vis excitation energies and C=O vibrational frequencies. The results indicate that a transient [O] conformer with protonated Asp212 could indeed be sampled during the long-distance proton transfer to the proton release group. Our calculations suggest that, in the starting proton transfer state O, the retinal is strongly twisted and at least three water molecules are present in the active site.
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Affiliation(s)
- Prasad Phatak
- Institute of Physical and Theoretical Chemistry, TU Braunschweig, D-38106 Braunschweig, Germany
| | - Jan S. Frähmcke
- Institute of Physical and Theoretical Chemistry, TU Braunschweig, D-38106 Braunschweig, Germany
| | - Marius Wanko
- BCCMS, Universität Bremen, D-28334 Bremen, Germany
| | | | - Paul Strodel
- Accelrys Ltd., Cambridge CB4 0WN, United Kingdom
| | - Jeremy Smith
- Computational Molecular Biophysics, IWR, University of Heidelberg, Im Neuenheimer Feld 368, D-69120, Heidelberg, Germany
- Center for Molecular Biophysics, Oak Ridge National Laboratory, PO BOX 2008 MS6164, Oak Ridge, Tennessee 37831, USA
- Department of Biochemistry and Molecular Biology, University of Tennessee, M407 Walters Life Sciences, 1414 Cumberland Ave, Knoxville Tennessee 37996, USA
| | - Sándor Suhai
- Molecular Biophysics Department, German Cancer Research Institute, Im Neuheimer Feld 280, D-69120, Heidelberg, Germany
| | - Ana-Nicoleta Bondar
- Molecular Biophysics Department, German Cancer Research Institute, Im Neuheimer Feld 280, D-69120, Heidelberg, Germany
- Computational Molecular Biophysics, IWR, University of Heidelberg, Im Neuenheimer Feld 368, D-69120, Heidelberg, Germany
- Department of Physiology and Biophysics and the Center for Biomembrane Systems, University of California at Irvine, Med. Sci. I, D-347, Irvine, CA 92697, USA
| | - Marcus Elstner
- Institute of Physical and Theoretical Chemistry, TU Braunschweig, D-38106 Braunschweig, Germany
- Molecular Biophysics Department, German Cancer Research Institute, Im Neuheimer Feld 280, D-69120, Heidelberg, Germany
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22
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Balashov SP, Imasheva ES, Lanyi JK. Induced chirality of the light-harvesting carotenoid salinixanthin and its interaction with the retinal of xanthorhodopsin. Biochemistry 2006; 45:10998-1004. [PMID: 16953586 PMCID: PMC2528006 DOI: 10.1021/bi061098i] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
In xanthorhodopsin, a retinal protein-carotenoid complex of Salinibacter ruber, the carotenoid salinixanthin functions as a light-harvesting antenna in supplying additional excitation energy for retinal isomerization and proton transport. Another retinal protein, archaerhodopsin, has been shown to contain a carotenoid, bacterioruberin, but without an antenna function. We report here that the binding site confers a chiral geometry on salinixanthin in xanthorhodopsin and confirm that the same is true for bacterioruberin in archaerhodopsin. Cell membranes containing these rhodopsins exhibit CD spectra with sharp positive bands in the visible region where the carotenoids absorb, and in the case of xanthorhodopsin a negative band at 536 nm, as well as bands in the UV region. The carotenoid in ethanol has very weak optical activity in the visible region of the spectrum. Denaturation of the opsin upon deprotonation of the Schiff base at pH 12.5 eliminates the induced CD bands in both proteins. In one of these proteins, but not in the other, the carotenoid binding site depends entirely on the retinal. Hydrolysis of the retinal Schiff base of xanthorhodopsin with hydroxylamine eliminates the induced CD bands of salinixanthin. In contrast, hydrolysis of the Schiff base in archaerhodopsin does not abolish the CD bands of bacterioruberin. Thus, consistent with its antenna function, the carotenoid binding site interacts closely with the retinal only in xanthorhodopsin, and this interaction is the major source of the CD bands. In this protein, protonation of the counterion with a decrease in pH from 8 to 5 causes significant changes in the CD spectrum. The observed spectral features suggest that binding of salinixanthin in xanthorhodopsin involves the cyclohexenone ring of the carotenoid and its conformational heterogeneity is restricted.
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Affiliation(s)
- Sergei P Balashov
- Department of Physiology and Biophysics, University of California, D340 Medical Science I, Irvine, California 92697, USA.
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23
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Karnaukhova E, Schey KL, Crouch RK. Circular dichroism and cross-linking studies of bacteriorhodopsin mutants. Amino Acids 2006; 30:17-23. [PMID: 16477391 DOI: 10.1007/s00726-005-0255-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2005] [Accepted: 08/16/2005] [Indexed: 11/27/2022]
Abstract
Circular dichroism (CD) spectroscopy was employed for native (wild type, WT) bacteriorhodopsin (bR) and several mutant derivatives: R134K, R134H, R82Q, S35C, L66C, and R134C/E194C. Comparative analysis of the CD spectra in visible range shows that only R134C/E194C exhibits biphasic CD, typical for native bR, the other mutants demonstrate CD spectra with significantly smaller or absent negative band. Since the biphasic CD is a feature of hexagonal lattice structure composed by bR trimers in the purple membrane, these mutants and WT were examined by cross-linking studies, which confirmed the same trend towards trimeric organization. Therefore, a single amino acid substitution may lead to drastically different CD spectra without disruption of bR trimeric organization. Thus, although disruption of bR trimeric crystalline lattice structure (e.g., solubilization with detergents) directly results in the disappearance of characteristic bilobe in visible CD, the lack of the bilobe in the CD alone does not predict the absence of trimers.
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Affiliation(s)
- E Karnaukhova
- Division of Hematology, Center for Biologics Evaluation and Research, Food and Drug Administration, Bethesda, Maryland 20892, USA.
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24
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Karnaukhova E, Vasileiou C, Wang A, Berova N, Nakanishi K, Borhan B. Circular dichroism of heterochromophoric and partially regenerated purple membrane: Search for exciton coupling. Chirality 2005; 18:72-83. [PMID: 16385624 DOI: 10.1002/chir.20222] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
In order to determine the origin of the bisignate CD spectra of native purple membrane, heterochromophoric analogues containing bacteriorhodopsin regenerated with native all-trans-retinal and retinal analogues were investigated. The data collected for the purple membrane samples containing two different chromophores suggest the additive character of the CD spectra. This conclusion was supported by a series of spectra using 5,6-dihydroretinal and 3-dehydroretinal and by using 33% regenerated PM in buffer and in presence of osmolytes. Our results support the idea of conformational heterogeneity of the chromophores in the bR in the trimer, suggesting that the three bR subunits in the trimer are not conformationally equal, and therefore, the bisignate CD spectrum of bR in the purple membrane occurs rather due to a superposition of the CD spectra from variously distorted bR subunits in the trimer than interchromophoric exciton-coupling interactions.
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Affiliation(s)
- Elena Karnaukhova
- Center for Biologics Evaluation and Research, Food and Drug Administration, Bethesda, MD 20892, USA
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25
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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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26
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Wang J, Heyes CD, El-Sayed MA. Refolding of Thermally Denatured Bacteriorhodopsin in Purple Membrane. J Phys Chem B 2001. [DOI: 10.1021/jp013131a] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Jianping Wang
- Laser Dynamics Laboratory, School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332-0400
| | - Colin D. Heyes
- Laser Dynamics Laboratory, School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332-0400
| | - Mostafa A. El-Sayed
- Laser Dynamics Laboratory, School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332-0400
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27
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Aharoni A, Weiner L, Lewis A, Ottolenghi M, Sheves M. Nonisomerizable non-retinal chromophores initiate light-induced conformational alterations in bacterioopsin. J Am Chem Soc 2001; 123:6612-6. [PMID: 11439048 DOI: 10.1021/ja004035a] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The photoactivation of retinal proteins is usually interpreted in terms of C=C photoisomerization of the retinal moiety, which triggers appropriate conformational changes in the protein. In this work several dye molecules, characterized by a completely rigid structure in which no double-bond isomerization is possible, were incorporated into the binding site of bacteriorhodopsin (bR). Using a light-induced chemical reaction of a labeled EPR probe, it was observed that specific conformational alterations in the protein are induced following light absorption by the dye molecules occupying the binding site. The exact nature of these changes and their relationship to those occurring in the bR photocycle are still unclear. Nevertheless, their occurrence proves that C=C or C=NH(+) isomerization is not a prerequisite for protein conformational changes in a retinal protein. More generally, we show that conformational changes, leading to changes in reactivity, may be induced in proteins by optical excitation of simple nonisomerizable dyes located in the macromolecular matrix.
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Affiliation(s)
- A Aharoni
- Department of Organic Chemistry and Department of Chemical Services, The Weizmann Institute of Science, Rehovot 76100, Israel
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28
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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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29
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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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30
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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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31
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Volkov V, Svirko YP, Kamalov VF, Song L, El-Sayed MA. Optical rotation of the second harmonic radiation from retinal in bacteriorhodopsin monomers in Langmuir-Blodgett film: evidence for nonplanar retinal structure. Biophys J 1997; 73:3164-70. [PMID: 9414228 PMCID: PMC1181219 DOI: 10.1016/s0006-3495(97)78342-5] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
We observed optical rotation of the plane of polarization of the second harmonic (SH) radiation at 532 nm (in resonance with the retinal absorption) generated in reflection geometry in Langmuir-Blodgett film of bacteriorhodopsin (bR). The analysis of the experimental data showed that this effect arises from the nonvanishing contribution of the antisymmetrical part of the hyperpolarizability tensor. This requires that the dipole moment of the resonant electronic transition, the change of the dipole moment upon electronic excitation, and the long axis of the retinal not be coplanar. Such conditions are satisfied only if the retinal has a nonplanar geometry, a conclusion that could lend support to the heterogeneity model of the origin of the biphasic band shape of the linear CD spectrum of the retinal in bR. On the basis of our theoretical analysis, we were able to estimate the angle between the induced dipole moment and the plan that contains the long axis of the chromophore and the transition dipole moment of the retinal absorption.
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Affiliation(s)
- V Volkov
- Department of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta 30322, USA
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32
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Song X, Perlstein J, Whitten DG. Supramolecular Aggregates of Azobenzene Phospholipids and Related Compounds in Bilayer Assemblies and Other Microheterogeneous Media: Structure, Properties, and Photoreactivity1. J Am Chem Soc 1997. [DOI: 10.1021/ja971291n] [Citation(s) in RCA: 163] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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33
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Affiliation(s)
- R W Woody
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins 80523, USA
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34
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Ulrich AS, Watts A, Wallat I, Heyn MP. Distorted structure of the retinal chromophore in bacteriorhodopsin resolved by 2H-NMR. Biochemistry 1994; 33:5370-5. [PMID: 8180159 DOI: 10.1021/bi00184a003] [Citation(s) in RCA: 56] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Structural details about the geometry of the retinal chromophore in the binding pocket of bacteriorhodopsin are revealed by measuring the orientations of its individual methyl groups. Solid-state 2H-NMR measurements were performed on macroscopically oriented samples of purple membrane patches, containing retinal specifically deuterium-labeled at one of the three methyl groups along the polyene chain (C18, C19, C20). The deuterium quadrupole splitting of each "zero-tilt" spectrum is used to calculate the orientation of the corresponding C-CD3 bond vector with respect to the membrane normal; however, two possible solutions may arise. These ambiguities in angle could be resolved by recording a tilt series of spectra at different sample inclinations to the magnetic field and analyzing the resulting complex line shapes with the aid of computer simulations. The angles for the C18, C19, and C20 group are found to be 37 +/- 1 degree, 40 +/- 1 degree, and 32 +/- 1 degree, respectively. These highly accurate values imply that the polyene chain of the retinal chromophore is not straight but rather has an in-plane curvature and possibly an out-of-plane twist. Together with the angles of the remaining methyl groups on the cyclohexene ring that have been measured previously, an overall picture has thus emerged of the intramolecular conformation and the three-dimensional orientation of retinal within bacteriorhodopsin. The deduced geometry confirms and refines the known structural information on the chromophore, suggesting that this 2H-NMR strategy may serve as a valuable tool for other membrane proteins.
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Affiliation(s)
- A S Ulrich
- Department of Biochemistry, University of Oxford, U.K
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35
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Kataoka M, Mihara K, Kamikubo H, Needleman R, Lanyi JK, Tokunaga F. Trimeric mutant bacteriorhodopsin, D85N, shows a monophasic CD spectrum. FEBS Lett 1993; 333:111-3. [PMID: 8224146 DOI: 10.1016/0014-5793(93)80385-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The structure of mutant bacteriorhodopsin (bR), D85N, was examined by CD and X-ray diffraction at pH 7. The absorption maximum of D85N at pH 7 is located at 605 nm, which is similar to the acid-blue form of wild-type bR. D85N shows a monophasic CD band, the maximum of which is at 575 nm, although the crystalline arrangement and the trimeric structure is maintained. The acid-blue form of wild-type bR shows a biphasic CD despite the similarity in absorption spectra.
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Affiliation(s)
- M Kataoka
- Department of Biology, Faculty of Science, Osaka University, Toyonaka, Japan
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36
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McDonagh AF, Pu YM, Lightner DA. Effect of volatile anesthetics on the circular dichroism of bilirubin bound to human serum albumin. EXPERIENTIA 1992; 48:246-8. [PMID: 1547853 DOI: 10.1007/bf01930465] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The characteristic circular dichroism of bilirubin bound to human serum albumin undergoes a remarkable sign inversion on addition of halothane, chloroform and other volatile anesthetics. This sign inversion, which is completely reversed by removal of the anesthetic, reflects a pronounced conformational change of the bound ligand; probably a complete inversion of chirality. The observation suggests that association of volatile anesthetics with proteins can markedly alter the internal topography of receptor sites and potentially influence the stereoselectivity of ligand binding.
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Affiliation(s)
- A F McDonagh
- Liver Center, University of California San Francisco 94143-0538
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37
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Spectroscopic properties of LHC-II, the main light-harvesting chlorophyll a/b protein complex from chloroplast membranes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1992. [DOI: 10.1016/s0005-2728(05)80331-7] [Citation(s) in RCA: 130] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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