51
|
Kouyama T, Kanada S, Takeguchi Y, Narusawa A, Murakami M, Ihara K. Crystal Structure of the Light-Driven Chloride Pump Halorhodopsin from Natronomonas pharaonis. J Mol Biol 2010; 396:564-79. [DOI: 10.1016/j.jmb.2009.11.061] [Citation(s) in RCA: 96] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2009] [Revised: 11/21/2009] [Accepted: 11/24/2009] [Indexed: 10/20/2022]
|
52
|
Imasheva ES, Balashov SP, Choi AR, Jung KH, Lanyi JK. Reconstitution of Gloeobacter violaceus rhodopsin with a light-harvesting carotenoid antenna. Biochemistry 2009; 48:10948-55. [PMID: 19842712 DOI: 10.1021/bi901552x] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We show that salinixanthin, the light-harvesting carotenoid antenna of xanthorhodopsin, can be reconstituted into the retinal protein from Gloeobacter violaceus expressed in Escherichia coli. Reconstitution of gloeobacter rhodopsin with the carotenoid is accompanied by characteristic absorption changes and the appearance of CD bands similar to those observed for xanthorhodopsin that indicate immobilization and twist of the carotenoid in the binding site. As in xanthorhodopsin, the carotenoid functions as a light-harvesting antenna. The excitation spectrum for retinal fluorescence emission shows that ca. 36% of the energy absorbed by the carotenoid is transferred to the retinal. From excitation anisotropy, we calculate the angle between the two chromophores as being ca. 50 degrees , similar to that in xanthorhodopsin. The results indicate that gloeobacter rhodopsin binds salinixanthin in a manner similar to that of xanthorhodopsin and suggest that it might bind a carotenoid also in vivo. In the crystallographic structure of xanthorhodopsin, the conjugated chain of the carotenoid lies on the surface of helices E and F, and the 4-keto ring is immersed in the protein at van der Waals distance from the ionone ring of the retinal. The 4-keto ring is in the space occupied by a tryptophan in bacteriorhodopsin, which is replaced by the smaller glycine in xanthorhodopsin and gloeobacter rhodopsin. Specific binding of the carotenoid and its light-harvesting function are eliminated by a single mutation of the gloeobacter protein that replaces this glycine with a tryptophan. This indicates that the 4-keto ring is critically involved in carotenoid binding and suggests that a number of other recently identified retinal proteins, from a diverse group of organisms, could also contain carotenoid antenna since they carry the homologous glycine near the retinal.
Collapse
Affiliation(s)
- Eleonora S Imasheva
- Department of Physiology and Biophysics, University of California, Irvine, California 92697, USA
| | | | | | | | | |
Collapse
|
53
|
Fujimoto KJ, Hayashi S. Electronic Coulombic Coupling of Excitation-Energy Transfer in Xanthorhodopsin. J Am Chem Soc 2009; 131:14152-3. [DOI: 10.1021/ja905697n] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Kazuhiro J. Fujimoto
- Department of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8520, Japan
| | - Shigehiko Hayashi
- Department of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8520, Japan
| |
Collapse
|
54
|
Yamamoto M, Hayakawa N, Murakami M, Kouyama T. Crystal structures of different substrates of bacteriorhodopsin's M intermediate at various pH levels. J Mol Biol 2009; 393:559-73. [PMID: 19712684 DOI: 10.1016/j.jmb.2009.08.047] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2009] [Revised: 08/18/2009] [Accepted: 08/19/2009] [Indexed: 11/16/2022]
Abstract
The hexagonal P622 crystal of bacteriorhodopsin, which is made up of stacked membranes, is stable provided that the precipitant concentration in the soaking solution is higher than a critical value (i.e., 1.5 M ammonium sulfate). Diffraction data showed that the crystal lattice shrank linearly with increasing precipitant concentration, due primarily to narrowing of intermembrane spaces. Although the crystal shrinkage did not affect the rate of formation of the photoreaction M intermediate, its lifetime increased exponentially with the precipitant concentration. It was suggested that the energetic barrier of the M-to-N transition becomes higher when the motional freedom of the EF loop is reduced by crystal lattice force. As a result of this property, the M state accumulated predominantly when the crystal that was soaked at a high precipitant concentration was illuminated at room temperature. Structural data obtained at various pH levels showed that the overall structure of M is not strongly dependent on pH, except that Glu194 and Glu204 in the proton release complex are more separated at pH 7 than at pH 4.4. This result suggests that light-induced disruption of the paired structure of Glu194 and Glu204 is incomplete when external pH is lower than the pK(a) value of the proton release group in the M state.
Collapse
Affiliation(s)
- Masataka Yamamoto
- Department of Physics, Graduate School of Science, Nagoya University, Nagoya, Japan
| | | | | | | |
Collapse
|
55
|
Wu J, Ma D, Wang Y, Ming M, Balashov SP, Ding J. Efficient Approach to Determine the pKa of the Proton Release Complex in the Photocycle of Retinal Proteins. J Phys Chem B 2009; 113:4482-91. [DOI: 10.1021/jp804838h] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Jia Wu
- Key Laboratory of Molecular Engineering of Polymers of Ministry of Education, Department of Macromolecular Science, Advanced Materials Laboratory, Fudan University, Shanghai 200433, China and Department of Physiology and Biophysics, University of California, Irvine 92697, USA
| | - Dewang Ma
- Key Laboratory of Molecular Engineering of Polymers of Ministry of Education, Department of Macromolecular Science, Advanced Materials Laboratory, Fudan University, Shanghai 200433, China and Department of Physiology and Biophysics, University of California, Irvine 92697, USA
| | - Yazhuo Wang
- Key Laboratory of Molecular Engineering of Polymers of Ministry of Education, Department of Macromolecular Science, Advanced Materials Laboratory, Fudan University, Shanghai 200433, China and Department of Physiology and Biophysics, University of California, Irvine 92697, USA
| | - Ming Ming
- Key Laboratory of Molecular Engineering of Polymers of Ministry of Education, Department of Macromolecular Science, Advanced Materials Laboratory, Fudan University, Shanghai 200433, China and Department of Physiology and Biophysics, University of California, Irvine 92697, USA
| | - Sergei P. Balashov
- Key Laboratory of Molecular Engineering of Polymers of Ministry of Education, Department of Macromolecular Science, Advanced Materials Laboratory, Fudan University, Shanghai 200433, China and Department of Physiology and Biophysics, University of California, Irvine 92697, USA
| | - Jiandong Ding
- Key Laboratory of Molecular Engineering of Polymers of Ministry of Education, Department of Macromolecular Science, Advanced Materials Laboratory, Fudan University, Shanghai 200433, China and Department of Physiology and Biophysics, University of California, Irvine 92697, USA
| |
Collapse
|
56
|
Hayakawa N, Kasahara T, Hasegawa D, Yoshimura K, Murakami M, Kouyama T. Effect of Xenon Binding to a Hydrophobic Cavity on the Proton Pumping Cycle in Bacteriorhodopsin. J Mol Biol 2008; 384:812-23. [PMID: 18930734 DOI: 10.1016/j.jmb.2008.09.075] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2008] [Revised: 09/21/2008] [Accepted: 09/25/2008] [Indexed: 11/25/2022]
|
57
|
Crystallographic structure of xanthorhodopsin, the light-driven proton pump with a dual chromophore. Proc Natl Acad Sci U S A 2008; 105:16561-5. [PMID: 18922772 DOI: 10.1073/pnas.0807162105] [Citation(s) in RCA: 180] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Homologous to bacteriorhodopsin and even more to proteorhodopsin, xanthorhodopsin is a light-driven proton pump that, in addition to retinal, contains a noncovalently bound carotenoid with a function of a light-harvesting antenna. We determined the structure of this eubacterial membrane protein-carotenoid complex by X-ray diffraction, to 1.9-A resolution. Although it contains 7 transmembrane helices like bacteriorhodopsin and archaerhodopsin, the structure of xanthorhodopsin is considerably different from the 2 archaeal proteins. The crystallographic model for this rhodopsin introduces structural motifs for proton transfer during the reaction cycle, particularly for proton release, that are dramatically different from those in other retinal-based transmembrane pumps. Further, it contains a histidine-aspartate complex for regulating the pK(a) of the primary proton acceptor not present in archaeal pumps but apparently conserved in eubacterial pumps. In addition to aiding elucidation of a more general proton transfer mechanism for light-driven energy transducers, the structure defines also the geometry of the carotenoid and the retinal. The close approach of the 2 polyenes at their ring ends explains why the efficiency of the excited-state energy transfer is as high as approximately 45%, and the 46 degrees angle between them suggests that the chromophore location is a compromise between optimal capture of light of all polarization angles and excited-state energy transfer.
Collapse
|
58
|
Ihara K, Narusawa A, Maruyama K, Takeguchi M, Kouyama T. A halorhodopsin-overproducing mutant isolated from an extremely haloalkaliphilic archaeonNatronomonas pharaonis. FEBS Lett 2008; 582:2931-6. [DOI: 10.1016/j.febslet.2008.07.030] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2008] [Revised: 06/21/2008] [Accepted: 07/18/2008] [Indexed: 11/25/2022]
|
59
|
Lanyi JK, Balashov SP. Xanthorhodopsin: a bacteriorhodopsin-like proton pump with a carotenoid antenna. BIOCHIMICA ET BIOPHYSICA ACTA 2008; 1777:684-8. [PMID: 18515067 PMCID: PMC2532838 DOI: 10.1016/j.bbabio.2008.05.005] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2007] [Revised: 04/30/2008] [Accepted: 05/08/2008] [Indexed: 11/25/2022]
Abstract
Xanthorhodopsin is a light-driven proton pump like bacteriorhodopsin, but made more effective for collecting light by its second chromophore, salinixanthin, a carotenoid. Action spectra for transport and fluorescence of the retinal upon excitation of the carotenoid indicate that the carotenoid functions as an antenna to the retinal. The calculated center-to-center distance and angle of the transition moments of the two chromophores are 11 A and 56 degrees , respectively. As expected from their proximity, the carotenoid and the retinal closely interact: tight binding of the carotenoid, as indicated by its sharpened vibration bands and intense induced circular dichroism in the visible, is removed by hydrolysis of the retinal Schiff base, and restored upon reconstitution with retinal. This antenna system, simpler than photosynthetic complexes, is well-suited to study features of excited-state energy migration.
Collapse
Affiliation(s)
- Janos K Lanyi
- Department of Physiology and Biophysics, University of California, Irvine, CA 92697, USA.
| | | |
Collapse
|
60
|
Excitation energy-transfer and the relative orientation of retinal and carotenoid in xanthorhodopsin. Biophys J 2008; 95:2402-14. [PMID: 18515390 DOI: 10.1529/biophysj.108.132175] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The cell membrane of Salinibacter ruber contains xanthorhodopsin, a light-driven transmembrane proton pump with two chromophores: a retinal and the carotenoid, salinixanthin. Action spectra for transport had indicated that light absorbed by either is utilized for function. If the carotenoid is an antenna in this protein, its excited state energy has to be transferred to the retinal and should be detected in the retinal fluorescence. From fluorescence studies, we show that energy transfer occurs from the excited singlet S(2) state of salinixanthin to the S(1) state of the retinal. Comparison of the absorption spectrum with the excitation spectrum for retinal emission yields 45 +/- 5% efficiency for the energy transfer. Such high efficiency would require close proximity and favorable geometry for the two polyene chains, but from the heptahelical crystallographic structure of the homologous retinal protein, bacteriorhodopsin, it is not clear where the carotenoid can be located near the retinal. The fluorescence excitation anisotropy spectrum reveals that the angle between their transition dipole moments is 56 +/- 3 degrees . The protein accommodates the carotenoid as a second chromophore in a distinct binding site to harvest light with both extended wavelength and polarization ranges. The results establish xanthorhodopsin as the simplest biological excited-state donor-acceptor system for collecting light.
Collapse
|