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Thomas YG, Szundi I, Lewis JW, Kliger DS. Microsecond time-resolved circular dichroism of rhodopsin photointermediates. Biochemistry 2010; 48:12283-9. [PMID: 19905009 DOI: 10.1021/bi901657b] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Time-resolved circular dichroism measurements, over a spectral range from 300 to 700 nm, were made at delays of 5, 100, and 500 micros after room-temperature photoexcitation of bovine rhodopsin in a lauryl maltoside suspension. The purpose was to provide more structural information about intermediate states in the activation of rhodopsin and other G protein-coupled receptors. In particular, information was sought about photointermediates that are isochromic or nearly isochromic in their unpolarized absorbance. The circular dichroism spectrum of lumirhodopsin, obtained after correcting the 5 micros difference CD data for the bleached rhodopsin, was in reasonable agreement with the lumirhodopsin CD spectrum obtained previously by thermal trapping at -76 degrees C. Similarly, the metarhodopsin II spectrum obtained with a 500 micros delay was also in agreement with the results of previous work on the temperature-trapped form of metarhodopsin II. However, the CD of the mixture formed with a 100 micros delay after photoexcitation, whose only visible absorbing component is lumirhodopsin, could not be accounted for near 480 nm in terms of the initially formed, 5 micros lumirhodopsin CD spectrum. Thus, the CD spectrum of lumirhodopsin changes on the time scale from 5 to 100 micros, showing reduced rotational strength in its visible band, possibly associated with either a process responsible for a small spectral shift that occurs in the lumirhodopsin absorbance spectrum at earlier times or the Schiff base deprotonation-reprotonation which occurs during equilibration of lumirhodopsin with the Meta I(380) photointermediate. Either explanation suggests a chromophore conformation change closely associated with deprotonation which could be the earliest direct trigger of activation.
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Affiliation(s)
- Yiren Gu Thomas
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, California 95064, USA
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Pescitelli G, Sreerama N, Salvadori P, Nakanishi K, Berova N, Woody RW. Inherent Chirality Dominates the Visible/Near-Ultraviolet CD Spectrum of Rhodopsin. J Am Chem Soc 2008; 130:6170-81. [DOI: 10.1021/ja711009y] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Affiliation(s)
- Gennaro Pescitelli
- Dipartimento di Chimica e Chimica Industriale, Università degli Studi di Pisa, via Risorgimento 35, I-56126 Pisa, Italy, Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, Colorado 80523, and Department of Chemistry, Columbia University, 3000 Broadway, MC 3114, New York 10027
| | - Narasimha Sreerama
- Dipartimento di Chimica e Chimica Industriale, Università degli Studi di Pisa, via Risorgimento 35, I-56126 Pisa, Italy, Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, Colorado 80523, and Department of Chemistry, Columbia University, 3000 Broadway, MC 3114, New York 10027
| | - Piero Salvadori
- Dipartimento di Chimica e Chimica Industriale, Università degli Studi di Pisa, via Risorgimento 35, I-56126 Pisa, Italy, Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, Colorado 80523, and Department of Chemistry, Columbia University, 3000 Broadway, MC 3114, New York 10027
| | - Koji Nakanishi
- Dipartimento di Chimica e Chimica Industriale, Università degli Studi di Pisa, via Risorgimento 35, I-56126 Pisa, Italy, Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, Colorado 80523, and Department of Chemistry, Columbia University, 3000 Broadway, MC 3114, New York 10027
| | - Nina Berova
- Dipartimento di Chimica e Chimica Industriale, Università degli Studi di Pisa, via Risorgimento 35, I-56126 Pisa, Italy, Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, Colorado 80523, and Department of Chemistry, Columbia University, 3000 Broadway, MC 3114, New York 10027
| | - Robert W. Woody
- Dipartimento di Chimica e Chimica Industriale, Università degli Studi di Pisa, via Risorgimento 35, I-56126 Pisa, Italy, Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, Colorado 80523, and Department of Chemistry, Columbia University, 3000 Broadway, MC 3114, New York 10027
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