Interconversions of the M, N, and O intermediates in the bacteriorhodopsin photocycle

Journal Article · Tue Apr 10 04:00:00 EDT 1990 · Biochemistry; (USA)

DOI:https://doi.org/10.1021/bi00467a029· OSTI ID:6194099

Varo, G; Duschl, A; Lanyi, J K ^[1]

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1. Univ. of California, Irvine (USA)

The reaction sequence in the second half of the bacteriorhodopsin (BR) photocycle (i.e., the steps which involve the M,N, and O intermediates) was investigated with a gated multichannel analyzer. The difference spectra, obtained between 0.4 and 25 ms after laser photoexcitation, were converted to absolute spectra of the mixtures of intermediates at each delay time. From these, the time courses of the concentrations of M,N, O, and BR in a single turnover were reconstructed. The authors found that in 1 M Na{sub 2}SO{sub 4}, between pH 4 and 7, the measurements were not complicated by multiple kinetic forms of M; thus, the progressive changes in the rise and decay kinetics of N and O, as well as the recovery of BR, with pH could be followed. The data are inconsistent with a linear sequence but suggest a model in which N is produced directly from M, and returns to BR via two pathways. The individual rate constants of the reactions vary characteristically with pH. Comparison of these results with the initial rate of proton transport between pH 4 and 7 indicates that proton translocation does not require that the BR photocycle pass through O.

• OSTI ID: 6194099
• Journal Information: Biochemistry; (USA), Journal Name: Biochemistry; (USA) Vol. 29:14; ISSN 0006-2960; ISSN BICHA
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
140505* -- Solar Energy Conversion-- Photochemical
Photobiological
& Thermochemical Conversion-- (1980-)
ABSORPTION SPECTRA
CHEMICAL REACTIONS
MEMBRANES
ORGANIC COMPOUNDS
PH VALUE
PHOTOCHEMICAL REACTIONS
PHOTOSYNTHESIS
PHOTOSYNTHETIC BACTERIA
PHOTOSYNTHETIC MEMBRANES
PIGMENTS
PROTEINS
REACTION INTERMEDIATES
RHODOPSIN
SPECTRA
SYNTHESIS