Electrogenic proton-pumping capabilities of the m-fast and m-slow photocycles of bacteriorhodopsin.

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TitleElectrogenic proton-pumping capabilities of the m-fast and m-slow photocycles of bacteriorhodopsin.
Publication TypeJournal Article
Year of Publication2008
AuthorsHendler, RW, Meuse, CW
JournalBiochemistry
Volume47
Issue19
Pagination5396-405
Date Published2008 May 13
ISSN1520-4995
KeywordsBacteriorhodopsins, Electrons, Halobacterium salinarum, Kinetics, Photochemistry, Time Factors
Abstract

The parallel model for the bacteriorhodopsin (BR) photocycle at neutral pH and a temperature near 20 degrees C contains an M-fast cycle with steps BR-->K-->L-->Mf-->N-->O-->BR and an M-slow cycle which contains steps BR-->K-->L-->Ms-->BR. With increasing actinic laser strength, the M-fast cycle at first rises faster than the M-slow cycle, but reaches saturation sooner and at a lower level than the M-slow cycle. The O-intermediate shows the same saturation behavior as Mf. In this paper, we show that the peak current of proton flux and the apparent voltages developed by this flux show the same saturation behavior as Ms, which is very different from that of both M f and O. It is further shown that most of the proton-charge displacement is connected with the step Ms-->BR. The optical and electrical data in these studies were collected simultaneously by a newly designed and built spectrometer which is described separately.

DOI10.1021/bi701748n
Alternate JournalBiochemistry
PubMed ID18422349
PubMed Central IDPMC2679990
Grant ListZ01 HL000518-04 / HL / NHLBI NIH HHS / United States
Z99 HL999999 / HL / NHLBI NIH HHS / United States