Electrogenic Proton-Pumping Capabilities of the M-Fast and M-Slow Photocycles of Bacteriorhodopsin
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- 作者：Richard W. Hendler ; Curtis W. Meuse
- 刊名：Biochemistry
- 出版年：2008
- 出版时间：May 13, 2008
- 年：2008
- 卷：47
- 期：19
- 页码：5396 - 5405
- 全文大小：890K
- 年卷期：v.47,no.19(May 13, 2008)
- ISSN：1520-4995
文摘
The parallel model for the bacteriorhodopsin (BR) photocycle at neutral pH and a temperature near 20 °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 Mf 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.