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Proton-Pumping Capabilities of the M-Fast and M-Slow Photocycles of Bacteriorhodopsin



R W. Hendler, John Kakareka, P D. Smith, T J. Pohida, Curtis W. Meuse


The parallel model for the bacteriorhodopsin (BR) photocycle at neutral pH and a temperature near 20 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 Mfast 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 as well as 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 data in these studies were collected by a newly designed and built spectrometer which is described in the Appendix of the paper.
Journal of Physical Chemistry B


bacteriorhodopsin, M-fast cycle, M-slow cycle, peak current, proton flux, proton-charge displacement, saturation behavior


Hendler, R. , Kakareka, J. , Smith, P. , Pohida, T. and Meuse, C. (2021), Proton-Pumping Capabilities of the M-Fast and M-Slow Photocycles of Bacteriorhodopsin, Journal of Physical Chemistry B (Accessed May 28, 2024)


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Created October 12, 2021