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Effects of Triton X-100 on proton transfer and in the photocycle of archaerhodopsin 4.

Authors
Type
Published Article
Journal
Bioscience Biotechnology and Biochemistry
1347-6947
Publisher
Informa UK (Taylor & Francis)
Publication Date
Volume
76
Issue
2
Pages
250–256
Identifiers
PMID: 22313750
Source
Medline
License
Unknown

Abstract

Archaerhodopsin 4 (AR4), a retinal-containing membrane protein, exhibits a reversed order of proton release and uptake at neutral pH, as compared to the well-known bacteriorhodopsin (BR). In a preceding report, we stated that Triton X-100 solubilized the claret membrane containing AR4 (CM) into monomeric proteins and altered the time order in AR4 at neutral pH. The present study examined the mechanism underlying this phenomenon. We employed a photoelectrochemical cell suitable for observation of the proton pumping behaviors of both the membrane patch and detergent-solubilized proteins over a wide pH range. The pK(a) values of the proton release complex (PRC) in the initial state and the M state were determined with this device. The pK(a) of PRC of monomeric AR4 decreased to a value lower than 7.0 in the photocycle, allowing early proton release at neutral pH. The pK(a) of PRC in the initial state was also strongly affected by solubilization.

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