pH dependence of light‐induced proton release by bacteriorhodopsin

FEBS Letters

Ebrey, Thomas G.¹  Misra, Saurav¹  Kono, Masahiro¹ 

[1] Biophysics Program and Department of Cell and Structural Biology, University of Illinois, 156 Davenport Hall, Urbana, IL 61801, USA

关键词: Purple membrane;    Proton pump;   

DOI  :  10.1016/0014-5793(93)80291-2

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

We have measured the current generated by light-activated proton release from bacteriorhodopsin into solution as a function of both pH and ionic strength. We find that proton release into solution decreases with increasing pH with an intrinsic pK _a of 8.2 ± 0.2. This pH dependence indicates that the deprotonation of a certain group inhibits or abolishes proton release. Under physiological conditions, this group either releases a proton directly into solution or interacts with the site of proton release. The most immediate candidates for this protonatable species are tyrosine-57, tyrosine-185, arginine-82, and water; acting individually or cooperatively. The salt dependence of the apparent pK _a of this group also allows us to calculate the surface charge density of about −5 charges per bacteriorhodopsin, compatible with previous estimates.

【 授权许可】

Unknown