Subunit III-depleted cytochrome c oxidase provides insight into the process of proton uptake by proteins

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• 作者：Lakshman Varanasi ^{lvaranasi@umc.edu} ; Jonathan P. Hosler ; ^{jhosler@umc.edu}
• 关键词：Aa ; arachidonic acid ; CC ; catalytic cycle ; CcO III (&minus ; ) ; cytochrome c oxidase lacking subunit III ; TN ; turnover number ; as e鈹€ or H+ consumed per second per CcO
• 刊名：Biochimica et Biophysica Acta (BBA)/Bioenergetics
• 出版年：2012
• 期刊代码：13_00052728
• 类别：bio
• 出版时间：April, 2012
• 卷：1817
• 期：4
• 页码：545-551
• 文件大小：631 K

摘要

We review studies of subunit III-depleted cytochrome c oxidase (CcO III (鈭?) that elucidate the structural basis of steady-state proton uptake from solvent into an internal proton transfer pathway. The removal of subunit III from R. sphaeroides CcO makes proton uptake into the D pathway a rate-determining step, such that measurements of the pH dependence of steady-state O₂ consumption can be used to compare the rate and functional pK_a of proton uptake by D pathways containing different initial proton acceptors. The removal of subunit III also promotes spontaneous suicide inactivation by CcO, greatly shortening its catalytic lifespan. Because the probability of suicide inactivation is controlled by the rate at which the D pathway delivers protons to the active site, measurements of catalytic lifespan provide a second method to compare the relative efficacy of proton uptake by engineered CcO III (鈭? forms. These simple experimental systems have been used to explore general questions of proton uptake by proteins, such as the functional value of an initial proton acceptor, whether an initial acceptor must be surface-exposed, which side chains will function as initial proton acceptors and whether multiple acceptors can speed proton uptake. This article is part of a Special Issue entitled: Respiratory Oxidases.