文章基本信息

标题：Understanding the essential proton-pumping kinetic gates and decoupling mutations in cytochrome c oxidase
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作者：Ruibin Liang ; Jessica M. J. Swanson ; Mårten Wikström 等
期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2017
卷号：114
期号：23
页码：5924-5929
DOI：10.1073/pnas.1703654114
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Cytochrome c oxidase (C c O) catalyzes the reduction of oxygen to water and uses the released free energy to pump protons against the transmembrane proton gradient. To better understand the proton-pumping mechanism of the wild-type (WT) C c O, much attention has been given to the mutation of amino acid residues along the proton translocating D-channel that impair, and sometimes decouple, proton pumping from the chemical catalysis. Although their influence has been clearly demonstrated experimentally, the underlying molecular mechanisms of these mutants remain unknown. In this work, we report multiscale reactive molecular dynamics simulations that characterize the free-energy profiles of explicit proton transport through several important D-channel mutants. Our results elucidate the mechanisms by which proton pumping is impaired, thus revealing key kinetic gating features in C c O. In the N139T and N139C mutants, proton back leakage through the D-channel is kinetically favored over proton pumping due to the loss of a kinetic gate in the N139 region. In the N139L mutant, the bulky L139 side chain inhibits timely reprotonation of E286 through the D-channel, which impairs both proton pumping and the chemical reaction. In the S200V/S201V double mutant, the proton affinity of E286 is increased, which slows down both proton pumping and the chemical catalysis. This work thus not only provides insight into the decoupling mechanisms of C c O mutants, but also explains how kinetic gating in the D-channel is imperative to achieving high proton-pumping efficiency in the WT C c O.
关键词：proton pump ; decoupling mutants ; cytochrome c oxidase ; proton transport ; multiscale