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：19
页码：4960-4965
DOI：10.1073/pnas.1700801114
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：FoF1-ATP synthase (FoF1) couples H+ flow in Fo domain and ATP synthesis/hydrolysis in F1 domain through rotation of the central rotor shaft, and the H+/ATP ratio is crucial to understand the coupling mechanism and energy yield in cells. Although H+/ATP ratio of the perfectly coupling enzyme can be predicted from the copy number of catalytic β subunits and that of H+ binding c subunits as c /β, the actual H+/ATP ratio can vary depending on coupling efficiency. Here, we report actual H+/ATP ratio of thermophilic Bacillus FoF1, whose c /β is 10/3. Proteoliposomes reconstituted with the FoF1 were energized with ΔpH and Δψ by the acid−base transition and by valinomycin-mediated diffusion potential of K+ under various [ATP]/([ADP]⋅[Pi]) conditions, and the initial rate of ATP synthesis/hydrolysis was measured. Analyses of thermodynamically equilibrated states, where net ATP synthesis/hydrolysis is zero, show linear correlation between the chemical potential of ATP synthesis/hydrolysis and the proton motive force, giving the slope of the linear function, that is, H+/ATP ratio, 3.3 ± 0.1. This value agrees well with the c /β ratio. Thus, chemomechanical coupling between Fo and F1 is perfect.
关键词：FoF1-ATP synthase ; chemiosmotic coupling theory ; ATPase ; proton motive force ; electrochemical potential
