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：2018
卷号：115
期号：22
页码：5750-5755
DOI：10.1073/pnas.1803147115
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：The angular velocity profile of the 120° F1-ATPase power stroke was resolved as a function of temperature from 16.3 to 44.6 °C using a ΔμATP = −31.25 k B T at a time resolution of 10 μs. Angular velocities during the first 60° of the power stroke (phase 1) varied inversely with temperature, resulting in negative activation energies with a parabolic dependence. This is direct evidence that phase 1 rotation derives from elastic energy (spring constant, κ = 50 k B T ·rad−2). Phase 2 of the power stroke had an enthalpic component indicating that additional energy input occurred to enable the γ-subunit to overcome energy stored by the spring after rotating beyond its 34° equilibrium position. The correlation between the probability distribution of ATP binding to the empty catalytic site and the negative E a values of the power stroke during phase 1 suggests that this additional energy is derived from the binding of ATP to the empty catalytic site. A second torsion spring (κ = 150 k B T ·rad−2; equilibrium position, 90°) was also evident that mitigated the enthalpic cost of phase 2 rotation. The maximum Δ G ǂ was 22.6 k B T , and maximum efficiency was 72%. An elastic coupling mechanism is proposed that uses the coiled-coil domain of the γ-subunit rotor as a torsion spring during phase 1, and then as a crankshaft driven by ATP-binding–dependent conformational changes during phase 2 to drive the power stroke.
关键词：F1-ATPase ; F-type ATP synthase ; single molecule ; FOF1 ATP synthase ; power stroke mechanism
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