Activation of pausing F1 motor by external force
Activation of pausing F1 motor by external force
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DOI：
10.1073/pnas.0406486102
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发表时间：
2005-03-22
影响因子：
11.1
通讯作者：
Noji, H
中科院分区：
文献类型：
--
作者：
Hirono-Hara, Y;Ishuzuka, K;Noji, H
旋转电机 F-1 是 ATP 合酶的催化部分，由一个 ATP 的水解驱动进行 120 度步进旋转，其中包括分别由 ATP 结合以及可能由 ADP 和/或 P-i 解离引发的 800 度和 40 度分步。在主动旋转期间，F-1 自发地 ADP 释放失败，并在 80 度子步后暂停，这称为 ADP 抑制形式。在目前的工作中，我们发现，当用磁力镊子推动>+40度时，暂停的F-1在释放抑制性ADP后恢复其主动旋转。机械活化的速率常数随着推动角度呈指数增加，这意味着随着角度的前进，F-1 减弱了其催化位点对 ADP 的亲和力。这一发现不仅解释了它的单向旋转性质，还解释了它在 ATP 合成中的生理功能；当 ATP 合酶中的 F-o 电机向后旋转时，它很容易与溶液中的 ADP 结合。此外，强制旋转的机械功有效地转化为将ADP从催化位点排出的功，支持旋转和催化事件之间的紧密耦合。
A rotary motor F-1, a catalytic part of ATP synthase, makes a 120 degrees step rotation driven by hydrolysis of one ATP, which consists of 800 and 40 degrees substeps initiated by ATP binding and probably by ADP and/or P-i dissociation, respectively. During active rotations, F-1 spontaneously fails in ADP release and pauses after a 80 degrees substep, which is called the ADP-inhibited form. in the present work, we found that, when pushed >+40 degrees with magnetic tweezers, the pausing F-1 resumes its active rotation after releasing inhibitory ADP. The rate constant of the mechanical activation exponentially increased with the pushed angle, implying that F-1 weakens the affinity of its catalytic site for ADP as the angle goes forward. This finding explains not only its unidirectional nature of rotation, but also its physiological function in ATP synthesis; it would readily bind ADP from solution when rotated backward by an F-o motor in the ATP synthase. Furthermore, the mechanical work for the forced rotation was efficiently converted into work for expelling ADP from the catalytic site, supporting the tight coupling between the rotation and catalytic event.