F1F0 ATP synthase (ATPase) either facilitates the synthesis of ATP in themitochondrial membranes and bacterial inner membranes in a process driven bythe proton moving force (pmf), or uses the energy from ATP hydrolysis to pumpprotons against the concentration gradient across the membrane. ATPase iscomposed of two rotary motors, F0 and F1, which generate the opposing rotationand compete for control of their shared central gamma-shaft. Here we present aself-consistent physical model of the F1 motor as a simplified two-stateBrownian ratchet based on the asymmetry of torsional elastic energy of thecoiled-coil gamma-shaft. This stochastic model unifies the physical descriptionof linear and rotary motors and explains the stepped unidirectional rotation ofthe $\gamma$-shaft, in agreement with the `binding-change' ideas of Boyer.Substituting the model parameters, all independently known from recentexperiments, our model quantitatively reproduces the ATPase operation, e.g. the`no-load' angular velocity is ca. 400~rad/s anticlockwise at 4 mM ATP, in closeagreement with experiment. Increasing the pmf torque exerted by F0 can slow,stop and overcome the torque generated by F1, switching from ATP hydrolysis tosynthesis at a very low value of `stall torque'. We discuss the matters of themotor efficiency, which is very low if calculated from the useful mechanicalwork it produces - but is quite high when the `useful outcome' is measured inthe number of H+ pushed against the chemical gradient in the F1 ATP-drivenoperation.
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机译：F1F0 ATP合酶（ATPase）可以在质子移动力（pmf）驱动的过程中促进线粒体膜和细菌内膜中ATP的合成，也可以利用ATP水解的能量逆着跨膜的浓度梯度泵送质子。 ATPase由两个旋转电机F0和F1组成，它们产生相反的旋转并竞争控制它们共享的中央伽马轴。在这里，我们基于线圈螺旋伽玛轴的扭转弹性能的不对称性，提出了F1电动机的自洽物理模型，作为简化的两态布朗棘轮。这个随机模型统一了线性和旋转电机的物理描述，并解释了\\γ$轴的单向步进旋转，这与博耶（Boyer）的“装订变化”思想相一致。模型定量地再现ATPase操作，例如空载角速度约为在4 mM ATP下逆时针旋转400〜rad / s，与实验结果基本一致。增加F0施加的pmf转矩可以减慢，停止并克服F1产生的转矩，从而以非常低的“失速转矩”值从ATP水解转变为合成。我们讨论了电动机效率的问题，如果通过电动机产生的有用机械功来计算，电动机效率是非常低的；但是，在F1 ATP驱动的操作中，相对于化学梯度推入的H +数量来衡量“有用的结果”时，电动机效率非常高。
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