Department of Physics, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan.
Department of Physics, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan.
Biophys J. 2014 Jun 3;106(11):2450-7. doi: 10.1016/j.bpj.2014.04.034.
F1-ATPase (or F1), the highly efficient and reversible biochemical engine, has motivated physicists as well as biologists to imagine the design principles governing machines in the fluctuating world. Recent experiments have clarified yet another interesting property of F1; the dissipative heat inside the motor is very small, irrespective of the velocity of rotation and energy transport. Conceptual interest is devoted to the fact that the amount of internal dissipation is not simply determined by the sequence of equilibrium pictures, but also relies on the rotational-angular dependence of nucleotide affinity, which is a truly nonequilibrium aspect. We propose that the totally asymmetric allosteric model (TASAM), where adenosine triphosphate (ATP) binding to F1 is assumed to have low dependence on the angle of the rotating shaft, produces results that are most consistent with the experiments. Theoretical analysis proves the crucial role of two time scales in the model, which explains the universal mechanism to produce the internal dissipation-free feature. The model reproduces the characteristic torque dependence of the rotational velocity of F1 and predicts that the internal dissipation upon the ATP synthesis direction rotation becomes large at the low nucleotide condition.
F1-ATP 酶（或 F1）是一种高效且可逆的生化引擎，激发了物理学家和生物学家去想象在波动的世界中控制机器的设计原理。最近的实验阐明了 F1 的另一个有趣的特性；无论旋转速度和能量传递如何，发动机内部的耗散热量都非常小。概念上的兴趣在于耗散的量不仅仅取决于平衡图的顺序，还依赖于核苷酸亲和力的旋转角依赖性，这是一个真正的非平衡方面。我们提出了全不对称变构模型（TASAM），其中假设 F1 中三磷酸腺苷（ATP）的结合对旋转轴的角度依赖性较低，该模型产生的结果与实验最一致。理论分析证明了模型中两个时间尺度的关键作用，这解释了产生内部无耗散特征的普遍机制。该模型再现了 F1 旋转速度的特征扭矩依赖性，并预测在低核苷酸条件下，ATP 合成方向旋转的内部耗散会变大。
