Coupling between switching regulation and torque generation in bacterial flagellar motor.
Coupling between switching regulation and torque generation in bacterial flagellar motor.
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DOI：
10.1103/physrevlett.108.178105
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发表时间：
2012-04-27
影响因子：
8.6
通讯作者：
Xing J
中科院分区：
文献类型：
--
作者：
Bai F;Minamino T;Wu Z;Namba K;Xing J
细菌鞭毛运动在细菌运动和趋化中起着至关重要的作用。最近的实验表明，电机的开关动力学取决于电机的转速，因此电机转矩是非单调的。本文提出了基于实验转矩-速度曲线的电机转矩产生和基于构象扩散模型的转矩相关切换的统一数学模型。该模型成功地再现了观察到的开关速率作为旋转速度的函数，并提供了一个独立于大多数细节的通用物理解释。定子通过两种机制影响开关动力学：加速单个转子开关单元的构象翻转速率，当定子工作在高转矩和低速时，这一作用最大；并且在单位时间内影响较多的转矩单元，其贡献在电机高速旋转时最大。因此，切换速率在中等速度下显示最大值，此时上述两种机制找到最优输出。负载切换关系可以作为一种感知物理环境的机制，类似于感知化学环境的趋化机制。它还可以协调同一单元内电机的开关动态。
The bacterial flagellar motor plays a crucial role in both bacterial locomotion and chemotaxis. Recent experiments reveal that the switching dynamics of the motor depend on the rotation speed of the motor, and thus the motor torque, non-monotonically. Here we present a unified mathematical model which treats motor torque generation based on experimental torque-speed curves and the torque-dependent switching based on the conformational spread model. The model successfully reproduces the observed switching rate as a function of the rotation speed, and provides a generic physical explanation independent of most details. A stator affects the switching dynamics through two mechanisms: accelerating the conformational flipping rate of individual rotor-switching units, which contributes most when the stator works at a high torque and thus a low speed; and influencing a larger number of rotor-switching units within unit time, whose contribution is the greatest when the motor rotates at a high speed. Consequently, the switching rate shows a maximum at intermediate speed, where the above two mechanisms find an optimal output. The load-switching relation may serve as a mechanism for sensing the physical environment, similar to the chemotaxis mechanism for sensing the chemical environment. It may also coordinate the switch dynamics of motors within the same cell.