Catch bond drives stator mechanosensitivity in the bacterial flagellar motor.
Catch bond drives stator mechanosensitivity in the bacterial flagellar motor.
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DOI：
10.1073/pnas.1716002114
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发表时间：
2017-12-05
影响因子：
11.1
通讯作者：
Pedaci F
中科院分区：
文献类型：
--
作者：
Nord AL;Gachon E;Perez-Carrasco R;Nirody JA;Barducci A;Berry RM;Pedaci F
细菌鞭毛马达（BFM）是许多能动细菌游动的旋转马达。这种分子机器的许多组成部分是动态的，这一特性允许细胞根据周围环境优化其行为。一个主要的例子是定子单元，一个膜结合的离子通道，负责向转子施加扭矩。定子单元是机械敏感的，接合单元的数量取决于电机上的粘性负载。我们测量定子的动力学作为粘性负载的函数，并发现BFM的mechanosensitivity是由一个捕捉键：一个违反直觉的类型的债券，在力下变得更强。细菌鞭毛马达（BFM）是旋转每个细菌鞭毛的旋转马达，为许多能动细菌的游泳和群集提供动力。扭矩由定子单元提供，已知在BFM中动态组装和拆卸的离子动力驱动的离子通道。这种翻转是机械敏感的，接合单元的数量取决于马达通过鞭毛所经历的粘性载荷。然而，驱动BFM机械敏感性的分子机制是未知的。在这里，我们通过分析高分辨率的电机速度记录，直接测量单个电机中定子单元的到达和离开的动力学，同时通过外部磁转矩动态地改变电机上的负载。所获得的动力学速率，相对于所应用的吸附模型的细节鲁棒，表明组装的定子单元的寿命增加时，更高的力施加到其在细胞壁中的锚定点。这提供了强有力的证据表明，一个捕捉债券（债券加强，而不是削弱的力量）驱动鞭毛电机复合体的机械敏感性。这些结果将BFM添加到一个简短但不断增长的展示捕获键的系统列表中，这表明这种“分子策略”是一种广泛的感知和响应机械应力的机制。我们建议，力增强定子粘附允许细胞适应异质性环境粘度，并可能最终发挥作用，在表面传感在群集和生物膜形成。
The bacterial flagellar motor (BFM) is the rotary motor powering swimming of many motile bacteria. Many of the components of this molecular machine are dynamic, a property which allows the cell to optimize its behavior in accordance with the surrounding environment. A prime example is the stator unit, a membrane-bound ion channel that is responsible for applying torque to the rotor. The stator units are mechanosensitive, with the number of engaged units dependent on the viscous load on the motor. We measure the kinetics of the stators as a function of the viscous load and find that the mechanosensitivity of the BFM is governed by a catch bond: a counterintuitive type of bond that becomes stronger under force. The bacterial flagellar motor (BFM) is the rotary motor that rotates each bacterial flagellum, powering the swimming and swarming of many motile bacteria. The torque is provided by stator units, ion motive force-powered ion channels known to assemble and disassemble dynamically in the BFM. This turnover is mechanosensitive, with the number of engaged units dependent on the viscous load experienced by the motor through the flagellum. However, the molecular mechanism driving BFM mechanosensitivity is unknown. Here, we directly measure the kinetics of arrival and departure of the stator units in individual motors via analysis of high-resolution recordings of motor speed, while dynamically varying the load on the motor via external magnetic torque. The kinetic rates obtained, robust with respect to the details of the applied adsorption model, indicate that the lifetime of an assembled stator unit increases when a higher force is applied to its anchoring point in the cell wall. This provides strong evidence that a catch bond (a bond strengthened instead of weakened by force) drives mechanosensitivity of the flagellar motor complex. These results add the BFM to a short, but growing, list of systems demonstrating catch bonds, suggesting that this “molecular strategy” is a widespread mechanism to sense and respond to mechanical stress. We propose that force-enhanced stator adhesion allows the cell to adapt to a heterogeneous environmental viscosity and may ultimately play a role in surface-sensing during swarming and biofilm formation.
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影响因子：
2.9
作者：
Kim, Eun A.;Price-Carter, Marian;Carlquist, William C.;Blair, David F.
通讯作者：
Blair, David F.
影响因子：
3
作者：
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Thirumalai D
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