The C-terminal periplasmic domain of MotB is responsible for load-dependent control of the number of stators of the bacterial flagellar motor.
The C-terminal periplasmic domain of MotB is responsible for load-dependent control of the number of stators of the bacterial flagellar motor.
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DOI：
10.2142/biophysics.9.173
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发表时间：
2013
期刊：
影响因子：
--
通讯作者：
Namba K
中科院分区：
文献类型：
--
作者：
Castillo DJ;Nakamura S;Morimoto YV;Che YS;Kami-Ike N;Kudo S;Minamino T;Namba K
细菌鞭毛马达由转子和定子组成。在沙门氏菌中，大约有12个MotA/B复合物通过MotB的c端肽聚糖结合域锚定在马达周围的肽聚糖层上，成为活性定子和质子通道。MotB由309个残基组成，形成一个单跨膜螺旋（30-50），一个柄（51-100）和一个c端肽聚糖结合域（101-309）。虽然电机产生转矩时，柄是可有可无的，但它是高效电机性能所必需的。残留51至72防止在定子组装进入电机之前通过质子通道过早泄漏质子。然而，残基72-100的作用仍然未知。在这里，我们分析了MotB（Δ72-100）电机的转矩-转速关系。在接近失速的低速下，这个突变的马达产生了野生型的扭矩。然而，与野生型电机不同的是，扭矩在外部负载的轻微减少下急剧下降，然后在更大的负载范围内进一步减少，显示出缓慢的指数衰减。由于已知定子是一个机械传感器，并且有源定子的数量以负载相关的方式变化，因此我们将这种不寻常的转矩-速度关系解释为有源定子数量的负载相关控制中的异常。结果表明，对转子周围活动定子的数量进行适当的负载相关控制需要72-100的MotB残留量。
The bacterial flagellar motor is made of a rotor and stators. In Salmonella it is thought that about a dozen MotA/B complexes are anchored to the peptidoglycan layer around the motor through the C-terminal peptidoglycan-binding domain of MotB to become active stators as well as proton channels. MotB consists of 309 residues, forming a single transmembrane helix (30–50), a stalk (51–100) and a C-terminal peptidoglycan-binding domain (101–309). Although the stalk is dispensable for torque generation by the motor, it is required for efficient motor performance. Residues 51 to 72 prevent premature proton leakage through the proton channel prior to stator assembly into the motor. However, the role of residues 72–100 remains unknown. Here, we analyzed the torque-speed relationship of the MotB(Δ72–100) motor. At a low speed near stall, this mutant motor produced torque at the wild-type level. Unlike the wild-type motor, however, torque dropped off drastically by slight decrease in external load and then showed a slow exponential decay over a wide range of load by its further reduction. Since it is known that the stator is a mechano-sensor and that the number of active stators changes in a load-dependent manner, we interpreted this unusual torque-speed relationship as anomaly in load-dependent control of the number of active stators. The results suggest that residues 72–100 of MotB is required for proper load-dependent control of the number of active stators around the rotor.