The role of a cytoplasmic loop of MotA in load‐dependent assembly and disassembly dynamics of the MotA/B stator complex in the bacterial flagellar motor
The role of a cytoplasmic loop of MotA in load‐dependent assembly and disassembly dynamics of the MotA/B stator complex in the bacterial flagellar motor
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DOI：
10.1111/mmi.13843
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发表时间：
2017-11
影响因子：
3.6
通讯作者：
Seyedeh Noorolhoda Shajari Pourjaberi;Naoya Terahara;K. Namba;T. Minamino
中科院分区：
文献类型：
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作者：
Seyedeh Noorolhoda Shajari Pourjaberi;Naoya Terahara;K. Namba;T. Minamino
肠沙门氏菌的质子驱动鞭毛马达可以以负载依赖的方式容纳12个MotA/B定子。MotB的C端质周结构域作为一个结构开关，在响应负载变化时调节电机中有源定子的数量。称为MotAC的细胞质环负责与旋翼蛋白FliG相互作用。在这里，为了测试MotAC是否以负载依赖的方式负责转子周围的定子组装，我们分析了MotAC突变M76V， L78W, Y83C, Y83H, I126F, R131L， A145E和E155K在广泛的外部负载下对电机性能的影响。所有这些MotAC突变都将马达的最大速度降低到接近零负载，这表明它们降低了MotAC的构象动力学速率，并通过MotA/B质子通道进行质子易位。与野生型电机相比，M76V、Y83H和A145E突变促进了定子与转子的分离，减少了负载。在极高的负载下，E155K突变将电机中的主动定子数量从10个减少到6个。我们提出MotAC负责MotA/B定子单元的负载相关的组装和拆卸动力学。
The proton‐driven flagellar motor of Salmonella enterica can accommodate a dozen MotA/B stators in a load‐dependent manner. The C‐terminal periplasmic domain of MotB acts as a structural switch to regulate the number of active stators in the motor in response to load change. The cytoplasmic loop termed MotAC is responsible for the interaction with a rotor protein, FliG. Here, to test if MotAC is responsible for stator assembly around the rotor in a load‐dependent manner, we analyzed the effect of MotAC mutations, M76V, L78W, Y83C, Y83H, I126F, R131L, A145E and E155K, on motor performance over a wide range of external load. All these MotAC mutations reduced the maximum speed of the motor near zero load, suggesting that they reduce the rate of conformational dynamics of MotAC coupled with proton translocation through the MotA/B proton channel. Dissociation of the stators from the rotor by decrease in the load was facilitated by the M76V, Y83H and A145E mutations compared to the wild‐type motor. The E155K mutation reduced the number of active stators in the motor from 10 to 6 under extremely high load. We propose that MotAC is responsible for load‐dependent assembly and disassembly dynamics of the MotA/B stator units.