Novel Insights into Conformational Rearrangements of the Bacterial Flagellar Switch Complex
Novel Insights into Conformational Rearrangements of the Bacterial Flagellar Switch Complex
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DOI：
10.1128/mbio.00079-19
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发表时间：
2019-04
期刊：
影响因子：
6.4
通讯作者：
Tomofumi Sakai;T. Miyata;Naoya Terahara;K. Mori;Y. Inoue;Yusuke V. Morimoto;Takayuki Kato;K. Namba;T. Minamino
中科院分区：
文献类型：
--
作者：
Tomofumi Sakai;T. Miyata;Naoya Terahara;K. Mori;Y. Inoue;Yusuke V. Morimoto;Takayuki Kato;K. Namba;T. Minamino
细菌鞭毛马达是一种双向旋转的运动和趋化马达，在感染过程中起着重要作用。马达是由转子和多个定子单元组成的大型跨膜蛋白复合物，其也充当质子通道。运动扭矩是通过它们的循环缔合和解离以及通过质子通道的质子移位产生的。马达的一个大的细胞质环，称为C环，通过与定子相互作用来负责旋转和切换，但其机制仍然未知。通过分析野生型电机和突变电机的结构和功能的C环连接本身与跨膜转子环，同时保持定子相互作用域的双向扭矩生成完整的缺失部分，我们发现有趣的线索，在C环构象的变化，开关和旋转，涉及松散和紧密的亚基间的相互作用。摘要鞭毛马达可以逆时针和顺时针旋转。鞭毛马达由一个转子和多个定子单元组成，它们充当质子通道。转子由FliF构成的跨膜MS环和FliG、FliM和FliN构成的细胞质C环组成。C环直接参与旋转和方向切换。沙门氏菌FliF-FliG缺失融合马达从FliF的C末端缺失56个残基和从FliG的N末端缺失94个残基，保持负责与定子相互作用的结构域完整，但其马达功能显著降低。在这里，我们报告的FliF-FliG缺失融合马达的结构和功能。FliF-FliG缺失融合不仅导致了强的CW开关偏置，而且还影响了转子-定子相互作用以及通过定子单元的质子通道的质子移位。缺失融合马达的能量偶联效率与野生型马达的能量偶联效率相同。FliG、FliM或FliN中的基因外抑制基因突变不仅减轻了强CW开关偏置，而且在低负载下增加了电机速度。与野生型马达相比，FliF-FliG缺失融合使C环蛋白之间的亚基间相互作用更紧密，而抑制突变影响这种更紧密的亚基间相互作用。我们建议，改变亚基之间的相互作用的C环蛋白可能需要高速电机旋转以及方向切换。细菌鞭毛马达是一种双向旋转的运动马达和趋化马达，在感染过程中起重要作用。马达是由转子和多个定子单元组成的大型跨膜蛋白复合物，其也充当质子通道。运动扭矩是通过它们的循环缔合和解离以及通过质子通道的质子移位产生的。马达的一个大的细胞质环，称为C环，通过与定子相互作用来负责旋转和切换，但其机制仍然未知。通过分析野生型电机和突变电机的结构和功能的C环连接本身与跨膜转子环，同时保持定子相互作用域的双向扭矩生成完整的缺失部分，我们发现有趣的线索，在C环构象的变化，开关和旋转，涉及松散和紧密的亚基间的相互作用。
The bacterial flagellar motor is a bidirectional rotary motor for motility and chemotaxis, which often plays an important role in infection. The motor is a large transmembrane protein complex composed of a rotor and multiple stator units, which also act as a proton channel. Motor torque is generated through their cyclic association and dissociation coupled with proton translocation through the proton channel. A large cytoplasmic ring of the motor, called C ring, is responsible for rotation and switching by interacting with the stator, but the mechanism remains unknown. By analyzing the structure and function of the wild-type motor and a mutant motor missing part of the C ring connecting itself with the transmembrane rotor ring while keeping a stator-interacting domain for bidirectional torque generation intact, we found interesting clues to the change in the C ring conformation for the switching and rotation involving loose and tight intersubunit interactions. ABSTRACT The flagellar motor can spin in both counterclockwise (CCW) and clockwise (CW) directions. The flagellar motor consists of a rotor and multiple stator units, which act as a proton channel. The rotor is composed of the transmembrane MS ring made of FliF and the cytoplasmic C ring consisting of FliG, FliM, and FliN. The C ring is directly involved in rotation and directional switching. The Salmonella FliF-FliG deletion fusion motor missing 56 residues from the C terminus of FliF and 94 residues from the N terminus of FliG keeps a domain responsible for the interaction with the stator intact, but its motor function is reduced significantly. Here, we report the structure and function of the FliF-FliG deletion fusion motor. The FliF-FliG deletion fusion not only resulted in a strong CW switch bias but also affected rotor-stator interactions coupled with proton translocation through the proton channel of the stator unit. The energy coupling efficiency of the deletion fusion motor was the same as that of the wild-type motor. Extragenic suppressor mutations in FliG, FliM, or FliN not only relieved the strong CW switch bias but also increased the motor speed at low load. The FliF-FliG deletion fusion made intersubunit interactions between C ring proteins tighter compared to the wild-type motor, whereas the suppressor mutations affect such tighter intersubunit interactions. We propose that a change of intersubunit interactions between the C ring proteins may be required for high-speed motor rotation as well as direction switching. IMPORTANCE The bacterial flagellar motor is a bidirectional rotary motor for motility and chemotaxis, which often plays an important role in infection. The motor is a large transmembrane protein complex composed of a rotor and multiple stator units, which also act as a proton channel. Motor torque is generated through their cyclic association and dissociation coupled with proton translocation through the proton channel. A large cytoplasmic ring of the motor, called C ring, is responsible for rotation and switching by interacting with the stator, but the mechanism remains unknown. By analyzing the structure and function of the wild-type motor and a mutant motor missing part of the C ring connecting itself with the transmembrane rotor ring while keeping a stator-interacting domain for bidirectional torque generation intact, we found interesting clues to the change in the C ring conformation for the switching and rotation involving loose and tight intersubunit interactions.