The flagellar motor of Vibrio alginolyticus undergoes major structural remodeling during rotational switching.
The flagellar motor of Vibrio alginolyticus undergoes major structural remodeling during rotational switching.
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作者：
Carroll BL;Nishikino T;Guo W;Zhu S;Kojima S;Homma M;Liu J
细菌鞭毛马达在逆时针（CCW）和顺时针（CW）之间切换旋转方向以指导细胞的迁移。马达的细胞质环（C环）由FliG、FliM和FliN组成，已知用于控制鞭毛的旋转感。然而，旋转开关的机制仍然难以捉摸。在这里，我们部署冷冻电子断层扫描可视化溶藻弧菌的两个旋转偏置突变体的C环。我们确定了C-环的分子结构，提供了新的见解旋转开关的机制。我们报告说，C-环保持34倍对称性在两个旋转的意义上，和蛋白质的组成保持不变。这两种结构显示FliG构象变化引起转子复合物的大的构象重排，其与鞭毛的旋转切换一致。FliM和FliN形成C环的稳定螺旋形基部，可能在构象重塑期间稳定C环。
The bacterial flagellar motor switches rotational direction between counterclockwise (CCW) and clockwise (CW) to direct the migration of the cell. The cytoplasmic ring (C-ring) of the motor, which is composed of FliG, FliM, and FliN, is known for controlling the rotational sense of the flagellum. However, the mechanism underlying rotational switching remains elusive. Here, we deployed cryo-electron tomography to visualize the C-ring in two rotational biased mutants in Vibrio alginolyticus. We determined the C-ring molecular architectures, providing novel insights into the mechanism of rotational switching. We report that the C-ring maintained 34-fold symmetry in both rotational senses, and the protein composition remained constant. The two structures show FliG conformational changes elicit a large conformational rearrangement of the rotor complex that coincides with rotational switching of the flagellum. FliM and FliN form a stable spiral-shaped base of the C-ring, likely stabilizing the C-ring during the conformational remodeling.