Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, Connecticut, USA.
Microbial Sciences Institute, Yale University, West Haven, Connecticut, USA.
J Bacteriol. 2020 Jan 29;202(4). doi: 10.1128/JB.00592-19.
The bacterial flagellum is a biological nanomachine that rotates to allow bacteria to swim. For flagellar rotation, torque is generated by interactions between a rotor and a stator. The stator, which is composed of MotA and MotB subunit proteins in the membrane, is thought to bind to the peptidoglycan (PG) layer, which anchors the stator around the rotor. Detailed information on the stator and its interactions with the rotor remains unclear. Here, we deployed cryo-electron tomography and genetic analysis to characterize structure of the bacterial flagellar motor in , which is best known for its polar sheathed flagellum and high-speed rotation. We determined structure of the motor at unprecedented resolution and revealed the unique protein-protein interactions among -specific features, namely the H ring and T ring. Specifically, the H ring is composed of 26 copies of FlgT and FlgO, and the T ring consists of 26 copies of a MotX-MotY heterodimer. We revealed for the first time a specific interaction between the T ring and the stator PomB subunit, providing direct evidence that the stator unit undergoes a large conformational change from a compact form to an extended form. The T ring facilitates the recruitment of the extended stator units for the high-speed motility in species. The torque of flagellar rotation is generated by interactions between a rotor and a stator; however, detailed structural information is lacking. Here, we utilized cryo-electron tomography and advanced imaging analysis to obtain a high-resolution flagellar basal body structure in , which is a Gram-negative marine bacterium. Our high-resolution motor structure not only revealed detailed protein-protein interactions among unique -specific features, the T ring and H ring, but also provided the first structural evidence that the T ring interacts directly with the periplasmic domain of the stator. Docking atomic structures of key components into the motor map allowed us to visualize the pseudoatomic architecture of the polar sheathed flagellum in spp. and provides novel insight into its assembly and function.
细菌鞭毛是一种生物纳米机器，通过旋转使细菌能够游动。鞭毛旋转时，通过转子和定子之间的相互作用产生扭矩。定子由膜中的 MotA 和 MotB 亚基蛋白组成，被认为与肽聚糖（PG）层结合，将定子固定在转子周围。关于定子及其与转子相互作用的详细信息尚不清楚。在这里，我们通过冷冻电镜断层扫描和遗传分析来研究 细菌鞭毛马达的结构，这种鞭毛马达以其极性鞘鞭毛和高速旋转而闻名。我们以空前的分辨率确定了马达的结构，并揭示了独特的蛋白质-蛋白质相互作用，包括 H 环和 T 环。具体而言，H 环由 26 个 FlgT 和 FlgO 组成，而 T 环由 26 个 MotX-MotY 异二聚体组成。我们首次揭示了 T 环与定子 PomB 亚基之间的特异性相互作用，这为定子单元从紧凑形式到扩展形式发生大的构象变化提供了直接证据。T 环促进了扩展定子单元的募集，从而实现了 物种的高速运动。鞭毛旋转的扭矩是由转子和定子之间的相互作用产生的；然而，详细的结构信息是缺乏的。在这里，我们利用冷冻电镜断层扫描和先进的成像分析获得了高分辨率的 鞭毛基部结构，这是一种革兰氏阴性海洋细菌。我们的高分辨率马达结构不仅揭示了独特的 -特异性特征之间的详细蛋白质-蛋白质相互作用，包括 T 环和 H 环，而且还提供了第一个结构证据，表明 T 环与定子的周质域直接相互作用。将关键组件的原子结构对接到底物马达图谱中，使我们能够可视化 种极性鞘鞭毛的拟原子结构，并为其组装和功能提供了新的见解。
