The structure of the flagellar motor protein complex PomAB : Implications for the torque-generating conformation
The structure of the flagellar motor protein complex PomAB : Implications for the torque-generating conformation
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鞭毛运动蛋白复合物 PomAB 的结构：对扭矩生成构象的影响
DOI：
10.1128/jb.05021-11
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发表时间：
2011
期刊：
影响因子：
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通讯作者：
Michio Homma
中科院分区：
文献类型：
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作者：
Koji Yonekura;Saori Maki-Yonekura;Michio Homma
细菌鞭毛马达由离子流驱动，离子流通过大肠杆菌或沙门氏菌中称为MotAB的通道和溶藻弧菌中的PomAB。PomAB由两个跨膜（TM）组分PomA和PomB组成，并将钠离子通量转化为鞭毛的旋转。它的同系物MotAB利用质子而不是钠离子。PomB/MotB在周质结构域中具有肽聚糖（PG）结合基序，允许其通过锚定到PG层而起到定子的作用。为了产生扭矩，PomAB/MotAB被认为经历由离子通量触发的构象变化，并与转子的组件FliG直接相互作用。在这里，我们提出了第一个三维结构的这种扭矩产生定子单元的电子显微镜分析。PomAB的结构揭示了两个臂结构域，其包含PG结合位点，连接到由TM和胞质结构域组成的大碱基。臂向下倾斜到膜表面，可能表示“堵塞”构造，这将防止离子通过通道泄漏。我们提出了一个模型，PomAB单位被放置在鞭毛基体作为扭矩发生器。
The bacterial flagellar motor is driven by an ion flux through a channel called MotAB in Escherichia coli or Salmonella and PomAB in Vibrio alginolyticus. PomAB is composed of two transmembrane (TM) components, PomA and PomB, and converts a sodium ion flux to rotation of the flagellum. Its homolog, MotAB, utilizes protons instead of sodium ions. PomB/MotB has a peptidoglycan (PG)-binding motif in the periplasmic domain, allowing it to function as the stator by being anchored to the PG layer. To generate torque, PomAB/MotAB is thought to undergo a conformational change triggered by the ion flux and to interact directly with FliG, a component of the rotor. Here, we present the first three-dimensional structure of this torque-generating stator unit analyzed by electron microscopy. The structure of PomAB revealed two arm domains, which contain the PG-binding site, connected to a large base made of the TM and cytoplasmic domains. The arms lean downward to the membrane surface, likely representing a “plugged” conformation, which would prevent ions leaking through the channel. We propose a model for how PomAB units are placed around the flagellar basal body to function as torque generators.