Structure of Vibrio FliL, a New Stomatin-like Protein That Assists the Bacterial Flagellar Motor Function
Structure of Vibrio FliL, a New Stomatin-like Protein That Assists the Bacterial Flagellar Motor Function
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DOI：
10.1128/mbio.00292-19
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发表时间：
2019-03-01
期刊：
影响因子：
6.4
通讯作者：
Imada, Katsumi
中科院分区：
文献类型：
--
作者：
Takekawa, Norihiro;Isumi, Miyu;Imada, Katsumi
许多能动的细菌利用丝状旋转细胞器鞭毛游动或群集。FliL是鞭毛马达的组成蛋白，已知在某些细菌中在高负荷条件下增强马达性能。在这里，我们确定了溶藻弧菌极鞭毛的FliL（FliL（Peri））的周质区的结构。FliL（Peri）显示出与气孔蛋白家族蛋白的气孔蛋白/抑制蛋白/flotillin/HflK/C（SPFH）结构域的显著结构相似性，其中一些涉及多种生物体中离子通道活性的调节。FliL（Peri）在晶体中形成环组装，内径约为8 nm，与定子单元的尺寸相当。突变分析表明，FliL环与定子单元形成复合物，并且FliL和定子B亚基的周质接头的长度对于复合物的形成是必不可少的。我们提出了一个模型的FliL定子复合物来讨论如何弧菌FliL调制定子功能的条件下，高viscosity.IMPORTANCE一些鞭毛细菌调节电机转矩响应外部负载的变化。这种行为对生存至关重要，但其机制仍然未知。本论文以溶藻弧菌的一个关键蛋白FliL为研究对象，对其周质区的晶体结构进行了解析。FliL（Peri）揭示了与气孔蛋白的保守结构域的惊人的结构相似性，气孔蛋白在一些生物体（包括哺乳动物）中参与离子通道调节。FliL（Peri）形成一个内径与定子单元尺寸相当的环。突变分析表明，定子单元周围FliL的环状组装体的存在增强了弧菌细胞的表面群集。我们的研究数据还表明，从细菌到哺乳动物，离子通道调节的结构元件是保守的。
Many motile bacteria swim or swarm using a filamentous rotating organelle, the flagellum. FliL, a component protein of the flagellar motor, is known to enhance the motor performance under high-load conditions in some bacteria. Here we determined the structure of the periplasmic region of FliL (FliL(Peri)) of the polar flagellum of Vibrio alginolyticus. FliL(Peri) shows a remarkable structural similarity to the stomatin/prohibitin/flotillin/HflK/C (SPFH) domain of stomatin family proteins, some of which are involved in modulation of ion channel activities in various organisms. FliL(Peri) forms a ring assembly in the crystal with an inner diameter of around 8 nm ,which is comparable to the size of the stator unit. Mutational analyses suggest that the FliL ring forms a complex with the stator unit and that the length of the periplasmic linkers of FliL and the stator B-subunit is essential for the complex formation. We propose a model of the FliL-stator complex to discuss how Vibrio FliL modulates stator function in the bacterial flagellar motor under conditions of high viscosity.IMPORTANCE Some flagellated bacteria regulate motor torque in response to the external load change. This behavior is critical for survival, but the mechanism has remained unknown. Here, we focused on a key protein, FliL of Vibrio alginolyticus, and solved the crystal structure of its periplasmic region (FliL(Peri)). FliL(Peri) reveals striking structural similarity to a conserved domain of stomatin, which is involved in ion channel regulation in some organisms, including mammals. FliL(Peri) forms a ring with an inner diameter that is comparable in size to the stator unit. The mutational analyses suggested that the presence of the ring-like assembly of FliL around the stator unit enhances the surface swarming of Vibrio cells. Our study data also imply that the structural element for the ion channel regulation is conserved from bacteria to mammals.