Hoop-like role of the cytosolic interface helix in Vibrio PomA, an ion-conducting membrane protein, in the bacterial flagellar motor
Hoop-like role of the cytosolic interface helix in Vibrio PomA, an ion-conducting membrane protein, in the bacterial flagellar motor
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DOI：
10.1093/jb/mvac001
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发表时间：
2022-03-31
影响因子：
2.7
通讯作者：
Kojima，Seiji
中科院分区：
文献类型：
--
作者：
Nishikino，Tatsuro;Sagara，Yugo;Kojima，Seiji
弧菌有一个由钠离子驱动的极性鞭毛，用于游泳。发电定子单元由PomA和PomB组成。PomA包含四个跨膜区和一个约100个残基的胞质结构域，其与转子蛋白FliG相互作用，对于旋转力的产生是重要的。定子的3D结构显示PomA的胞质界面（CI）螺旋平行于内膜定位。在这项研究中，我们研究了CI螺旋的功能及其作为定子的作用。系统的脯氨酸诱变表明残基K64、F66和M67对于该功能是重要的。变异的定子没有组装在转子周围。此外，这些突变抑制了由PomB插入缺失引起的生长缺陷。我们推测，突变影响的螺旋结构从TM3和TM4延伸，并降低定子复合物的结构稳定性。本研究表明，平行于内膜的螺旋在多个过程中发挥重要作用，如在确保定子复合物的稳定性和离子传导途径中的环状功能，这可能导致阐明定子的离子渗透和组装机制。
Vibriohas a polar flagellum driven by sodium ions for swimming. The force-generating stator unit consists of PomA and PomB. PomA contains four transmembrane regions and a cytoplasmic domain of approximately 100 residues, which interacts with the rotor protein, FliG, to be important for the force generation of rotation. The 3D structure of the stator shows that the cytosolic interface (CI) helix of PomA is located parallel to the inner membrane. In this study, we investigated the function of CI helix and its role as stator. Systematic proline mutagenesis showed that residues K64, F66 and M67 were important for this function. The mutant stators did not assemble around the rotor. Moreover, the growth defect caused by PomB plug deletion was suppressed by these mutations. We speculate that the mutations affect the structure of the helices extending from TM3 and TM4 and reduce the structural stability of the stator complex. This study suggests that the helices parallel to the inner membrane play important roles in various processes, such as the hoop-like function in securing the stability of the stator complex and the ion conduction pathway, which may lead to the elucidation of the ion permeation and assembly mechanism of the stator.