Institute for Protein Research, Osaka University, 3-2 Yamadaoka, Suita, Osaka 565-0871, Japan.
Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan.
J Biochem. 2022 Mar 31;171(4):443-450. doi: 10.1093/jb/mvac001.
Vibrio has 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.
弧菌有一个由钠离子驱动的极性鞭毛用于游泳。力产生定子单元由 PomA 和 PomB 组成。PomA 包含四个跨膜区域和大约 100 个残基的细胞质结构域，与旋转蛋白 FliG 相互作用对于旋转的力产生很重要。定子的 3D 结构表明，PomA 的胞质界面（CI）螺旋与内膜平行。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。系统脯氨酸突变显示残基 K64、F66 和 M67 对该功能很重要。突变定子没有围绕转子组装。此外，PomB 插件缺失引起的生长缺陷被这些突变所抑制。我们推测这些突变会影响从 TM3 和 TM4 延伸的螺旋的结构，并降低定子复合物的结构稳定性。这项研究表明，与内膜平行的螺旋在各种过程中发挥重要作用，例如在确保定子复合物稳定性的箍状功能和离子传导途径，这可能有助于阐明定子的离子渗透和组装机制。
