Zhu Shiwei, Kumar Ananthanarayanan, Kojima Seiji, Homma Michio
Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya, 464-8602, Japan.
Mol Microbiol. 2015 Oct;98(1):101-10. doi: 10.1111/mmi.13103. Epub 2015 Jul 17.
Flagellar motors generate torque to rotate flagellar filaments and drive bacterial cells. Each motor is composed of a rotor and many stators. The stator is a force-generating complex that converts ion flux into torque. Previous reports have suggested that the membrane protein FliL is located near the stator and is involved in torque generation. We investigated the role of FliL in the sodium-driven polar flagellar motor of Vibrio alginolyticus. Our results revealed that FliL is a cytoplasmic membrane protein and is located at the base of flagellum. The deletion of fliL did not affect the cell morphology or flagellation but resulted in a significant decrease of swimming speed, especially at a higher load thus suggesting that FliL is important for torque generation at high load conditions. Furthermore, the polar localization of the stator was decreased in a ΔfliL mutant, but the sodium-dependent assembly of the stator complex was still retained. The polar localization of FliL was lost in the absence of the stator complex, indicating that FliL interacts directly or indirectly with the stator. Our results suggest that FliL is localized along with the stator in order to support the motor functioning for swimming at high load conditions by maintaining the stator assembly.
鞭毛马达产生扭矩以旋转鞭毛丝并驱动细菌细胞。每个马达由一个转子和许多定子组成。定子是一个将离子通量转化为扭矩的力产生复合体。先前的报道表明，膜蛋白FliL位于定子附近并参与扭矩的产生。我们研究了FliL在溶藻弧菌钠驱动的极鞭毛马达中的作用。我们的结果表明，FliL是一种细胞质膜蛋白，位于鞭毛基部。fliL的缺失不影响细胞形态或鞭毛形成，但导致游泳速度显著降低，尤其是在较高负载下，这表明FliL在高负载条件下对扭矩产生很重要。此外，在ΔfliL突变体中，定子的极性定位降低，但定子复合体的钠依赖性组装仍保留。在没有定子复合体的情况下，FliL的极性定位丧失，表明FliL与定子直接或间接相互作用。我们的结果表明，FliL与定子一起定位，以便通过维持定子组装来支持马达在高负载条件下游泳的功能。
