Kojima Seiji, Shinohara Akari, Terashima Hiroyuki, Yakushi Toshiharu, Sakuma Mayuko, Homma Michio, Namba Keiichi, Imada Katsumi
Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-Ku, Nagoya 464-8602, Japan.
Proc Natl Acad Sci U S A. 2008 Jun 3;105(22):7696-701. doi: 10.1073/pnas.0800308105. Epub 2008 May 27.
Rotation of the sodium-driven polar flagellum of Vibrio alginolyticus requires four motor proteins: PomA, PomB, MotX, and MotY. PomA and PomB form a sodium-ion channel in the cytoplasmic membrane that functions as a stator complex to couple sodium-ion flux with torque generation. MotX and MotY are components of the T-ring, which is located beneath the P-ring of the polar flagellar basal body and is involved in incorporation of the PomA/PomB complex into the motor. Here, we describe the determination of the crystal structure of MotY at 2.9 A resolution. The structure shows two distinct domains: an N-terminal domain (MotY-N) and a C-terminal domain (MotY-C). MotY-N has a unique structure. MotY-C contains a putative peptidoglycan-binding motif that is remarkably similar to those of peptidoglycan-binding proteins, such as Pal and RmpM, but this region is disordered in MotY. Motility assay of cells producing either of the MotY-N and MotY-C fragments and subsequent biochemical analyses indicate that MotY-N is essential for association of the stator units around the rotor, whereas MotY-C stabilizes the association by binding to the peptidoglycan layer. Based on these observations, we propose a model for the mechanism of stator assembly around the rotor.
PomA、PomB、MotX和MotY。PomA和PomB在细胞质膜中形成一个钠离子通道，其作为定子复合体发挥作用，将钠离子通量与扭矩产生相耦合。MotX和MotY是T环的组成部分，T环位于极鞭毛基体的P环下方，参与将PomA/PomB复合体整合到马达中。在此，我们描述了以2.9埃分辨率测定MotY的晶体结构。该结构显示出两个不同的结构域：一个N端结构域（MotY-N）和一个C端结构域（MotY-C）。MotY-N具有独特的结构。MotY-C包含一个假定的肽聚糖结合基序，该基序与肽聚糖结合蛋白（如Pal和RmpM）的基序非常相似，但该区域在MotY中是无序的。对产生MotY-N和MotY-C片段之一的细胞进行的运动性测定以及随后的生化分析表明，MotY-N对于定子单元围绕转子的缔合至关重要，而MotY-C通过与肽聚糖层结合来稳定这种缔合。基于这些观察结果，我们提出了一个关于定子围绕转子组装机制的模型。
