Chang Yi-Wei, Rettberg Lee A, Treuner-Lange Anke, Iwasa Janet, Søgaard-Andersen Lotte, Jensen Grant J
California Institute of Technology, Pasadena, CA 91125, USA. Howard Hughes Medical Institute, Pasadena, CA 91125, USA.
Howard Hughes Medical Institute, Pasadena, CA 91125, USA.
Science. 2016 Mar 11;351(6278):aad2001. doi: 10.1126/science.aad2001. Epub 2016 Mar 10.
Type IVa pili are filamentous cell surface structures observed in many bacteria. They pull cells forward by extending, adhering to surfaces, and then retracting. We used cryo-electron tomography of intact Myxococcus xanthus cells to visualize type IVa pili and the protein machine that assembles and retracts them (the type IVa pilus machine, or T4PM) in situ, in both the piliated and nonpiliated states, at a resolution of 3 to 4 nanometers. We found that T4PM comprises an outer membrane pore, four interconnected ring structures in the periplasm and cytoplasm, a cytoplasmic disc and dome, and a periplasmic stem. By systematically imaging mutants lacking defined T4PM proteins or with individual proteins fused to tags, we mapped the locations of all 10 T4PM core components and the minor pilins, thereby providing insights into pilus assembly, structure, and function.
IVa型菌毛是在许多细菌中观察到的丝状细胞表面结构。它们通过伸展、粘附于表面然后收缩来推动细胞向前移动。我们使用完整的黄色粘球菌细胞的冷冻电子断层扫描技术，以3到4纳米的分辨率在原位观察了IVa型菌毛以及组装和收缩它们的蛋白质机器（IVa型菌毛机器，或T4PM），包括菌毛形成和未形成的状态。我们发现T4PM由一个外膜孔、周质和细胞质中的四个相互连接的环形结构、一个细胞质盘和穹顶以及一个周质杆组成。通过系统地对缺乏特定T4PM蛋白的突变体或与标签融合的单个蛋白进行成像，我们确定了所有10个T4PM核心成分和次要菌毛蛋白的位置，从而深入了解了菌毛的组装、结构和功能。
