Kubori T, Yamaguchi S, Aizawa S
Department of Biosciences, School of Science and Engineering, Teikyo University, Toyosatodai, Utsunomiya, Japan.
J Bacteriol. 1997 Feb;179(3):813-7. doi: 10.1128/jb.179.3.813-817.1997.
The cytoplasmic portion of the bacterial flagellum is thought to consist of at least two structural components: a switch complex and an export apparatus. These components seem to assemble around the MS ring complex, which is the first flagellar basal body substructure and is located in the cytoplasmic membrane. In order to elucidate the process of assembly of cytoplasmic substructures, the membrane localization of each component of the switch complex (FliG, FliM, and FliN) in various nonflagellated mutants was examined by immunoblotting. It was found that all these switch proteins require the MS ring protein FliF to associate with the cell membrane. FliG does not require FliM and FliN for this association, but FliM and FliN associate cooperatively with the membrane only through FliG. Furthermore, all three switch proteins were detected in membranes isolated from fliE, fliH, fliI, fliJ, fliO, fliP, fliQ, fliR, flhA, flhB, and flgJ mutants, indicating that the switch complex assembles on the MS ring complex without any other flagellar proteins involved in the early stage of flagellar assembly. The relationship between the switch complex and the export apparatus is discussed.
一个开关复合体和一个输出装置。这些成分似乎围绕着MS环复合体组装，MS环复合体是鞭毛基体的第一个亚结构，位于细胞质膜中。为了阐明细胞质亚结构的组装过程，通过免疫印迹法检测了开关复合体各成分（FliG、FliM和FliN）在各种无鞭毛突变体中的膜定位。发现所有这些开关蛋白都需要MS环蛋白FliF才能与细胞膜结合。FliG在这种结合中不需要FliM和FliN，但FliM和FliN仅通过FliG与膜协同结合。此外，在从fliE、fliH、fliI、fliJ、fliO、fliP、fliQ、fliR、flhA、flhB和flgJ突变体中分离的膜中检测到了所有三种开关蛋白，这表明开关复合体在MS环复合体上组装，而没有任何其他参与鞭毛组装早期阶段所需的鞭毛蛋白。文中还讨论了开关复合体与输出装置之间的关系。
