|Budget Amount *help
¥3,100,000 (Direct Cost : ¥3,100,000)
Fiscal Year 1998 : ¥1,000,000 (Direct Cost : ¥1,000,000)
Fiscal Year 1997 : ¥2,100,000 (Direct Cost : ¥2,100,000)
During flagellar morphogenesis in Salmonella typhirnurium, the genes involved in filament assembly are expressed fully only after completion of hook assembly. This coupling of gene expression to morphogenesis is achieved by exporting the flagellum-specific anti-sigma factor, FlgM, out of the cell through the mature hook-basal body structure. Therefore, the flagellum-specific export apparatus must be able to sense the assembly state of the flagellar structure and to turn on FlgM export at the specific stage of hook assembly. In this study, this export switching machinery was dissected at a molecular level. The main conclusions are as follows. (1) The export gate for FlgM is double locked by FlhB and RflH proteins before completion of hook assembly. (2) These locks are opened in the mutants which produce abnormally elongated rods lacking hooks. This indicates that the monitor system of hook length measures the length of the rod plus the hook. (3) The FlgM gate is also involved in the export control of the late flagellar proteins, FlgK, FlgL, FliD, and FliC.FlhB is also responsible for shutting-off process of the export of hook protein after completion of hook assembly. (4) Mutants in which the RflH lock is opened constitutively were isolated. Genetic analysis of these mutants suggested that at least two proteins are involved in the opening process of the RflH lock. (5) The FlhB lock is opened at the early stage of hook assembly, whereas the RflH lock is opened upon completion of hook assembly.