| σF (σ28; green) is required for the expression of genes required late in the assembly of the flagellar motility motor. The genes needed for the synthesis and assembly of the initial hook-basal body complex, as well as σF and the anti-sigma factor FlgM (pink triangles), which inhibits σF, are transcribed by RNA polymerase containing the housekeeping sigma factor σD (σ70; blue). FlgM binds σF and prevents the sigma factor from interacting with the RNA polymerase core enzyme. However, once the intermediate hook and basal body structure of the flagellum has been completed, FlgM, which carries late export determinants, is secreted out of the cell. The released σF then can interact with the RNA polymerase core enzyme and directs transcription of genes required for the completion of the flagellar structure. |
