Assembly dynamics and the roles of FliI ATPase of the bacterial flagellar export apparatus.

For construction of the bacterial flagellum, FliI ATPase forms the FliH2-FliI complex in the cytoplasm and localizes to the flagellar basal body (FBB) through the interaction of FliH with a C ring protein, FliN. FliI also assembles into a homo-hexamer to promote initial entry of export substrates into the export gate. The interaction of FliH with an export gate protein, FlhA, is required for stable anchoring of the FliI6 ring to the gate.

Roles of the extreme N-terminal region of FliH for efficient localization of the FliH-FliI complex to the bacterial flagellar type III export apparatus.

Most bacterial flagellar proteins are exported by the flagellar type III protein export apparatus for their self-assembly. FliI ATPase forms a complex with its regulator FliH and facilitates initial entry of export substrates to the export gate composed of six integral membrane proteins. The FliH-FliI complex also binds to the C ring of the basal body through a FliH-FliN interaction for efficient export.