FliIcontaining

FliI-containing refers to protein complexes or molecules that include the flagellar export ATPase FliI, a central component of the bacterial flagellum's type III secretion system (T3SS). FliI is encoded by the fliI gene and functions as the cytoplasmic ATPase that powers the export of flagellar building blocks through the basal body and the export gate.

In the cytoplasm, FliI forms an oligomeric complex with FliH and FliJ. FliI belongs to the AAA+ family and, as a hexamer, hydrolyzes ATP to drive the unfolding and translocation of substrates into the export channel. FliH modulates FliI activity and helps recruit the FliI-FliH complex to the export apparatus, while FliJ serves as a central stalk linking the ATPase to the membrane-embedded export gate.

FliI-containing complexes assemble at the cytoplasmic face of the export apparatus and coordinate with the proton motive force to export flagellar components. The energy from ATP hydrolysis by FliI is coupled with the secretion process, enabling timely export of substrates necessary for basal body assembly, rod, hook, and filament formation.

Significance and context: FliI-containing assemblies are essential for functional flagellar export and motility. Mutations in fliI, fliH, or fliJ disrupt ATPase activity, complex formation, or interaction with the export gate, leading to defective flagellar assembly and impaired motility. The term is commonly used in discussions of the flagellar export machinery and related protein–protein interaction studies, where FliI-containing complexes are analyzed or described.