Flagellin is the subunit protein which polymerizes to form the filaments of bacterial flagella. FlaA is required to form a core or scaffold into which the other flagellins are inserted to provide structural integrity. Essential for flagellar synthesis and motility; important for full virulence. Heteromer of multiple flagellin subunits including FlaA, FlaB, FlaC, FlaD and FlaE. V.cholerae is able to differentially regulate the flagellins within the flagellum maybe to produce flagella which are particularly suited for motility within a given environment. A flagellar filament composed exclusively of FlaA is fragile and easily broken. Belongs to the bacterial flagellin family.