Flagellin is the subunit protein which polymerizes to form the filaments of bacterial flagella. FlaD is not essential for flagellar synthesis and motility. 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. Belongs to the bacterial flagellin family.