Flagellin

Flagellin is the principal structural protein forming the filament of bacterial flagella, which are whip-like appendages responsible for motility in many bacteria[1][3][4]. The protein self-polymerizes into long helical filaments that extend from the cell surface. Its N-terminal and C-terminal regions are highly conserved across species and essential for export through the type III secretion system and subsequent assembly at the tip of growing filaments[1][2]. The central region is hypervariable among different bacteria, contributing to antigenic diversity. Flagellins play crucial roles not only in locomotion but also act as potent activators of innate immunity due to their recognition by host pattern recognition receptors such as Toll-like receptor 5. While not an enzyme or classical receptor, it serves both structural functions within bacteria and acts indirectly on host cells via immune signaling pathways. Flagellins have been studied extensively both structurally—due to their self-polymerizing properties—and functionally—as targets for antibiotic screening assays aimed at disrupting bacterial movement[2].

Other names

FliC (commonly used gene name in *Salmonella* and *E. coli*)FlaA (gene name in *Helicobacter pylori* and other species)Bacterial flagellin protein

Not applicable for direct drug targeting; however, drugs or compounds that inhibit assembly or function of flagellin can impair bacterial motility[2].