Bacterial flagellin

Bacterial flagellin is the principal protein subunit of the filament portion of the bacterial flagellum, which is the organelle responsible for motility in flagellated bacteria[1][2]. Flagellin monomers (~40 kDa) assemble into a helical, hollow filament structure, forming the propeller-like apparatus that drives bacterial movement[1][2][3]. The flagellin protein is highly conserved at the N- and C-terminal regions, responsible for polymerization and core structure, but displays significant variability in its central region[1]. Flagellin is a potent immunostimulatory molecule, recognized by the host’s immune system (notably Toll-like receptor 5, TLR5), leading to rapid activation of inflammatory pathways[1]. As such, flagellin is a key virulence factor in many pathogenic bacteria, playing roles in both infection (by facilitating bacterial motility and colonization) and immune evasion (due to its antigenic variability)[3]. It is also being investigated as a vaccine adjuvant and as a model for understanding host-pathogen interactions. Caveats/Notes: - Bacterial flagellin is a structural protein and not a receptor, enzyme, or transporter, but is a validated immune target and therapeutic research focus[1][3]. - No approved drugs currently target flagellin therapeutically, but its immune-stimulating properties are under investigation for vaccine adjuvants and anti-infective strategies[1][3]. - Some confusion may arise because “flagellin” refers to a family of proteins across bacterial species, but it is well defined as the primary component of the bacterial flagellar filament[1].

Other names

FlagellinFliC (in E. coli and Salmonella)FljB (in Salmonella)FlaA (in Helicobacter pylori)flagellin protein

For adjuvant or vaccine strategies: Activates innate immunity via Toll-like receptor 5 (TLR5) - For targeting bacteria: Antibodies or immune responses can neutralize bacterial motility or flagellin-mediated signaling