Flagellin

Flagellin is a protein that polymerizes to form the filament of bacterial flagella. It is the main structural component of the flagellum and is responsible for its characteristic helical shape.

Flagellin monomers assemble to form a hollow cylinder, which then extends to create the long, whip-like structure of the flagellum. The flagellum rotates like a propeller, driven by a motor complex located at the base of the flagellum, allowing bacteria to move through liquid environments.

Different bacterial species produce different types of flagellin, and these variations can be used for taxonomic identification. The amino acid sequence of flagellin can vary significantly between species, and even within a single species, there can be multiple flagellin genes, leading to different flagellar serotypes.

Flagellin is also a potent immune stimulant. It is recognized by the Toll-like receptor 5 (TLR5) on immune cells, triggering an inflammatory response. This interaction plays a critical role in the immune system's detection and response to bacterial infections. The ability of flagellin to activate TLR5 has also made it a target for vaccine adjuvants and immunotherapeutic agents. Furthermore, flagellin's adjuvant properties are being explored for potential use in cancer immunotherapy. Research indicates that flagellin-TLR5 interactions can stimulate both innate and adaptive immune responses.