Bacterial Flagellum

A bacterial flagellum is primarily built from three main structural protein types: flagellin (FliC), which forms the long, helical filament; hook proteins (FlgE and FlgK/FlgL), which create the flexible hook connecting the filament to the motor; and multiple motor and basal body proteins (like MotA, MotB, FliF, FliG, FliM, and FliN) that anchor the structure in the cell membrane and generate torque.

Over 30 different proteins coordinate to assemble and power the flagellum, enabling the bacterium’s rotary movement and directional control through chemotaxis.