Bacterial Flagellar Motor: Overview
The bacterial flagellar motor is an ion-driven rotary motor embedded in the cell membrane that drives a long helical filament (5–10 μm long with a diameter of ∼15 nm) enabling the cell to swim. The motor is connected to the filament by a short flexible hook about 100 nm long. Hook and filament form the flagellum. The flagellum/motor complex self-assembles and is the result of the coordinated, sequential expression of over 50 genes. The final structure is composed of at least 13 different proteins, all present in different copy numbers, ranging from a few to hundreds of them.
In peritrichously flagellated bacteria such as Escherichia coli, hooks allow multiple filaments to come together to form a bundle that propels the cell forward. This happens when all the motors driving these filaments rotate in the same direction (counterclockwise). Flagellar motors are also able to rotate in the reverse direction,...