The flagellar motor sits in the bacterial cell envelope and turns a long helical filament. Stator units in the inner membrane let ions flow into the cell and push on a rotor ring, the C-ring. When the signal protein CheY-P binds the C-ring, the motor reverses. The switch between runs and tumbles steers the cell toward food.
- Where
- Cell envelope of flagellated bacteria such as Escherichia coli, Salmonella, Vibrio, Campylobacter and spirochetes. The rotor spans the cytoplasm, inner membrane, peptidoglycan and outer membrane.
- Power
- Inward flow of protons (E. coli, Salmonella, Campylobacter) or sodium ions (Vibrio polar flagella) across the inner membrane.
1,260 pN·nm
Stall torque, E. coli (fully induced)
1~200 Hz
Knee speed, E. coli (23 °C)
2~350 Hz
Zero-torque speed, E. coli (23 °C)
2