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The stall torque of the bacterial flagellar motor

1987; Elsevier BV; Volume: 52; Issue: 3 Linguagem: Inglês

10.1016/s0006-3495(87)83230-7

1542-0086

Markus Meister, Howard C. Berg,

Photoreceptor and optogenetics research

The bacterial flagellar motor couples the flow of protons across the cytoplasmic membrane to the rotation of a helical flagellar filament. Using tethered cells, we have measured the stall torque required to block this rotation and compared it with the torque of the running motor over a wide range of values of proton-motive force and pH. The stall torque and the running torque vary identically: both appear to saturate at large values of the proton-motive force and both decrease at low or high pH. This suggests that up to speeds of approximately 5 Hz the operation of the motor is not limited by the mobility of its internal components or the rates of proton transfer reactions coupled to flagellar rotation.