MotI (DgrA) acts as a molecular clutch on the flagellar stator protein MotA in Bacillus subtilis

Significance Bacterial flagella are nanomachines rotated by powerful motors and drive motility that is often associated with virulence. Regulators that inhibit motor function are potentially reversible and arrest flagellar rotation either as a brake, to increase resistance, or as a clutch, to cut power to the machine, analogous to their counterparts in a car. Here we show that MotI ofBacillus subtilis acts like a molecular clutch by interacting with the power-transducing protein MotA and separating it from the drivetrain protein FliG. We further demonstrate that partial motility inhibition by clutch proteins decreases swimming speed.