Figure 4.

Schematic representation of the turnstile model of rotary motors. Upon entering from the bottom entrance, the mobile ions take a ride on the rotor. The electrostatic interactions among the charges on the stator and the rotor, as well as the rotational Brownian motion of the rotor, result in the noisy directed rotation of the rotor. Each hitchhiking ion disembarks from the rotor after being transported up to a certain distance by the rotor. Once the ion leaves, the rotor remains locked in its current position and waits for the arrival of the next ion. The F0 part of the ATP synthase exploits this mechanism (adapted from Chapter4 of Schliwa (13)).