Fig. 1.
A Model for the flagellar rotary motor. (A) Schematic illustration of the rotor–stators spatial arrangement. The rotor contains 26 FliG proteins and there are multiple stators, each with 2 subunits (dark and light springs). (B) A sequence of 3 rotor–stator configurations (from top to bottom) illustrating the hand-over-hand interaction between the 2 subunits of a stator and the FliG proteins in the rotor. (C) The same sequence as in B is shown in the potential landscape. The solid arrow represents the physical rotation of the rotor angle (θ) down a given (V-shaped) potential, the dotted arrow represents the chemical change (switching of hands) that shifts the potential. (D) The full motor model with multiple stators in the angle space. Each stator is represented by its internal angle θS. The rotor is pulled forward by the stators in front of it and dragged back by the stators behind it. The stator angle can only change by jumping forward with rate k that depends on the relative angle Δθ = θ − θS. The form of k(Δθ) used in this article is given in E, which shows the dragging stators have a higher jump rate k− > k+ and a cutoff angle −δc where k(Δθ < −δc) = 0.