Figure 2. Rotational states of ATP synthase.

(A) Atomic models of the three rotational states of Bacillus PS3 ATP synthase with subunits coloured the same as in Figure 1. (B) Top view of the c-ring and subunit a of the three rotational states from the cytoplasm when the F₁ regions of the three states are aligned. Rotation steps of the complex between states are ~3, 4, and 3 c-subunits. (C) Comparison of the atomic models of subunits b, δ, and other F₁ region subunits in the different rotational states. The b subunits appear to be the most flexible part of the enzyme.