Figure 1-7. Model for F1Fo ATP synthase peripheral stalk orientation dependent upon the
 direction of rotation during ATP synthesis or hydrolysis. The subunits are
 color coded as follows: ot, light blue; P, grey; y, dark blue; E, green; 6, orange;
 a, yellow; b, red; c, cyan. The panel on the left indicates the orientation of the
 b2 dimer if the enzyme is actively synthesizing ATP. The panel on the right
 represents the position of the b2 dimer during ATP hydrolysis. The arrows
 indicate the direction of rotation of the rotor stalk subunits (ysclo). The red
 cylinders indicate regions of the b subunits for which there is no high-
 resolution structure.