Rotor architecture in the yeast and bovine F1-c-ring complexes of F-ATP synthase

The F₁F_O-ATP synthase is a rotary molecular nanomotor. F₁ is a chemical motor driven by ATP hydrolysis while F_O is an electrical motor driven by the proton flow. The two stepping motors are mechanically coupled through a common rotary shaft. Up to now, the three available crystal structures of the F₁c₁₀ sub-complex of the yeast F₁F_O-ATP synthase were isomorphous and then named yF₁c₁₀(I). In this crystal form, significant interactions of the c₁₀-ring with the F₁-head of neighboring molecules affected the overall conformation of the F₁-c-ring complex. The symmetry axis of the F₁-head and the inertia axis of the c-ring were tilted near the interface between the F₁-central stalk and the c-ring rotor, resulting in an unbalanced machine. We have solved a new crystal form of the F₁c₁₀ complex, named yF₁c₁₀(II), inhibited by adenylyl-imidodiphosphate (AMP-PNP) and dicyclohexylcarbodiimide (DCCD), at 6.5 Å resolution in which the crystal packing has a weaker influence over the conformation of the F₁-c-ring complex. yF₁c₁₀(II) provides a model of a more efficient generator. yF₁c₁₀(II) and bovine bF₁c₈ structures share a common rotor architecture with the inertia center of the F₁-stator close to the rotor axis.