Structure of a Complete ATP Synthase Dimer Reveals the Molecular Basis of Inner Mitochondrial Membrane Morphology

Highlights

• Cryo-EM structure of a yeast F₁F_o-ATP synthase dimer

• Inhibitor-free X-ray structure of the F₁ head and rotor complex

• Mechanism of ATP generation by rotary catalysis

• Structural basis of cristae formation in the inner mitochondrial membrane

Summary

We determined the structure of a complete, dimeric F₁F_o-ATP synthase from yeast Yarrowia lipolytica mitochondria by a combination of cryo-EM and X-ray crystallography. The final structure resolves 58 of the 60 dimer subunits. Horizontal helices of subunit a in F_o wrap around the c-ring rotor, and a total of six vertical helices assigned to subunits a, b, f, i, and 8 span the membrane. Subunit 8 (A6L in human) is an evolutionary derivative of the bacterial b subunit. On the lumenal membrane surface, subunit f establishes direct contact between the two monomers. Comparison with a cryo-EM map of the F₁F_o monomer identifies subunits e and g at the lateral dimer interface. They do not form dimer contacts but enable dimer formation by inducing a strong membrane curvature of ∼100°. Our structure explains the structural basis of cristae formation in mitochondria, a landmark signature of eukaryotic cell morphology.