Cell Death Differ. 2026 Jul 03.
Mammalian mitochondrial ATP synthase typically organizes into rows of V-shaped dimers that impose significant membrane curvature essential for mitochondrial cristae formation. Using gentle, column-free purification combined with single-particle cryo-electron microscopy, we have identified a previously unrecognized planar dimeric form of bovine ATP synthase exhibiting minimal membrane bending. This planar dimer is characterized structurally by anti-parallel arrangement of two ATP synthase complexes linked by a straight conformation of inhibitory factor 1 (IF1), a sharp contrast to the kinked IF1 observed in tetrameric assemblies. Molecular dynamics simulations confirm that transitioning between straight and kinked IF1 conformations occurs without significant energetic barriers. The planar dimer also displays distinct peripheral stalk positioning relative to its adjacent α subunit. These structural divergences suggest a specialized function and a distinct localization for planar ATP synthase dimers, providing structural support for a division of labor within mitochondrial ATP synthase populations.