Subtomogram averages of mitochondrial ATP synthase dimers from plants show a conserved extra density at the peripheral stalk

Abstract

Electron cryo-tomography of ATP synthase dimers in plant mitochondria indicates a wide dimer angle and a plant-specific subunit in the peripheral stalk.

We analyzed ATP synthase dimers in mitochondria purified from four plant species by subtomogram averaging, using Saccharomyces cerevisiae as a control. The purified mitochondria were plunge-frozen and broken mitochondria were examined by electron cryo-tomography. In each case, the ATP synthase dimers formed extensive rows along the tightly curved cristae ridges. ATP synthase dimer particles of each species were picked and averaged. Subtomogram averages of all four plant ATP synthases revealed an extra density at the tip of the peripheral stalk next to the OSCP hinge that is not seen in S. cerevisae. The dimer angle between the ATP synthase monomers is wider than in Polytomella, S. cerevisae or mammals, but less wide than in Caenorhabditis elegans. Slight variations in dimer angle indicate that ATP synthase dimers of plant mitochondria are more flexible than others.