Arrangement of electron transport chain components in bovine mitochondrial supercomplex I1III2IV1

The respiratory chain in the inner mitochondrial membrane contains three large multi-enzyme complexes that together establish the proton gradient for ATP synthesis, and assemble into a supercomplex. A 19-angstrom 3D map of the 1.7-MDa amphipol-solubilized supercomplex I1III2IV1 from bovine heart obtained by single-particle electron cryo-microscopy reveals an amphipol belt replacing the membrane lipid bilayer. A precise fit of the X-ray structures of complex I, the complex III dimer, and monomeric complex IV indicates distances of 13nm between the ubiquinol-binding sites of complexes I and III, and of 10-11 nm between the cytochrome c binding sites of complexes III and IV. The arrangement of respiratory chain complexes suggests two possible pathways for efficient electron transfer through the supercomplex, of which the shorter branch through the complex III monomer proximal to complex I may be preferred. The EMBO Journal (2011) 30, 4652-4664. doi: 10.1038/emboj.2011.324; Published online 9 September 2011