Oligomeric hypercomplex of the complete oxidative phosphorylation system in heart mitochondria

Abstract

The existence of a complete oxidative phosphorylation system supercomplex including both electron transport system and ATP synthases has long been assumed based on functional evidence. However, no conclusive structural evidence has been obtained. In this study cryo-electron tomography was used to reveal the supramolecular architecture of the rat heart mitochondria cristae obtained by a mild destruction of mitochondria. For the first time the complete oxidative phosphorylation supercomplexes were observed in mitochondrial membrane under phosphorylating conditions. We show that rows of respiratory chain supercomplexes (respirasomes) are connected with rows of ATP synthases forming the oligomeric hypercomplex. We thus demonstrate that the distance between respirasomes and ATP synthases in hypercomplexes ensures a direct proton transfer from pumps to ATP synthase without proton solvation in the aqueous phase.