Structural studies of the mitochondrial ATP synthetic machinery

The structure of mitochondrial ATP synthase (F0F1) was studied by electron microscopy (EM) and its F1 moiety by X-ray crystallography. The phosphate carrier (PIC) and adenine nucleotide carrier (ANC) associate with the ATP synthase at a stoichiometric ratio 1:1:1 to form a super-complex named "ATP synthasome". By three-dimensional reconstruction the shape of the membrane base piece of the ATP synthasome was determined to be significantly oblong, with an extended mass which can fit an ANC molecule plus a PIC molecule, but not a dimer of PIC plus a dimer of ANC.; To help elucidate the mechanism of ATP synthesis, the structure of F 1 with vanadate (Vi) bound at its active site was solved by X-ray crystallography at atomic resolution. The Vi binding induced a significant conformational change at the active site bringing Ala 158, the third amino acid residue in the P-loop, close to Vi. This novel conformational change is consistent with previous biochemical photo-cleavage studies conducted in this laboratory. The ADP-Vi-Mg-F1 complex is thought to be in a transition-like state, and a model of the catalytic mechanism is proposed.; Finally, the localizations of candidate components of the peripheral stalk, subunits F6, OSCP and d, were determined by immuno-electron microscopy. The F6 and OSCP subunits are proximal to the head piece, and the d subunit proximal to the base piece. A model of the peripheral stalk assembly was proposed based on these data.