Dimerization of F0F1ATP synthase from bovine heart is independent from the binding of the inhibitor protein IF1

Solubilization of heavy bovine heart mitochondria with Triton X- 100 leads to the selective extraction of FOF I ATP synthase monomer and dimer in a 2:1 ratio, as revealed by blue native gel electrophoresis (BN-PAGE). Second dimensional SDS-PAGE and immunoblotting with IF1 and F-1 antibodies following BN-PAGE show that both aggregation states of the ATP synthase contain IF1. The monomer/dimer ratio does not change in extracts from mitochondria subjected to different energy conditions accompanied by IF, binding modulation or from submitochondrial particles differing in IF1 content. In addition, the usual monomer/dimer ratio is observed even in submitochondrial particles deprived of IF1. Histochemical staining for ATPase activity demonstrates that the dimer is inactive, irrespective of its IF1 content. It is concluded that in the membrane of bovine heart mitochondria the ATP synthase dimer is a stable inactive structure, whose formation is not mediated by IF1 binding. (C) 2002 Elsevier Science B.V. All rights reserved.