CROSS-RECONSTITUTION STUDIES WITH POLYPEPTIDES OF ESCHERICHIA-COLI AND BOVINE HEART MITOCHONDRIAL F0F1 ATP SYNTHASE

Abstract

To characterize the role of supernumerary subunits of the mammalian F0F1 ATP synthase, cross-reconstitution of mitochondrial and bacterial F0F1 complexes has been carried out. Escherichia coli F-1 (EcF(1)) can be reconstituted with F-1-stripped everted membranes of E. coli (UPEc) and of bovine heart mitochondria (USMP). Bovine heart mitochondrial F-1 (BHF1) can also be reconstituted with both membranes. Both EcF(1) and BHF1, when reconstituted with UPEc, exhibited oligomycin-insensitive ATP-hydrolase activity. Subunits of the mammalian F-0, in particular F0I-PVP protein, F-6 and oligomycin-sensitivity-conferring protein (OSCP) conferred oligomycin sensitivity to the catalytic activity of EcF(1) or BHF1 reconstituted with UPEc. Reaction of N,N'-dicyclohexylcarbodiimide and development of inhibition of passive H+ conduction was, in UPEc, considerably slower and exhibited a lower apparent affinity than in USMP. The ATP hydrolase activity of UPEc+EcF(1) or UPEc+BHF1 was, also, less sensitive to inhibition by N,N'-dicyclohexylcarbodiimide than USMP+EcF(1), or USMP+BHF1. Addition of mitochondrial F0I-PVP to UPEc enhanced the sensitivity of H+ conduction to oligomycin. F0I-PVP and OSCP added to UPEc, promoted inhibition by N,N'-dicyclohexylcarbodiimide of passive H+ conduction and increased its binding affinity to subunit c of E. coli F-0. The presence of F0I-PVP and OSCP also promoted inhibition by N,N'-dicyclohexylcarbodiimide of the ATP-hydrolase activity of EcF(1), or BHF1 reconstituted with UPEc.