F-1 and F-0 connections in the bovine mitochondrial ATP synthase - The role of the of alpha subunit N-terminus, oligomycin-sensitivity conferring protein (OCSP) and subunit d

We have studied the functional effect of limited proteolysis by trypsin of the constituent subunits in the native and reconstituted F1F0 complex and i solated F-1 of the bovine heart mitochondrial ATP synthase (EC 3.6.1.34). C hemical cross-linking of oligomycin-sensitivity conferring protein (OSCP) w ith other subunits of the ATP synthase and the consequent functional effect s were also investigated. The results obtained show that the alpha subunit N-terminus is essential fo r the correct, functional connection of F-1 to F-0. The alpha-subunit N-ter minus contacts OSCP which, in turn, contacts the F0I-PVP(b) and the F-0-d s ubunits. The N-terminus of subunit alpha, OSCP, a segment of subunit d and the C-terminal and central region of F0I-PVP(b) subunits are peripherally l ocated with respect to subunits gamma and delta which are completely shield ed in the F1F0 complex against trypsin digestion. This qualifies the N-term inus of subunit alpha, OSCP, subunit d and F0I-PVP(b) as components of the lateral element of the stalk. These subunits, rather than being confined at one side of the complex which would leave most of the central part of the gamma subunit uncovered, surround the gamma and the delta subunits located in the central stalk.