Membrane Topology of ATP Synthase from Bovine Heart Mitochondira and Escherichia coli

Abstract

The polypeptides exposed to lipids in the membranous F0 sector of the mitochondrial and Escherichia coli ATP synthases were labeled with radioactive photoreactive lipids. Highly resolving gel electrophoretic conditions were used to separate all the 18 components forming the bovine heart mitochondrial enzyme. The hydrophobic labeling was performed on fully active and inhibitor-sensitive ATP synthases. In the mitochondrial enzyme prepared according to Serrano et al. (1976), 7 polypeptides of MW 30,500, 11,500, 10,500, 10,000, 9500, 8500 and 4500 were labeled. The major amount of radioactivity was associated with the 30,500-MW component, which is thought to be the adenine nucleotide carrier. In the preparation of Galante et al. (1979), which almost completely lacks this component, 9 polypeptides of MW of 25,000, 21,000, 11,500, 10,500, 10,000, 9500, 9200, 8500 and 4500 were labeled. In the ATP synthase from E. coli the major amount of labeling was associated with subunit b and only a minor portion with subunit c.