Identification of an uncoupling mutation affecting the b subunit of F 1F 0 ATP synthase in Escherichia coli

Abstract

A specific b subunit arginine, b Arg-36 in Escherichia coli, displays evolutionary conservation among bacterial F 1F 0 ATP synthases. Site-directed mutagenesis was used to generate a collection of mutations affecting b Arg-36. The phenotype differed depending upon the substitution, and the b Arg-36→Glu and b Arg-36→Ile substitutions virtually abolished enzyme function. Although the total amounts of F 1F 0 ATP synthase present in the membranes prepared from mutant strains were reduced, the primary effect of the b Arg-36 substitutions was on the activities of the intact enzyme complexes. The most interesting result was that the b Arg-36→Glu substitution results in the uncoupling of a functional F 0 from F 1 ATP hydrolysis activity.