IDENTIFICATION OF AN UNCOUPLING MUTATION AFFECTING THE B-SUBUNIT OF F1F0 ATP SYNTHASE IN ESCHERICHIA-COLI

A specific b subunit arginine, b(Arg-36) in Escherichia coli, displays evolutionary conservation among bacterial F1F0 ATP synthases. Site-di rected mutagenesis was used to generate a collection of mutations affe cting b(Arg-36). The phenotype differed depending upon the substitutio n, and the b(Arg-36-->Glu) and b(Arg-36-->Ile) substitutions virtually abolished enzyme, function. Although the total amounts of F1F0 ATP sy nthase present in the membranes prepared from mutant strains were redu ced, the primary effect of the b(Arg-36) substitutions was on the acti vities 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. (C) 1998 Federation o f European Biochemical Societies.