Properties of membranes from mutant strains of Escherichia coli in which the β-subunit of the adenosine triphosphatase is abnormal

Abstract

Five uncoupled mutant strains of E. coli carrying mutations in the uncD gene were studied. In each of these mutant strains the .beta.-subunit of the F1 portion of the membrane-bound ATPase is abnormal. In 1 of the mutant strains (carrying the uncD412 allele) an F1-ATPase aggregate was formed which was purified and it had low ATPase activity. ATPase activity was absent in the other 4 strains and the abnormal .beta.-subunits were tightly bound to the membranes. Membranes from these strains exhibited various proton permeabilities as indicated by NADH-dependent atebrin-fluorescence quenching and bound different amounts of normal F1-ATPase. The amounts of reconstitution of energy-linked reactions after the addition of normal F1-ATPase also varied depending on the mutant allele. Considerable phenotypic variations can occur between strains carrying mutations in the same unc gene.