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

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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.