Partial diploids of Escherichia coli carrying normal and mutant alleles affecting oxidative phosphorylation

Abstract

A plasmid was isolated which included the region of the E. coli chromosome carrying the known genes of oxidative phosphorylation (unc genes). This plasmid was used to prepare partial diploids carrying normal unc alleles on the episome and 1 of 3 mutant alleles (uncA401, uncB402 or unc-405) on the chromosome. These strains were compared with segregants from which the plasmid was lost. Dominance of normal or mutant unc alleles was determined by growth on succinate, growth yields on glucose, Mg-ATPase [EC 3.6.1.3] activity and atebrin-fluorescence quenching, ATP-dependent transhydrogenase activity and oxidative phosphorylation. In all the above tests dominance of the normal allele was observed. In membranes from the diploid strains which carried a normal allele and either of the mutant alleles affecting Mg-ATPase activity (uncA401 or unc-405), the energy-linked functions were only partially restored.