Mu-induced polarity in the unc operon of Escherichia coli

Abstract

Mutant strains of E. coli were isolated in which mutator (Mu) phage was inserted into various unc genes. Partial diploid strains were prepared from each of the Mu-induced unc mutants by using F-plasmids carrying mutations in 1 of the known unc genes (uncA, uncB, uncC or uncD). The partial diploid strains and the corresponding segregant strains were examined for their ability to grow on succinate. The aerobic growth yields on limiting concentrations of glucose were also determined. Mg-stimulated ATPase activities, ATP-dependent transhydrogenase activities and Atebrin fluorescence quenching activities were determined by using membrane preparations from each strain. Genetic complementation was assessed from the results obtained, and apparently the 4 unc genes examined are part of a single transcriptional unit and they are transcribed in the order uncBADC.