Subunits of the Adenosine Triphosphatase Complex Translated In Vitro from the Escherichia coli unc Operon

Abstract

The unc operon of Escherichia coli was split into two fragments by the restriction endonuclease Hin dIII. The operator-proximal portion was cloned into plasmid pACYC184, forming plasmid pAN51, which included the genes uncB, uncE , and uncA . When plasmid pAN51 was used as template in an in vitro transcription/translation system, the α subunit (from the uncA gene) and δ subunit of the F 1 adenosine triphosphatase (ATPase) were formed. In addition, three polypeptides of molecular weights 18,000, 17,000, and 14,000 were formed, and the significance of these polypeptides is discussed. The operator-distal portion of the unc operon was also cloned into plasmid pACYC184, forming plasmid pAN36, which included the uncD and uncC genes. When this plasmid was used as template in an in vitro transcription/translation system, the β subunit (from the uncD gene) and the ε subunit (from the uncC gene) of the F 1 ATPase were formed. A polypeptide of a molecular weight similar to the ε subunit but of different net charge was also formed. Plasmid pAN45, carrying the complete unc operon, was isolated after digestion of a mixture of plasmids pAN51 and pAN36 with the restriction endonuclease Hin dIII and then religation with T4 deoxyribonucleic acid ligase. It was concluded that a Hin dIII restriction site occurred within the newly described uncG gene, which was shown, by complementation studies with Mu-induced mutants, to be located between the uncA and uncD genes to give the gene order uncBEAGDC . The uncG gene appears to code for the γ subunit of the F 1 ATPase.