Molecular cloning of pheR in Escherichia coli K-12.

The regulator gene pheR, which in Escherichia coli controls the expression of pheA, the structural gene for chorismate mutase P-prephenate dehydratase, was cloned on to multicopy plasmids directly from the E. coli chromosome; this was achieved with the aid of the tetracycline resistance transposon, Tn10, that had been inserted very close to the pheR gene. Subsequently, pheR was subcloned on a 1.1-kilobase-pair fragment on the plasmid vector pBR322; its position on the plasmid was localized by the method of gamma delta-mediated transpositional inactivation. The pheR gene product was identified in maxicells and found to be a protein of subunit molecular weight 19,000, suggesting that the coding segment of the gene is about 500 nucleotide pairs long.