Regulation of phenylalanine biosynthesis in Escherichia coli K-12: control of transcription of the pheA operon.

Bacteriophage lambda ppheA-lac was used to obtain strains of Escherichia coli K-12 in which pheA and lacZ are each transcribed from a separate pheA promoter. Mutants in which both beta-galactosidase and chorismate mutase P-prephenate dehydratase (the pheA gene product) were derepressed were isolated, and a transacting gene (pheR) was identified. pheR was mapped at min 93 on the E. coli chromosome; pheR mutants acquired the wild-type phenotype when either F117 (which covers the 93-min region) or F116 (which covers min 59 to 65) was introduced into the cell. A rifampin resistance mutation, rpoB366, was found to derepress transcription of the pheA operon. pheR and rpoB366 affected two different systems for the phenylalanine-mediated control of pheA. A mutation in miaA (trpX), a gene known to be involved in attenuation in the tryptophan operon, was also shown to increase transcription of the pheA gene.