Transcription regulation coupling of the divergent argG and metY promoters in Escherichia coli K-12.

The cAMP-catabolite activator protein (CAP) complex is a pleiotropic regulator that regulates a vast number of Escherichia coli genes, including those involved in carbon metabolism. We identified two new targets of this complex: argG, which encodes the arginosuccinate synthase involved in the arginine biosynthetic pathway, and metY, which encodes one of the two methionine tRNA initiators, tRNAf2Met. The cAMP-CAP complex activates argG transcription and inhibits metY transcription from the same DNA position. We also show that ArgR, the specific repressor of the arginine biosynthetic pathway, together with its arginine cofactor, acts on the regulation of metY mediated by CAP. The regulation of the two divergent promoters is thus simultaneously controlled not only by the cAMP-CAP complex, a global regulator, but also by a specific regulator of arginine metabolism, suggesting a previously unsuspected link between carbon metabolism and translation initiation.