Physical mapping of the scattered methionine genes on the Escherichia coli chromosome

Methionine is an important amino acid which acts not only as a substrate for protein elongation but also as the initiator of protein synthesis. The genes of the met regulon, which consists of 10 biosynthetic genes (metA, metB, metC, metE, metF, metH, metK, metL, metQ, and metX), two regulatory genes (metJ and metR), and the methionyl tRNA synthetase gene (metG), are scattered throughout the chromosome. The only linked genes are metK and metX at 63.6 min, metE and metR at 86.3 min, and the metJBLF gene cluster at 89 min. metBL form the only met operon.