Six methionine auxotrophs were isolated from an E. coli K-12 strain which required up to 100 times as much methionine for growth as a conventional auxotroph. In these mutants, the methionyl-tRNA synthetase had an increased Km for methionine. The Km value for the mutants ranged from 0.48 to 1.63 mM, compared to 0.078 mM for the wild type. The Km (methionine) for S-adenosyl methionine synthetase was not altered.
31P NMR of the reversible methionine activation reaction catalyzed by methionyl-tRNA synthetase of Escherichia coli. Equilibrium, interconversion rates, and NMR parameters of the enzyme-bound species.