Glutamyl-γ-methyl ester acts as a methionine analogue inEscherichia coli: analogue resistant mutants map at themetJandmetKloci

SUMMARY Escherichia coliK-12 mutants resistant to glutamyl-γ-methyl ester were isolated. A mutation leading to resistance of up to 1·4 mg/ml of the methionine analogue maps at min 63 and is 13% cotransducible withserAindicating an alteration in themetKgene. Another mutation leading to resistance to 3 mg/ml of the analogue and cross-resistance to other amino acid analogues maps at min 87. This mutation, which has the phenotype of MetJ−, is shown to be situated between theglpKandmetBgenes and thus indicates a different gene order from the published one.