Methionine Transport in Wild-type and Transport-defective Mutants of Salmonella typhimurium

SUMMARY: Salmonella typhimurium possesses a permease specific for L-methionine (Km of 0.1 to 0.2 µM). Competition studies have shown that the permease has little or no affinity for the other L-amino acids commonly found in proteins. Methionine uptake was competitively inhibited by the growth inhibitory analogues DL-ethionine, α-methyl-DL-methionine and DL-methionine-DL-sulphoximine. Mutants resistant to α-methyl-methionine and methionine sulphoximine have been isolated which were severely defective in the methionine specific permease. Two of these mutants, metP760 and metP761, mapped away from all previously located methionine structural and regulatory genes.