title: Stereospecificity of tripeptide utilization in a methionine auxotroph of Escherichia coli K-12.
abstract: The stereospecificity of peptide utilization in Escherichia coli K-12 4212, a methionine auxotroph, was investigated using diastereomers of trimethionine and trimethionine methyl ester. Of the eight stereoisomers examined, only l-Met-l-Met-l-Met, l-Met-l-Met-d-Met, and d-Met-l-Met-l-Met and the corresponding methyl esters serve as growth substrates. Triornithine-resistant mutants of strain 4212 were isolated which failed to transport d-Met-l-Met-l-Met. These results provide evidence that an oligopeptide containing a d residue at its amine terminus can enter E. coli by the oligopeptide transport system.
mesh_terms: D002474:Cell-Free System; D004590:Electrophoresis, Paper; D010450:Endopeptidases / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology / Q000254:growth & development / Q000378:metabolism*; D008715:Methionine / Q000378:metabolism*; D009154:Mutation; D009842:Oligopeptides / Q000378:metabolism*; D009952:Ornithine / Q000378:metabolism; D013237:Stereoisomerism
chemical_list: D009842:Oligopeptides; D008715:Methionine; D009952:Ornithine; D010450:Endopeptidases