title: Multiplicity of oligopeptide transport systems in Escherichia coli.
abstract: The ability of Escherichia coli K-12 4212 to utilize a variety of oligopeptides as sources of required amino acids was examined. Triornithine-resistant mutants of this strain were oligopeptide permease deficient (Opp-) as judged by their inability to utilize (Lys)3 and (Lys)4 as sources of lysine and their resistance to the toxic tripeptide (Val)3. These same mutants were able to grow when Met-Met-Met, Met-Gly-Met, Met-Gly-Gly, Gly-Met-Gly, Gly-Gly-Met, Gly-Met-Met, Met-Met-Gly, or Leu-Leu-Leu were supplied in place of the requisite amino acid. The system mediating the uptake of these peptides, herein designated Opr I, was not able to transport N-alpha-acetylated peptides, nor the tetrapeptides Met-Gly-Met-Met, Met-Met-Gly-Met, or Met-Met-Met-Gly. Competition experiments indicated that trimethionine and trileucine enter E. coli K-12 via either Opp or Opr I. Analogous results were found using the methionine, leucine-requiring auxotroph E. coli B163. It appears that more than one oligopeptide transport system exists in E. coli and that the system mediating peptide uptake is complex.
mesh_terms: D001693:Biological Transport, Active; D002474:Cell-Free System; D004590:Electrophoresis, Paper; D004926:Escherichia coli / Q000201:enzymology / Q000254:growth & development / Q000378:metabolism*; D005998:Glycine / Q000378:metabolism; D007930:Leucine / Q000378:metabolism; D008239:Lysine / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000378:metabolism; D008715:Methionine / Q000378:metabolism; D009154:Mutation; D009842:Oligopeptides / Q000378:metabolism*; D009952:Ornithine / Q000378:metabolism
chemical_list: D026901:Membrane Transport Proteins; D009842:Oligopeptides; D008715:Methionine; D009952:Ornithine; D007930:Leucine; D008239:Lysine; D005998:Glycine