title: Specificity of peptide transport systems in Lactococcus lactis: evidence for a third system which transports hydrophobic di- and tripeptides.
abstract: A proton motive force-driven di-tripeptide carrier protein (DtpT) and an ATP-dependent oligopeptide transport system (Opp) have been described for Lactococcus lactis MG1363. Using genetically well-defined mutants in which dtpT and/or opp were inactivated, we have now established the presence of a third peptide transport system (DtpP) in L. lactis. The specificity of DtpP partially overlaps that of DtpT. DtpP transports preferentially di- and tripeptides that are composed of hydrophobic (branched-chain amino acid) residues, whereas DtpT has a higher specificity for more-hydrophilic and charged peptides. The toxic dipeptide L-phenylalanyl-beta-chloro-L-alanine has been used to select for a di-tripeptide transport-negative mutant with the delta dtpT strain as a genetic background. This mutant is unable to transport di- and tripeptides but still shows uptake of amino acids and oligopeptides. The DtpP system is induced in the presence of di- and tripeptides containing branched-chain amino acids. The use of ionophores and metabolic inhibitors suggests that, similar to Opp, DtpP-mediated peptide transport is driven by ATP or a related energy-rich phosphorylated intermediate.
authors.affiliation: Station de Recherches Laitières, Institut National de la Recherche Agronomique, Jouy-en-Josas, France.
authors.forename: C
authors.initials: C
authors.lastname: Foucaud
authors.forename: E R
authors.initials: ER
authors.lastname: Kunji
authors.forename: A
authors.initials: A
authors.lastname: Hagting
authors.forename: J
authors.initials: J
authors.lastname: Richard
authors.forename: W N
authors.initials: WN
authors.lastname: Konings
authors.forename: M
authors.initials: M
authors.lastname: Desmazeaud
authors.forename: B
authors.initials: B
authors.lastname: Poolman
mesh_terms: D000595:Amino Acid Sequence; D001692:Biological Transport / Q000235:genetics; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D004151:Dipeptides / Q000378:metabolism* / Q000494:pharmacology; D004352:Drug Resistance, Microbial / Q000235:genetics; D015870:Gene Expression; D006863:Hydrogen-Ion Concentration; D013294:Lactococcus lactis / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation; D009842:Oligopeptides / Q000378:metabolism*; D013379:Substrate Specificity
chemical_list: D002352:Carrier Proteins; D004151:Dipeptides; D009842:Oligopeptides; C095142:phenylalanyl-beta-chloroalanine