title: Characterization of the transport of lysine-containing dipeptides by PepT1 orthologs expressed in Xenopus laevis oocytes.
abstract: During digestion, dietary proteins cleaved in di and tri-peptides are translocated from the intestinal lumen into the enterocytes via PepT1 (SLC15A1) using an inwardly directed proton electrochemical gradient. The kinetic properties in various PepT1 orthologs (Dicentrarchus labrax, Oryctolagus cuniculus, Danio rerio) have been explored to determine the transport efficiency of different combinations of lysine, methionine, and glycine. Species-specific differences were observed. Lys-Met resulted the best substrate at all tested potentials in sea bass and rabbit PepT1, whereas in the zebrafish transporter all tested dipeptides (except Gly-Lys) elicited similar currents independently on the charge position or amino acid composition. For the sea bass and rabbit PepT1, kinetic parameters, K(0.5) and I(max) and their ratio, show the importance of the position of the charged lysine in the peptide. The PepT1 transporter of these species has very low affinity for Lys-Lys and Gly-Lys; this reduces the transport efficiency which is instead higher for Lys-Met and Lys-Gly. PepT1 from zebrafish showed relatively high affinity and excellent transport efficiency for Met-Lys and Lys-Met. These data led us to speculate about the structural determinants involved in substrate interaction according to the model proposed for this transporter.
authors.affiliation: Department of Biotechnology and Life Science, University of Insubria, Via J.H. Dunant 3, I-21100 Varese, Italy.
authors.forename: Eleonora
authors.initials: E
authors.lastname: Margheritis
authors.forename: Genciana
authors.initials: G
authors.lastname: Terova
authors.forename: Ayodele Stephen
authors.initials: AS
authors.lastname: Oyadeyi
authors.forename: Maria Daniela
authors.initials: MD
authors.lastname: Renna
authors.forename: Raffaella
authors.initials: R
authors.lastname: Cinquetti
authors.forename: Antonio
authors.initials: A
authors.lastname: Peres
authors.forename: Elena
authors.initials: E
authors.lastname: Bossi
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001492:Bass; D016384:Consensus Sequence; D004151:Dipeptides / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008564:Membrane Potentials; D008969:Molecular Sequence Data; D009865:Oocytes / Q000378:metabolism*; D000074011:Peptide Transporter 1; D021381:Protein Transport; D011817:Rabbits; D011994:Recombinant Proteins / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity; D027981:Symporters / Q000737:chemistry / Q000378:metabolism*; D014982:Xenopus laevis; D015027:Zebrafish; D029961:Zebrafish Proteins / Q000737:chemistry / Q000378:metabolism*
chemical_list: D004151:Dipeptides; D000074011:Peptide Transporter 1; D011994:Recombinant Proteins; D027981:Symporters; D029961:Zebrafish Proteins; C000613207:slc15a1b protein, zebrafish