Ligand binding analyses of the putative peptide transporter YjdL from E. coli display a significant selectivity towards dipeptides.
Proton-dependent oligopeptide transporters (POTs) are secondary active transporters that couple the inwards translocation of di- and tripeptides to inwards proton translocation. Escherichia coli contains four genes encoding the putative POT proteins YhiP, YdgR, YjdL and YbgH. We have over-expressed the previously uncharacterized YjdL and investigated the peptide specificity by means of uptake inhibition. The IC(50) value for the dipeptide Ala-Ala was measured to 22 mM while Ala-Ala-Ala was not able to inhibit uptake. In addition, IC(50) values of 0.3 mM and 1.5 mM were observed for Ala-Lys and Tyr-Ala, respectively, while the alanyl-extended tripeptides Ala-Lys-Ala, Ala-Ala-Lys, Ala-Tyr-Ala and Tyr-Ala-Ala displayed values of 8, >50, 31 and 31 mM, respectively. These results clearly indicate that unlike most POT members characterized to date, including YdgR and YhiP, YjdL shows significantly higher specificity towards dipeptides.
Ernst
Heidi A
HA
Biostructural Research, Department of Medicinal Chemistry, Faculty of Pharmaceutical Sciences, University of Copenhagen, Universitetsparken 2, 2100 Copenhagen, Denmark.
Pham
Antony
A
Hald
Helle
H
Kastrup
Jette S
JS
Rahman
Moazur
M
Mirza
Osman
O
D003374:Coumarins / Q000378:metabolism; D004151:Dipeptides / Q000378:metabolism*; D004926:Escherichia coli / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D008024:Ligands; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D009842:Oligopeptides / Q000378:metabolism
D003374:Coumarins; D004151:Dipeptides; D029968:Escherichia coli Proteins; D008024:Ligands; D026901:Membrane Transport Proteins; D009842:Oligopeptides; C544083:YjdL protein, E coli; C118033:alanyl-lysyl-amca