Interaction of β-Lactam Antibiotics with Histidine Residue of Rat H⁺/Peptide Cotransporters, PEPT1 and PEPT2*

Abstract

Peptide transporters mediate the H⁺-coupled uphill transport of oligopeptides and peptide-like drugs such as β-lactam antibiotics in the intestinal and renal brush-border membranes. Two H⁺/peptide cotransporters, PEPT1 and PEPT2, have been cloned and functionally characterized. In this study, we examined the interaction of the dipeptides and β-lactam antibiotics with the histidine residue of rat PEPT1 and PEPT2 transfected into the renal epithelial cell line LLC-PK₁. Diethylpyrocarbonate (DEPC), which is a histidine residue modifier, abolished the glycylsarcosine uptake by both transfectants. The DEPC-induced inhibition of glycylsarcosine uptakevia PEPT1 or PEPT2 was attenuated by an excess of dipeptide or aminocephalosporin. In contrast, anionic cephalosporins without an α-amino group and bestatin, which is an antineoplastic drug with a β-amino group, did not attenuate the DEPC-induced inactivation of PEPT1 and PEPT2. The DEPC inactivation of PEPT1 was almost prevented by various charged dipeptides, which suggests that the inability of the drugs without an α-amino group to prevent the DEPC inactivation was not due to their ionic charge. These findings suggest that the α-amino group of β-lactam antibiotics interacts with the histidine residue of PEPT1 and PEPT2 and may be involved in the mechanism of substrate recognition by the peptide transporters.