Pept1

PEPT1, also called SLC15A1, belongs to the SLC15 family (solute carrier proteins). The SLC series comprises genes encoding passive transporters, ion-coupled secondary active transporters, and exchangers. A transporter is assigned to a specific SLC family if it has at least 20–25% sequence amino-acid similarity to other members of that family. The SLC15 family comprises four members, namely SLC15A1 (PEPT1), SLC15A2 (PEPT2), SLC15A3 (PHT2, PTR3), and SLC15A4 (PHT1, PTR4). These four members of the SLC15 family belong to the proton-dependent oligopeptide transporter (POT) family. The POT proteins function as symporters with protons, which provide the driving force for transport across the plasma membrane. The four mammalian proteins are known to transport dipeptides, whereas the transport of tripeptides has been shown only for PEPT1 and PEPT2. Both PEPT1 and PEPT2 are thought to be capable of transporting the 400 dipeptides and 8,000 tripeptides that are derived from the 20 natural L-amino acids, the main source for food-derived proteins. Moreover, both proteins transport ω-amino fatty acids carrying a positively and a negatively charged headgroup separated by at least four methylene groups. Beside their role in active absorption of food-derived dipeptides and tripeptides, both transporters are known to transport a large number of bioactive, structurally related compounds such as various cephalosporins, angiotensin-converting enzyme inhibitors, and 5′-amino acid esters of the antiviral nucleosides, acyclovir and zidovudine (AZT).