Proton-dependent uptake of di- or tripeptides, and to a minor extent tetrapeptides. Transport is independent of sodium and chloride ions. Protein shows high affinity to peptide substrates. Expressed in vulval, pharyngeal and anal muscles. Gradual increase in expression during development from embryo through to adult with highest levels of expression in the late larval and adult stages. Belongs to the major facilitator superfamily. Proton-dependent oligopeptide transporter (POT/PTR) (TC 2.A.17) family.