Proteins of the Proton-dependent Oligopeptide Transporter (POT) Family (also called the PTR (peptide transport) family) are found in animals, plants, yeast, archaea and both Gram-negative and Gram-positive bacteria, and are part of the major facilitator superfamily. The transport of peptides into cells is a well-documented biological phenomenon which is accomplished by specific, energy-dependent transporters found in a number of organisms as diverse as bacteria and humans. The proton-dependent oligopeptide transporter (PTR) family of proteins is distinct from the ABC-type peptide transporters and was uncovered by sequence analyses of a number of recently discovered peptide transport proteins.^[1] These proteins that seem to be mainly involved in the intake of small peptides with the concomitant uptake of a proton.^[2]

While most members of the POT family catalyze peptide transport, one is a nitrate permease and one can transport histidine, as well as peptides. Some of the peptide transporters can also transport antibiotics. They function by proton symport, but the substrate:H⁺ stoichiometry is variable: the high-affinity rat PepT2 carrier catalyzes uptake of 2 and 3 H⁺ with neutral and anionic dipeptides, respectively, while the low affinity PepT1 carrier catalyzes uptake of one H⁺ per neutral peptide.^[3][4]

The generalized transport reaction catalyzed by the proteins of the POT family is:

substrate (out) + H (out) → substrate (in) H⁺ (in)

The proteins are of about 450-600 amino acyl residues in length with the eukaryotic proteins in general being longer than the bacterial proteins. They exhibit 12 putative or established transmembrane α-helical spanners.

Pairs of salt bridge interactions between transmembrane helices work in tandem to orchestrate alternating access transport within the PTR family.^[5] Key roles for residues conserved between bacterial and eukaryotic homologues suggest a conserved mechanism of peptide recognition and transport that in some cases has been subtly modified in individual species.

• Oligopeptide transporter, peptide:H+ symporter InterPro: IPR004768
• Amino acid/peptide transporter InterPro: IPR005279

FP12591; PEPT1; PTR4; SLC15A1; SLC15A2; SLC15A3; SLC15A4; hPEPT1-RF;

As of this edit, this article uses content from "2.A.17 The Proton-dependent Oligopeptide Transporter (POT/PTR) Family", which is licensed in a way that permits reuse under the Creative Commons Attribution-ShareAlike 3.0 Unported License, but not under the GFDL. All relevant terms must be followed.

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