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76  structures 4220  species 0  interactions 28124  sequences 199  architectures

Family: PTR2 (PF00854)

Summary: POT family

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This is the Wikipedia entry entitled "Proton-dependent oligopeptide transporter". More...

Proton-dependent oligopeptide transporter Edit Wikipedia article

POT family
OPM superfamily15
OPM protein2xut

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]

Transport Reaction

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

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

Structure and Mechanism

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.


Human proteins containing this domain

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


  1. ^ Naider F, Becker JM, Steiner HY (1995). "The PTR family: a new group of peptide transporters". Mol. Microbiol. 16 (5): 825–834. doi:10.1111/j.1365-2958.1995.tb02310.x. PMID 7476181.
  2. ^ Skurray RA, Paulsen IT (1994). "The POT family of transport proteins". Trends Biochem. Sci. 19 (10): 404–404. doi:10.1016/0968-0004(94)90087-6. PMID 7817396.
  3. ^ Bucking, Carol; Schulte, Patricia M. (2012-04-01). "Environmental and nutritional regulation of expression and function of two peptide transporter (PepT1) isoforms in a euryhaline teleost". Comparative Biochemistry and Physiology. Part A, Molecular & Integrative Physiology. 161 (4): 379–387. doi:10.1016/j.cbpa.2011.12.008. ISSN 1531-4332. PMID 22227314.
  4. ^ Chen, Xing-Zhen (29 Jan 1999). "Stoichiometry and kinetics of the high-affinity H+-coupled peptide transporter PepT2". Journal of Biological Chemistry. 274 (5). doi:10.1074/jbc.274.5.2773. PMID 9915809.
  5. ^ Doki, Shintaro; Kato, Hideaki E.; Solcan, Nicolae; Iwaki, Masayo; Koyama, Michio; Hattori, Motoyuki; Iwase, Norihiko; Tsukazaki, Tomoya; Sugita, Yuji (2013-07-09). "Structural basis for dynamic mechanism of proton-coupled symport by the peptide transporter POT". Proceedings of the National Academy of Sciences of the United States of America. 110 (28): 11343–11348. doi:10.1073/pnas.1301079110. ISSN 1091-6490. PMC 3710879. PMID 23798427.

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.

This article incorporates text from the public domain Pfam and InterPro: IPR000109

This page is based on a Wikipedia article. The text is available under the Creative Commons Attribution/Share-Alike License.

This tab holds the annotation information that is stored in the Pfam database. As we move to using Wikipedia as our main source of annotation, the contents of this tab will be gradually replaced by the Wikipedia tab.

POT family Provide feedback

The POT (proton-dependent oligopeptide transport) family all appear to be proton dependent transporters [1].

Literature references

  1. Paulsen IT, Skurray RA; , Trends Biochem Sci 1994;19:404-404.: The POT family of transport proteins. PUBMED:7817396 EPMC:7817396

Internal database links

External database links

This tab holds annotation information from the InterPro database.

InterPro entry IPR000109

The proton-dependent oligopeptide transporter (POT) family (also known as the peptide transport (PTR) family) is made up of a group of energy-dependent transporters found in organisms as diverse as bacteria and humans. The POT family of proteins is distinct from the ABC-type peptide transporters and was uncovered by sequence analyses of peptide transport proteins [ PUBMED:7476181 ]. They seem to be mainly involved in the intake of small peptides [ PUBMED:7817396 ]. However, some family members are nitrate permeases and others are involved in histidine transport [ PUBMED:17481610 ].

Gene Ontology

The mapping between Pfam and Gene Ontology is provided by InterPro. If you use this data please cite InterPro.

Domain organisation

Below is a listing of the unique domain organisations or architectures in which this domain is found. More...

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Pfam Clan

This family is a member of clan MFS (CL0015), which has the following description:

The major facilitator superfamily (MFS) is one of the two largest families of membrane transporters found on Earth [1]. It is present ubiquitously in bacteria, archaea, and eukarya and includes members that can function by solute uniport, solute/cation symport, solute/cation antiport and/or solute/solute antiport with inwardly and/or outwardly directed polarity [1]. All permeases of the MFS possess either 12 or 14 transmembrane helices [1].

The clan contains the following 23 members:

Acatn ATG22 BT1 Folate_carrier FPN1 LacY_symp MFS_1 MFS_1_like MFS_2 MFS_3 MFS_4 MFS_5 MFS_Mycoplasma Nodulin-like Nuc_H_symport Nucleoside_tran OATP PTR2 PUCC Sugar_tr TLC TRI12 UNC-93


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Curation and family details

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Curation View help on the curation process

Seed source: Pfam-B_571 (release 3.0)
Previous IDs: none
Type: Family
Sequence Ontology: SO:0100021
Author: Bateman A
Number in seed: 21
Number in full: 28124
Average length of the domain: 320.70 aa
Average identity of full alignment: 20 %
Average coverage of the sequence by the domain: 70.58 %

HMM information View help on HMM parameters

HMM build commands:
build method: hmmbuild -o /dev/null HMM SEED
search method: hmmsearch -Z 57096847 -E 1000 --cpu 4 HMM pfamseq
Model details:
Parameter Sequence Domain
Gathering cut-off 21.9 21.9
Trusted cut-off 21.9 21.9
Noise cut-off 21.8 21.8
Model length: 397
Family (HMM) version: 23
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Species distribution

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Colour assignments

Archea Archea Eukaryota Eukaryota
Bacteria Bacteria Other sequences Other sequences
Viruses Viruses Unclassified Unclassified
Viroids Viroids Unclassified sequence Unclassified sequence


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For those sequences which have a structure in the Protein DataBank, we use the mapping between UniProt, PDB and Pfam coordinate systems from the PDBe group, to allow us to map Pfam domains onto UniProt sequences and three-dimensional protein structures. The table below shows the structures on which the PTR2 domain has been found. There are 76 instances of this domain found in the PDB. Note that there may be multiple copies of the domain in a single PDB structure, since many structures contain multiple copies of the same protein sequence.

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