TCDB is operated by the Saier Lab Bioinformatics Group
TCIDNameDomainKingdom/PhylumProtein(s)
*2.A.17.1.1









Di- or tripeptide:H+ symporter
Bacteria
Firmicutes
DtpT of Lactococcus lactis (P0C2U2)
*2.A.17.1.2









The di/tripeptide:H+ symport permease, TppB (DtpA or YdgR) (transports di and tripeptides and peptidomimetics such as aminocephalosporins (Weitz et al., 2007).  The transporter has two alternate conformations, one of which is promoted by inhbitor binding (Bippes et al. 2013).

Bacteria
Proteobacteria
TppB of E. coli (P77304)
*2.A.17.1.3









The dipeptide/tripeptide:H+ symport permease, DtpB (YhiP) (transports glycyl-sarcosine (Gly-Sar) with low affinity (6mM) and the toxic dipeptide, alafosfalin (Harder et al., 2008)
Bacteria
Proteobacteria
DtpB of E. coli (P36837)
*2.A.17.1.4









DtpD (YbgH) peptide transporter.  A projection structure at 19 Å resolution and a high resolution x-ray structure are available; Casagrande et al., 2009; Zhao et al. 2014). Glu21 is the only conserved proton-titratable amino acyl residue (among POTs) that is located in the central cavity, and it is critical for in vivo transport (Zhao et al. 2014).

Bacteria
Proteobacteria
DtpD of E. coli (P75742)
*2.A.17.1.5









Peptide transporter, YjdL (preference for di-peptides) (Ernst et al., 2009; Gabrielsen et al., 2011; Jensen et al., 2011).  The motif, ExxERFxxYY has been shown to be involved in proton translocation, and the nearby K117 may play a dual role in protonation and substrate binding (Jensen et al. 2014).

Bacteria
Proteobacteria
YjdL of E. coli (P39276)
*2.A.17.1.6









POT famiy di- and tri-peptide porter, DtpT. 3-d structures (PDB:24APS; 5MMT: 5D58' 5D59) are available for an inward open conformation. A hinge-like movement in the C-terminal half facilitates opening of an intracellular gate controlling access to a central peptide binding site. Salt bridges may orchestrate alternating access (Solcan et al., 2012; Quistgaard et al. 2017).

Bacteria
Firmicutes
Peptide porter, DtpT of Streptococcus thermophilus (Q5M4H8)
*2.A.17.1.7









Peptide uptake transporter of 496 aas, POT.  The 3-d structure has been determined to 1.9Å resolution leading to a proposed mechanism (Doki et al. 2013).  Glu310 first may bind the carboxyl group of the peptide substrate. Then deprotonation of Glu310 in the inward open state triggers the release of the bound peptide toward the intracellular space, and salt bridge formation between Glu310 and Arg43 induces the transition state to the occluded conformation.

Bacteria
Firmicutes
POT of Geobacillus kaustophilus
*2.A.17.1.8









Proton-coupled oligopeptide uptake transporter of 485 aas and 14 TMSs, DtpT or Pot.  Expression of the encoded gene is upregulated upon infection. Transports di- and tripeptides but can not accumulate peptides with a positively charged residue in the C-terminal position.  An aromatic residue patch in the active site of the transporter may be responsible for it's unusual specificity (Sharma et al. 2016).

Bacteria
Proteobacteria
DtpT of Neisseria meningitidis
*2.A.17.2.1









Peptide:H+ symporter
Eukaryota
Fungi
PTR2-A of Arabidopsis thaliana
*2.A.17.2.2









Peptide:H+ symporter (dipeptides preferred; Cai et al., 2007).
Eukaryota
Fungi
PTR2 of Saccharomyces cerevisiae
*2.A.17.2.3









Dipeptide uptake porter, Ptr2.  Transports dipeptides such as Ala-Leu, Ala-Tyr and Tyr-Ala (Belmondo et al. 2014).

Eukaryota
Fungi
Ptr2 of Rhizophagus irregularis (Arbuscular mycorrhizal fungus) (Glomus intraradices)
*2.A.17.3.1









Dual affinity Nitrate/Chlorate symporter, Nrt1.1; CHL1 (Martin et al., 2008).  The low affinity form is a homo-dimer and has Thr101 in the non-phosphorylated form; the high affinty form (0.1 micromolar Km) is a monomer and has Thr101 phosphorylated (Sun and Zheng 2015).

Eukaryota
Viridiplantae
Ntr1.1/CHL1 of Arabidopsis thaliana
*2.A.17.3.2









Histidine or peptide:H+ symporter
Eukaryota
Viridiplantae
PTR2-B (NTR1) of Arabidopsis thaliana
*2.A.17.3.3









Nitrate (chlorate) or histidine:H+ symporter
Eukaryota
Viridiplantae
RCH2 of Brassica napus
*2.A.17.3.4









Peptide transporter, PTR3-A (induced by histidine, leucine and phenylalanine in cotyledons and lower leaves; involved in stress tolerance in seeds during germination and in defense against virulent bacterial pathogens) (Karim et al., 2007; Karim et al., 2005)
Eukaryota
Viridiplantae
PTR3-A of Arabidopsis thaliana (Q9FNL7)
*2.A.17.3.5









The nitrate excretion transporter1, NaxT1 (in the plasma membranes of plant cells)
Eukaryota
Viridiplantae
NaxT1 of Arabidopsis thaliana (Q9M1E2)
*2.A.17.3.6









Chloroplast nitrite uptake system, Nitr1-L (Sugiura et al., 2007)
Eukaryota
Viridiplantae
Nitr1-L of Arabidopsis thaliana (Q9SX20)
*2.A.17.3.7









The root dipeptide/tripeptide transporter, PTRI (Komarova et al., 2008). Transport is electrogenic and dependent on protons. Leak currents are inhibited by Phe-Ala when this peptide binds at the active site with high affinity (Hammes et al., 2010).

Eukaryota
Viridiplantae
PTR1 of Arabidopsis thaliana (Q9M390)
*2.A.17.3.8









The germinating pollen dipeptide/tripeptide transporter, PTR5 (Komarova et al., 2008). Transport is electrogenic and dependent on protons. Leak currents are inhibited by Phe-Ala when this peptide binds at the active site with high affinity (Hammes et al., 2010).

Eukaryota
Viridiplantae
PTR5 of Arabidopsis thaliana (Q0WR84)
*2.A.17.3.9









solute carrier family 15, member 3, di- and tri-peptide uptake transporter in immune cells (Verri et al. 2016).

Eukaryota
Metazoa
SLC15A3 of Homo sapiens
*2.A.17.3.10









solute carrier family 15, member 5.  Function unknown as of 1/17, but probably a di- and tri-peptide uptake porter (Verri et al. 2016). The tissue expression profile has been reported (Sreedharan et al. 2011).

 

Eukaryota
Metazoa
SLC15A5 of Homo sapiens
*2.A.17.3.11









Solute carrier family 15 member 4 (Peptide transporter 4) (Peptide/histidine transporter 1) (hPHT1) present in immune cells (Verri et al. 2016).

Eukaryota
Metazoa
SLC15A4 of Homo sapiens
*2.A.17.3.12









Putative peptide/nitrate transporter At3g25280
Eukaryota
Viridiplantae
At3g25280 of Arabidopsis thaliana
*2.A.17.3.13









Probable peptide transporter At1g52190
Eukaryota
Viridiplantae
At1g52190 of Arabidopsis thaliana
*2.A.17.3.14









Nitrate transporter 1.6
Eukaryota
Viridiplantae
NRT1.6 of Arabidopsis thaliana
*2.A.17.3.15









Nitrate transporter 1.7
Eukaryota
Viridiplantae
NRT1.7 of Arabidopsis thaliana
*2.A.17.3.16









Nitrate transporter 1.2 (Nitrate transporter NTL1).  Low-affinity proton-dependent nitrate transporter involved in constitutive nitrate uptake but not histidine or dipeptides transport. Involved in (+)-abscisic acid (ABA) transport, but not in gibberellin, indole-3-acetic acid or jasmonic acid import (Kanno et al. 2013).

Eukaryota
Viridiplantae
NRT1.2 of Arabidopsis thaliana
*2.A.17.3.17









Transporter for glucosinolates (aliphatic but not indole glucosinolates such as 4-methylthiobutyl glucosinolate, major defence compounds, translocated to seeds on maturation) as well as gibberellic acid and jasmonoyl-L-isoleucine, GTR1 or NPF2.10, of 636 aas and 12 TMSs (Nour-Eldin et al. 2012; Ishimaru et al. 2017). Regulated at the transcriptional level, but also postranslationally.  Dimerization of GTR1, possibly induced by dephosphorylation of a Thr residue, regulates its plasma membrane localization, leading to increased transport of glucosinolates and gibberellic acid (Ishimaru et al. 2017).

Eukaryota
Viridiplantae
GTR1 of Arabidopsis thaliana
*2.A.17.3.18









Nitrate transporter 1.4
Eukaryota
Viridiplantae
NRT1.4 of Arabidopsis thaliana
*2.A.17.3.19









Nitrate transporter 1.5
Eukaryota
Viridiplantae
NRT1.5 of Arabidopsis thaliana
*2.A.17.3.20









High-affinity, proton-dependent glucosinolate-specific transporter-2, GTP2 or NPF2.11. Involved in apoplasmic phloem-loading of glucosinolates and in bidirectional long-distance transport of aliphatic but not indole glucosinolates. May be involved in removal of glucosinolates from the xylem in roots (Nour-Eldin et al. 2012; Andersen et al. 2013).

Eukaryota
Viridiplantae
GTR2 of Arabidopsis thaliana
*2.A.17.3.21









Low affinity nitrate transporter, Nrt1, of 584 aas and 13 putative TMSs.  Two splice variants, Ntr1.1a and Ntr1.1b, have been identified.  Under low nitrogen condition, Nrt1.1b accumulates more nitrogen in plants and improves rice growth, but Ntr1.1a had no such effect (Fan et al. 2015).

Eukaryota
Viridiplantae
Ntr1 of Oryza sativa (Rice)
*2.A.17.4.1









Peptide:H+ symporter (transports cationic, neutral and anionic dipeptides including glycylsarcosine (gly-sar) (Søndergaard et al., 2008) as well as anserine (β-alanyl-1-N-methyl-L-histidine) and carnosine (β-alanyl-L-histidine) (Geissler et al., 2010); also transports β-lactam antibiotics, the antitumor agent, bestatin, and various protease inhibitors). It is competitively inhibited by L-4,4'-biphenylalanyl-L-proline (Bip-Pro) with ~10-20µM affinity. Inhibitors/substrates include cefadroxil, Ala-4-nitroanilide and δ-aminolevulinic acid (Knutter et al., 2007). The intracellular loop linking transmembrane domains 6 and 7 of the human dipeptide transporter hPEPT1 includes two amphipathic alpha-helices, with net positive and negative charges which interact and influence conformational changes of hPEPT1 during and after glycylsarcosine transport (Xu et al., 2010).  The rabbit orthologue provides the main pathway for dietary nitrogen uptake. Five tyrosyl residues are important for function and/or substrate binding (Pieri et al. 2009).  Human PepT1 is modified by N-glycosylation, and all six asparagine residues in the large extracellular loop between transmembrane domains 9 and 10 are subject to N-glycosylation (Chan et al. 2016).

Eukaryota
Metazoa
PepT1 of Rattus norvegicus
*2.A.17.4.2









Oligopeptide transporter 1
Eukaryota
Metazoa
Oligopeptide transporter of Drosophila melanogaster
*2.A.17.4.3









High affinity oligopeptide transporter, CPTA. It transports di-, tri- and tetra peptides with low specificity. Neuropeptides (FMRF-amide and N-acetyl-Asp-Glu) are also transported (Fei et al. 1998).

Eukaryota
Metazoa
CPTA of Caenorhabditis elegans
*2.A.17.4.4









The renal brush-border electrogenic, proton-coupled, broad specificity, high affinity, peptide transporter, PepT2 (Rubio-Aliaga et al., 2000). It is competitively inhibited by L-4,4'-Biphenylalanyl-L-Proline (Bip-Pro) with ~10-20┬ÁM affinity. Inhibitor/substrates includes cefadroxil, Ala-4-nitroanilide and delta-aminolevulinic acid (Knutter et al., 2007).
Eukaryota
Metazoa
PepT2 of Mus musculus (Q9ES07)
*2.A.17.4.5









The high affinity, low capacity, peptide transporter, PepT2 (SLC15A2) [affinity for glycyl-L-glutamine=18μM] (Romano et al., 2006)
Eukaryota
Metazoa
PepT2 of Danio rerio (NP_0010349)
*2.A.17.4.6









Oligopeptide transporter, PepT1 (Slc15A1b) (Bucking and Schulte, 2012) (expressed in freshwater acclimated fish)

Eukaryota
Metazoa
PepT1b of Fundulus heteroclitus (H2DJV9)
*2.A.17.4.7









Di-/Tri-peptide porter. 3-d structure (PDB: 2XUT) known revealing a probable alternating access mechanism of transport (Newstead et al., 2011).  A second structure shows the protein in an inward open conformation with the peptidommetic, alafosfalin, bound (Guettou et al. 2013).

Bacteria
Proteobacteria
Di-/Tri-peptide permease of Shewanella oneidensis (Q8EKT7)
*2.A.17.4.8









Solute carrier family 15 member 2 (Kidney H+:peptide cotransporter) (Oligopeptide transporter, kidney isoform) (Peptide transporter 2, PEPT2) (Verri et al. 2016).

Eukaryota
Metazoa
SLC15A2 of Homo sapiens
*2.A.17.4.9









Solute carrier family 15 member 1 (Intestinal H+:peptide cotransporter) (Oligopeptide transporter, small intestine isoform) (Peptide transporter 1, PepT1).  Takes up oligopeptides of 2 to 4 amino acids with a preference for dipeptides, a major route for the absorption of protein digestion end-products. PepT1 is modified by N-glycosylation, and all six asparagine residues in the large extracellular loop between TMSs 9 and 10 are subject to N-glycosylation.  This allows proper association with the plasma membrane and/or stabilization (Chan et al. 2016).

Eukaryota
Metazoa
PepT1 of Homo sapiens
*2.A.17.4.10









Peptide transporter 3 (Oligopeptide transporter 3)
Eukaryota
Metazoa
Pept-3 of Caenorhabditis elegans
*2.A.17.4.11









Peptide transporter, Pep1, also called CptB, Opt-2 and Pep-2.  It is of 835 aas and 11 TMSs.  It transports di-, tri- and tetra-peptides including phenylalanylmethionylarginylphenylalaninamide (FMRFamide) and N-acetylaspartylglutamate, both neuropeptides found throughout the animal kingdom. In contrast to CptA (TC# 2.A.17.4.3), CptB has low-affinity for its substrates (Fei et al. 1998).

Eukaryota
Metazoa
CptB of Caenorhabditis elegans