TCDB is operated by the Saier Lab Bioinformatics Group
TCIDNameDomainKingdom/PhylumProtein(s)
2.A.41.1.1









Pyrimidine nucleoside:H+ symporter, NupC (Craig et al. 1994; Patching et al. 2005). Wild-type NupC had an apparent affinity for uridine of 22.2 +/- 3.7 muM and an apparent binding affinity of 1.8-2.6 mM, and various mutants with alterred properties were isolated and characterized (Sun et al. 2017). ADP-glucose is also a substrate of this system (Almagro et al. 2018).

Bacteria
Proteobacteria
NupC of E. coli (P0AFF2)
2.A.41.1.2









Pyrimidine-specific nucleoside:H+ symporter, NupC
Bacteria
Firmicutes
NupC of Bacillus subtilis
2.A.41.1.3









The purine nucleoside uptake transporter NupG (YxjA) (Johansen et al., 2003)
Bacteria
Firmicutes
NupG of Bacillus subtilis (P42312)
2.A.41.2.1









Purine-specific nucleoside:Na+ symporter
Eukaryota
Metazoa
The bile canalicular purine-specific nucleoside:Na+ symporter of Rattus norvegicus (Q62773)
2.A.41.2.2









Nonspecific nucleoside:Na+ symporter
Eukaryota
Metazoa
The nucleoside:Na+ symporter of Rattus norvegicus (Q62674)
2.A.41.2.3









Pyrimidine-preferring nucleoside:Na+ symporter, CNT1 (Na+/nucleoside = 2)(transports uridine, gemcitabine and 5'-deoxy-5'-fluorouridine) (Larráyoz et al., 2004), but in addition to pyrimidine nucelosides, it transports adenosine (Altaweraqi et al. 2020).

Eukaryota
Metazoa
SLC28A1 of Homo sapiens
2.A.41.2.4









Purine nucleoside, uridine, and 2'3'dideoxyinosine cladribrine:Na+ symporter, CNT2 (Na+/nucleoside = 1) (Owen et al., 2006; Altaweraqi et al. 2020).

Eukaryota
Metazoa
SLC28A2 of Homo sapiens
2.A.41.2.5









Broadly selective nucleoside:Na+ cotransporter, hfCNT (transports uridine, thymidine, inosine, 3'-azido-3'deoxythymidine, 2'3'dideoxycytidine, and 2'3'dideoxyinosine) (Na+/uridine = 2)
Eukaryota
Metazoa
hfCNT of Eptatretus stouti (Q9UA35)
2.A.41.2.6









Broad-specificity nucleoside:Na+, H+ and Li+ symporter, hCNT3 (Slc28a3) transports a broad range of both purine and pyrimidine nucleosides as well as anticancer and antiviral nucleoside drugs, but guanosine, 3'azido-3-deoxythymidine and 2',3'-dideoxycytidine, which are substrates with Na+, are not substrates with H+. Both of the two cation-binding sites can apparently bind Na+, but only one can bind H+, and the Na+ and H+ forms transport different ranges of substrates. (Note: Cnt1 and Cnt2 are Na+-specific.) (Smith et al., 2005).  (Na+/nucleoside = 2; Na+ + H+/nucleoside = 2; H+/nucleoside = 1).  The matricellular protein, cysteine-rich angiogenic inducer 61 (CYR61), negatively regulates synthesis of the nucleoside transporters hENT1 and hCNT3, both of which transport the anti-cancer agent, gemcitabine (Hesler et al. 2016). Also probably transports gemcitabine, 3'-azido-3'-deoxythymidine (AZT), ribavirin and 3-deazauridine. Modeling revealed mobility of selected binding site and homotrimer interface residues (Latek 2017). The 3-D structure has been solved at 3.6 Å resolution by cryoEM (Zhou et al. 2020). As for its bacterial homologs, hCNT3 presents a trimeric architecture with additional N-terminal transmembrane helices to stabilize the conserved central domains. The conserved binding sites for the substrate and sodium ions unravel the selective nucleoside transport and distinct coupling mechanism (Zhou et al. 2020).

Eukaryota
Metazoa
CNT3 of Homo sapiens (Q9ERH8)
2.A.41.2.7









Broad specificity nucleoside:H+ symporter (1:1 stoichiometry). Adenosine, uridine, inosine, and guanosine are transported but not cytidine, thymidine or the nucleobase hypoxanthine (Km range: 15-65 μM). Purine and uridine nucleoside drug analogues including cordycepin (3'-deoxyadenosine) are substrates.

Eukaryota
Fungi
CNT of Candida albicans, (Q874I3)
2.A.41.2.8









Solute carrier family 28 member 3 (Concentrative Na+-nucleoside cotransporter 3) (CNT 3) (hCNT3).  This protein is distinct from TC# 2.A.41.2.6 (78% identity) although these two proteins are called Slc28a3 and CNT3 and have the same description in UniProt (see 2.A.41.2.6 for a more complete description). 

Eukaryota
Metazoa
SLC28A3 of Homo sapiens
2.A.41.2.9









Putative pseudouridine transporter, PsuT

Bacteria
Proteobacteria
PsuT of Escherichia coli
2.A.41.2.10









Nucleoside permease NupX

Bacteria
Proteobacteria
NupX of Escherichia coli
2.A.41.2.11









Concentrative nucleoside transporter, CNT, of 418 aas and 12 TMSs. A repeat-swapped model of VcCNT predicts that nucleoside transport occurs via a mechanism involving an elevator-like substrate binding domain movement across the membrane (Vergara-Jaque et al. 2015).

Bacteria
Proteobacteria
CNT of Vibrio cholerae