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SLC29 family C

Unless otherwise stated all data on this page refer to the human proteins. Gene information is provided for human (Hs), mouse (Mm) and rat (Rn).


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SLC29 family members are composed of 11 TM segments with cytoplasmic N-termini and extracellular C-termini. ENT1, ENT2 and ENT4 are primarily cell-surface transporters, while ENT3 is intracellular, possibly lysosomal [2]]. ENT2 isoforms may also play a role in the nucleolar transport of nucleosides [9]. ENT1-3 are described as broad-spectrum equilibrative nucleoside transporters. ENT4 is primarily a polyspecific organic cation transporter at neutral pH [12], but transports adenosine and analogues such as 2-chloroadenosine, with affinities similar to other members of the SLC29 family, at acidic pH [17].


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ENT1 (Equilibrative nucleoside transporter 1 / SLC29A1) C Show summary »

Target Id 1117
Nomenclature Equilibrative nucleoside transporter 1
Systematic nomenclature SLC29A1
Common abbreviation ENT1
Previous and unofficial names equilibrative NBMPR-sensitive nucleoside transporter | equilibrative nitrobenzylmercaptopurine riboside-sensitive nucleoside transporter | nucleoside transporter, es-type | solute carrier family 29 (nucleoside transporters) member 1 | solute carrier family 29 (equilibrative nucleoside transporter), member 1 | solute carrier family 29 (nucleoside transporters)
Genes SLC29A1 (Hs), Slc29a1 (Mm), Slc29a1 (Rn)
Ensembl ID ENSG00000112759 (Hs), ENSMUSG00000023942 (Mm), ENSRNOG00000019752 (Rn)
UniProtKB AC Q99808 (Hs), Q9JIM1 (Mm), O54698 (Rn)
Bioparadigms SLC Tables SLC29A1 (Hs)
Endogenous substrates in order of increasing Km: adenosine < inosine < uridine < guanosine < cytidine < hypoxanthine < adenine < thymine
Endogenous substrates
adenosine [22]
inosine [22]
hypoxanthine [22]
uridine [22]
guanosine [22]
thymine [22]
thymidine [22]
cytidine [22]
adenine [22]
atenolol [15]
formycin B
ribavirin [5]
abacavir [4]
nitrobenzylmercaptopurine ribonucleoside pKi 9.7
draflazine pKi 9.6 [10]
KF24345 pKi 9.4 [11]
NBTGR pKi 9.3
dilazep pKi 9.0
dipyridamole pKi 8.8 [11]
ticagrelor pKi 7.3 [1]
Labelled ligands
[3H]nitrobenzylmercaptopurine ribonucleoside pKd 9.3
Stoichiometry Equilibrative
Comment SLC29A1 (ENT1) has 100-1000-fold lower affinity for nucleobases as compared with nucleosides [22]. The affinities of draflazine, dilazep, KF24345 and dipyridamole at SLC29A1 transporters are species dependent, exhibiting lower affinity at rat transporters than at human transporters [11,16]. Dilazep and nitrobenzylmercaptopurine ribonucleoside have distinct but overlapping binding domains in the SLC29A1 crystal structure [21]. The loss of SLC29A1 activity in SLC29A1-null mice has been associated with a hypermineralization disorder similar to human diffuse idiopathic skeletal hyperostosis [20]. Lack of SLC29A1 also results in the Augustine-null blood type [6]. SLC29A1 forms homodimers and heterodimers (with SLC29A2) [8].

ENT2 (Equilibrative nucleoside transporter 2 / SLC29A2) C Show summary »

ENT3 (Equilibrative nucleoside transporter 3 / SLC29A3) C Show summary »

PMAT (Plasma membrane monoamine transporter / SLC29A4) C Show summary »

Further reading

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NC-IUPHAR subcommittee and family contributors

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How to cite this family page

Database page citation (select format):

Concise Guide to PHARMACOLOGY citation:

Alexander SPH, Fabbro D, Kelly E, Mathie AA, Peters JA, Veale EL, Armstrong JF, Faccenda E, Harding SD, Davies JA et al. (2023) The Concise Guide to PHARMACOLOGY 2023/24: Transporters. Br J Pharmacol. 180 Suppl 2:S374-469.