TCDB is operated by the Saier Lab Bioinformatics Group
TCIDNameDomainKingdom/PhylumProtein(s)
2.A.123.1.1









Alfalfa Nodulin MtN3

Eukaryota
Viridiplantae, Streptophyta
MtN3 of Medicago truncatula (P93332)
2.A.123.1.2









Sweet family member of 305 aas and 7 TMSs.  Mediates both low-affinity uptake and efflux of sugars across the membrane. (Wu et al., 2008)

Eukaryota
Viridiplantae, Streptophyta
Sweet of Citrus clementina
2.A.123.1.3









Senescence-associated protein 29, SAG29 (SWEET15)

Eukaryota
Viridiplantae, Streptophyta
SAG29 of Arabidopsis thaliana (Q9FY94)
2.A.123.1.4









Stromal cell protein (SCP) homologue, HsSWEET1 or RAG1AP1. Transports glucose and galactose bidirectionally. Present in the ER, Golgi and plasma membrane (Chen et al., 2010).

Eukaryota
Metazoa, Chordata
SLC50A1 of Homo sapiens
2.A.123.1.5









Ruptured pollen Grain-1, Sweet8 or Nodulin MtN3 family protein (essential for pollen viability). (Guan et al., 2008; Chen et al. 2010).

Eukaryota
Viridiplantae, Streptophyta
RPGI of Arabidoposis thaliana (Q8LFH5)
2.A.123.1.6









Host disease susceptible protein, Xa13 or Os8N3, for bacterial blight (Yang et al., 2006; Chu et al., 2006). Bidirectional sugar transporter, Sweet 11 (Chen et al., 2010)

Eukaryota
Viridiplantae, Streptophyta
Oryza sativa (Q6YZF3)
2.A.123.1.7









Nec1; predominantly expressed in nectaries; involved in sugar metabolism and nectar secretion (Ge et al., 2000)

Eukaryota
Viridiplantae, Streptophyta
Nec1 of Petunia hybrida (Q9FPN0)
2.A.123.1.8









Rga (Recombination-activating gene 1) (Hamada et al., 2005)

Eukaryota
Metazoa, Chordata
Rga of Mus musculus (Q9CXK4)
2.A.123.1.9









Sweet1: bidirectional low affinity glucose uniporter, Km = ~9 mM (Does not transport mannose, fructose or galactose) (Chen et al. 2010). The structure is know, and three regions, each containing several well conserved essential residues, comprise the substrate-binding pocket, the extrafacial gate, and the intrafacial gate (Xuan et al. 2013; Tao et al. 2015).  The orthologous SWEET1 in Camellia sinensis (tea) transports glucose, glucose analogues, and other hexoses (Wang et al. 2018).

Eukaryota
Viridiplantae, Streptophyta
Sweet1 of Arabidopsis thalinana (Q8L9J7)
2.A.123.1.10









Golgi/E.R. Sweet1 glucose/galactose facilitator (Km ≥ 50mM) (Chen et al. 2010)

Eukaryota
Metazoa, Nematoda
Sweet1 of Caenorhabditis elegans (O45102)
2.A.123.1.11









The sea squirt sugar transporter, Rga or Sweet1; required for normal development (Hamada et al., 2007; Chen et al., 2010).

Eukaryota
Metazoa, Chordata
Rga of Ciona intestinalis (F6U696)
2.A.123.1.12









Sugar transporter SWEET1 (Protein saliva)
Eukaryota
Metazoa, Arthropoda
Slv of Drosophila melanogaster
2.A.123.1.13









Bidirectional sugar (sucrose) transporter SWEET11 (AtSWEET11).  Oligomerization, probably to the dimeric form, has been demonstrated (Xuan et al. 2013). Important for phloem loading.

Eukaryota
Viridiplantae, Streptophyta
SWEET11 of Arabidopsis thaliana
2.A.123.1.14









Sugar transporter SWEET1
Eukaryota
Evosea
slc50a1 of Dictyostelium discoideum
2.A.123.1.15









SWEET homologue of 375 aas and 7 TMSs in a 3 + 4 arrangement.

Eukaryota
Bacillariophyta
SWEET homologue of Phaeodactylum tricornutum
2.A.123.1.16









Uncharacterized protein of 262 aas and 7 TMSs

Eukaryota
Rhodophyta
UP of Galdieria sulphuraria (Red alga)
2.A.123.1.17









MtN3-like protein of 686 aas and 7-8 TMSs, 1 N-terminal and 7 between residues 380 and 590.

Eukaryota
Apicomplexa
MtN3-like protein of Plasmodium falciparum
2.A.123.1.18









SWEET2b sugar transporter. Sequesters sugars in root vacuoles.  The 3-d structure is known. The subunit consists of two asymetic triple helix bundles (TMSs 1-3 and 5-7) connected by TMS4. SWEET2b is in an apparent inward (cytosolic) open state forming homomeric trimers. TMS4 tightly interacts with the first triple-helix bundle within a protomer and mediates key contacts among protomers (Tao et al. 2015).

Eukaryota
Viridiplantae, Streptophyta
SWEET2b of Oryza sativa
2.A.123.1.19









Sweet1 (SLC50A1).  99.6% identical to the goat (Capra hircus) mammary gland epithelial homologue which has been characterized (Zhu et al. 2015).

Metazoa, Chordata
Sweet1 of Ovis aries (sheep)
2.A.123.1.20









Uncharacterized protein of 197 aas and 7 TMSs

Bacteria
Actinomycetota
UP of Acidimicrobium sp. BACL27
2.A.123.1.21









Uncharacterized duplicated protein of 709 aas and 15 TMSs in a 7 + 7 + 1 arrangement. The protein contains two 7 TMS Sweet domains followed by an Atrophin-1 domain. There is no close homologue in the NCBI database, suggesting that it could be a result of a sequencing artifact.

Eukaryota
Viridiplantae, Streptophyta
UP of Ananas comosus
2.A.123.1.22









Uncharacterized protein of 1089 aas and 28 TMSs in a 7 + 7 + 7 + 7 arrangement.

Eukaryota
Oomycota
UP of Phytophthora ramorum (Sudden oak death agent)
2.A.123.1.23









Vacuolar hexose (fructose) transporter of 230 aas and 7 TMSs, Sweet16 (Eom et al. 2015). It plays an iimportant role in cold tolerance (Wang et al. 2018).

Eukaryota
Viridiplantae, Streptophyta
Sweet16 of Arabidopsis thaliana (Mouse-ear cress)
2.A.123.1.24









Sweet9 of 258 aas and 7 TMSs.  Important for nectar secretion (Eom et al. 2015).

Eukaryota
Viridiplantae, Streptophyta
Sweet9 of Arabidopsis thaliana (Mouse-ear cress)
2.A.123.1.25









Sweet family member of 89 aas and 3 TMSs.  Associated with a trehalose phosphatase, possibly suggesting al role in trehalose transport.

Archaea
Euryarchaeota
Semi-sweet of Methanobacterium lacus
2.A.123.1.26









Sweet13 (Sweet12) of 294 aas and 7 TMSs.  Transports the plant hormone, gibberellin (GA).  Sweet14 also transports gibberellin.  A double mutant has a defect in anther dehiscence. This mutant also exhibits altered long distant transport of exogenously applied GA and altered responses to GA during germination and seedling stages (Kanno et al. 2016).  In dragon fruit (pitaya; H. undatus) Sweets function in phloem loading, seed filling, nectar secretion, and fruit sweetness development (Jiang et al. 2023).

Eukaryota
Viridiplantae, Streptophyta
SWEET13 of Arabidopsis thaliana (Mouse-ear cress)
2.A.123.1.27









SWEET transporter 1 of 262 aas and 7 TMSs. Plays a role in the D. officinale symbiotic germination process (Zhang et al. 2016). This organism provides a traditional chinese medicine. There are 25 SWEET genes in this organism (Hao et al. 2023). Most have 7 TMSs and contain two conserved MtN3/saliva domains. They were divided into four clades, and are found in various tissues. Sixteen were significantly regulated under cold, drought, and MeJA treatment (Hao et al. 2023).

Eukaryota
Viridiplantae, Streptophyta
Sweet transporter of Dendrobium officinale
2.A.123.1.28









Bidirectional sugar transporter, SWEET2a, of 2243 aas and 7 TMSs.  It mediates both low-affinity uptake and efflux of sugars across the plasma membrane and plays a role in early seed development in Litchi chinensis (Xie et al. 2019).

Eukaryota
Viridiplantae, Streptophyta
SWEET2a of Oryza sativa subsp. japonica (Rice)
2.A.123.1.29









Bidirectional sugar transporter SWEET3b of 2252 aas and 7 TMSs.  It mediates both low-affinity uptake and efflux of sugars across the plasma membrane and plays a role in early seed development in Litchi chinensis (Xie et al. 2019).

Eukaryota
Viridiplantae, Streptophyta
SWEET3b of Oryza sativa subsp. japonica (Rice)
2.A.123.1.30









Bidirectional sugar transporter SWEET7, of 258 aas and 7 TMSs. It mediates both low-affinity uptake and efflux of sugar across the plasma membrane. AtSWEET7 transports glucose and xylose simultaneously with no inhibition (Kuanyshev et al. 2021).

 

Eukaryota
Viridiplantae, Streptophyta
SWEET7 of Arabidopsis thaliana (Mouse-ear cress)
2.A.123.2.1









The 7 TMS (242aa) bacterial MtN3 homologue

Bacteria
Mycoplasmatota
MtN3 homologue of Mycoplasma arthritidis (B3PMT4)
2.A.123.2.2









3 TMS MtN3 homologue (85aas)

Bacteria
Cyanobacteriota
MtN3 of MtN3 of Prochlorococcus marinus (A2BS89)
2.A.123.2.3









Half sized (3 TMS) bacterial MtN3 protein homologue (85aas)

Bacteria
Fusobacteriota
MtN3 homologue of Fusobacterium mortiferum (C3WG44)
2.A.123.2.4









3 TMS bacterial MtN3 homologue (96aas)

Bacteria
Spirochaetota
MtN3 homologue of Leptospira interrogans (Q8F4F7)
2.A.123.2.5









3 TMS Sweet homologue, MJ_0110 (93aas)

Archaea
Euryarchaeota
MJ_0110 of Methanocaldococcus jannashii (Q57574)
2.A.123.2.6









SemiSWEET half glucose transporter of 93 aas and 3 TMSs with an N-terminal amphipathic α-helix.  The protein occurs as a tight homodimer with the translocation channel between the two monomers.  The 3-d structure is known at 2.4 Å resolution revealing the outward open conformation (Xu et al. 2014). The occluded state of the Vibrio sp. N418 SemiSWEET (9.A.58.3.1) has been solved at 1.7 Å resolution (Xu et al. 2014).  The presence of these two states argues in favor of a carrier (rocker switch) mechanism rather than a channel-type mechanism (Xu et al. 2014).

Bacteria
Spirochaetota
SemiSWEET of Leptospira biflexa
2.A.123.2.7









SemiSWEET homologue of 89 aas and 3 TMSs

Bacteria
Pseudomonadota
SemiSWEET of Rickettsia bellii
2.A.123.2.8









SWEET homologue of 141 aas and 4 putative TMSs.

Bacteria
Cyanobacteriota
SWEET homologue of Anabaena variabilis
2.A.123.2.9









SWEET homologue of 231 aas and 7 TMSs

Bacteria
Mycoplasmatota
SWEET homologue of Mycoplasma hyopneumoniae
2.A.123.2.10









SWEET homologue of 125 aas and 3 TMSs; resembles 2.A.123.2.3 with all 3 TMSs overlapping.

Oomycota
SWEET homologue of Phytophthora sojae (Soybean stem and root rot agent) (Phytophthora megasperma f. sp. glycines)
2.A.123.2.11









SWEET homologue of 125 aas and 3 TMSs.  Closely related to 2.A.123.2.10.

Eukaryota
Oomycota
SWEET homologue of Phytophthora parasitica
2.A.123.2.12









SWEET homologue of 84 aas and 3 TMSs

Archaea
Euryarchaeota
SWEET homologue of Methanocella conradii
2.A.123.2.13









Uncharacterized protein of 728 aas and 5 putative TMSs with 4 N-terminal TMSs, where the first 3 are homologous to semisweets of 3 TMSs. The long sequence with one large centrally located peak of hydrophobicity includes several recognized protein domains following the SWEET domain in the following order:  Cache-3 - Cache-1 - dimerization interface domain - HAMP domain - followed by two PAS domains.  Another protein (UniProt acc #I3IJJ5 of 762 aas), has residues 3 - 635 aas) showing 83% sequence identity with residues 96 - 728 in 2.A.123.2.13.

Bacteria
Planctomycetota
UP of Candidatus Jettenia caeni
2.A.123.2.14









SemiSWEET of 86 aas and 3 TMSs specific for sucrose. The basic unit of SWEETs may be a 3-TMS unit, and it has been suggested that a functional transporter contains at least four such domains, although this suggestion has not been substantiated (Xuan et al. 2013).

Bacteria
Pseudomonadota
SemiSWEET of Bradyrhizobium diazoefficiens
2.A.123.2.15









Putative uncharacterized protein of 99 aas and 3 TMSs

Bacteria
Candidatus Saccharibacteria
Hypothetical protein UW38 of Candidatus Saccharibacteria bacterium
2.A.123.2.16









Facilitated glucose/sucrose/sugar/monoolein transporter of 89 aas and 3 TMSs. The homodimer mediates transmembrane sugar transport down a concentration gradient. Transport is probably effected by rocking-type movements, where a cargo-binding cavity opens first on one and then on the other side of the membrane (Lee et al. 2015).

Bacteria
Pseudomonadota
Semisweet sugar transporter of E. coli
2.A.123.3.1









SemiSWEET half putative sugar transporter of 97 aas and 3 TMSs with an N-terminal amphipathic α-helix.  The protein occurs as a tight homodimer with the translocation channel between the two monomers.  The 3-d structure is known at 1.7 Å resolution revealing the occluded conformation (Xu et al. 2014). The outward open state of the Leptospira biflexa SemiSWEET (2.a.123.2.6) has been solved at 2.4 Å resolution (Xu et al. 2014).  The presence of these two states argues in favor of a carrier (rocker switch) mechanism rather than a channel-type mechanism (Xu et al. 2014).

Bacteria
Pseudomonadota
SemiSWEET of Vibrio sp. N418
2.A.123.3.2









Uncharacterized protein of 107 aas.

Bacteria
Pseudomonadota
UP of Rhodobacteraceae bacterium KLH11
2.A.123.3.3









Uncharacterized conserved protein of 273 aas and 7 TMSs containing PQ loop repeats.

Bacteria
Actinomycetota
UP of Geodermatophilus obscurus
2.A.123.3.4









Uncharacterized protein of 97 aas and 3 TMSs.

Bacteria
Pseudomonadota
UP of Photobacterium leiognathi
2.A.123.4.1









Membrane protein of 209 aas and 7 TMSs with a putative N-terminal lipid A disaccharide synthase domain.  This protein is a member of the "Lipid A Biosynthesis, N-terminal (LAB_N) domain in Pfam/CDD, related to the SWEET family.

Bacteria
Bacteroidota
Membrane protein of Gramella forsetii
2.A.123.4.2









Uncharacterized protein of 115 aas and 3 TMSs.

Bacteria
Pseudomonadota
UP of Frateuria aurantia (Acetobacter aurantius)
2.A.123.4.3









Uncharacterized protein (putative lipid A synthesis protein domain) of 115 aas and 3 TMSs.

Bacteria
Pseudomonadota
UP of Stenotrophomonas maltophilia (Pseudomonas maltophilia) (Xanthomonas maltophilia)
2.A.123.5.1









Uncharacterized protein of 208 aas and 2 N-terminal TMSs.

Bacteria
Balneolota
UP of Balneolaceae bacterium (soda lake metagenome)
2.A.123.5.2









Uncharacterized protein of 207 aas and 2 or 3 N-terminal TMSs

Bacteria
Actinomycetota
UP of Serinicoccus sediminis
2.A.123.5.3









Uncharacterized protein of 204 aas and 3 N-terminal TMSs followed by a large hydrophilic domain, characteristic of this subfamily (TC# 2.A.123.5).

Bacteria
Actinomycetota
UP of Janibacter terrae (hydrocarbon metagenome)
2.A.123.5.4









Uncharacterized protein of 210 aas and 3 N-terminal TMSs.

Bacteria
Bacteroidota
UP of Chitinophagaceae bacterium (ecological metagenome)
2.A.123.5.5









Uncharacterized protein of 207 aas and 3 or more TMSs

Euryarchaeota
UP of Methanohalobium evestigatum