TCDB is operated by the Saier Lab Bioinformatics Group
TCIDNameDomainKingdom/PhylumProtein(s)
*2.A.2.1.1









Melibiose permease. Catalyzes the coupled stoichiometric symport of a galactoside with a cation (either Na+, Li+, or H+). Based on LacY, a 3-d model has been derived (Yousef and Guan, 2009). Asp55 and Asp59 are essential for Na+ binding. Asp124 may play a critical role by allowing Na+-induced conformational changes and sugar binding. Asp19 may facilitate melibiose binding (Granell et al., 2010).  The alternate access mechanism fits better into a flexible gating mechanism rather than the archetypical helical rigid- body rocker-switch mechanism (Wang et al. 2016).  Crystal structures of Salmonella typhimurium MelB in two conformations, representing an outward partially occluded and an outward inactive state (Ethayathulla et al. 2014). MelB adopts a typical MFS fold and contains a previously unidentified cation-binding motif. Three conserved acidic residues form a pyramidal-shaped cation-binding site for Na+, Li+ or H+, which is in close proximity to the sugar-binding site. Both cosubstrate-binding sites are mainly contributed by the residues from the amino-terminal domain (Ethayathulla et al. 2014). The Glucose Enzyme IIA protein of the PTS binds MelB either in the absence or presence of a galactoside, and binding decreases the affinity for melibiose, giving rise to inducer exclusion (Saier 1989; Hariharan and Guan 2014).

Bacteria
Proteobacteria
MelB of E. coli (A7ZUZ0)
*2.A.2.1.2









Probable fucosyl-α-1,6-N-acetylglucosamine uptake porter, AlfD (next to and in an operon with a fucosidase (AlfA) specific for this disaccharide which is present in mammalian glycoproteins, glycolipids and milk (Rodríguez-Díaz et al. 2012).

Bacteria
Firmicutes
AlfD of Lactobacillus casei
*2.A.2.2.1









Lactose permease, LacS. Mediates uptake of β-galactooligosaccharides, lactitol, and a broad range of prebiotic β-galactosides that selectively stimulate beneficial gut microbiota (Andersen et al., 2011). 

Bacteria
Firmicutes
LacS of Streptococcus thermophilus
*2.A.2.2.2









Raffinose permease
Bacteria
Firmicutes
RafP of Pediococcus pentosaceus
*2.A.2.2.3









Galactose permease
Bacteria
Firmicutes
GalP of Lactococcus lactis
*2.A.2.3.1









Glucuronide permease, UidB, GusB, UidP (Liang et al., 2005; Moraes and Reithmeier 2012)

Bacteria
Proteobacteria
GusB of E. coli
*2.A.2.3.2









Pentoside permease
Bacteria
Firmicutes
XynC (YnaJ) of Bacillus subtilis
*2.A.2.3.3









Isoprimeverose (α-D xylopyranosyl-(1,6)-D-glucopyranose) permease [xylose is not a substrate] (Heuberger et al., 2001)

Bacteria
Firmicutes
XylP of Lactobacillus pentosus
*2.A.2.3.4









Probable α-xyloside uptake permease, YicJ (Laikova et al., 2001)
Bacteria
Proteobacteria
YicJ of E. coli (P31435)
*2.A.2.3.5









Probable β-xyloside uptake permease, YagG (Laikova et al., 2001)
Bacteria
Proteobacteria
YagG of E. coli (P75683)
*2.A.2.3.6









The putative cellobiose porter, BglT (Rodionov et al. 2010)

Bacteria
Proteobacteria
BglT of Shewanella amazonensis (A1S5F2)
*2.A.2.3.7









The putative arabinoside porter, AraT (Rodionov et al., 2010)

Bacteria
Proteobacteria
AraT of Shewanella sp. MR-4 (Q0HIQ0)
*2.A.2.3.8









Major Facilitator Superfamily Domain containing 2A, MFSD2A (543aas, 12 TMSs). Plays a role in thermogenesis via β-adrenergic signaling. Takes up Tunicamycin (TM), a mixture of related species of nucleotide sugar analogs fatty-acylated with alkyl chains of varying lengths and degrees of unsaturation, produced by several Streptomyces species (Bassik and Kampmann, 2011; Reiling et al., 2011).  It is a sodium-dependent lysophosphatidylcholine (LPC) transporter expressed at the blood-brain barrier endothelium. It is the primary route for import of docosahexaenoic acid and other long-chain fatty acids into foetal and adult brain, and is essential for mouse and human brain growth and function (Quek et al. 2016). In addition to a conserved sodium-binding site, three structural features were identified: A phosphate headgroup binding site, a hydrophobic cleft to accommodate a hydrophobic hydrocarbon tail, and three sets of ionic locks that stabilize the outward-open conformation. Ligand docking studies and biochemical assays identified Lys436 as a key residue for transport. It forms a salt bridge with the negative charge on the phosphate headgroup. Mfsd2a transports structurally related acylcarnitines but not a lysolipid without a negative charge, demonstrating the necessity of a negative charged headgroup interaction with Lys436 for transport. These findings support a novel transport mechanism by which LPCs are flipped within the transporter cavity by pivoting about Lys436 leading to net transport from the outer to the inner leaflet of the plasma membrane (Quek et al. 2016).

Eukaryota
Metazoa
MFSD2A of Homo sapiens (Q8NA29)
*2.A.2.3.9









Inner membrane symporter YihP

Bacteria
Proteobacteria
YihP of E. coli
*2.A.2.3.10









Transmembrane protein 180
Eukaryota
Metazoa
TMEM180 of Homo sapiens
*2.A.2.3.11









Putative transporter

Eukaryota
Kinetoplastida
Putative transporter of Trypanosoma cruzi
*2.A.2.3.12









Putative sugar transporter

Bacteria
Deinococcus-Thermus
TT_P0219 pf Thermus thermophilus
*2.A.2.4.1









Sucrose:H+ symporter, Suc1 (provides osmotic driving force for anther dehiscence, pollen germination and pollen tube growth; also transports other glucosides such as maltose and phenylglucosides. Km (sucrose)= 0.5 mM. (Stadler et al., 1999)).  In wheat (Triticum aesticum), there are at least three isoforms designated Sut2A, Sut2B and Sut2D (Deol et al. 2013).

Eukaryota
Viridiplantae
Suc1 of Arabidopsis thaliana
*2.A.2.4.2









Phloem-localized sucrose:H+ symporter, Sut1 (mediates sucrose uptake or efflux dependent on the sucrose gradient and the pmf; Carpaneto et al., 2005). Sut1 is a sucrose protein symporter. Protons can move in the absence of sucrose (Carpaneto et al., 2010), but upon addition of sucrose, it becomes a symporter.  Arg-188 in the rice orthologue and homologues are essential (Sun and Ward 2012).

Eukaryota
Viridiplantae
Sut1 of Zea mays (BAA83501)
*2.A.2.4.3









Sucrose:H+ symporter, Suc3 or Sut3 of 464 aas. Expressed in cells adjacent to the vascular tissue and in a carpel cell layer). Km (sucrose)= 1.9 mM; maltose is a competitor (Meyer et al., 2000).

Eukaryota
Viridiplantae
Suc3 of Arabidopsis thaliana
(O80605)
*2.A.2.4.4









The brain proton:associated sugar (glucose) transporter, PAST-A (Shimokawa et al., 2002)
Eukaryota
Metazoa
PAST-A of Rattus norvegicus (Q8K4S3)
*2.A.2.4.5









The proton:sucrose uptake symporter, Sut1 (Zhang & Turgeon et al., 2009).

Eukaryota
Viridiplantae
Sut1 of Verbascum phoeniceum (D1GC38)
*2.A.2.4.6









Vacuolar sucrose;H+ symporter Suc4, Catalyzes sucrose export from vacuoles (Schulz et al., 2011)

Eukaryota
Viridiplantae
Suc4 of Arabidopsis thaliana (Q9FE59)
*2.A.2.4.7









Solute carrier family 45, member 4, SLC45A4.  Transports sucrose by a proton symport mechanism.  Found ubiquitously throughout the tissues of the body (Bartölke et al. 2014).

Eukaryota
Metazoa
SLC45A4 of Homo sapiens
*2.A.2.4.8









solute carrier family 45, member 3, Slc45A3.  Sucrose:proton symporter associated with prostate cancer and myelination (Bartölke et al. 2014).

Eukaryota
Metazoa
SLC45A3 of Homo sapiens
*2.A.2.4.9









Solute carrier family 45, member 2, Slc45A2, also called melanocyte-restricted antigen or melanoma antigen, PatP, Aim-1 or Aim1.  Transports sucrose with protons, possibly into vesicular structures that contain melanin.  Found in skin and hair; involved in pigmentation (Bartölke et al. 2014).  Defects give rise to oculocutaneous albinism (Meyer et al. 2011). One such mutation in dogs, G493D in TMS 11, gives rise to albinisms (Wijesena and Schmutz 2015). OCA type IV (OCA4, OMIM 606574) develops due to homozygous or compound heterozygous mutations in the solute carrier family 45, member 2 (SLC45A2) gene, and many mutations in this human gene have been identified (Inagaki et al. 2006; Tóth et al. 2017).

Eukaryota
Metazoa
SLC45A2 of Homo sapiens
*2.A.2.4.10









Proton:glucose symporter A; proton-associated sugar transporter A  (PAST-A) (present in brain and deleted in neuroblastoma 5 (DNb-5).  Solute carrier family 45 member 1, SLC45A1 (Bartölke et al. 2014).

Eukaryota
Metazoa
SLC45A1 of Homo sapiens
*2.A.2.4.11









Sucrose transport protein SUT5 (Sucrose permease 5) (Sucrose transporter 5) (OsSUT5) (Sucrose-proton symporter 5)
Eukaryota
Viridiplantae
SUT5 of Oryza sativa subsp. japonica
*2.A.2.4.12









Sucrose:H+ symporter, SUC5.  Also transports biotin and possibly maltose (Pommerrenig et al. 2012).

Eukaryota
Viridiplantae
SUC5 of Arabidopsis thaliana
*2.A.2.4.13









Scratch, orthologue 1, SCRT; SLC45A2; transports sucrose into pigment-containing vesicles or granules.  Mutations give rise to oculocutaneous albinism (Meyer et al. 2011).

Eukaryota
Metazoa
SCRT of Drosophila melanogaster
*2.A.2.4.14









Melanocyte-specific antigen or melanoma antigen, MatP, Slc45a2, Aim-1, AIM1, at the mouse underwhite locus.  Regulated by a melanocyte-specific transcription factor essential for pigmentation, MITF (Du and Fisher 2002). Mutations in MatP in humans cause oculocutaneous albinism type IV (OCA4), an autosomal recessive inherited disorder which is characterized by reduced biosynthesis of melanin pigmentation in skin, hair and eyes. The MATP protein consists of 530 amino acids which contains 12 TMSs (Kamaraj and Purohit 2016).  The D93N mutation causes oculocutaneous albinism 4 (OCA4), and the L374F mutatioin correlates with light pigmentation in European populations. Corresponding mutations were produced in the related and well-characterized sucrose transporter from rice, OsSUT1, and transport activity was measured by heterologous expression in Xenopus laevis oocytes and 14C-sucrose uptake in yeast. The D93N mutant had completly lost transport activity while the L374F mutant showed a 90% decrease in transport activity, although the substrate affinity was unaffected (Kamaraj and Purohit 2016).  Mutations in MATP protein showed loss of stability and became more flexible, which alter its structural conformation and function (Kamaraj and Purohit 2016).

Eukaryota
Metazoa
Aim1 of Mus musculus
*2.A.2.5.1









Saturated and unsaturated oligogalacturonide transporter, TogT (transports di- to tetrasaccharide pectin degradation products which consist of D-galacuronate, sometimes with 4-deoxy-L-threo-5- hexosulose uronate at the reducing position)

Bacteria
Proteobacteria
TogT of Erwinia chrysanthemi 3937
*2.A.2.5.2









The putative rhamnogalacturonide porter, RhiT (Rodionov et al. 2004).

Bacteria
Proteobacteria
RhiT of Erwinia carotovora subsp. atroseptica (Q6D188)
*2.A.2.6.1









Maltose/sucrose H+ : symporter, Sut1 (maltose, Km = 6 %u03BCM; sucrose, Km = 36 %u03BCM)

Eukaryota
Fungi
Sut1 of Schizosaccharomyces pombe
*2.A.2.6.2









The maltose/maltooligosaccharide transporter, MalI (541 aas) (Lohmiller et al., 2008).

Bacteria
Proteobacteria
MalI of Caulobacter crescentus (Q9A612)
*2.A.2.6.3









The putative maltose porter, MalT (Rodionov et al., 2010)

Bacteria
Proteobacteria
MalT of Shewanella oneidensis (Q8EEC4)
*2.A.2.7.1









The insect Bm-re (Bombyx mori red eye) protein; mutants lose ommochromes as well as pigmentation of eggs, eyes, and bodies. May function in pigment transport (Osanai-Futahashi et al., 2012).

Eukaryota
Metazoa
Bm-re of Bombyx mori (I0IYT1)
*2.A.2.7.2









Bm-re homologue of Tribolium castaneum (Osanai-Futahashi et al., 2012).

Eukaryota
Metazoa
Bm-re homologue of Tribolium castaneum (D6W6W0)