TABLE 3.
Properties of families of transport systems included in the TC system
| TC no. | Family | Substrate(s)a | Size rangeb (no. of residues) | nTMSsc | Organismsd | No. of members | Examples |
|---|---|---|---|---|---|---|---|
| 1.A. α-Type channel-forming proteins and peptides | |||||||
| 1.A.1 | VIC | Na+; K+; Ca2+; multiple cations | Widely varied | (2)4; (4)2; (6)4; (8)2; (12)2; (24)1; often heterooligomeric | E, A, B | >500 | Voltage-gated Na+ channels; voltage-gated Ca2+ channels; K+ channels sensitive to voltage, Ca2+, or cyclic nucleotides of Homo sapiens |
| 1.A.2 | IRK-C | K+ | 390–430 | (2)n | E (An) | >10 | Inward rectifier K+ channels (ATP activated or G-protein regulated) of Homo sapiens |
| 1.A.3 | RIR-CaC | Ca2+ | 5,000 or 2,500 | (6)n | E (An) | >10 | Ryanodine receptor Ca2+ channels; inositol 1,4,5-triphosphate receptor Ca2+ channels of Homo sapiens |
| 1.A.4 | TRP-CC | Ca2+ | 800; 1,300 | (6)n | E (An) | >10 | Transient receptor potential Ca2+ channel (TRP) of Drosophila melanogaster |
| 1.A.5 | PCC | Na+, K+, Ca2+ | 4,000 | 16–18 | E (An) | 3 | Polycystin 1 of Homo sapiens |
| 1.A.6 | ENaC | Na+; cations | 640–700 | (2)3 | E (An) | >20 | Epithelial Na+ channels; degenerins; peptide-gated ionotropic receptors of animals |
| 1.A.7 | ACC | Cations (monovalent cations; Ca2+) | 380–600 | (2)n | E (An) | 10 | ATP-gated cation channel (P2X1) of Homo sapiens |
| 1.A.8 | MIP | H2O; glycerol, urea, polyols, NH3, CO2 | 220–310 | (6)2 or 4 | B, A, E | >100 | Aquaporins (Aqp1) of Homo sapiens; glycerol facilitators (GlpF) of E. coli |
| 1.A.9 | LIC | Cations or chloride | 400–500 | (3–5)5; often heterooligomeric | E (An) | >100 | Acetylcholine or serotonin-activated cation channels; glycine, glutamate or GABA-regulated Cl− channels of Homo sapiens |
| 1.A.10 | GIC | Monovalent cations and Ca2+ | 800–1,000 | (3–5)5 | E (An) | 10 | Glutamate-regulated ionotropic channels of Rattus norvegicus |
| 1.A.11 | ClC | Cl−, anions | 400–1,000 | 10–12 | B, A, E | >30 | Voltage-gated Cl− channel (ClCl) of Homo sapiens |
| 1.A.12 | O-ClC | Cl−, anions | 240–440 | (2)n | E (An) | >10 | Organellar voltage-sensitive Cl− channels of Bos taurus |
| 1.A.13 | E-ClC | Cl−, anions | 900–1,000 | (4)n | E (An), B | >20 | Ca2+-activated Cl− channel-2 of Homo sapiens |
| 1.A.14 | NSCC1 | Monovalent cations: Na+, Li+, K+ | 423 | (4)n | E (An) | 1 | Nonselective cation channel (NSC1) of Mus musculus |
| 1.A.15 | NSCC2 | Monovalent cations: Na+, K+, Cs+ as well as Ca2+ (slow) | 283–402 | (2)n | E (An, Y, F) | >10 | Nonspecific channel translocation protein-1 (NS1) of Homo sapiens; Sec62 of Saccharomyces cerevisiae |
| 1.A.16 | Mid1 | Ca2+ | 540 | 1 or 2 | E (Y) | 2 | Mid1 of Saccharomyces cerevisiae |
| 1.A.17 | CSC | Ions; solutes | 177 | β-Structure? | E (Pl) | 1 | Chloroplast outer envelope solute channel (CSC) of Pisum sativum |
| 1.A.18 | Tic110 | Anions; proteins | 1,000 | 2 | E (Pl) | 1 | Protein import-related anion-selective channel (Tic110) |
| 1.A.19 | IVC | H+ | ∼100 | (1)n (n = 4?) | E (influenza virus) | 1 | Matrix protein (M2) of influenza virus |
| 1.A.20 | CybB | H+ | 740 | 6 | E (Pl, An) | ∼20 | gp91phox human phagocyte NADPH oxidase-associated cytochrome b558 H+ channel |
| 1.A.22 | MscL | Proteins, ions (slightly cation selective) | 130–140 | (2)6 | B | 10 | Large mechanosensitive ion channels (MscL) of E. coli |
| 1.A.23 | MscS | Ions (slight anion selectivity) | 240–1,120 | 2–14 | B, A | ∼50 | Small conductance mechanosensitive ion channel (KefA) of E. coli |
| 1.A.24 | Connexin | Small molecules (no discrimination) | 200–600 | (4)n | E (An) | >50 | Vertebrate connexin 43 (gap junction α-1 protein) (CX43) of Rattus norvegicus |
| 1.A.25 | Innexin | Small molecules (no discrimination) | 300–600 | (4)n | E (An) | >50 | Invertebrate innexin (UNC-7) of Caenorhabditis elegans |
| 1.A.26 | SAT | NH4+ | 346 | (1)n | E (Pl) | 1 | Symbiotic NH4+ transporter-1 (SAT1) of Glycine max |
| 1.A.27 | PLM | Cl− (anion selective), taurine, lactate, glutamate, isethionate, gluconate | 70–100 | (1)n | E (An) | >10 | Phospholemman; Cl− conductance inducer protein Mat-8 |
| 1.A.28–1.A.43 | Holin functional superfamily (16 families) | Proteins; small molecules | 70–150 | (2–4)n | B, phage, plasmids | >50 | Lysis protein S of phage lambda |
| 1.A.44 | UT | Urea, water | 380–400 | 10 | E (An) | >10 | Kidney vasopressin-regulated urea transporter (UT2) |
| 1.A.45 | Mot | H+; Na+ | 500–1,000 (2 subunits) | 4 (A) + 1 (B) | B | ∼10 | H+ uptake-driven flagellar motor (MotAB) of E. coli |
| 1.B. Outer membrane porins (β-structure) | |||||||
| 1.B.1–1.B.26e | Various outer membrane porins and export proteins | 250–1,000 | 8–24 β-strands | G-B; phage; E (mito, plastids) | >200 | OmpF of E. coli; VDAC of Bos taurus; AidA of E. coli | |
| 1.C. Toxins | |||||||
| 1.C.1 | Colicin | Ions; small molecules | 500–700 (150–180 for the channel domain) | (4?)n | B, plasmids | 10 | Colicin E1 of E. coli |
| 1.C.2 | IPC | Ions; small molecules | 500–1,300 (∼220 for the channel domain) | (6?)n | B | >50 | Cry3A insecticidal γ-endotoxin of Bacillus thuringiensis |
| 1.C.3 | αHL | Ions; small molecules | 300–400 | (2β)7 | B | >10 | α-Hemolysin of Staphylococcus aureus |
| 1.C.4 | Aerolysin | Ions; small molecules | 440–490 | (2β)7 | B, E (Pl) | 7 | Aerolysin of Aeromonas hydrophila |
| 1.C.5 | ɛ-Toxin | Ions; small molecules | 330 | ? | B | ∼10 | ɛ-Toxin of Clostridium perfringens |
| 1.C.6 | YKT-K1 | Cation selective | 300 | ? | E (Y) | 1 | Yeast killer toxin of Saccharomyces cerevisiae |
| 1.C.7 | DT | DT, A-chain (protein) | 340 | ? | B | 1 | Diphtheria toxin (DT) of corynebacteriophage β |
| 1.C.8 | BTT | BTT, L-chains | 800 | (2?)n | B | >10 | Botulinum and tetanus toxin channels of Clostridium species |
| 1.C.9 | VacA | Ions; small molecules | 1,290 | (?)6 | B | 1 | VacA of Helicobacter pylori |
| 1.A.21 | Bcl-2 | Protein (cytochrome c) | 200–240 | (1–5)n (n = 2?) | E (An) | >20 | Apoptosis regulator [Bcl-X(L)] of Homo sapiens |
| 1.C.10 | HlyE | Ions/moderately cation selective | 305 | ? | B | 1 | HlyE of E. coli |
| 1.C.11 | RTX-toxin | Ions; small molecules | 900–1,100 | ? | B | >10 | Hemolysin A (HlyA) of E. coli |
| 1.C.12 | TAC | Ions; small molecules | 470–580 | ? | B | >50 | Perfringolysin O of Clostridium perfringens |
| 1.C.13 | Ctx | Ions | 286 | ? | B | 1 | Leucocidin cytotoxin (Ctx) of Pseudomonas aeruginosa phage phiCTX |
| 1.C.14 | CHL | Ions and other solutes | 500–800 | ? | B | ∼10 | Cytohemolysin (HlyA) of Vibrio cholerae |
| 1.C.15 | WSP | Small molecules | 400 | ? | An | 2 | Whipworm stichosome porin of Tichuris trichiura |
| 1.C.16–1.C.30 | Channel-forming peptide functional superfamily (15 families) | Ions | 25–75 small peptides, often from large precursors | (1 or 2)n | B, A, E | >1,000 | Maganins; cecropins; melittin, defensins; bacteriocins |
| 1.C.31 | Colicin V | Ions; small molecules | 100 | (1–2)n | B (plasmid) | 1 | Colicin V of E. coli |
| 1.C.32 | Mastoparan | Small molecules | 13–14 | (1)n | E (insects) | >10 | Mastoparan of Vespa xanthoptera |
| 1.C.33 | Cathilicidin | Small molecules | 90–220 (precursor), 18 (mature) | (1)n | E (An) | >10 | premyeloid cathilicidin 1 of Equus caballus |
| 1.C.34 | Tachyplesin | Small molecules | 18–77 | (1)n | E (An) | >10 | Tachyplesin I of Tachyplesus tridentatus |
| 1.C.35 | Amoebapore | Small molecules | 90–100 | (1)n | E (Pr) | >10 | Amoebapore of Entamoeba histolytica |
| 1.C.36 | IIITCP | Proteins | 300–600 | (2)n | B | >20 | Type III protein secretion target cell pore protein (YopB) of Yersinia pseudotuberculosis |
| 1.C.37 | Lactococcin 972 | Small molecules | 60–90 | (1)n | B | 1 | Lactococcin 972 of Lactococcus lactis |
| 1.C.38 | Equinatoxin | Small molecules | 170–220 | (1)3 or 4 | An (sea urchins) | >10 | Equinatoxin of Actinia tenebrosa |
| 2.A. Carrier-type facilitators | |||||||
| 2.A.1 | MFS | Various small molecules | 400–600 | 12 or 14 | B, A, E | >1,000 | Lactose permease (LacY) of E. coli; drug efflux permease (EmrD) of E. coli |
| 2.A.2 | GPH | Sugars | ∼500 | 12 | B, A, E (An, Pl) | >20 | Melibiose permease (MelB) of E. coli |
| 2.A.3 | APC | Amino acids, polyamines, choline | 440–630 | 12 | B, A, E | >100 | Lysine permease (LysP) of E. coli |
| 2.A.4 | CDF | Cd2+, Co2+, Ni2+ | 300–750 | 6 | B, A, E | >10 | Heavy-metal uptake and efflux permeases of bacteria, eukaryotic plasma membranes, and mitochondria (CzcD of Ralstonia eutropha) |
| 2.A.5 | ZIP | Zn2+, Fe2+ | 220–430 | 8 | E (Y, Pl, An) | >10 | Zinc uptake transporter (Zrt1) of Saccharomyces cerevisiae |
| 2.A.6 | RND | Heavy metal ions; multiple drugs; oligosaccharides; organic solvents, fatty acids, phospholipids; cholesterol | 800–1,200 | ∼12 | B, A, E | >100 | Drug efflux pump (AcrA) of E. coli |
| 2.A.7 | SMR | Multiple drugs and dyes (mostly cationic) | 110 | (4)3 | B | >20 | Cationic drug efflux pump (Smr) of Staphylococcus aureus |
| 2.A.8 | GntP | Gluconate, iodonate | 450 | 12–14 | B | >10 | Gluconate permease (GntP) of Bacillus subtilis |
| 2.A.9 | RhaT | Sugars | 280–340 | 10 | B | 5 | Rhamnose transporter (RhaT) of E. coli |
| 2.A.10 | KDGT | 2-Keto-3-deoxygluconate | 400 | 10–12 | B | 5 | 2-Keto-3-deoxygluconate transporter (KdgT) of Erwinia chrysanthemi |
| 2.A.11 | CitMHS | Citrate | 400 | 12 | B | 5 | Citrate:Me2+:H+ symporter (CitM) of Bacillus subtilis |
| 2.A.12 | AAA | ATP, ADP | 500 | 12 | B, E (Pl) | >10 | ATP/ADP exchange translocase of Rickettsia prowazekii |
| 2.A.13 | Dcu | C4-dicarboxylates | 440 | 12 | G−B | 5 | Dicarboxylate uptake porter-A (DcuA) of E. coli |
| 2.A.14 | LctP | Lactate | 510–516 | 12 | B, A | 10 | Lactate permease (LctP) of E. coli |
| 2.A.15 | BCCT | Glycine betaine; carnitine; choline | 480–680 | 12 | B | 10 | Carnitine transporter (CaiT) of E. coli |
| 2.A.16 | TDT | Tellurite; dicarboxylates | 320–440 | 10 | B, A, E | >10 | Tellurite uptake permease (TehA) of E. coli |
| 2.A.17 | POT | Peptides; nitrates; amino acids | 450–600 | 12 | B, E | >30 | Dipeptide transporter (DtpT) of Lactococcus lactis |
| 2.A.18 | AAAP | Amino acids and their derivatives | 400–710 | 11 | E (An, Pl, Y, F) | >30 | Amino acid/auxin:H+ symporter (Aux-1) of Arabidopsis thaliana |
| 2.A.19 | CaCA | Ca2+ | 460–1,200 | 10–12 | B, A, E | >30 | Ca2+:H+ antiporter (ChaA) of E. coli |
| 2.A.20 | PiT | Inorganic phosphate | 410–680 | 10–12 | B, A, E | >20 | Phosphate transporter (PitA) of E. coli |
| 2.A.21 | SSS | Sugars; amino acids; vitamins; nucleosides; inositols; iodide; urea | 400–700 | 12–15 | B, A, E | >30 | Pantothenate:Na+ symporter (PanF) of E. coli |
| 2.A.22 | NSS | Neurotransmitters; amino acids; osmolytes; taurine; creatine | 600–700 | 12 | B, A, E (An) | >50 | Serotonin:Na+ symporter of Homo sapiens |
| 2.A.23 | DAACS | C4-dicarboxylates; acidic and neutral amino acids | 420–580 | 10–12 | B, A, E | >20 | Glutamate/aspartate permease (GltP) of E. coli |
| 2.A.24 | CCS | Mono-, di-, and tricarboxylates | 450 | 12 | B | >10 | Citrate:Na+ symporter (CitS) of Klebsiella pneumoniae |
| 2.A.25 | AGCS | Alanine, glycine | 440–540 | 8–12 | B | 10 | Alanine/glycine transporter (DagA) of Alteromonas haloplanktis |
| 2.A.26 | LIVCS | Branched-chain amino acid | ∼440 | 12 | B | 10 | Branched-chain amino acid transporter (BraB) of Pseudomonas aeruginosa |
| 2.A.27 | ESS | Glutamate | ∼400 | 12 | B | 5 | Glutamate:Na+ symporter (GltS) of E. coli |
| 2.A.28 | BASS | Bile acids | 360–480 | 12 | B, E (An) | 10 | Bile acid uptake system of Rattus norvegicus |
| 2.A.29 | MC | ATP/ADP; Pi; organic anions; H+; carnitine/acyl carnitine; basic amino acids; FAD | 300 | 6 | E (mito) | >100 | ATP/ADP exchanger of Homo sapiens |
| 2.A.30 | CCC | K+, Na+, Cl− | 1,000–1,200 | 12 | B, A, E (An, Pl, Y) | >30 | NaCl/KCl cotransporter of Rattus norvegicus |
| 2.A.31 | AE | Inorganic anions | 900–1,250 | 14 | E (An, Y) | >20 | Anion exchanger (AE1) of Homo sapiens |
| 2.A.32 | Sit | Silicate | 550 | 12 | E (diatoms) | 6 | Sit1 of Cylindrotheca fusiformis |
| 2.A.33 | NhaA | Na+/H+ | ∼400 | 12 | B | 10 | Na+:H+ antiporter (NhaA) of E. coli |
| 2.A.34 | NhaB | Na+/H+ | ∼520 | 12 | B | 5 | Na+:H+ antiporter (NhaB) of E. coli |
| 2.A.35 | NhaC | Na+/H+ | ∼460 | 12 | B | 5 | Na+:H+ antiporter (NhaC) of Bacillus firmus |
| 2.A.36 | CPA1 | Na+/H+; Na+ or K+/H+ | 500–900 | 10–12 | B, A, E | >40 | Na+:H+ antiporter (Nhe-1) of Rattus norvegicus |
| 2.A.37 | CPA2 | Na+/H+ or K+/H+ | 330–630 | 10–12 | B, A, E | >20 | K+ efflux protein-C (KefC) of E. coli |
| 2.A.38 | Trk | K+:H+? | 420–560 | 10–12 | B, A, E | >10 | K+ uptake permease (TrkH) of E. coli |
| 2.A.39 | NCS1 | Nucleobases; thiamine; nucleosides | 420–640 | 12 | B, A, E | >20 | Cytosine permease (CodB) of E. coli |
| 2.A.40 | NCS2 | Nucleobases; urate | 420–600 | 12 | B, A, E | >20 | Uracil permease (UraA) of E. coli |
| 2.A.41 | CNT | Nucleosides | 390–660 | 12–14 | B, A, E | >20 | Nucleoside:H+ symporter (NupC) of E. coli |
| 2.A.42 | HAAAP | Hydroxy and aromatic amino acids | 400–450 | 11 | B | >20 | Tyrosine permease (TyrP) of E. coli; serine permease (SdaC) of E. coli |
| 2.A.43 | LCT | Cystine | 300–400 | 7 | E (An, Pl, Y) | >20 | Lysosomal cystine transporter (cystinosin) of Homo sapiens |
| 2.A.44 | FNT | Formate; nitrite; acetate | 250–630 | 6–8 | B, A, E (Y) | >10 | Formate efflux permease (FocA) of E. coli |
| 2.A.45 | ArsB | Arsenite, antimonite | 400–900 | 12 | B, A, E | >20 | Arsenical resistance efflux pump of Staphylococcus aureus |
| 2.A.46 | BenE | Benzoate | 400 | 12 | B | 2 | Benzoate:H+ symporter (BenE) of Acinetobacter calcoaceticus |
| 2.A.47 | DASS | Dicarboxylates; phosphate; sulfate | 430–920 | 11–14 | B, A, E | >20 | Dicarboxylate translocator (SodiT1) of Spinacia oleracea |
| 2.A.48 | RFC | Reduced folate | 500–600 | 12 | E (An) | >10 | Reduced folate carrier (RFC) of Mus musculus |
| 2.A.49 | Amt | Ammonium | 390–620 | 12 | B, A, E | >20 | Ammonium transporter (AmtB) of E. coli |
| 2.A.50 | TP-NST | Triosephosphates; glucose 6-phosphate, Pi; nucleotide sugars; nucleotides | 300–450 | 5–12 | E (An, Pl, Y) (chloroplasts; plastids; other organelles) | >20 | Triosephosphate translocator (TPT) of Zea mays chloroplasts; UDP-galactose:UDP exchange transporter of Homo sapiens endoplasmic reticulum and Golgi |
| 2.A.51 | CHR | Chromate; sulfate (uptake or efflux) | ∼400 | 10 | B, A | ∼10 | Chromate transporter (ChrA) of Alcaligenes eutrophus |
| 2.A.52 | NiCoT | Ni2+, Co2+ | 300–400 | 8 | B | >10 | Ni2+ uptake permease (HoxN) of Ralstonia eutropha |
| 2.A.53 | SulP | Sulfate | 430–900 | 10–13 | B, A, E | >50 | Sulfate permease (SulP) of Homo sapiens |
| 2.A.54 | MTC | Di- and tricarboxylates | ∼290 | 3–6 | E (mito) | >10 | Mitochondrial tricarboxylate carrier (MTC) of Rattus norvegicus |
| 2.A.55 | Nramp | Divalent metal ions (uptake) | 540–580 | 8–12 | B, A, E | ∼20 | Divalent metal ion; H+ symporter (Nramp2) of Homo sapiens |
| 2.A.56 | TRAP-T | C4-dicarboxylates; acidic amino acids; sugars? | ∼1,000 (three components) | 12 + 4 | B, A | >20 | Dicarboxylate transporter (DctPQM) of Rhodobacter capsulatus |
| 2.A.57 | ENT | Nucleosides | ∼450 | 11 | E | >10 | Equilibrative nucleoside transporter-1 (hENT1) of Homo sapiens |
| 2.A.58 | PNaS | Inorganic phosphate | 300–650 | >10 | B, E | >20 | Renal Na+-dependent phosphate transporter-2 (NPT2) of Rattus norvegicus |
| 2.A.59 | ACR3 | Arsenite | 400 | 10 | B, A, E | 1 | Arsenical resistance-3 protein (ACR3) of S. cerevisiae |
| 2.A.60 | OAT | Organic anions; prostaglandins; bile acids; bile conjugates | 600–700 | 10–12 | E (An) | 10 | Organic anion transporter (OATP1) of Rattus norvegicus; prostaglandin transporter (PGT) of Rattus norvegicus |
| 2.A.61 | DcuC | Dicarboxylates | 461 | 10–12 | B | 10 | C4-dicarboxylate uptake-C porter (DcuC) of E. coli |
| 2.A.62 | NhaD | Na+/H+ | 410–430 | 10–12 | B, A | 3 | Na+/H+ antiporter (NhaD) of Vibrio parahaemolyticus |
| 2.A.63 | CPA3 | K+ or Na+/H+ | >700; possibly multiple components | 17 (+?) | B | 2 | K+:H+ antiporter (PhaA-G) of Rhizobium meliloti; Na+:H+ antiporter (Nha1) of an alkalophilic Bacillus species |
| 2.A.64 | Tat | Redox proteins | >800 (5 subunits) | 9 (1+1+5 or 6+0+1) | B, A, E | >10 | Redox protein targeting and translocation (MttA-E) (TatA-E) system of E. coli |
| 2.A.65 | BRT | Bilirubin | 340 | 5 | E (An) | 1 | Bilirubin transporter of Rattus norvegicus |
| 2.A.66 | MATE | Drugs | 400–700 | 12 | B, A, E | >40 | Norfloxacin and other drug efflux pump (NorM) of Vibrio parahaemolyticus |
| 2.A.67 | OPT | Peptides | 600–900 | 12–15 | B, A, E | >20 | Oligopeptide transporter (OPT1) of Candida albicans |
| 2.A.68 | AbgT | Aminobenzoylglutamate | ∼500 | 12–13 | B | 1 | Aminobenzoylglutamate transporter (AbgT) of E. coli |
| 2.A.69 | AEC | Auxin (efflux) | 600–700 | 8–12 | B, A, E | ∼20 | Auxin efflux carrier (PIN1) |
| 2.A.70 | MSS | Malonate | 255 + 129 | 7 + 4 | B | <10 | Malonate:Na+ symporter (MadLM) of Malonomonas rubra |
| 2.A.71 | FBT | Folate, biopterin, methotrexate | 450–650 | 12 | B, E (Pr, Pl) | <10 | Folate-biopterin transporter of Leishmania donovani |
| 2.A.72 | KUP | K+ (uptake) | 400–800 | 12 | B, E (Y, Pl) | ∼30 | The K+:H+ symporter (Hak1) of Neurospora crassa |
| 2.A.73 | ICT | HCO3− | 380–480 | 10 | B | 3 | HCO3−:Na+ symporter of Synechococcus PCC7942 |
| 2.A.74 | MET | Thymidine, drugs, steroids | 230–270 | 4 | E (An) | 5 | Lysosomal hydrophobe/ amphiphile transporter (MTP) of Mus musculus |
| 2.A.75 | LysE | Basic amino acids | 190–240 | 5 | B | 10 | Lysine/arginine exporter (LysE) of Corynebacterium glutamicum |
| 2.A.76 | RhtB | Neutral amino acids and their derivatives | 190–230 | 5 | B | 10 | Neutral amino acid exporter (RhtB) of E. coli |
| 2.A.77 | CadD | Cd2+; cations | 190–220 | 5 | B | 4 | Cadmium resistance protein (CadD) of Staphylococcus aureus |
| 2.A.78 | CAAT | Carboxylates, amino acids, amines (efflux) | 280–320 | 10 | B, A | >50 | MadN of Malonomonas rubra |
| 2.C. Ion gradient-driven energizers | |||||||
| 2.C.1 | TonB | H+?; drives solute uptake across outer bacterial membranes | ∼1,000 | 1 + 3 + 1 | B | >10 | TonB-ExbBD outer membrane energizer of E. coli |
| 3.A. Pyrophosphate bond hydrolysis-driven transporters | |||||||
| 3.A.1 | ABC | All sorts of inorganic and organic molecules of small, intermediate, and large sizes, from simple ions to macromolecules | 1,000–2,000 (multidomain; usually multisubunit | 10 or 12; variable | B, A, E | >1,000 | Maltose permease (MalEFGK) of E. coli; multidrug resistance protein (MDR) of Homo sapiens |
| 3.A.2 | F-ATPase | H+; Na+ | >4,000 (multiple subunits) | (2)12, + (1)2, + (6)1 | B, A, E (chloro; mito) | >100 | F0F1-ATPase of E. coli |
| 3.A.3 | P-ATPase | Na+; H+; K+; Ca2+; Mg2+; Cd2+; Cu2+; Zn2+, Cd2+, Co2+, Ni2+; Ag+; phospholipids (flipping) | 600–1,200 (sometimes multisubunit) | 6–12 | B, A, E | >100 | KdpABC (K+ uptake) of E. coli |
| 3.A.4 | ArsAB | Arsenite, antimonite, tellurite | ∼1,100 (multidomain; two subunits) | 12 | B, A, E | >10 | Arsenite efflux pump (ArsAB) of E. coli |
| 3.A.5 | IISP | Proteins | >2,000 (multiple subunits) | SecY (10) | B, A, E | >50 | Type II secretory pathway system (SecAYEDFG) of E. coli |
| 3.A.6 | IIISP | Proteins | >2,000 (multiple subunits) | 6 integral membrane constituents | B | >20 | Type III secretory pathway system (YscNDRSTUC; LcrD) of Yersinia species |
| 3.A.7 | IVSP | Proteins, protein-DNA complexes | >2,000 (multiple subunits) | 3 integral membrane constituents | B | >20 | Type IV secretory pathway system (VirB4, B6, B7, B9, B10, B11) of Agrobacterium tumefaciens |
| 3.A.8 | MPT | Mitochondrial proteins | >2,000 (multiple subunits) | 9 integral membrane constituents | E (mito) | 2 | Mitochondrial protein translocase (Tom and Tim) proteins of Saccharomyces cerevisiae |
| 3.A.9 | CEPT | Chloroplast proteins | >2,000 (multiple subunits) | Several integral membrane constituents | E (chloro) | 2 | Chloroplast envelope protein translocase (IAP) proteins of Pisum sativum |
| 3.A.10 | H+-PPase | H+ | 660–780 | 15 | E (plant vacuoles), B, A | >10 | Vacuolar H+-pyrophosphatase (V-PPase) of Arabidopsis thaliana |
| 3.A.11 | DNA-T | Single-stranded DNA | >1,000 (multiple subunits) | 3 subunits | B | 5 | Competence-related DNA transformation transporter (ComEA-EC-FA) of Bacillus subtilis |
| 3.B. Decarboxylation-driven active transporters | |||||||
| 3.B.1 | NaT-DC | Na+ | ∼1,000 (3 subunits) | 11 (β-subunit) | B, A | 10 | Oxaloacetate decarboxylase of Salmonella typhimurium |
| 3.C. Methyl transfer-driven active transporters | |||||||
| 3.C.1 | NaT-MMM | Na+ | ∼8 subunits; most integral membrane constituents | ? | A | 2 | Na+-transporting methyltetrahydromethanopterin:coenzyme M methyltransferase of Methanobacterium thermoautotrophicum |
| 3.D. Oxidoreduction-driven active transporters | |||||||
| 3.D.1 | NDH | H+ or NA+(efflux) | 14–40 subunits | Multiple integral membrane subunits | B, E (mito, chloro) | >10 | NDH of E. coli |
| 3.D.2 | PTH | H+ (efflux) | ∼2,000 (1–3 proteins; 3 domains; dimeric) | (12–14)2 | B, E (mito) | >10 | PTH of E. coli |
| 3.D.3 | QCR | H+ (efflux) | 2,000–6,000 multiple (3–11) subunits; dimeric | (13)2 | B, E (mito; chloro) | >20 | Cytochrome bc1 complex of Paracoccus denitrificans |
| 3.D.4 | COX | H+ (efflux) | 2,000–6,000 multiple (3–11) subunits; dimeric | (12–20)2 | B, A, E (mito) | >20 | Quinol oxidase (Cyo) of E. coli |
| 3.D.5 | Na-NDH | Na+ (efflux) | Multiple subunits | ? | B | 1 | Na+-translocating NADH-quinol reductase of Vibrio alginolyticus |
| 3.D.6 | NFO | H+ or Na+ (efflux) | Multiple subunits | ? | B | ∼10 | H+- or Na+-translocating NADH:ferredoxin oxidoreductase (RnfA–H) of Rhodobacter capsulatus |
| 3.D.7 | HHO | H+ (efflux) | Multiple subunits | ? | A | ∼5 | H2:heterodisulfide oxidoreductase of Methanosarcina mazei Göl |
| 3.D.8 | FMF-DH | H+ or Na+ (efflux) | Multiple subunits | ? | A | ∼5 | Formyl methanofuran dehydrogenase (FwdA-G) of Methanobacterium thermoautotrophicum |
| 3.E. Light-driven active transporters | |||||||
| 3.E.1 | FAR | H+ efflux; Cl− uptake | ∼250 | 7 | A, E (Y, F) | >20 | Bacteriorhodopsin of Halobacterium salinarum |
| 3.E.2 | PRC | H+ (efflux) | Multiple subunits | - | B, E (plant chloro) | >20 | Reaction center and cytochrome b6f complex of Rhodobacter sphaeroides |
| 4.A. Phosphotransferase systems | |||||||
| 4.A.1 | Glc | Glucose; N-acetylglucosamine; α- and β-glucosides | ∼2,000 (3 domains; dimeric) | (8)2 | B | ∼30 | Glucose IICB-IIA of E. coli |
| 4.A.2 | Fru | Fructose; mannitol | ∼2,000 (3 domains; dimeric) | (6)2 | B | ∼30 | Fructose IIB′BC-IIAMH of E. coli |
| 4.A.3 | Lac | Lactose; cellobiose; N,N′-diacetylchitobiose | ∼2,000 (3 domains; dimeric) | ∼(8)2 | B | ∼20 | Lactose IICB-IIA of Staphylococcus aureus |
| 4.A.4 | Gut | Glucitol | ∼2,000 (3 domains; dimeric) | (8)2 | B | 2 | Glucitol IICB-IIA of E. coli |
| 4.A.5 | Gat | Galactitol | ∼2,000 (3 domains; dimeric) | ∼(8)2 | B | 1 | Galactitol IIC-IIB-IIA of E. coli |
| 4.A.6 | Man | Glucose, mannose, fructose, sorbose, etc. | ∼2,000 (4 domains; probably dimeric) | (6(IIC) + 1(IID))2 | B | 5 | Mannose IIAB-IIC-IID of E. coli |
| 9.A. Transporters of unknown classification | |||||||
| 9.A.1 | PST | Polysaccharides (export) | 400–500 | 12 | B | >10 | Lipopolysaccharide exporter (RfbX1) of E. coli |
| 9.A.2 | MerTP | Hg2+ (uptake) | ∼200 | 2 | B | ∼10 | Mercuric ion transporter (MerTP), encoded on the IncJ plasmid pMERPH of Shewanella putrefaciens |
| 9.A.3 | MerC | Hg2+ (uptake) | 137 | 1 | B | ∼10 | Mercuric ion uptake transporter (MerC), encoded on the IncJ plasmid pMERPH of Shewanella putrefaciens |
| 9.A.4 | PnuC | Nicotinamide mononucleotide (uptake) | ∼320 | 7 | B | ∼10 | Nicotinamide mononucleotide uptake permease (PnuC) of Salmonella typhimurium |
| 9.A.5 | Oxal | Proteins | 400–600 | 3–5 | B, E (mito; chloro) | ∼10 | Cytochrome oxidase biogenesis protein Oxal of Saccharomyces cerevisiae |
| 9.A.6 | INT | Nucleosides | 230–270 | 4 | E (An) | ∼10 | Intracellular nucleoside transporter (MTP) of Mus musculus |
| 9.A.8 | FeoB | Fe2+ (uptake) | ∼800 | 8–13 | B, A | ∼10 | Fe2+ uptake transporter (FeoB) of E. coli |
| 9.A.9 | FeT | Fe2+ (Co2+, Cd2+) (uptake) | 552 | 6 | E (Y) | 1 | Fe2+ transporter (Fet4p) of Saccharomyces cerevisiae |
| 9.A.10 | OFeT | Fe2+ (uptake) | 404 | 6 | B, A, E | ∼10 | Oxidase-dependent Fe2+ transporter (Ftr1p) of Saccharomyces cerevisiae |
| 9.A.11 | Ctr1 | Cu2+ (uptake) | 406 | 2–3 | E (Y) | 1 | Copper transporter (Ctr1p) of Saccharomyces cerevisiae |
| 9.A.12 | Ctr2 | Cu2+ (uptake) | 160–200 | 3 | E | ∼10 | Copper transporter (Ctr2p) of Saccharomyces cerevisiae |
| 9.A.13 | scFAT | Short-chain fatty acids (uptake) | ∼470 | 12 | B, A | ∼5 | AtoE of E. coli |
| 9.A.14 | NPC | RNA; proteins, small molecules, etc. | 30–50 proteins | — | E | — | Nuclear pore complex of Saccharomyces cerevisiae |
| 9.A.15 | Ami | Short-chain aliphatic amides; urea (uptake) | 170–210 | 6 | B | ∼5 | Amide transporter (AmiS) of Pseudomonas aeruginosa |
| 9.A.16 | SDT | DNA | ∼800 | 4 | B | >10 | Septum DNA translocation pore (SpoIIIE) of Bacillus subtilis |
| 9.A.17 | MIT | Heavy-metal ions, Mg2+, Mn2+, Co2+, Ni2+, Fe2+; Al3+; Mn2+ | 200–360 | 2–3 | B, A, E | >50 | Metal uptake and efflux permease (CorA) of E. coli |
| 9.A.18 | PUP | Peptides, antibiotics (uptake) | 406 | 7 | B | 2 | Microbin uptake permease (SbmA) of E. coli |
| 9.A.19 | MgtE | Mg2+, Co2+ (uptake) | 310–470 | 4–5 | B, A | 10 | Mg2+ transporter E (MgtE) of Bacillus firmus |
| 9.A.20 | LCT | Monovalent cations | 570 | 8–10 | E (Pl) | 1 | Low-affinity cation transporter (LCT1) of Triticum aestivum |
a
Substrates of single transporters within a family are separated by commas; substrates transported by different protein members of the family are separated by semicolons.
b
Size range (in number of amino acyl residues) when a single type of subunit is present, or for the entire complex when several types of subunits are present.
c
nTMSs, number of transmembrane α-helical segments in a polypeptide chain. Subscripts refer to the number of polypeptide chains in the complex when known. A subscript n indicates an oligomeric structure of unknown or poorly defined number of subunits. If alternative structures are found for different transporters within a single family, these are separated by semicolons. In a few ambiguous cases, the subunit is indicated in parentheses.
d
Abbreviations: B, bacteria; A, archaea; E, eukaryotes; G− B, gram-negative bacteria; G+ B, gram-positive bacteria; Y, yeasts; F, fungi; Pr, protozoans; Pl, plants; An, animals; mito, mitochondria; chloro, chloroplasts; plastids, nonphotosynthetic plastids of plants; phage, bacteriophages. These abbreviations are used in the tables. Other abbreviations are defined in Table 2 or the text.