Table 1.

Families within the MFS

Family no.Family nameAbbreviationNo. of proteinsSource(s)aSize range (aa)Putative TMSs (no.)Mechanism(s)PolaritiesSubstratesRepresentative example(s)
1Sugar porterSP133Bac, Ar, Pr, Y, An, Pl404–81812Sugar uniport Sugar:proton symport Sugar:sugar antiportNone In BothMonosaccharides (hexoses, pentoses), disaccharides, quinate, organo-cations, inositolsXylE of E. coli
2Drug:H+ antiporter (14 TMS)DHA1430Bac, Y14Drug:H+antiportOutMultiple or single drugsQacA of S. aureus
3Drug:H+ antiporter (12 TMS)DHA1246Bac, Ar, Y, An12Drug:H+antiportOutMultiple or single drugsBmr of B. subtilis
4Organophosphate:PiantiporterOPA12Bac, An439–49512Organo phosphate:Pi antiportBothSugar-phosphates, glycerol phosphate, phosphoglycerates, phosphoenolpyruvateUhpT ofE. coli
5Oligosaccharide:H+symporterOHS6Bac415–42512Sugar:H+symport Sugar:sugar antiportIn BothDi- and trisaccharidesLacY of E. coli
6Metabolite:H+ symporterMHS16Bac425–50012Solute:H+symportInCitrate, α-ketoglutarate, proline, betaine, methylphthalate, dicarboxylatesKgtP of E. coli
7Fucose-galactose-glucose:H+symporterFGHS4Bac404–43812Hexose uniport Hexose:H+symportNone In l-Fucose, glucose, galactoseFucP of E. coli
8Nitrate/nitrite porterNNP13Bac, Y, Pl395–54712Nitrite uniport? Nitrate:H+ symport?Out InNitrite, nitrateNarK of E. coli
9Phosphate:H+ symporterPHS11Y, Pl518–58712Pi:H+symportInInorganic phosphatePho-5 of N. crassa
10Nucleoside:H+ symporterNHS2G− Bac41812Nucleoside:H+symportInNucleosidesNupG of E. coli
11Oxalate:formate antiporterOFA5Bac, Ar, An373–47012Anion:anion antiportBothOxalate, formateOxlT of O. formigenes
12Sialate:H+ symporterSHS3G− Bac407–49614Substrate:H+symportInSialateNanT of E. coli
13Monocarboxylate porterMCP13Y, An450–80812Substrate:H+symportInPyruvate, lactate, mevalonateMct of H. sapiens
14Anion:cation symporterACS40Bac, Y, An411–59612Substrate:H+ or Na+symportInGlucarate, hexuronate, tartrate, 4-hydroxyphenyl acetate, inorganic phosphate, allantoateExtU of E. coli
15Aromatic acid:H+symporterAAHS7Bac418–46012Substrate:H+symportInMuconate, benzoate; 4-hydroxybenzoate; 2,4-dichlorophenoxy acetate, protocatachurate, 3-hydroxypropionatePcaK of P. putida
16Unknown major facilitatorUMF6Y600–63714UnknownUnknownUnknownYh1040c of S. cereisiae
17Cyanate permeaseCP3Bac393–40212Substrate:H+symport?InNCO CynX of E. coli
18Proton-dependent oligopeptide transporterPOT24Bac, Y, An, Pl463–78312Substrate:H+symportInPeptides, amino acids, nitrate, chlorate, nitriteDtpT of L. lactis
  • a The abbreviations for source organisms used here and in all subsequent tables are as follows: Bac, bacteria; G−, gram negative; Ar, archaea; Pr, eukaryotic protists (usually protozoans); Y, yeasts; F, fungi; Pl, plants; An, animals.