TABLE 1.

Classes, families, and subfamilies of ABC systemsa

Family and subfamilybNo. of systemsDefinitionModelcOther namedDomain(s)e
HCGNTC
Class 1 systems (transporters with fused TM and ABC domains)
    FAE99Very-long-chain fatty acid exportALD_HUMANABCDP-FATB, E
    DPL1,569Drugs, peptides, lipidsA, B, E
        BAE83Bacteriocin and peptide exportMESD_LEUMEPep2EB
        LAE95Lantibiotic exportNIST_LACLAPep1EB
        CHV131,2-beta-glucan exportCHVD_RHIMEGlucan EB
        SID64Siderophore uptakeQ9R7V3_YERPESIUTB
        HMT145Mitochondrial and bacterial transporters IIATM1_YEASTABCBHMTB, E
        MDL65Mitochondrial and bacterial transporters IMDL1_YEASTABCBMPEB, E
        LIP222Lipid A or glycerophospholipid exportMSBA_ECOLILipid EB
        LLP296LIP-like exportersA, B, E
        ARP27Antibiotic resistance or productionQ54203_STRGADrugE3B
        TAP38Peptide exportTAP1_HUMANABCBTAPE
        PED53Prokaryote drug exportLMRA_LACLADrugE2B
        HLY158RTX toxin exportHLYD_ECOLIProt1EB
        PRT69Proteases, lipases, S-layer protein exportPRTD_ERWCHProt2EB
        CYD93Cytochrome bd biogenesisCYDC_ECOLICydDC-EB
        p-gP135Eukaryote MDR and lipid exportMDR1_MOUSEABCBMDRE
    OAD190Organic anion conjugates, anions, drugsE
        CFTR19Chloride anion channelsCFTR_HUMANABCCCFTRE
        MRP158Conjugate drug exportersMRP1_HUMANABCCCT1-2E
        SUR13Potassium channel regulatorsSUR1_HUMANABCCE
    EPD250Eye pigment precursors and drugsB, E
        WHITE125Eye pigment precursors and drugsWHIT_DROMEABCGEPPB, E
        PDR125Pleiotropic drug resistancePDR5_YEASTPDRE
    MCM11UnknownA
    CCM94Cytochrome c biogenesisCCMA_ECOLIHemeEA, B, E
Class 2 systems (nontransport cellular processes and antibiotic resistance)
    RLI48RLIABCE1_HUMANABCEA, E
    ART714Antibiotic resistance and translation regulationA, B, E
        ARE104MLS antibiotic resistanceMSRA_STAEPDrugRA2B
        REG589Gene expression regulationGCN20_YEASTABCEB, E
        EF318Translation elongationEF3A_YEASTE
    UVR245DNA repair and drug resistanceUVRA_ECOLIA, B
Class 3 systems (separate TM and ATP-binding domains)
    CBY269Cobalt, nickel, and vitamin uptake
        CBU62Cobalt and nickel uptakeCBIO_SALTY5A, B
        Y179207Biotin and hydroxymethyl pyrimidine uptakeQ6GUB1_RHIETBIOMNYA, B
    MKL162Organic solvent resistanceQ9Z402_PSEPUHCHB, E
    YHBG129Translocation of LPS to the outer membraneLPTB_ECOLIB
    o228893Release of lipoproteins and drug resistanceLOLD_ECOLI6A, B
    CDI126Cell divisionFTSE_ECOLIB
    ISB167Iron-sulfur center biogenesisSUFC_ECOLIA, B, E
    DRA431Drug and antibiotic resistanceA, B, E
        NOD31NodulationNODI_RHISMLOSEB
        DRR314Polyketide drug resistanceDRRA_STRPEDrugE1A, B
        ABCA86Lipid transportABC1_HUMANABCACPRE
    DRI854Drug resistance, bacteriocin and lantibiotic immunityA, B
        BAI44Bacteriocin immunityBCRA_BACLIB
        LAI185Lantibiotic immunityQ45404_BACSUPep5EB
        DRB441Drug resistance (putative)A, B
        YHIH125DRB-like systemsYHIH_ECOLINatEA, B
        NOS59Nitrous oxide reductionNOSF_PSESTA, B
    CLS41Capsular polysaccharide, LPS biogenesisKST1_ECOLI1A, B
Class 3 systems (BPD importers)
    MET293Metallic cationsZNUC_ECOLIMZTA, B
    MOS599Monosaccharides and deoxyribonucleosidesRBSA_ECOLICUT2A, B
    DLM168d- and l-methionineMETN_ECOLIA, B
    MOI1,005Mineral and organic ionsPOTD_ECOLI2A, B
    PAO708Polar amino acid and opinesHISP_SALTYPAATA, B
    HAA399Hydrophobic amino acids and amidesLIVG_ECOLIHAATA, B
    OSP744Oligosaccharides and polyolsMALK_ECOLICUT1A, B
    OPN883Oligopeptides and nickelOPPD_SALTYPepTA, B
    PHN78Phosphonates and phosphitesPHNC_ECOLIPhnTB
    OTCN639Osmoprotectants taurine, cyanate, and nitrateTAUB_ECOLI3A, B
    ISVH927Iron-siderophores vitamin B12 and heminFHUC_ECOLI4A, B
    NO334Unclassified systemsA, B, E
  • a The three classes of ABC systems are as follows: class 1, systems with fused ABC and IM domains; class 2, systems with two duplicated fused ABC domains and no IM domains; and class 3, systems with IM and ABC domains carried by independent polypeptide chains. There are a few exceptions to this scheme, as discussed in the text: ABC proteins of the CcmA and MCM families cluster with class 1 systems but belong to systems similar to those of class 3 and class 2, respectively.

  • b Family names are abbreviations of the substrate or the biological process handled by the systems. For families comprised of systems of unknown function, an arbitrary name is given.

  • c For each family or subfamily, a typical ABC protein is indicated as an example, and when available, the Swissprot identification is given.

  • d Cross-references to the nomenclatures of ABC systems adopted by the Human Gene Nomenclature Committee (HGNC) (http://www.genenames.org/genefamily/abc.php) and by the Transport Commission (TC) (http://www.tcdb.org/tcdb/) are given. Some families described in this table are divided by the Transport Commission into subfamilies according to substrate type, as follows: 1, CPSE + LPSE; 2, PhoT + MolT + SulT + FeT + POPT + ThiT + BIT; 3, QAT + NitT + TauT; 4, B12T + FeCT; 5, CoT + NiT + NiCoT + BIOMNY; and 6, LPT + MacB + Pep4E.

  • e A, archaea; B, bacteria; E, eukaryotes.