Editing ABC transporter (section)

== Subfamilies ==
=== Mammalian subfamilies ===
There are 49 known ABC transporters present in humans, which are classified into seven families by the Human Genome Organization.

{| class="wikitable"
|-
! Family !! Members !! Function !! Examples
 |-
 | ABCA  || This family contains some of the largest transporters (over 2,100 amino acids long). Five of them are located in a cluster in the 17q24 chromosome. || Responsible for the transportation of cholesterol and lipids, among other things. || [[ABCA12]] [[ABCA1]]
 |-
 | ABCB || Consists of 4 full and 7 half transporters. || Some are located in the blood–brain barrier, liver, mitochondria, transports peptides and bile, for example. || [[ABCB5]]
 |-
 | ABCC || Consists of 12 full transporters.  || Used in ion transport, cell-surface receptors, toxin secretion.   Includes the CFTR protein, which causes [[cystic fibrosis]] when deficient. || [[ABCC6]]
 |-
 | ABCD || Consists of 4 half transporters || Are all used in [[peroxisome]]s. || [[ABCD1]]
 |-
 | ABCE/ABCF || Consists of 1 ABCE and 3 ABCF proteins. || These are not actually transporters but merely ATP-binding domains that were derived from the ABC family, but without the transmembrane domains. These proteins mainly regulate protein synthesis or expression.  || [[ABCE1]], [[ABCF1]], [[ABCF2]]
|-
 |-
 | ABCG || Consists of 6 "reverse" half-transporters, with the NBF at the NH<sub>3</sub><sup>+</sup> end and the TM at the COO- end. || Transports lipids, diverse drug substrates, bile, cholesterol, and other steroids. || [[ABCG2]] [[ABCG1]]
|}

A full list of human ABC transporters can be found from.<ref>{{cite journal |last1=Vasiliou |first1=V |last2=Vasiliou |first2=K |last3=Nebert |first3=DW |title=Human ATP-binding cassette (ABC) transporter family. |journal=Human Genomics |date=April 2009 |volume=3 |issue=3 |pages=281–90 |pmid=19403462 |pmc=2752038 |doi=10.1186/1479-7364-3-3-281 |doi-access=free }}</ref>

==== ABCA ====
The ABCA subfamily is composed of 12 full transporters split into two subgroups.  The first subgroup consists of seven genes that map to six different [[chromosome]]s.  These are [[ABCA1]], [[ABCA2]], [[ABCA3]], and [[ABCA4]], [[ABCA7]], [[ABCA12]], and [[ABCA13]]. The other subgroup consists of [[ABCA5]] and [[ABCA6]] and [[ABCA8]], [[ABCA9]] and [[ABCA10]]. A8-10.
All of subgroup 2 is organized into a head to tail cluster of chromosomes on [[chromosome 17 (human)|chromosome 17]]q24.  Genes in this second subgroup are distinguished from ABCA1-like genes by having 37-38 exons as opposed to the 50 exons in ABCA1.  
The ABCA1 subgroup is implicated in the development of genetic diseases.  In the recessive Tangier's disease, the [[ABCA1]] protein is mutated.  Also, the [[ABCA4]] maps to a region of chromosome 1p21 that contains the gene for Stargardt's disease.  This gene is found to be highly expressed in rod photoreceptors and is mutated in Stargardt's disease, recessive retinitis pigmentism, and the majority of recessive cone-rod dystrophy.<ref name="Dean_2001"/>

==== ABCB ====
The ABCB subfamily is composed of four full transporters and two half transporters.  This is the only human subfamily to have both half and full types of transporters.  [[ABCB1]] was discovered as a protein overexpressed in certain drug resistant tumor cells.  It is expressed primarily in the [[blood–brain barrier]] and liver and is thought to be involved in protecting cells from toxins.  Cells that overexpress this protein exhibit [[multi-drug resistance]].<ref name="Dean_2001"/>

==== ABCC ====
Subfamily ABCC contains thirteen members and nine of these transporters are referred to as the Multidrug Resistance Proteins (MRPs). The MRP proteins are found throughout nature and they mediate many important functions.<ref name="Chen_2011">{{cite journal | vauthors = Chen ZS, Tiwari AK | title = Multidrug resistance proteins (MRPs/ABCCs) in cancer chemotherapy and genetic diseases | journal = The FEBS Journal | volume = 278 | issue = 18 | pages = 3226–45 | date = Sep 2011 | pmid = 21740521 | pmc = 3168698 | doi = 10.1111/j.1742-4658.2011.08235.x }}</ref> They are known to be involved in ion transport, toxin secretion, and signal transduction.<ref name="Dean_2001"/> Of the nine MRP proteins, four of them, MRP4, 5, 8, 9, (ABCC4, 5, 11, and 12),  have a typical ABC structure with four domains, comprising two membrane spanning domains, with each spanning domain followed by a nucleotide binding domain.   These are referred to as short MRPs. The remaining 5 MRP's (MRP1, 2, 6, 7) (ABCC1, 2, 3, 6 and 10) are known as long MRPs and feature an additional fifth domain at their [[N terminus]].<ref name="Chen_2011"/>

[[Cystic fibrosis transmembrane conductance regulator|CFTR]], the transporter involved in the disease [[cystic fibrosis]], is also considered part of this subfamily. Cystic fibrosis occurs upon mutation and loss of function of CFTR.<ref name="Dean_2001"/>

The [[sulfonylurea receptor|sulfonylurea receptors (SUR)]], involved in insulin secretion, neuronal function, and muscle function, are also part of this family of proteins. Mutations in SUR proteins are a potential cause of [[Neonatal diabetes mellitus]]. SUR is also the binding site for drugs such as [[sulfonylureas]] and potassium-channel openers activators such as [[diazoxide]].

==== ABCD ====
The ABCD subfamily consists of four genes that encode half transporters expressed exclusively in the [[peroxisome]].  [[ABCD1]] is responsible for the X-linked form of [[Adrenoleukodystrophy]] (ALD) which is a disease characterized by neurodegeneration and adrenal deficiency that typically is initiated in late childhood.  The cells of ALD patients feature accumulation of unbranched saturated fatty acids, but the exact role of [[ABCD1]] in the process is still undetermined.  In addition, the function of other ABCD genes have yet to be determined but have been thought to exert related functions in [[fatty acid metabolism]].<ref name="Dean_2001"/>

==== ABCE and ABCF ====
Both of these subgroups are composed of genes that have ATP binding domains that are closely related to other ABC transporters, but these genes do not encode for trans-membrane domains.  ABCE consists of only one member, OABP or [[ABCE1]], which is known to recognize certain [[oligodendrocytes]] produced in response to certain viral infections.  Each member of the ABCF subgroup consist of a pair of ATP binding domains.<ref name="Dean_2001"/>

==== ABCG ====
Six half transporters with ATP binding sites on the N terminus and trans-membrane domains at the C terminus make up the ABCG subfamily.  This orientation is opposite of all other ABC genes. There are only 5 ABCG genes in the human genome, but there are 15 in the Drosophila genome and 10 in yeast.  
The ABCG2 gene was discovered in cell lines selected for high level resistance for [[mitoxantrone]] and no expression of [[ABCB1]] or [[ABCC1]]. [[ABCG2]] can export [[anthracycline]] anticancer drugs, as well as [[topotecan]], [[mitoxantrone]], or [[doxorubicin]] as substrates. [[Chromosomal translocations]] have been found to cause the ABCG2 amplification or rearrangement found in resistant cell lines.<ref name="Dean_2001"/>

===Cross-species subfamilies===
{{missing information|section|Pfam/InterPro mapping (bit hard to make, need them to improve data too)|date=December 2020}}
The following classification system for transmembrane solute transporters has been constructed in the TCDB.<ref name="pmid10839820">{{cite journal | vauthors = Saier MH | title = A functional-phylogenetic classification system for transmembrane solute transporters | journal = Microbiology and Molecular Biology Reviews | volume = 64 | issue = 2 | pages = 354–411 | date = Jun 2000 | pmid = 10839820 | pmc = 98997 | doi = 10.1128/MMBR.64.2.354-411.2000 }}; {{cite web | url = http://www.tcdb.org/search/result.php?tc=3.A.1 | title = 3.A.1 The ATP-binding Cassette (ABC) Superfamily | author =  Saier Lab Bioinformatics Group | work = Transporter Classification Database (TCDB) | publisher = University of California San Diego }}</ref>

Three families of ABC exporters are defined by their evolutionary origins.<ref name="Wang2009"/> ABC1 exporters evolved by intragenic triplication of a 2 TMS precursor (TMS = transmembrane segment.  A "2 TMS" protein has 2 transmembrane segments) to give 6 TMS proteins.  ABC2 exporters evolved by intragenic duplication of a 3 TMS precursor, and ABC3 exporters evolved from a 4 TMS precursor which duplicated either extragenicly to give two 4 TMS proteins, both required for transport function, or intragenicly to give 8 or 10 TMS proteins. The 10 TMS proteins appear to have two extra TMSs between the two 4 TMS repeat units.<ref name="Khwaja">{{cite journal | vauthors = Khwaja M, Ma Q, Saier MH | title = Topological analysis of integral membrane constituents of prokaryotic ABC efflux systems | journal = Research in Microbiology | volume = 156 | issue = 2 | pages = 270–7 | date = Mar 2005 | pmid = 15748994 | doi = 10.1016/j.resmic.2004.07.010 | doi-access = free }}</ref> Most uptake systems (all except 3.A.1.21) are of the ABC2 type, divided into type I and type II by the way they handle nucleotides. A special subfamily of ABC2 importers called ECF use a separate subunit for substrate recognition.<ref>{{cite journal |last1=Zheng |first1=WH |last2=Västermark |first2=Å |last3=Shlykov |first3=MA |last4=Reddy |first4=V |last5=Sun |first5=EI |last6=Saier MH |first6=Jr |title=Evolutionary relationships of ATP-Binding Cassette (ABC) uptake porters. |journal=BMC Microbiology |date=6 May 2013 |volume=13 |pages=98 |doi=10.1186/1471-2180-13-98 |pmid=23647830 |pmc=3654945 |doi-access=free }}</ref>

ABC1 ({{InterPro|IPR036640}}):
{{div col|colwidth=30em|rules=yes}}
* 3.A.1.106 The Lipid Exporter (LipidE) Family
* 3.A.1.108 The β-Glucan Exporter (GlucanE) Family
* 3.A.1.109 The Protein-1 Exporter (Prot1E) Family
* 3.A.1.110 The Protein-2 Exporter (Prot2E) Family
* 3.A.1.111 The Peptide-1 Exporter (Pep1E) Family
* 3.A.1.112 The Peptide-2 Exporter (Pep2E) Family
* 3.A.1.113 The Peptide-3 Exporter (Pep3E) Family
* 3.A.1.117 The Drug Exporter-2 (DrugE2) Family
* 3.A.1.118 The Microcin J25 Exporter (McjD) Family
* 3.A.1.119 The Drug/Siderophore Exporter-3 (DrugE3) Family
* 3.A.1.123 The Peptide-4 Exporter (Pep4E) Family
* 3.A.1.127 The AmfS Peptide Exporter (AmfS-E) Family
* 3.A.1.129 The CydDC Cysteine Exporter (CydDC-E) Family
* 3.A.1.135 The Drug Exporter-4 (DrugE4) Family
* 3.A.1.139 The UDP-Glucose Exporter (U-GlcE) Family (UPF0014 Family)
* 3.A.1.201 The Multidrug Resistance Exporter (MDR) Family (ABCB)
* 3.A.1.202 The Cystic Fibrosis Transmembrane Conductance Exporter (CFTR) Family (ABCC)
* 3.A.1.203 The Peroxysomal Fatty Acyl CoA Transporter (P-FAT) Family (ABCD)
* 3.A.1.206 The a-Factor Sex Pheromone Exporter (STE) Family (ABCB)
* 3.A.1.208 The Drug Conjugate Transporter (DCT) Family (ABCC) (Dębska et al., 2011)
* 3.A.1.209 The MHC Peptide Transporter (TAP) Family (ABCB)
* 3.A.1.210 The Heavy Metal Transporter (HMT) Family (ABCB)
* 3.A.1.212 The Mitochondrial Peptide Exporter (MPE) Family (ABCB)
* 3.A.1.21 The Siderophore-Fe3+ '''Uptake''' Transporter (SIUT) Family
{{Div col end}}

ABC2 ({{InterPro|IPR000412}} [partial]):
{{div col|colwidth=30em|rules=yes}}
* 3.A.1.101 The Capsular Polysaccharide Exporter (CPSE) Family
* 3.A.1.102 The Lipooligosaccharide Exporter (LOSE) Family
* 3.A.1.103 The Lipopolysaccharide Exporter (LPSE) Family
* 3.A.1.104 The Teichoic Acid Exporter (TAE) Family
* 3.A.1.105 The Drug Exporter-1 (DrugE1) Family
* 3.A.1.107 The Putative Heme Exporter (HemeE) Family
* 3.A.1.115 The Na+ Exporter (NatE) Family
* 3.A.1.116 The Microcin B17 Exporter (McbE) Family
* 3.A.1.124 The 3-component Peptide-5 Exporter (Pep5E) Family
* 3.A.1.126 The β-Exotoxin I Exporter (βETE) Family
* 3.A.1.128 The SkfA Peptide Exporter (SkfA-E) Family
* 3.A.1.130 The Multidrug/Hemolysin Exporter (MHE) Family
* 3.A.1.131 The Bacitracin Resistance (Bcr) Family
* 3.A.1.132 The Gliding Motility ABC Transporter (Gld) Family
* 3.A.1.133 The Peptide-6 Exporter (Pep6E) Family
* 3.A.1.138 The Unknown ABC-2-type (ABC2-1) Family
* 3.A.1.141 The Ethyl Viologen Exporter (EVE) Family (DUF990 Family; {{InterPro|IPR010390}})
* 3.A.1.142 The Glycolipid Flippase (G.L.Flippase) Family
* 3.A.1.143 The Exoprotein Secretion System (EcsAB(C))
* 3.A.1.144:  Functionally Uncharacterized ABC2-1 (ABC2-1) Family
* 3.A.1.145:  Peptidase Fused Functionally Uncharacterized ABC2-2 (ABC2-2) Family
* 3.A.1.146:  The actinorhodin (ACT) and undecylprodigiosin (RED) exporter (ARE) family
* 3.A.1.147:  Functionally Uncharacterized ABC2-2 (ABC2-2) Family
* 3.A.1.148:  Functionally Uncharacterized ABC2-3 (ABC2-3) Family
* 3.A.1.149:  Functionally Uncharacterized ABC2-4 (ABC2-4) Family
* 3.A.1.150:  Functionally Uncharacterized ABC2-5 (ABC2-5) Family
* 3.A.1.151:  Functionally Uncharacterized ABC2-6 (ABC2-6) Family
* 3.A.1.152:  The lipopolysaccharide export (LptBFG) Family ({{InterPro|IPR005495}})
* 3.A.1.204 The Eye Pigment Precursor Transporter (EPP) Family (ABCG)
* 3.A.1.205 The Pleiotropic Drug Resistance (PDR) Family (ABCG)
* 3.A.1.211 The Cholesterol/Phospholipid/Retinal (CPR) Flippase Family (ABCA)
* 9.B.74      The Phage Infection Protein (PIP) Family
* ''all uptake systems'' (3.A.1.1 - 3.A.1.34 except 3.A.1.21) 
** 3.A.1.1 Carbohydrate Uptake Transporter-1 (CUT1)
** 3.A.1.2 Carbohydrate Uptake Transporter-2 (CUT2)
** 3.A.1.3 Polar Amino Acid Uptake Transporter (PAAT)
** 3.A.1.4 Hydrophobic Amino Acid Uptake Transporter (HAAT)
** 3.A.1.5 Peptide/Opine/Nickel Uptake Transporter (PepT)
** 3.A.1.6 Sulfate/Tungstate Uptake Transporter (SulT)
** 3.A.1.7 Phosphate Uptake Transporter (PhoT)
** 3.A.1.8 Molybdate Uptake Transporter (MolT)
** 3.A.1.9 Phosphonate Uptake Transporter (PhnT)
** 3.A.1.10 Ferric Iron Uptake Transporter (FeT)
** 3.A.1.11 Polyamine/Opine/Phosphonate Uptake Transporter (POPT)
** 3.A.1.12 Quaternary Amine Uptake Transporter (QAT)
** 3.A.1.13 Vitamin B<sub>12</sub> Uptake Transporter (B12T)
** 3.A.1.14 Iron Chelate Uptake Transporter (FeCT)
** 3.A.1.15 Manganese/Zinc/Iron Chelate Uptake Transporter (MZT)
** 3.A.1.16 Nitrate/Nitrite/Cyanate Uptake Transporter (NitT)
** 3.A.1.17 Taurine Uptake Transporter (TauT)
** 3.A.1.19 Thiamin Uptake Transporter (ThiT)
** 3.A.1.20 Brachyspira Iron Transporter (BIT)
** 3.A.1.21 Siderophore-Fe3+ Uptake Transporter (SIUT)
** 3.A.1.24  The Methionine Uptake Transporter (MUT) Family (Similar to 3.A.1.3 and 3.A.1.12)
** 3.A.1.27  The γ-Hexachlorocyclohexane (HCH) Family (Similar to 3.A.1.24 and 3.A.1.12)
** 3.A.1.34  The Tryptophan (TrpXYZ) Family
** ''ECF uptake systems''
*** 3.A.1.18 The Cobalt Uptake Transporter (CoT) Family 
*** 3.A.1.22 The Nickel Uptake Transporter (NiT) Family
*** 3.A.1.23 The Nickel/Cobalt Uptake Transporter (NiCoT) Family
*** 3.A.1.25 The Biotin Uptake Transporter (BioMNY) Family
*** 3.A.1.26 The Putative Thiamine Uptake Transporter (ThiW) Family
*** 3.A.1.28 The Queuosine (Queuosine) Family
*** 3.A.1.29 The Methionine Precursor (Met-P) Family
*** 3.A.1.30 The Thiamin Precursor (Thi-P) Family
*** 3.A.1.31 The Unknown-ABC1 (U-ABC1) Family
*** 3.A.1.32 The Cobalamin Precursor (B12-P) Family
*** 3.A.1.33 The Methylthioadenosine (MTA) Family
{{Div col end}}

ABC3 ({{InterPro|IPR003838}}):
{{div col|colwidth=30em|rules=yes}}
* 3.A.1.114 The Probable Glycolipid Exporter (DevE) Family
* 3.A.1.122 The Macrolide Exporter (MacB) Family
* 3.A.1.125 The Lipoprotein Translocase (LPT) Family
* 3.A.1.134 The Peptide-7 Exporter (Pep7E) Family
* 3.A.1.136 The Uncharacterized ABC-3-type (U-ABC3-1) Family
* 3.A.1.137 The Uncharacterized ABC-3-type (U-ABC3-2) Family
* 3.A.1.140 The FtsX/FtsE Septation (FtsX/FtsE) Family
* 3.A.1.207 The Eukaryotic ABC3 (E-ABC3) Family
{{Div col end}}