ABC transporters are a family of integral membrane proteins that couple transport of chemically diverse substrates across the PL bilayer of cell membranes to the hydrolysis of ATP. ABC transporters can be divided into exporters and importers; importers mediate the uptake of essential nutrients into cells and are found predominantly in prokaryotes whereas exporters transport molecules out of cells or into organelles and are found in all organisms.The human genome codes for approximately 50 such transporters that are divided into seven subfamilies, designated ABCA through ABCG, based on organization of domains and amino acid homology. ABC transporters can be classified as importers (type I and II) or exporters; type I and II importers are only found in bacteria and their role is to uptake essential nutrients whereas exporters transport substrates out of the cell. Their core architecture is a dimeric transmembrane domain (TMD) that contains the ligand-binding site and a dimeric nucleotide-binding domain(NBD) whereas ATP binds and hydrolyzes. Their functional role is very diverse, ranging from importing essential nutrients inside bacterial cells to conferring multi-drug resistance in cancer cells.


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