ABC Drug-Transporters

The adenosine triphosphate (ATP)-binding cassette (ABC) transporters form the largest family of transmembrane proteins that use ATP-derived energy to transport various substances over cell membranes. Primary-active transporters, driven by energy released from ATP by inherent ATPase activity, that export substrates from the cell against a chemical gradient. Based on the arrangement of the nucleotidebinding domain and the topology of its transmembrane domains, human ABC transporters are classified into seven distinct families (ABC-A to ABC-G), including ABCB1 (P-glycoprotein), ABCC1 (MRP1), ABCC2 (cMOAT, MRP2), ABCC4 (MRP4), and ABCG2 (ABCP, MXR, BCRP). Structural characteristics based on their Walker motif (ATP-binding domain) and their nucleotide-binding folds across the membrane are responsible for their classification into this superfamily. Their localization pattern over the body suggests that they have an important role in the prevention of absorption as well as the excretion of potentially toxic metabolites and xenobiotics, both on a systemic and a cellular level. ABC drug transporters (may) show substrate overlap. Examples of mammalian ABC transporters include ▶ Pglycoprotein, MRP (▶multidrug resistance protein), ▶ cystic fibrosis transmembrane conductance regulator (CFTR), and transporter associated with antigen processing (TAP).