P-glycoprotein

P-glycoprotein is an ATP-powered membrane transporter that exports many drugs and other compounds from cells. In humans, it is encoded by the ABCB1 gene and is also called MDR1 or ABCB1.

ATP-binding cassette transporter: A membrane-protein family that uses ATP binding and hydrolysis to move substrates across membranes. P-glycoprotein is a prominent member of this transporter family.
Blood–brain barrier: A selective interface between circulating blood and the central nervous system, formed chiefly by brain endothelial cells. P-glycoprotein at this barrier exports many compounds and restricts their brain entry.
Victor Ling: A Canadian biochemist who helped identify P-glycoprotein in drug-resistant cancer cells. Ling’s group characterized the membrane glycoprotein associated with multidrug resistance.
ABCG2: An ATP-binding cassette transporter that exports drugs and other compounds from cells. ABCG2 is another major drug-efflux transporter, distinct from P-glycoprotein in sequence and substrate profile.
ATP hydrolysis: The chemical breakdown of ATP into ADP and inorganic phosphate, releasing usable free energy. ATP hydrolysis powers P-glycoprotein’s conformational cycle.
Intestinal drug absorption: The movement of orally administered drugs from the intestinal lumen into the bloodstream. P-glycoprotein can return absorbed drug molecules to the intestinal lumen.
ABCB1: The human gene encoding P-glycoprotein, also known as MDR1. ABCB1 is the gene whose expression produces P-glycoprotein.
MRP1: An ATP-binding cassette transporter, encoded by ABCC1, that exports diverse organic anions and drugs. MRP1 can produce multidrug resistance through a different transporter than P-glycoprotein.
Alternating access: A transport mechanism in which a membrane protein exposes its binding site to opposite sides in turn. P-glycoprotein alternates between inward-facing and outward-facing states to export substrates.
Multidrug resistance: The ability of cells or organisms to resist several drugs with different structures or targets. Elevated P-glycoprotein can lower intracellular drug concentrations and contribute to resistance.

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