What Is P-Glycoprotein?
P-gp is a phosphorylated and glycosylated plasma membrane protein belonging to the ATP-binding cassette superfamily of transport proteins. MDR1 P-gp (referred to simply as P-gp in this article) is a transmembrane protein that is 1,280 amino acids long and consists of two homologous halves of 610 amino acids joined by a flexible linker region of 60 amino acids. When viewed from above the plasma membrane, P-gp is donut shaped with 6-fold symmetry, a diameter of about 10 nm and a large central pore of about 5 nm in diameter. It has a thickness in the plane of the plasma membrane of about 8 nm. Since the depth of the plasma membrane lipid bilayer is about 4 nm, about half of the molecule is within the plasma membrane. Mechanism of Action, P-Gp Substrates and Inhibitors The majority of published data suggest that P-gp acts as a transmembrane pump which removes drugs from the cell membrane and cytoplasm. ATP hydrolysis provides the energy for active drug transport, which can occur against st
