Multidrug resistance protein 1 (MRP1, also known as P glycoprotein 1) is a member of a superfamily of proteins known as the ATP-binding cassette (ABC) transporters. This superfamiy is classified into seven subfamilies (A through G). Subfamily ABCC is composed of 12 proteins and includes MRP1 and is encoded by ABCC1.

MRP1 structure comprises five domains with two nucleotide binding domains (NBDs) that bind ATP, and 12 transmembrane domains.

MRP1 mediates the ATP-dependent efflux of a variety of solutes across membranes against a concentration gradient. These solutes include antineoplastic agents such as vincristine and doxorubicin, physiological organic anions such as the antioxidant GSH and the pro-inflammatory cysteinyl leukotriene C4, hydrophilic conjugated xenobiotic, various antibiotics, opiates, antiviral agents, citalopram, and statins. MRP1 is the only MRP-related protein with an acknowledged role in tumor multidrug resistance in clinical oncology. It also plays an important role in the efficacy and toxicity of drugs used for the treatment of nonmalignant diseasese^1,2.

Knock-out mouse model of Abcc1^−/− has shown that MRP1 can act as an important factor of drug disposition because of its presence in cells at the interface between many tissues. The protein also demonstrates chemoprotective properties¹.

Evidence suggests that ABC transporters also have an important role in normal cellular biology including regulation of cell differentiation, proliferation, and survival, including apoptosis, tumor promotion and modulation of immune function².