Fig. 2

ATP-binding cassette transporters P-glycoprotein (P-gp), multidrug resistance-associated protein 1 (MRP1), breast cancer resistance protein (BCRP). P-gp consists of 2 nucleotide binding domains (NBD) and 2 transmembrane domains (TMDs). MRP1 structure has 2 TMDs and 2 NBDs. It also has a third TMD (TMD0) with 5 transmembrane segments and an extra N-terminus. While BCRP is formed by only 1 NBD and 1 TMD. The TMD consist of 6 transmembrane fragments which is asymmetrically located in 2 membranes and facilitates transcellular transport of a drug or metabolites from intracellular to extracellular or vice versa within the cell