fig1

Figure 1. Schematic representation of the domain structure of P-gp, MRP1 and BCRP. P-gp has 2 TMD consisting of 6 α-helices each and 2 ATP bindings sites. MRP1 also contains 2 ATP-binding regions and 2 TMD containing 6 α-helices and it is extended by 1 additional TMD consisting of 5 α-helices and 1 amino terminus loop (L0). The half transporter ABCG2 contains 1 TMD of 6 α-helices and 1 ATP-binding domain. The ATP-binding site of this transporter is found on the amino-terminal side (N) in contrast to P-gp and MRP1. P-gp: P-glycoprotein; MRP1: multidrug resistance protein-1; BCRP: breast cancer resistance protein; TMD: transmembrane domain