Figure 4. Predicted binding position of A-803467 with homology modeled ABCG2.

A. Docked position of A-803467 within the drug-binding site of human ABCG2. Important residues are depicted as sticks with the atoms colored: carbon – green, hydrogen – white, nitrogen – blue, oxygen – red, sulfur – yellow. A-803467 is shown as ball and stick model with the same color scheme as above, except carbon atoms are represented in orange and chlorine in dark green. Ring centroids were represented as dark-green dots. Dotted yellow lines indicate hydrogen bonds. B. A two-dimensional ligand − receptor interaction diagram with important interactions observed in the docked complex of A-803467 with the drug-binding site residues of human ABCG2 is shown. The amino acids within 4 Å are shown as colored bubbles, red indicates negative charge, cyan indicates polar, and green indicates hydrophobic residues. Hydrogen bonds are shown by the purple dotted arrow, while π-π stacking aromatic interactions are shown by green lines. C. Location of predicted binding position of A-803467 (carbon atoms are represented in orange) and topotecan (carbon atoms are represented in purple) within transmembrane domain of ABCG2.