Fig. 3.

Structural diversity of ligand binding sites in GPCR structures. (A) Close up of the eticlopride binding site showing the protein-ligand interaction. (B) Chemical structure of eticlopride and interactions with the D3R residues; hydrophobic contacts are colored in gray dots, hydrogen bonds in blue, and salt bridges in red. The ligand binding sites in (C) D3R, (D) β₂AR (PDB ID: 2RH1), and (E) A_2AAR (PDB ID: 3EML) crystal structures are shown in exactly the same orientation. A semi-transparent skin shows the molecular surface of the receptor, colored by the residue properties (green-hydrophobic, red-acidic, and blue-basic). Corresponding ligands, (C) eticlopride, (D) carazolol, and (E) ZM241385 are shown with carbon atoms colored magenta. For the D3R pocket, residues conserved between D3R and β₂AR are colored turquoise and non-conserved are in gray.