Figure 6.

Three-dimensional structure of the agonist (2MeSADP; top) and antagonist (AZD1283; bottom) bound forms of the purinergic P2Y₁₂ receptor (a type Aδ GPCR). Structures [PDB IDs 4PXZ and 4NTJ (Zhang et al., 2014a; Zhang et al., 2014b)] are shown covered with a semi-transparent gray surface and the secondary protein structure indicated; ligands are highlighted as darker solid CPK structures. Both are shown from two different perspectives with the one on the right being a 90° rotated and somewhat enlarged view from the top. The ligands are faded as they buried inside the receptor and are obscured by the covering surfaces; however, the antagonist (bottom) is less buried than the agonist (top) so that part of its surface is not covered and accessible from outside as indicated by its more vivid colors where directly visible.