Figure 3.

The binding sites for ligand-mimetic antagonists and fibrinogen at the α/β subunit interface. a, Mapping of fibrinogen binding sensitive mutations^20,49,50 in α_IIbβ3. Cβ atoms of fibrinogen-binding sensitive residues are shown as spheres in the same colour as the domains in which they are present. The tirofiban-bound structure is shown. b–f, Binding of ligands or pseudoligands to α_IIbβ3 (b–e) and binding of (f) cyclo Arg-Gly-Asp-D-Phe-N-methyl-Val (cyclo RGDfV) to α_Vβ₃ (ref. 8). The orientation is identical to that in a. The α and β subunits are shown in magenta and cyan, respectively. Small molecules are shown as ball-and-stick models with their carbon, nitrogen, oxygen, sulphur and arsenic atoms coloured yellow, blue, red, green and grey, respectively. Hydrogen bonds are shown as dotted lines. Ca²⁺ and Mg²⁺ ions are gold and silver spheres, respectively. The ligand and S123 coordinations to the MIDAS metal are shown as thin grey lines.