The ligand binding site of α_Vβ₃ and the unliganded and liganded conformations of βA and αA domains. (A) Surface representation of the RGD ligand-binding site in the head section of α_Vβ₃. The ligand arginine-binding pocket is located in the α_V propeller (blue) and the aspartic acid–binding pocket in βA (red). The ligand peptide is shown as a ball-and-stick model (carbons are shown in green, amides in blue, and oxygens in red). (B) Superposition of the β_3A domain in the unliganded and liganded conformations. Ligand is in yellow. The 3 metal ions present in the liganded form (LIMBS, MIDAS, and ADMIDAS) are shown in gray, cyan, and magenta, respectively. (C) Superposition of CD11b A domain in the “closed” and “open” forms. Ligand is in yellow. The MIDAS cation is in cyan. In both panels B and C, the C-terminal βαβαβα structures are highlighted in color (blue for unliganded and red for liganded), and the remaining parts of the molecules are in gray. The C-terminal α helix (α₇) is boxed. In panel B, superpositions are generated for the whole molecule with TOP,⁵⁹  whereas in panel C, superpositions are based on the central β sheet only.