Critical residues for ligand binding in the α subunits of β₃ integrins.

(A) Comparison of critical residues for ligand binding in α_v with those in α_IIb. In α_IIb multiple residues (underlined) critical for ligand binding have been identified in both the W3 4-1 and W3 2-3 loops. In sharp contrast, in α_v only Y178 within the W3 2-3 loop is critical for ligand binding. The figures in panels B and C are adapted from a β-propeller model proposed by Springer,20 and they show the location of these critical residues. The view is shown from the top (B) and from the side (C).