Crystal structure of the recognition sites for the PA Abs. (A) Crystal structure of the recognition sites of group A made by PyMOL Version 1.4 software (DeLano Scientific LLC). W1:1-2 (blue) and W2:3-4 (green) loops and 4 critical residues (S29, R32, E136, R139) for the binding of PA Abs were indicated. (B) Crystal structure of the recognition sites of group B. W1:2-3 loop (orange) is located in the upper surface of αIIbβ3 interface, and W2:3-4 and W3:3-4 loops (green) are in the lower surface. Five critical residues (G44, P45, P135, E136, R139) for the binding of PA Abs were also indicated. (C) Crystal structure of the recognition sites of group C. W3:4-1 (red) and W4:4-1 (pink) loops were indicated. Both loops are located in the upper surface of αIIbβ3 interface, which is near the ligand binding site.