Rat GPIIIa acquired the ability to bind DDAb when selected amino acids were converted from rat to the corresponding human residue.

Conversion of 5 amino acids in rat GPIIIa (residues 50, 62, 63, 66, and 67) to their human counterparts led to acquisition of the binding site for DDAb 1 (A). A reaction was obtained with AP3, but not DDAb 1, when only rat residues 50, 62, and 63 were converted (B). A similar pattern of reactions was obtained with DDAbs 2 and 3 (not shown). None of the constructs were recognized by DDAbs 1 to 3 in the absence of drug (not shown). Human and rat sequences are depicted by closed and open boxes, respectively.