[Mutational analysis of platelet fibrinogen receptor ligand binding domain]

Platelet glycoprotein (GP) IIb-IIIa (alpha IIb beta 3) binds fibrinogen with high affinity. To identify structure responsible for the alpha IIb beta 3 specific fibrinogen binding, chimeric receptors between alpha IIb and alpha v were constructed, expressed on heterologous cells, and their function was analyzed. Chimeric receptors with mutations in calcium binding sequences showed similar ligand specificity as wild type receptor. However, those with replacements in amino-terminal regions revealed substitutions of the epitopes for specific receptor-blocking antibodies, indicating importance of this amino-terminal region for alpha IIb beta 3 specific ligand recognition.