aIIbb3, a member of the integrin family of adhesive protein receptors, is the most abundant glycoprotein on platelet plasma-membranes and binds to adhesive proteins via the recognition of short amino acid sequences, for example the ubiquitous RGD , elucidation of the ligand-binding domains of the receptor remains controversial, mainly owing to the fact that integrins are conformationally labile during purification and storage.