SearchPublisher and Institutes
You are here: Home :: Area NEM :: Medical science :: Human medicine
Tatsushiro Tamura, Takaaki Hato, Jun Yamanouchi, Shigeru Fujita
Critical residues for ligand binding in blade 2 of the propeller domain of the integrin IIb subunit
Ligand binding to integrin IIb3 is a key event of thrombus formation. The propeller domain of the IIb subunit has been implicated in ligand binding. Recently, the ligand binding site of the V propeller was determined by crystal structure analysis. However, the structural basis of ligand recognition by the IIb propeller remains to be determined. In this study, we conducted site-directed mutagenesis of all residues located in the loops extending above blades 2 and 4 of the IIb propeller, which are spatially close to, but distinct from, the loops that contain the binding site for an RGD ligand in the crystal structure of the V propeller. Replacement by alanine of Q111, H112 or N114 in the loop within the blade 2 (the W2:2-3 loop in the propeller model) abolished binding of a ligand-mimetic antibody and fibrinogen to IIb3 induced by different types of integrin activation including activation of IIb3 by 3 cytoplasmic mutation. CHO cells stably expressing recombinant Iib3 bearing Q111A, H112A or N114A mutation did not exhibit Iib3-mediated adhesion to fibrinogen. According to the crystal structure of V3, the V residue corresponding to IIbN114 is exposed on the integrin surface and close to the RGD binding site. These results suggest that the Q111, H112 and N114 residues in the loop within blade 2 of the IIb propeller are critical for ligand binding, possibly because of direct interaction with ligands or modulation of the RGD binding pocket.
Thrombosis and Haemostasis, Schattauer
Print ISSN: 0340-6245
Volume: 91, 01/2004
Pages: 111 - 118