The interaction of disagregin with the platelet fibrinogen receptor, glycoprotein IIb-IIIa.
Disagregin, a 6 kDa protein isolated from salivary glands of the tick Ornithodoros Moubata, is a potent and selective inhibitor of fibrinogen dependent platelet aggregation and of the adhesion of platelets to fibrinogen (Karczewski et al. (1994) J. Biol. Chem. 269, 6702-6708). In the current study the interaction of disagregin with purified glycoprotein IIb-IIIa (GPIIb-IIIa) was examined. Biotin-labeled disagregin (b-disagregin) bound to GPIIb-IIIa immobilized on the surface of the ELISA plate. This binding was specific, dependent on divalent cations, and was blocked by the peptides fibrinogen gamma-chain fg gamma (400-411), GPIIb(296-306) and by the RGD-containing peptide, GRGDSP. Disagregin also bound to soluble GPIIb-IIIa as demonstrated in studies using the chemical crosslinker, BS3. This binding was inhibited by the peptides fg gamma (400-411) and GPIIb(296-306). In contrast to the results in the solid phase, peptide GRGDSP had no effect on the binding of b-disagregin to soluble GPIIb-IIIa. These data demonstrate that disagregin binds to GPIIb-IIIa through a mechanism distinct from that used by RGD-containing disintegrins. Further analysis of the region(s) of disagregin which bind to GPIIb-IIIa should provide useful information for molecular modeling of the fibrinogen binding site on GPIIb-IIIa and for the design of a new class of potent fibrinogen receptor antagonists.
Karczewski
J
J
Department of Pharmacology, Merck Research Laboratories, West Point, Pennsylvania 19486, USA. jerzy-karczewski@merck.com
Connolly
T M
TM
D000818:Animals; D001667:Binding, Competitive; D003432:Cross-Linking Reagents; D006801:Humans; D010975:Platelet Aggregation Inhibitors / Q000378:metabolism*; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000737:chemistry / Q000378:metabolism*; D051381:Rats; D012471:Salivary Proteins and Peptides / Q000097:blood / Q000378:metabolism*; D012995:Solubility; D013987:Ticks
D003432:Cross-Linking Reagents; D010975:Platelet Aggregation Inhibitors; D019039:Platelet Glycoprotein GPIIb-IIIa Complex; D012471:Salivary Proteins and Peptides; C086086:disagregin