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  • Title: The interaction of disagregin with the platelet fibrinogen receptor, glycoprotein IIb-IIIa.
    Author: Karczewski J, Connolly TM.
    Journal: Biochem Biophys Res Commun; 1997 Dec 29; 241(3):744-8. PubMed ID: 9434779.
    Abstract:
    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.
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