Oct 15, 1989

Isolation of the von Willebrand factor domain interacting with platelet glycoprotein Ib, heparin, and collagen and characterization of its three distinct functional sites

The Journal of Biological Chemistry
H MohriZ M Ruggeri

Abstract

We have used purified proteolytic fragments of von Willebrand factor (vWF) to characterize three related functional sites of the molecule that support interaction with platelet glycoprotein Ib, collagen, and heparin. A fragment of 116 kDa was found to be dimeric and consisted of disulfide-linked subunits which, after reduction and alkylation, corresponded to the previously described 52/48-kDa fragment extending from residue 449 to 728. Fragment III-T2, also a dimer, was composed of two pairs of disulfide-linked subunits, two 35-kDa heavy chains (residues 273-511) and two 10-kDa light chains (residues 674-728). The 116-kDa fragment, but not the constituent 52/48-kDa subunit, supported ristocetin-induced platelet aggregation and retained 20% (on a molar basis) of the ristocetin cofactor activity of native vWF; fragment III-T2 retained less than 5% activity. All three fragments, however, inhibited vWF interaction with glycoprotein Ib. Both 116-kDa and 52/48-kDa fragments inhibited vWF binding to heparin with similar potency, while fragment III-T2 had no effect in this regard. Only the 116-kDa fragment inhibited vWF binding to collagen. These results indicate that dimeric fragments containing two glycoprotein Ib-binding sites posse...Continue Reading

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Mentioned in this Paper

Monoclonal Antibodies
Heparin
Aggregation
Antigenic Specificity
Platelet Membrane Glycoproteins
Platelet Membrane Glycoprotein Ib
Liquaemin
Ristomycin
Plasma Factor VIII Complex
Proteolytic Enzyme

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