Abstract
We have used purified proteolytic fragments of von Willebrand factor (vWF) to characterize the functional sites of the molecule interacting with platelet membrane glycoprotein (GP) Ib. A dispase-digestive 39/34kDa fragment extending residues 480/481 to 718, a trypsin-digestive 52/48 kDa fragment extending residues 449 to 728 and staphylococcus aureus V-8 and trypsin-digestive III-T2 (heavy chain; 273-511, light chain: 674-728) were evaluated. All these three fragments had similar inhibitory activity on ristocetin induced vWF binding to GPIb, suggesting that these three fragments of vWF include the entire binding domain to GPIb. 52K-2, a monoclonal antibody to vWF which inhibits vWF binding to GPIb, recognized all three fragments of vWF. However, another antibody, RG-46, recognized 52/48kDa fragment and III-T2, but failed to react with 39/34kDa fragment.
