This is a proposal to undertake a detailed study of structural features of human von Willebrand factor, and unusually large oligomeric glycoprotein that plays an important role in the formation of the platelet plug in hemostasis and blood coagulation. The protein acts as an adhesive bridge between platelets normally circulating in blood plasma and macromolecules such as collagen in the subendothelial extracellular matrix. The protein is found in blood plasma as a set of multimers of two to eighty identical subunits held together by disulfide bonds. We have established for each subunit the sequence of 2050 amino acid residues as well as the location of 22 oligosaccharide attachment sites and 26 disulfide bonds. These data are leading to the formulation of a structural model that accounts for the multiple ligand interactions of this multivalent molecule. Collaborative studies in our laboratory and elsewhere have tentatively identified several substructural domains, and we propose to explore their locations, boundaries and their mutual interactions using techniques of limited proteolysis and disulfide identification. Each isolated domain will be tested for independent folding of its polypeptide chain(s) and for this specific ligand binding capacity. We expect to refine the model of the protein in such detail that peptides can be designed as competitive ligands that could ameliorate thromobotic conditions. We expect to provide a molecular basis for understanding a wide range of variations collectively described as von Willebrand disease.
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