The adhesive protein von Willebrand factor mediates the initiation and progression of
thrombus formation at sites of vascular injury. von Willebrand factor is synthesized in
endothelial cells and megakaryocytes as a very large polymer composed of identical
subunits. In the plasma, it appears as a series of multimers of regularly decreasing
molecular mass, from several thousand to 500kDa. The size of circulating von Willebrand
factor multimers is controlled by proteolytic cleavage carried out by a specific protease. The …