Von Willebrand factor (VWF) is a large, multimeric blood glycoprotein that is required for normal hemostasis. Mutant forms are involved in the most common inherited bleeding disorder (von Willebrand disease: VWD). VWF mediates the adhesion of platelets to sites of vascular damage by binding to specific platelet membrane glycoproteins and to constituents of exposed connective tissue. It is also essential for the transport of the blood clotting factor VIII [1,2].

VWF is a large multidomain protein. Among those domains the type A domain is known to be distributed in at least 22 human proteins, all of them being extracellular. In VWF there is 3 repeats of the type A domain (A1,A2,A3) that have been shown to bind other proteins like collagen and heparin. The 3D structure of A1 and A3 has been published [3,4]. The domain adopts a classic α/β "Rossmann" fold.

The following proteins have been found to contain a VWFA domain:

• Complement factors B, C2, CR3 and CR4.
• Collagen type VI.
• Collagen type VII.
• Collagen type XII.
• Collagen type XIV.
• Integrin α chains. In these proteins, the VWFA domain is known as a 'I- domain'.
• Human cartilage matrix protein. Major component of the extracellular matrix of nonarticular cartilage. Binds to collagen.
• Mammalian calcium channel α-2/delta subunits.
• Cochlin. In human, defects in COCH are the cause of mucopolysaccharide depositions in the channels of cochlear and vesicular nerves. These depositions cause degeneration of dendritic fibers.
• Epithelial chloride channel protein. Voltage-gate chloride channel.
• Inter-α-trypsin inhibitor heavy chains H1, H2 and H4. They are involved in a variety of immune phenomena.
• Mouse matrilin-2.
• Plasmodium berghei sporozoite surface protein 2.
• Caenorhabditis elegans unc-36 protein.

We developed a profile that spans the whole domain.