A novel binding site for ADAMTS13 constitutively exposed on the surface of globular VWF.

ADAMTS13 metalloprotease regulates the multimeric size of von Willebrand factor (VWF) by cleaving the Tyr1605-Met1606 bond in the VWF A2 domain. The mechanisms of VWF recognition by ADAMTS13 have yet to be fully resolved. Most studies have focused on the role of exosites within the VWF A2 domain, involved in interaction with the ADAMTS13 spacer domain.

N-linked glycosylation of VWF modulates its interaction with ADAMTS13.

We examined the role of N-linked glycan structures of VWF on its interaction with ADAMTS13. PNGase F digestion followed by lectin analysis demonstrated that more than 90% of VWF N-linked glycan chains could be removed from the molecule (PNG-VWF) without disruption of its multimeric structure or its ability to bind to collagen. PNG-VWF had an approximately 4-fold increased affinity for ADAMTS13 compared with control VWF.

Autoantibodies to thrombin directed against both of its cryptic exosites.

Immunoglobulin G (IgG) anti-thrombin autoantibodies (ATA) were purified from the plasma of a patient referred for haematological investigation because of bleeding for 24 h following a dental extraction. The ATA did not inhibit the catalytic activity of thrombin against a chromogenic substrate, suggesting that they did not interact with the active site of thrombin. The ATA did, however, prolong the time required to generate thrombin in plasma, suggesting that they inhibited factor V and factor VIII activation.