von Willebrand factor A2 domain (VWF-A2)

The von Willebrand factor A2 domain is a critical mechanosensitive region within the large multimeric glycoprotein von Willebrand factor (VWF), which is essential for primary hemostasis (UniProt P04275). This domain functions as a molecular switch that unfolds in response to high fluid shear stress, such as that found in narrowed or injured blood vessels (PubMed: 19713526). Once unfolded, it exposes a specific peptide bond (Tyr1605-Met1606) that is the sole cleavage site for the plasma metalloprotease ADAMTS13 (PubMed: 11429324). This proteolytic regulation is vital for controlling the size of VWF multimers; without it, ultra-large VWF multimers accumulate and cause spontaneous platelet aggregation. Mutations in the A2 domain are frequently associated with Type 2A von Willebrand disease, characterized by an increased susceptibility to proteolysis and a loss of high-molecular-weight multimers, leading to bleeding (PubMed: 16224490). Conversely, the therapeutic administration of recombinant ADAMTS13 (e.g., Apadamtase alfa) targets this domain to treat thrombotic thrombocytopenic purpura (TTP) by restoring the normal cleavage of VWF (FDA: Adzynma Prescribing Information). The domain's unique ability to transition between a folded and unfolded state makes it a central regulator of blood clot formation and dissolution. Understanding the structural dynamics of the A2 domain is crucial for developing therapies for both bleeding and thrombotic disorders.

Other names

A2 domain of von Willebrand factorVWF A2 domainvon Willebrand factor domain A2

The A2 domain contains a cryptic cleavage site (Tyr1605-Met1606) that is exposed upon mechanical unfolding under high shear stress, allowing the metalloprotease ADAMTS13 to cleave the von Willebrand factor multimer into smaller, less prothrombotic fragments (PubMed: 11429324, 19713526).