The von Willebrand Factor mutant (I546V) A1 domain
[VWF_HUMAN] Defects in VWF are the cause of von Willebrand disease type 1 (VWD1) [MIM:193400]. A common hemorrhagic disorder due to defects in von Willebrand factor protein and resulting in impaired platelet aggregation. Von Willebrand disease type 1 is characterized by partial quantitative deficiency of circulating von Willebrand factor, that is otherwise structurally and functionally normal. Clinical manifestations are mucocutaneous bleeding, such as epistaxis and menorrhagia, and prolonged bleeding after surgery or trauma.  Defects in VWF are the cause of von Willebrand disease type 2 (VWD2) [MIM:613554]. A hemorrhagic disorder due to defects in von Willebrand factor protein and resulting in impaired platelet aggregation. Von Willebrand disease type 2 is characterized by qualitative deficiency and functional anomalies of von Willebrand factor. It is divided in different subtypes including 2A, 2B, 2M and 2N (Normandy variant). The mutant VWF protein in types 2A, 2B and 2M are defective in their platelet-dependent function, whereas the mutant protein in type 2N is defective in its ability to bind factor VIII. Clinical manifestations are mucocutaneous bleeding, such as epistaxis and menorrhagia, and prolonged bleeding after surgery or trauma. Defects in VWF are the cause of von Willebrand disease type 3 (VWD3) [MIM:277480]. A severe hemorrhagic disorder due to a total or near total absence of von Willebrand factor in the plasma and cellular compartments, also leading to a profound deficiency of plasmatic factor VIII. Bleeding usually starts in infancy and can include epistaxis, recurrent mucocutaneous bleeding, excessive bleeding after minor trauma, and hemarthroses.
[VWF_HUMAN] Important in the maintenance of hemostasis, it promotes adhesion of platelets to the sites of vascular injury by forming a molecular bridge between sub-endothelial collagen matrix and platelet-surface receptor complex GPIb-IX-V. Also acts as a chaperone for coagulation factor VIII, delivering it to the site of injury, stabilizing its heterodimeric structure and protecting it from premature clearance from plasma.
Publication Abstract from PubMed
The A1 domain of von Willebrand factor (vWF) mediates platelet adhesion to sites of vascular injury by binding to the platelet receptor glycoprotein Ib (GpIb), an interaction that is regulated by hydrodynamic shear forces. The GpIb binding surface of A1 is distinct from a regulatory region, suggesting that ligand binding is controlled allosterically. Here we report the crystal structures of the "gain-of-function" mutant A1 domain (I546V) and its complex with the exogenous activator botrocetin. We show that botrocetin switches the mutant A1 back toward the wild-type conformation, suggesting that affinity is enhanced by augmenting the GpIb binding surface rather than through allosteric control. Functional studies of platelet adhesion under flow further suggest that the activation mechanism is distinct from that of the gain-of-function mutation.
Structural basis of von Willebrand factor activation by the snake toxin botrocetin.,Fukuda K, Doggett TA, Bankston LA, Cruz MA, Diacovo TG, Liddington RC Structure. 2002 Jul;10(7):943-50. PMID:12121649
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.