title: Functional domains on von Willebrand factor. Recognition of discrete tryptic fragments by monoclonal antibodies that inhibit interaction of von Willebrand factor with platelets and with collagen.
abstract: We have identified two functional domains on the von Willebrand factor (VWF) moiety of the Factor VIII-von Willebrand factor complex (FVIII-VWF), one interacting with blood platelets, and one interacting with vessel wall collagens, by means of two monoclonal antibodies directed against the VWF molecule, CLB-RAg 35 and CLB-RAg 201. The monoclonal antibody CLB-RAg 35 inhibited virtually all platelet adherence to artery subendothelium and to purified vessel wall collagen type III, at relatively high wall shear rates. CLB-RAg 35 also inhibited the ristocetin-induced platelet aggregation and the binding of FVIII-VWF to the platelet in the presence of ristocetin but did not affect the binding of FVIII-VWF to collagen. The monoclonal antibody CLB-RAg 201 inhibited the binding of FVIII-VWF to purified vessel wall collagen type I and III and all platelet adherence to collagen type III and the platelet adherence to subendothelium that was mediated by FVIII-VWF in plasma. The two functional domains on FVIII-VWF that were recognized by CLB-RAg 35 and CLB-RAg 201 were identified by means of immunoprecipitation studies of trypsin-digested FVIII-VWF. The domains resided on different polypeptide fragments, with a Mr of 48,000 for the collagen binding domain and a Mr of 116,000 for the platelet binding domain. The 116,000-mol wt fragment consisted of subunits of 52,000/56,000 mol wt and 14,000 mol wt after reduction. The 52,000/56,000-mol wt subunits possessed the epitope for CLB-RAg 35.
mesh_terms: D000911:Antibodies, Monoclonal; D001667:Binding, Competitive; D001779:Blood Coagulation Factors / Q000502:physiology*; D001792:Blood Platelets / Q000502:physiology*; D003094:Collagen / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D007700:Kinetics; D010446:Peptide Fragments / Q000032:analysis; D010973:Platelet Adhesiveness; D011247:Pregnancy; D014357:Trypsin; D014469:Umbilical Arteries / Q000502:physiology; D014841:von Willebrand Factor / Q000502:physiology*
chemical_list: D000911:Antibodies, Monoclonal; D001779:Blood Coagulation Factors; D010446:Peptide Fragments; D014841:von Willebrand Factor; D003094:Collagen; D014357:Trypsin