title: Immunochemical studies of factor V of bovine platelets.
abstract: Immunochemical techniques were employed to investigate the molecular properties of bovine platelet factor V. An antiserum prepared against purified factor V rapidly inactivated platelet factor V, indicating that platelet factor V is antigenically related to plasma factor V. A reaction of identity between factor V in plasma and purified factor V was documented by immunodiffusion against an antibody to platelet factor V. When platelet factor V was extracted with Triton X-100 in the presence of protease inhibitors and subjected to immunoelectrophoresis against the antiserum to plasma factor V, a single antigenic component migrating toward the anode was observed. In the absence of protease inhibitors, following release by collagen or solubilization, platelet factor V appeared close to the origin suggesting proteolytic alteration. Platelet factor V released by collagen or extracted with Triton X-100 was activated by thrombin 7.4-fold and 4.5-fold respectively, compared to a 17-fold activation of factor V in plasma under identical conditions. The ability of thrombin to activate platelet factor V as well as the close correspondence of factor V activity and antigen released by collagen indicates that the molecule is largely in the unactivated form after release. A single component of molecular weight 270 000 was seen when platelet factor V released by collagen was immunoprecipitated and subjected to dodecylsulphate gel electrophoresis. Factor V coagulant assays and immunoelectrophoresis of subcellular fractions showed that platelet factor V is localized primarily in the alpha granules. Platelet factor V appears to be similar to, if not identical with, plasma factor V by the criteria of immunologic identity, similar electrophoretic mobility and virtually identical molecular weights.
mesh_terms: D000818:Animals; D001792:Blood Platelets / Q000378:metabolism*; D002417:Cattle; D003094:Collagen / Q000494:pharmacology; D005165:Factor V / Q000276:immunology* / Q000378:metabolism; D007120:Immunochemistry; D066298:In Vitro Techniques; D010447:Peptide Hydrolases / Q000097:blood; D010949:Plasma / Q000276:immunology / Q000378:metabolism; D013347:Subcellular Fractions / Q000378:metabolism; D013917:Thrombin / Q000494:pharmacology
chemical_list: D005165:Factor V; D003094:Collagen; D010447:Peptide Hydrolases; D013917:Thrombin