title: Plasminogen and tissue plasminogen activator interact with antithrombin III.
abstract: Human antithrombin III was demonstrated to bind plasminogen specifically in a time and concentration-dependent manner. The above binding was also confirmed using ligand western blot assays. The interaction of plasminogen was significantly (>90%) inhibited by lysine, indicating the involvement of kringles in binding antithrombin III. Plasminogen also bound to heparin-antithrombin III complex. In converse experiments, antithrombin III also interacted with immobilized plasminogen. Using carboxypeptidase B digestion, the plasminogen-binding site of antithrombin III was localized to the carboxy-terminus lysine of the anticoagulant protein. Tissue plasminogen activator also interacted with antithrombin III in a time- and concentration-dependent manner and its binding was also significantly (>90%) inhibited by lysine. Moreover, the interaction of plasminogen and tissue plasminogen activator with antithrombin III was competitive. These results provide the first evidence for the interaction of antithrombin III with fibrinolytic factors and suggest that antithrombin III may serve to localize these factors at the site of clot formation.
authors.affiliation: Bureau of Biologics and Radiopharmaceuticals, Therapeutic Products Programme, Health Canada, and Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Canada. anil_dudani@hc-sc.gc.ca
authors.forename: A K
authors.initials: AK
authors.lastname: Dudani
mesh_terms: D000990:Antithrombin III / Q000378:metabolism*; D001667:Binding, Competitive; D015153:Blotting, Western; D004305:Dose-Response Relationship, Drug; D004797:Enzyme-Linked Immunosorbent Assay; D004800:Enzymes, Immobilized; D006493:Heparin / Q000378:metabolism; D006801:Humans; D018082:Kringles / Q000502:physiology; D008239:Lysine / Q000378:metabolism; D010958:Plasminogen / Q000378:metabolism*; D011485:Protein Binding; D013997:Time Factors; D010959:Tissue Plasminogen Activator / Q000378:metabolism*
chemical_list: D004800:Enzymes, Immobilized; D000990:Antithrombin III; D010958:Plasminogen; D006493:Heparin; D010959:Tissue Plasminogen Activator; D008239:Lysine