CRYSTAL-STRUCTURE OF THE CATALYTIC DOMAIN OF HUMAN PLASMIN COMPLEXED WITH STREPTOKINASE

Streptokinase is a plasminogen activator widely used in treating blood -clotting disorders. Complexes of streptokinase with human plasminogen can hydrolytically activate other plasminogen molecules to plasmin, w hich then dissolves blood clots. A similar binding activation mechanis m also occurs in some key steps of blood coagulation. The crystal stru cture of streptokinase complexed with the catalytic unit of human plas min was solved at 2.9 angstroms. The amino-terminal domain of streptok inase in the complex is hypothesized to enhance the substrate recognit ion. The carboxyl-terminal domain of streptokinase, which binds near t he activation Loop of plasminogen, is Likely responsible for the conta ct activation of plasminogen in the complex.