HYDRODYNAMIC STUDIES ON THE STREPTOKINASE COMPLEXES OF HUMAN-PLASMINOGEN, VAL442-PLASMINOGEN, PLASMIN, AND THE PLASMIN-DERIVED LIGHT (B) CHAIN

Sedimentation velocity and sedimentation equilibrium studies were carried out on the Glu- and Lys- plasminogen-streptokinase complexes as well as on the complexes formed by Val442-plasmin and the light (B) chain of plasmin. Sedimentation equilibrium MW are consistent with a 1 to 1 molar complex in all cases and give values consistent with the differences in size of the plasminogen moieties. Sedimentation velocity determinations in the presence of protease inhibitors give values consistent with the conformational differences already reported for the Glu- and Lys-plasminogen molecules. Unlike Glu-plasminogen, the addition of .epsilon.-aminocaproic acid or lysine does not alter the conformation of the Glu-plasminogen complex. The values of the sedimentation coefficient and the MW of the plasmin and the Val442-plasmin-streptokinase complexes increase to those of a dimer when determined in the absence of active-site inhibitors but return to monomer values when these inhibitors are added. Dimer formation requires the presence of an available active site in at least 1 of the 2 molecules involved and is reversible.