A chimeric streptokinase with unexpected fibrinolytic selectivity.
Chimeric 59D8-SK was designed to confer fibrin-selectivity to streptokinase by fusion of the Fab fragment of anti-fibrin antibody 59D8 to the N-terminus of streptokinase (SK: Ile1-Lys414). It was expressed in a mouse hybridoma cell line and purified by affinity chromatography on a 59D8-antigen column. Chimeric 59D8-SK is a disulfide-linked heterodimer composed of an antibody light chain (Mr 27,000) and a N-glycosylated chimeric heavy chain (M(r) 90,000). The fibrin targeting by 59D8 increased plasma clot lysis by 2-fold, but connecting 59D8 to SK has provided 59D8-SK several unique properties: (i) 59D8-SK activated human Glu-plasminogen with a significant lag period that coincided with limited proteolysis of 59D8-SK similar to that observed for wild-type SK. In a kinetic study, both gave very similar kinetic parameters for the activation of Glu-plasminogen even though 59D8-SK was N-glycosylated in its SK portion; (ii) 59D8-SK was relatively inactive in human plasma, compared to SK, but it became activated in the presence of clots; (iii) 59D8-SK lysed clots slowly but completely whereas SK lysed clots rapidly but incompletely. Even though the mechanism behind these new properties is not fully understood, they are characteristics of a second-generation plasminogen activator.
Goldstein
J
J
Macromolecular Structure, Bristol-Myers Squibb Pharmaceutical Research Institute, Princeton, NJ 08540, USA.
Matsueda
G R
GR
Shaw
S Y
SY
D000818:Animals; D005337:Fibrin / Q000276:immunology; D005342:Fibrinolysis / Q000187:drug effects*; D006801:Humans; D007140:Immunoglobulin Fab Fragments / Q000235:genetics / Q000276:immunology / Q000494:pharmacology*; D051379:Mice; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000494:pharmacology*; D013300:Streptokinase / Q000235:genetics / Q000494:pharmacology*
D007140:Immunoglobulin Fab Fragments; D011993:Recombinant Fusion Proteins; D005337:Fibrin; D013300:Streptokinase