Functional properties of a recombinant chimeric plasminogen activator with platelet-targeted fibrinolytic and anticoagulant potential.

The construction, purification, and characterization of dscuPA33khC, a bifunctional protein designed for thrombosis treatment is described. The chimera was designed to consist of a decorsin (platelet aggregation inhibitor), a low molecular mass (33kDa) single-chain urokinase (scuPA-33k), and a thrombin inhibitory domain. We have successfully produced this recombinant protein in the Escherichia coli expression system, in which the target protein exists in the form of inclusion bodies. After refolding by dilution in vitro, the chimeric protein was purified to homogeneity by immobilized metal affinity chromatography, ion-exchange chromatography, and gel filtration chromatography. The dscuPA33khC could directly activate plasminogen following Michaelis-Menten kinetics with K(m) = 1.52 microM and K(2) = 0.0024 s(-1). The specific activity of the chimera detected by fibrin plate determination was 11,000 IU/mg, which suggested a high thrombolysis effect. However, the chimeric dscuPA33khC bound the activated platelet and significantly increased affinity to platelet clots as compared to fibrin clots. It was found to inhibit ADP-induced platelet aggregation in a concentration-dependent manner as well as it exhibits antithrombin activity. These results suggest that the chimeric protein not only has platelet-targeted thrombolytic activity but also obtains anti-thrombus function.