Construction,Expression and Refolding of a Bifunctional Fusion Protein Consisting of C-Terminal 12-Residue of Hirudin-PA and Reteplase

To obtain a bifunctional protein simultaneously showing bioactivity of anticoagulant and fibrinolytic for use in the treatment of thrombotic diseases, we constructed a fusion protein (HV12p–rPA) containing C-terminal 12-residue of hirudin-PA (HV12p) and reteplase (rPA). The fusion protein, in which HV12p was linked to rPA via Gly–Gly–Gly, was successfully expressed in an inactive form of inclusion bodies in Escherichia coli. HV12p–rPA was identified by sodium dodecylsulfate-polyacrylamide gel electrophoresis. The expression level of HV12p–rPA was optimized by an orthogonal method and finally enhanced from 12 % to approximate 30 %. We also deeply investigated the condition of renaturation of HV12p–rPA, and the inactive protein was partly renatured through various conditions. The refolding efficacy of HV12p–rPA estimated by the recovery of fibrinolytic activity varied from 0.03 % to 16.6 % and the anticoagulant activity fluctuated in the range from 41 to 2,297 ATU/mg. Bioassays indicated that the resulted fusion protein, as expected, exhibited both fibrinolytic and anticoagulant activities. These works laid a foundation for further characterization of HV12p–rPA.