High-level expression and purification of human pro-UK cDNA in Escherichia coli

A chemically synthesized human pro-urokinase (pro-UK) CDNA was cloned into the expression vector PET-11d and expressed in E. coli BL21(DE3) pLysS under the control of the T7 promoter. Using 0.1 mmol/L IPTG induction, the expression level of the recombinant pro-UK attained up to 15% of the total bacterial proteins and existed as inclusion bodies. After denaturation and renaturation in vitro, the expressed pro-UK was purified to be identified by Zn2+ selective precipitation, immuno-affinity chromatography, and benzamidine affinity adsorption. The specific activity of the purified human pro-UK was about 110,000 IU/mg.