Prokaryotic expression,purification and identification of recombinant staphylokinase-HC fusion protein

AIM: To construct the prokaryotic expression plasmid pEGX-6P-1-SAK-HC,express it in E.coli,and identify its biological activity.METHODS: The fusion gene(SAK-HC) was obtained by overlap-extension PCR and then inserted into prokaryotic soluble pEGX-6P-1 vector with GST tag to construct expression plasmid(pEGX-6P-1-SAK-HC).GST-SAK-HC was expressed by E.coli B834(DE3) under the induction of IPTG and purified by Glutathion-Sepharose 4B(GST) affinity chromatography and negative-ion exchange column(DEAE) chromatography.PreScission protease was used to remove the GST tag.The purity of the fusion protein was analyzed by SDS-PAGE and the fibrinolytic activity of SAK-HC in vitro was characterized by soluble fibrin plate method.RESULTS: PCR,sequencing and restriction enzyme digestion analysis demonstrated that the recombinant plasmid was constructed successfully.The fusion protein was expressed in E.coli B834(DE3),Mr being 36 000 as shown by SDS-PAGE.After purified by GST affinity and DEAE chromatography,SAK-HC fusion protein of high purity was obtained from the cell supernantants.In vitro experiments showed that the fibrinolytic activity of the recombinant SAK-HC was about 9.4×104 IU/mg.CONCLUSION: The SAK-HC fusion protein we obtained was successfully expressed in E.coli and exhibited a fibrinolytic activity as high as the urokinase standard,which offers a base for the identification of immunogenicity of the fusion protein.