Cloning, expression, purification and bioassay of human vasostatin

Vasostatin gene was amplified from a human liver cDNA library by PCR method. The fragment was cloned into the pUC19 vector and sequenced. By inserting the vasostatin fragment into the pQE-30 vector, the recombinant pQE-30/vaso plasmid was constructed. After it was transformed into E. coli M15, the recombinant proteins were expressed successfully when induced with IPTG. The expressed recombinant protein accounted for more than 50% of total bacterial proteins. The expressed products formed inclusion body in E. coli. After extracted from bacterial cells and washed, it was dissolved in solution containing 8 mol/L urea. and then purified by using immobilized metal ion affinity chromatography (IMAC) effectively with a purity of over 95%. Then the recombinant protein was renatured after the denaturants were removed gradually by dialysis. The protein was identified by the determination of its N-terminal amino acid sequence, molecular mass, isoelectric point etc. The results indicated that the primary structure of the expressed protein accorded with the theoretics. Endothelial cell proliferation assay, endothelial cell migration assay and chick chorioallantoic member assay, the bioactivity of vasostatin was investigated. It was proved that vasostatin can inhibit endothelial cell proliferation and migration, and inhibit angiogenesis of chick chorioallantoic member.