High-efficient and Soluble Expression, Purification and Bioassay of IGFBP-3

A cDNA fragment encoding insulin-like growth factor binding protein 3(IGFBP-3) was cloned, and a recombinant plasmid pET-DsBA-IGFBP-3 was constructed and transferred into the competent cells of E. coli BL21(DE3)plysS. An engineered bacteria was then obtained, and induced to express a fusion protein of IGFBP-3 (i.e. D-IGFBP3). D-IGFBP3 mainly exists in a soluble form, which was purified by His-affinity column chromatography. The recombinant fusion protein IGFBP-3 with over 95 % purity was obtained. Western blot demonstrated a specific band with the corresponding molecular weight. Bioassay showed that this fusion protein has a certain inhibition on the growth of MCF-7 cells and binding activity with IGF-I in vitro.