Recombinant expression, biochemical characterization and biological activities of the Human Bone Morphogenetic Protein 2 (BMP2)

Bone Morphogenetic Proteins (BMP) are multifunctional growth factors belonging to the Transforming Growth Factors β (TBFβ) superfamily. BMPs basically play an important role in cartilage and bone development. These proteins are effective in stimulating the differentiation of mesenchymal cells into osteogenic cells. They are also effective in cell proliferation and functions in the embryonic and postnatal period, and in bone homeostasis in the adult period. BMP2 is a clinically and commercially important protein that is frequently used in orthopedic treatments and dentistry. When expressed in E. coli expression systems, the human recombinant BMP2 (rhBMP2) protein transform into an insoluble form, largely in the form of inclusion bodies, than undergo aggregation. In this study, rhBMP2 protein was initially expressed in E. coli BL21(DE3) pLysE cells as a fusion with Superfolder Green Fluorescent Protein (sfGFP). For higher production efficiency, co-expression was performed in E. coli BL21-AI cells with plasmids pG-KJE8, pGro7, pKJE7, pG-Tf2 and pTf16 using a system containing five different chaperone plasmids. As a result of the measurements, the pTf16 plasmid, which produces the tig chaperone with optimum benefit for co-expression, was preferred. Alternative refolding processes were also applied to obtain a high purity and correctly folded product. Ultimately, the sfGFP-rhBMP2 fusion protein was purified with the 6xHis-tag using nickel-based affinity chromatography and then qualitatively analyzed by SDS-PAGE method. Cell culture studies were carried out by testing sfGFP-rhBMP2 protein, which was obtained and purified under optimum conditions, on human osteosarcoma-2 (Saos-2) cell lines.