A Comparison of Bone Morphogenetic Protein-7 Mutant Expression in Prokaryotic and Eukaryotic Hosts

Objective: Bone morphogenetic protein-7 (BMP-7) is a multifunctional growth factor predominantly recognized for its osteoinductive properties. Due to the high cost of this protein, the availability of BMP-7 for treatment is limited. The heterologous production of recombinant hBMP-7 has been performed in a number of expression systems. In this study a novel form of BMP-7 was expressed in eukaryotic and prokaryotic hosts. Methods: For expression in the prokaryotic system, the novel protein was secreted to the periplasmic space of Escherichia coli using a pelB signal sequence followed by singlestep purification by Ni 2+ -charged column chromatography. In the mammalian cell expression system, we transferred a full-length cDNA encoding precursor of the novel protein to CHO cells then selected stable clones by using the appropriate antibiotic concentration. Expressions in both systems were confirmed by Western blot analysis. Results: The novel recombinant protein was produced as a 36-38 kDa dimer in the CHO cell line and a 16 kDa monomer in the Escherichia coli system. Quantitative analysis according to ELISA showed that the expression levels of the mutant protein in the eukaryotic and prokaryotic expression systems were 40 ng/ml and 135 ng/ml of the culture media, respectively. Conclusion: In this study, the expression level in Escherichia coli was at least three times more than observed in the CHO cells. However, further optimization is required to obtain a dimer protein in Escherichia coli. The results show that periplasmic expression may be suitable for the production of complex proteins such as BMPs.