Periplasmic Expression of a Novel Human Bone Morphogenetic Protein-7 Mutant in Escherichia coli

Background: Bone Morphogenetic Proteins (BMPs) belong to the transforming growth factor-β (TGF-β) superfamily, and play an important role in bone metabolism. Recombinant forms of BMP-2 and BMP-7 are the only BMPs used clinically. In this study the mature part of human bone morphogenetic protein-7 (BMP-7) was engineered through substitution of the BMP-7 N-terminal sequence by heparin-binding site of BMP-2. This targeted substitution was made to enhance the binding affinity of the novel protein to the extracellular matrix components such as heparin and heparan sulfate proteoglycans (HSPGs). Methods: The engineered protein was expressed in Escherichia coli (E.coli). The PelB signal sequence was used to translocate soluble pro¬teins into the periplasmic space of E.coli. The protein was purified from periplasmic extract using Ni-NTA chromatography and the SDS-PAGE and western blot analysis confirmed the successful expression of the novel protein. Results: The novel hBMP-7 mutant was produced as approximately 16 kDa monomer. It was found that the heparin binding of this protein was approximately 50% more than that of the wild-type at a protein concentration of 500 ng/ml. Conclusion: The findings showed that the periplasmic expression may be suitable to produce complex proteins like BMPs.