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

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 Nterminal 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). The engineered protein was expressed in Escherichia coli (E.coli). The PelB signal sequence was used to translocate soluble proteins 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. 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. The findings showed that the periplasmic expression may be suitable to produce complex proteins like BMPs.