Periplasmic expression of a novel human bone morphogenetic protein-7 mutant in escherichia coli

ABSTRACT

Bone Morphogenetic Proteins [BMPs] belong to the transforming growth factor-beta [TGF-beta] 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