On-column refolding of bone morphogenetic protein-2 using cation exchange resin

Refolding is often the bottle-neck step in producing recombinant proteins from inclusion bodies of Escherichia coli, especially for dimer proteins. The refolding process is protein specific, engaging a lot of time and cost to optimize conditions so that the thermodynamics favor protein refolding over competitive aggregation. Bone morphogenetic protein-2 (BMP-2) is a potent osteogenic agent having significant applications in bone regeneration therapy. In this study, we present a novel solid-phase refolding method for rapid and efficient refolding of recombinant BMP-2 dimer from E. coli. We employed a weak cation exchange resin as the adsorbing support, with decreasing gradient of denaturing agent and exposure to oxidizing conditions for adequate disulfide bond formation. Refolded BMP-2 was further purified using size exclusion chromatography and analyzed for its secondary structure and biological activity. The purified BMP-2 dimer showed dose-dependent induction of alkaline phosphatase (ALP) activity in MC3T3 pre-osteoblast cells, thus translating the success of our refolding method. This simple and rapid method can also be applied in refolding and purification of other BMP-2 like dimer proteins.