Purification of human recombinant granulocyte colony stimulating factor from Escherichia coli

In Escherichia coli, recombinant proteins were produced either as three dimensionally folded forms or as unfolded forms, inclusion body (IB). The formation of IB was a frequent consequence of high-level protein production and inadequacy of folding agents namely chaperones in the cytoplasm. The structure of the protein in inclusion bodies was poorly understood but it has been hypothesized that the protein may form misfolded β sheet aggregates. In order to procure the active protein, IBs must then be solubilised, refolded and purified. A study was done to determine the purity of recombinant protein which was produced as IBs in E. coli. The IBs were recovered by centrifugation and washed with salts and detergents to remove the host cell proteins and then solubilised with mild buffer at alkaline pH. The solubilised IBs were refolded under redox conditions, purified using cation exchange resins. It was experimentally verified that the final recovery of protein was 30% with 99% purity.Key words: Granulocyte colony-stimulating factor (GCSF), inclusion body (IB), refolding, solubilisation, Escherichia coli