The Periplasmic Expression of Recombinant Human Epidermal Growth Factor (hEGF) in Escherichia coli

Expression of recombinant eukaryotic proteins in Escherichia coli often results in the formation of inclusion bodies. In the case of disulfide-bonded proteins such as hEGF, inclusion body formation can be anticipated if the protein is produced in the bacterial cytosol. The consequence is improper folding which results in aggregation. Proper folding and solubility of such protein are pre-requisite for its biological activity. This is not achieved in cytoplasmic expression in E. coli because of the absence of disulfide bonds formation. The human epidermal growth factor (hEGF) gene has been cloned into the pFLAG fusion protein expression vector. The expression system used OmpA signal sequence to translocate processed and soluble proteins into the periplasm of E. coli cells. Molecular weight of secreted hEGF into periplasmic space was found approximately 6.8 kDa, similar size to the original protein which confirmed by SDS-PAGE and western blotting analysis. The findings obtained, showed in favor of periplasmic expression system, which may be suitable to produce the small eukaryotic disulfide-bonded proteins like hEGF.