Large quantities secretion to culture medium with epidermal growth factor and trigger factor fused protein in Escherichia coli

Abstract

Recombinant protein secretion system to periplasmic space or culture medium in E. coli is beneficial for protein folding improvement, low proteolytic activity and easy downstream process. In this study, we designed and synthesized the xylanase signal sequence (originated from Bacillus subtilis)-human epidermal growth factor-E. coli trigger factor fused protein (XSP-hEGF-TF) gene for expression the protein in E. coli periplasm. The synthesized gene was cloned into pET11a expression vector and expressed in E. coli BL21(DE3). Previously reported that xylanase signal peptide (XSP) is known to move target proteins into periplasmic space in E. coli. However, we observed that the XSP-hEGF-TF protein is secreted in large quantities (700 mg/liter) to culture medium. The reason maybe the effect of signal peptide, combinations of the proteins, or unknown effects. In our other study, XSP moved the target protein (human superoxide desmutase) to periplasmic space in E. coli. Addtional experiments are needed to find out the reasons behind this phenomenon. Then it will be beneficial for simplified downstream purification process and to increase the potential of efficient protein production method.