Expression and purification of human epidermal growth factor (hEGF) fused with GB1

Abstract

Fusion expression is a promising strategy for the production of bioactive peptides in Escherichia coli. In this study, we constructed a new recombinant expression plasmid containing the coding sequence of 56-residue B1 domain of streptococcal protein G (GB1). For easy purification and cleavage of the recombinant proteins, except GB1, an engineered hexahistidine and tobacco etch virus (TEV) protease recognition sites were included in the fusion sequence. Next, we cloned the coding sequence of human epidermal growth factor (hEGF) into this new plasmid and produced the recombinant hEGF in E. coli. The bioactive hEGF is a 53-amino acid peptide and is stabilized by three intramolecular disulphide bonds. Compared with glutathione S-transferase, thioredoxin and small ubiquitin-related modifier, GB1 greatly improved the expression and solubility of hEGF. Moreover, the recombinant hEGF bound to the nickel nitrilotriacetic acid resin column, was easily cleaved by TEV protease and the free hEGF was released. The results showed that this new plasmid was appropriate for recombinant production of small bioactive peptides, such as hEGF, which contains a high proportion of hydrophobic residues and intramolecular disulphide linkages.