Production of rat epidermal growth factor by Escherichia coli cells containing a secretion plasmid

A DNA sequence encoding rat submaxillary epidermal growth factor (EGF) was designed and chemically synthesized based on the amino acid sequence described by Simpson et al. [(1985) Eur. J. Biochem. 153, 629–637]. A secretion plasmid pREGF2 was constructed which contains a hybrid gene coding for rat EGF directly preceded by the signal sequence of E. coli β-lactamase. Rat EGF having the natural structure was secreted into the periplasm and culture medium from E. coli cells containing the secretion plasmid. Purified synthetic rat EGF was found to possess various biological activities as reported. The effect upon [ 3H]thymidine incorporation into DNA of Balb/c 3T3 cells at low dosages were slightly weaker than those of human and mouse EGFs, which might be due to the species difference among EGFs in the binding affinity to the receptor used.