Synthesis and cloning of a gene coding for a fusion protein containing mouse epidermal growth factor.: Isolation from transformed Escherichia coli and some physical, chemical and biological characteristics of the growth factor

A gene coding for a fusion protein containing the sequence of mouse epidermal growth factor (mEGF) was constructed for expression in Escherichia coli. An E. coli trp promoter-operator and part of the trp E gene was linked to a synthetic EGF gene with an intervening lysine codon in the correct reading frame. The gene construct was incorporated into a pAT153-based plasmid vector, yielding pWRL500 that was used to transform E. coli strain HB101. The fusion protein Trp E′-Lys-EGF was extracted from bacterial cultures and treated with a lysine-specific endoproteinase. Epidermal growth factor was purified from the digestion mixture. The plasmid-derived recombinant mouse EGF (rmEGF) has been separated into one major and two minor fractions by high-performance liquid chromatography. The main peak (80% of the total) was shown by structure-determining techniques to be identical to mEGF-α. Similarly, the biological activity of rmEGF was comparable with that of mEGF.