Epidermal growth factor (EGF) enhances the growth of various cell types and has wide clinical applications. EGF gene has been expressed in E coli but its expressed product is usually unstable because of its low molecular weight. In this study

mouse EGF gene was cloned into GST gene fusion vector pGEX 2T. The resultant plasmid pGEX 2T EGF was used to transform E coli DH5α

where the GST EGF fusion protein was expressed efficiently. After purification with Sepharose 4B GSH affinity column and digestion with thrombin

immunoactive mEGF was obtained

indicating that the GST fusion gene system is not only able to increase the gene product stability but also helpful to product purification.