Expression of a fusion protein of human proinsulin with glutathione-S-transferase in Escherichia coli

摘要

A DNA sequence encoding for the human proinsulin was designed according to the codon bias of Escherichia coli and then chemically synthesized. The synthesized DNA fragment was subcloned into pGEX-3X for expression in E. coli BL21 (DE3) and E. coli BL21 Star (DE3), respectively. Conditions for the highest expression of the GST-proinsulin fusion proteins were optimized. These conditions are that cells of E. coli BL21 star (DE3) are incubated in lOOmL of the LB medium with 2 mmol/L IPTG and 60ng/mL ampicillin at 26°Cfor 4h. After disrupted E. coli cells with ultrasonication, inclusion bodies were precipitated from cell lysis and washed. Fusion proteins from the inclusion bodies were redissolved in 8mmol/L of urea. After dialysed in purified water, fusion proteins were analysed by SDS-PAGE. The purity of the fusion protein is about 80.5% in total. The fusion protein from SDS-PAGE was further identified by mass/mass spectrum. GST in the dyad protein is confirmed by the 9 matched sequences. However, the left part is proved a polypeptide of which is completely different from the human proinsulin.