Significant expression of a Chinese scorpion peptide, BmK1, in Escherichia coli through promoter engineering and gene dosage strategy

Heterologous expression is an efficient alternative to conventional extraction to produce a specific Buthus martensii Karsch (BmK) peptide. In this work, BmK1 was successfully expressed in Escherichia coli after genetic codon optimization, but BmK1 content was <6% of total cellular protein. To improve BmK1 expression, a trc promoter library with a wide relative strength was constructed, and three promoters, P(pJF136) (0.55), P(pJF325) (1.29), and P(pJF288) (2.31), were selected to control BmK1 expression. A higher BmK1 expression (>13.9% of total protein) was obtained using a stronger promoter, P(pJF325). Furthermore, a maximum BmK1 content (>21.7% of total protein) was obtained by combining promoter P(pJF325) and three copies of the BmK1 gene. The yield of the purified BmK1 achieved 196.74 mg L(−1) in E. coli BL21(DE3) pJF431, which was improved 2.09-fold compared with the control. This was the highest reported production of scorpion peptides in E. coli.