TrxA mediating fusion expression of antimicrobial peptide CM4 from multiple joined genes in Escherichia coli.

Abstract Antimicrobial peptide CM4, a small cationic linear α-helical peptide that consists of 35 amino acids, was isolated from Bombyx mori . To improve the expression level of CM4 in Escherichia coli , tandem repeats of CM4 gene were constructed and expressed as fusion proteins (TrxA-nCM4, n  = 1, 2, 3,…,8) by constructing the vectors of pET32-nCM4 ( n  = 1, 2, 3,…,8). Comparison among the expression levels of soluble fusion protein TrxA-nCM4 ( n  = 1, 2, 3,…,8) suggested that BL21 (DE3)/pET32-3CM4 was an ideal recombinant strain for CM4 production. Under the selected conditions of cultivation and isopropylthiogalactoside (IPTG) induction, the expression level of CM4 was as high as 68 mg/l with about 21% of fusion protein in soluble form, which was the highest yield of CM4 reported so far.