Codon optimization enhances the expression of porcine β-defensin-2 in Escherichia coli

Porcine β-defensin-2 (pBD2) is a cationic antimicrobial peptide that has therapeutic potential. The amount of pBD2 in nature is limited, and the expression of pBD2 in Escherichia coli is low, probably because a different gene codon is used by prokaryotic organisms to that used by eukaryotes. Codon preference optimization is one of the ways to increase heterologous expression of pBD2. To achieve high expression of pBD2, the pBD2 gene was redesigned according to the preferred codon in E. coli without altering the amino acid sequence. The optimized gene was inserted into expression vector pET-30a and transformed into E. coli BL21 (DE3) plysS. Our results showed that pBD2 was expressed as His-Tag fusion protein at a level that was approximately 4-6 times greater than from the native gene, based on total protein expression. Expressed fusion pBD2 showed antimicrobial activity against both E. coli and Staphylococcus aureus. Moreover, pBD2 showed weak hemolytic activity and strong heat resistance. These results indicate that fusion pBD2 is functional and has similar properties to those of pBD2 from the native gene. Our current study demonstrated that codon optimization could enhance pBD2 expression in E. coli without altering its function. Therefore, the expression of pBD2 after codon optimization in heterologous host cells might be useful and is worthy of further research.