Molecular cloning, expression, purification, and functional characterization of palustrin-2CE, an antimicrobial peptide of Rana chensinensis

Antimicrobial peptides are effector molecules of the innate immunity of amphibians. Here, one antimicrobial peptide cDNA precursor, prepropalustrin-2CE3, from the tadpole of the Chinese brown frog Rana chensinensis was cloned. The coding sequence corresponding to the mature palustrin-2CE peptide was subcloned into pGEX-6p-1. The soluble GST-palustrin-2CE fusion protein was successfully expressed in the BL21(DE3)pLysS strain at 16 °C, and the proportion of the fusion protein reached 35%-39% of the total cellular protein. After removal of the GST-fusion tag, the purity of the palustrin-2CE obtained by Sephadex G50 chromatography was about 97%. Moreover, the purified palustrin-2CE displayed obviously inhibitory activities against the sensitive bacteria Staphylococcus aureus, Bacillus subtilis, Pseudomonas aeruginosa, and Escherichia coli, and multi-drug resistant S. aureus and E. coli. These findings suggest that the tadpole of the Chinese brown frog is a unique source of antimicrobial peptides and indicates the therapeutic potential of the palustrin-2CE peptide.