A novel antimicrobial peptide, Ranatuerin-2PLx, showing therapeutic potential in inhibiting proliferation of cancer cells.

Antimicrobial peptides are a promising resource for developing novel antibiotic and even anticancer drugs. Here, a 28-mer polypeptide, Ranatuerin-2PLx (R2PLx), was identified from lyophilised skin secretions. The chemically synthetic replicates exhibited moderate and broadspectrum antimicrobial effect against various microorganisms including methicillin-resistant Staphylococcus aureus (MRSA, minimal inhibitory concentration = 256 µM). In addition, R2PLx was found to inhibit the proliferation of several tumour cells, especially showing more potent effect on prostate cancer cell, PC-3. The early cell apoptosis was observed in 6 h by Annexin V-FITC/propidium iodide staining, as well as the activation of Caspase-3 at 5 µM peptide concentration. R2PLx may therefore be promising for developing new therapeutic approach for cancer treatment. Moreover, the artificial deficiency of conserved rana-box loop or net positive charge in C-terminal domain notably reduced the biological activities of the truncated and substituted isoforms, respectively, suggesting for maintaining their biological potency of ranatuerin family requires both cysteine-bridged segment and cationincity within the loop domain in C-terminus.