Molecular cloning and functional characterization of an antimicrobial peptide from the skin secretion of the dark-spotted frog, Pelophylax nigromaculatus

In this study, a new peptide sequence was identified from the skin secretion of Pelophylax nigromaculatus by obtaining the cDNA through molecular cloning and then analysing the cDNA sequence using bioinformatics tools.

The peptide was then synthesised using solid-phase peptide synthesis (SPPS) and purified by high-performance liquid chromatography (HPLC). Its biological activity and toxicity were evaluated through antibacterial assays, haemolysis tests, and MTT assays. The results showed that QUB-3028 exhibited strong antibacterial activity against S. aureus NCTC 10788, E. coli NCTC 10418 with a MIC value of 2 µM, and moderate antimicrobial activity against C. albicans ATCC 10231 with a MIC value of 32 µM. It was also potent against human adenocarcinoma cell line NCI-H838 in the MTT assay with a IC50 value of 4.6 µM, while demonstrating 25% haemolytic activity at the concentration of 128 µM. Therefore, QUB-3028 has strong antibacterial and antiproliferative activities, with its effective concentration for biological activity being much lower than that required to induce haemolytic activity.