Structural identification and bioactivity assessment of QUB-2999, an antimicrobial peptide from the skin secretion of Pelophylax nigromaculatus

These secretions also have medicinal functions, which some ancient people utilised to cure diseases. With more pathogens developing resistance to clinical antibiotics nowadays, there is an urgent need for new antibiotic resources, and amphibian skin secretions can be a treasure trove for bioactive peptide discovery.<br><br>In this study, an antimicrobial peptide was obtained from the frog skin secretion of Pelophylax nigromaculatus by molecular cloning, which mature peptide sequence was GILKDTLKGAATNVAGVLLDKLKCKITGGC.

The peptide was named QUB-2999 in this thesis based on its molecular mass and was classified into the Ranatuerin-2 family according to NCBI-BLAST results. Its secondary structure was predicted by the software of RPBS Web-portal and CI-TASSER, indicating there are α-helix and Rana-Box in its structure.<br> <br>Then, QUB-2999 was synthesised by the solid-phase peptide synthesis (SPPS) method, purified by reversed-phase high-performance liquid chromatography (RP-HPLC), and identified by Matrix-Assisted Laser Desorption Ionisation Time-of-Flight (MALDI-TOF) MS.