Identification and in vitro characterization of QUB-3358: a novel antimicrobial peptide from Amolops torrentis skin secretion

Abstract

Faced with the challenges of the increasing proliferation of antibiotics and the continuous evolution of super bacteria, antimicrobial peptides (AMPs) are being explored as potential new treatments. Amphibian skin secretions contain a large number of AMPs, which are an essential host defence mechanism against bacteria. This paper utilised the freeze-dried skin secretions of the frog, Amolops torrentis, to identify a biosynthetic peptide precursor cDNA sequence, encoding a peptide named, QUB-3358, using the "shotgun" cloning method. QUB-3358 belongs to Brevinin-2 peptide family structurally, and the mature peptide sequence was synthesised using solid-phase peptide synthesis (SPPS) technology and purified by reverse-phase high-performance liquid chromatography (RP-HPLC). The molecular mass of the peptide was determined by MALDI-TOF mass spectrometry. Its structure was simulated, and its physicochemical properties were analysed by PEPFOLD and HeliQuest on-line programmes. Finally, antibacterial, haemolytic and anti-proliferative assays were performed to evaluate the biological activity of the peptide. The biological activity testing demonstrated that QUB-3358 was antimicrobial and exhibited MICs against S. aureus, E. coli, and C. albicans of 8 μM, 16 μM, and 32 μM, respectively. It was almost non-haemolytic within the effective antibacterial concentration with only 9% at 128 μM. In addition, the IC50 of QUB-3358 against H838 lung cancer cells was 20.35 μM. Its anti-proliferative activity on MRC-5 normal lung cells (IC50: 20.41 μM) is the same as that on H838 lung cancer cells (IC50: 20.35 μM). In conclusion, QUB-3358 exhibited broad-spectrum antimicrobial activity, had low haemolysis, and possessed anti-proliferative properties against cancer cells, highlighting its significant potential as a novel therapeutic agent.

Thesis is embargoed until 31 December 2030.

Date of Award	Dec 2025
Original language	English
Awarding Institution	Queen's University Belfast
Supervisor	Lei Wang (Supervisor), Chengbang Ma (Supervisor) & Tianbao Chen (Supervisor)