Identification and functional study of the bioactive peptide QUB-2830 from the skin secretion of the blue-side leaf frog, Agalychnis annae

Abstract

With the failure of traditional antibiotics in recent years, it is urgent to find new antimicrobial drug. Antimicrobial peptides (AMPs) secreted from amphibian skin have many important bioactivities and act as the first line to defence against invading microorganisms. The aim of this project is isolate, identify, and characterise a bioactive peptide from the skin secretion of the Blue-side leaf frog (Agalychnis annae). In this thesis, QUB-2830, a peptide belonging to the Dermaseptin superfamily, was discovered in the skin secretion of the Blue-side leaf frog (Agalychnis annae). The peptide sequence was obtained by molecular cloning through constructing a cDNA library with isolated mRNA from frog skin secretion. The peptide was synthesised by solid phase peptide synthesis, purified by reversed-phase high performance liquid chromatography (RP-HPLC) and its structure was confirmed by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF MS). In antimicrobial assays, QUB-2830 showed significant antimicrobial activity against a Gram-negative bacterium, Escherichia coli (E. coli ATCC CRM8739), a Gram-positive bacterium, Staphylococcus aureus (S. aureus ATCC CRM6538), and a yeast, Candida albicans (C. albicans ATCC CRM10231). For S. aureus, the minimum inhibitory concentration (MIC) was 1 μM, for E. coli, the concentration was 2 μM, for C. albicans, it was 4 μM. In terms of the MTT assay, QUB-2830 was shown to have antiproliferation activity against NCI-H838 cancer cells at a concentration of 10-4 M. In a haemolysis assay, QUB-2830 showed haemolytic activity at concentrations between 16 ~ 128 μM. In summary, QUB-2830 exhibited a remarkable antimicrobial ability and may be expected to become a safe antimicrobial drug in the future after its haemolysis activity is reduced through structural modification.

Thesis embargoed until 31 December 2026.

Date of Award	Dec 2021
Original language	English
Awarding Institution	Queen's University Belfast
Sponsors	Queen's University & China Scholarship Council
Supervisor	Lei Wang (Supervisor), Mei Zhou (Supervisor), Tianbao Chen (Supervisor) & Yuan Ying (Supervisor)