Identification and functional assessment of a bioactive peptide QUB-2984 from the skin secretion of the red-eyed tree frog, Agalychnis callidryas

Abstract

Bioactive peptides secreted from amphibians have been studied broadly for their potency as alternative drugs to treat human diseases. This thesis is about a caerin-related peptide derived from red-eyed leaf frog, Agalychnis callidryas, which provided ideas for further antibiotic research. Herein, the objectives included the isolation, identification, and bioactivity assessment of this bioactive peptide named QUB-2984. Agalychnis callidryas skin secretions were collected by stimulating the frogs’ skin. The sequence of QUB-2984 (GMWGTVFKGIKTVAKHLLPHVFSSQQS) was obtained by ‘shotgun’ cloning through constructing a cDNA library with isolated mRNA, and tested by DNA Sanger sequencing. It was synthesised by solid phase peptide synthesis, purified by reversed-phase high-performance liquid chromatography and structurally-confirmed by MALDI-TOF MS. The MIC value against gram-positive bacteria S.aureus was 2μM, gram-negative bacteria E.coli was 2μM, and against the pathogenic yeast C. albicans was 8μM. QUB-2984 showed anticancer potency at the minimum concentration of 10-5M towards human cancer cells. In terms of haemolysis, it caused around 50% haemolytic effect at 64μM. Its haemolytic effect implied the possibility of side-effects towards mammalian cells, but its ability to exert both antibacterial and anticancer biological activity makes this study valuable as a pre-study foundation for designing new antibiotics against cancer or infectious diseases.

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	Mei Zhou (Supervisor), Lei Wang (Supervisor), Tianbao Chen (Supervisor) & Yuan Ying (Supervisor)