Identification and evaluation of the bioactive peptide QUB-2925 from the defensive skin secretion of Phyllomedusa tomopterna

Abstract

The antimicrobial peptides secreted by amphibian skin have many important biological activities and are the first defence against microbial invasion. Due to the long-term and frequent use of traditional antibiotics, there is an urgent need to seek new drugs to resist drug-resistant microorganism, so cationic AMPs are attracting more and more attention. In this thesis, QUB-2925 is described as a Dermaseptin superfamily peptide derived from the skin secretion of Phyllomedusa tomopterna. The main purpose of this study was to evaluate the multiple biological activities of this peptide. The cDNA library was constructed from mRNA isolated from frog skin secretions, and the peptide sequences were obtained by molecular cloning. The peptide was synthesised by solid-phase synthesis, purified by reversed-phase high-performance liquid chromatography (RP-HPLC), and structurally-confirmed by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF MS). In broth microdilution assays, QUB-2925 showed significant antimicrobial activities against the Gram-negative bacterium, Escherichia coli (E. coli ATCC CRM8739) at 1 µM, the Gram-positive bacterium, Staphylococcus aureus (S. aureus ATCC CRM6538) at 2 µM and the yeast, Candida albicans (C. albicans ATCC CRM10231) at 8 µM. In the MTT anticancer cell proliferation assay, QUB-2925 significantly inhibited the proliferation of NCI-H838 cells at a concentration of 10-5 M, with an inhibition of 80.1%. Also, it showed haemolytic activity with 8.5% haemolysis at 64 μM. In conclusion, QUB-2925 showed obvious antibacterial activity against E. coli, S. aureus and C. albicans at a non-haemolytic concentration and had strong antiproliferation activity against NCI-H838 cells. It may be optimised by modification and is expected to be a promising polypeptide drug.

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)