The discovery of the novel peptide QUB-2049 from the skin secretion of Odorrana versabilis

Abstract

In 1929, the British bacteriologist Fleming discovered an antibiotic, penicillin, and he found that this substance had curative properties. Over the following decades, different types of antibiotics with different effects have been discovered, studied and applied. But with heavy use, drug resistance developed. To solve this problem, bioactive peptides obtained from the skin of amphibians have been extensively studied. Nowadays, some antimicrobial peptides from frog skin have been investigated for their bioactivities. The aims of this research project are to find a new AMP from the skin of the frog, Odorrana versabilis, and to study its bioactivities. In this thesis, QUB-2049, a bioactive peptide belonging to the nigrocin superfamily, was extracted from the frog Odorrana versabilis by ‘shotgun’ molecular cloning. A substantial quantity of peptide was obtained by solid-phase synthesis, and this was purified by reversed-phase high performance liquid chromatogram (RP-HPLC) and the molecular mass was determined by Matrix-Assisted Laser Desorption Ionisation-Time of flight (MALDI-TOF) mass spectrometry to ensure that the pure peptide (QUB-2049) was obtained. The functional assay was carried out on the peptide. Then QUB-2049 was tested in several biological experiments and found to inhibit the growth of Escherichia coli (E. coli ATCC CRM 8739) (Minimum inhibitory concentration = 8 μM), Staphylococcus aureus (S.aureus ATCC CRM 6538) ((MIC = 64 μM), and Candida albicans (C.albicans ATCC CRM 10231) (MIC = 128 μM). In the haemolysis assay peptide QUB-2049 showed an obvious haemolytic activity (% haemolysis >10) at concentrations ≥16 μM. The result of the antiproliferative assay showed that QUB-2049 had inhibitory activity against ATCC H838 cells at a concentration of 100 µM in which a significant loss of cell viability was observed. According to the experimental results, peptide QUB-2049 is a good candidate for developing an antibacterial agent against Gram negative bacteria, but optimisation would be needed to reduce its haemolytic effects.

Thesis embargoed until 31 December 2026.

Date of Award	Dec 2021
Original language	English
Awarding Institution	Queen's University Belfast
Supervisor	Tianbao Chen (Supervisor), Mei Zhou (Supervisor), Lei Wang (Supervisor) & Xiaoling Chen (Supervisor)