Characterisation and analysis of QUB-1400: a peptide from the skin secretion of the Chinese frog, (Rana pleuraden)

Abstract

Antimicrobial peptides (AMPs) have emerged as promising alternatives to conventional antibiotics due to their broad-spectrum antimicrobial activity and low likelihood of inducing resistance. This thesis focuses on a newly discovered AMP, QUB-1400, belonging to the pleurain family, which was isolated from the skin secretion of the Chinese southwestern frog, Rana pleuraden. Initially, the cDNA encoding the biosynthetic precursor of QUB-1400 was successfully cloned using 'shotgun' cloning techniques. From this sequence, the structure of the mature peptide was deduced as FLGGLLSGIFKHL-NH2. Following this, the peptide was identified in the frog's skin secretion and synthesised for further investigation. QUB-1400 is a probable member of the pleurain-B AMP family. It underwent a series of bioactivity assays, including antimicrobial assays, a haemolysis assay, and an anti-proliferation assay. These assays aimed to assess the peptide's efficacy in combating microorganisms, its potential toxicity to mammalian cells, and its ability to inhibit cell proliferation.QUB-1400 demonstrated potent antimicrobial activity against various pathogens. Specifically, it displayed a low minimum inhibitory concentration (MIC) and mini-mum bactericidal concentration (MBC) against Staphylococcus aureus (MIC = 4 μM; MBC = 4 μM) and Escherichia coli (MIC = 4 μM; MBC = 8 μM), as well as Can-dida albicans (MIC = 16 μM; MBC = 32 μM). Additionally, it exhibited an-ti-proliferative properties against the NCI-H838 lung cancer cell line, with an IC50 value of 21.29 μM. However, despite its promising bioactivity, the QUB-1400 pep-tide showed a relatively high half-maximal haemolysis concentration (HC50) of 50.12 μM. This could potentially limit its clinical utility and warrants further opti-misation to enhance its safety profile.

Thesis embargoed until 31 December 2029.

Date of Award	Dec 2024
Original language	English
Awarding Institution	Queen's University Belfast
Supervisor	Chengbang Ma (Supervisor), Lei Wang (Supervisor) & Tianbao Chen (Supervisor)