QUB-1942

: A bioactive peptide from Phyllomedusa hypochodrialis skin secretion

Abstract

Antimicrobial peptides, separated and identified from frog and toad skin secretions, have been studied for years. In this thesis, QUB-1942, a peptide belonging to the phylloseptin family, was derived from the skin secretion of the orange-legged leaf frog, Phyllomedusa hypochondrialis. The peptide sequence was obtained through ‘shotgun’ cloning by constructing a cDNA library using frog skin secretion isolated mRNA. The peptide was then synthesised by solid-phase peptide synthesis, purified by reversed-phase high-performance liquid chromatography, and structural-confirmed by matrix-assisted, laser desorption, ionisation, time-of-flight mass spectrometry. In bioassays, QUB-1942 showed inhibitory effects on the Gram-positive bacterium, Staphylococcus aureus (S. aureus ATCC CRM6538)at a concentration from 2 μM, the Gram-negative bacterium, Escherichia coli (E. coli ATCC CRM8739) at a concentration from 8 μM, and the yeast, Candida albicans (C. albicans ATCC CRM10231) at a concentration 64 μM. The minimum inhibitory concentration (MIC) value of the three microbes are 4 μM , 8 μM, 64 μM, respectively. In terms of MTT anticancer cell proliferation assay, QUB-1942 was proven to have anti-proliferative activity against a human lung cancer cell line (H838) in a range of concentrations from 10-6 M to 10-4 M. The trypan blue exclusion assay confirmed the killing effect of the peptide on H838 cells. However, QUB-1942 had a haemolytic effect higher than 20% on horse red blood cells when the concentration was higher than 64 μM. In conclusion, QUB-1942 has potential to become a safe antimicrobial and anticancer drug in the future after its haemolytic toxicity at high concentrations can be substantially decreased through structural modification.

Thesis embargoed until 31 December 2027

Date of Award	Dec 2022
Original language	English
Awarding Institution	Queen's University Belfast
Supervisor	Lei Wang (Supervisor) & Tianbao Chen (Supervisor)