Identification and functional evaluation of a bioactive peptide QUB-2669 from the skin secretion of the American bullfrog Lithobates catesbeiana

Abstract

Due to the prevalence of antimicrobial resistance, researching potential antibiotic substitutes against the multi-drug resistant bacteria has become a global concern. Amphibian skin, secreting many bioactive peptides, is a rich source of novel antimicrobial peptides. In this thesis, QUB-2669, derived from the skin secretion of the American bullfrog, Lithobates catesbeiana, was identified as a member of the ranatuerin-1 family. During the process of peptide synthesis, the methionine residue, containing a sulphur, was accidentally oxidised, therefore, another peptide named MetO-QUB-2669 was obtained. QUB-2669 presented moderate antimicrobial activities against Escherichia coli (minimum inhibitory concentration (MIC) was 32 μM) and Candida albicans (MIC was 64 μM), but was not sensitive against the Gram-positive bacterium Staphylococcus aureus (MIC was 128 μM). Apart from these, QUB-2669 showed slight antiproliferative effects against the cancer cell line NCI H838 at a concentration of 10-4 M. Besides, the haemolytic activity of QUB-2669 was lower than 20 % at the concentration range from 1 μM to 16 μM. Compared with QUB-2669, MetO-QUB-2669 showed lower antimicrobial, antiproliferative and haemolytic activities. Hence, QUB-2669 could be further modified by reducing the haemolytic ability and increasing the antimicrobial activities to become a potential candidate against microbial infections.

Thesis embargoed until 31 December 2026.

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