Identification and functional study of a nigrocin peptide, QUB-1973, from the defensive skin secretion of the frog, Odorrana andersonii

Abstract

Antimicrobial peptides (AMPs) as alternatives to antibiotics are being gradually put under the spotlight to overcome the antimicrobial resistance challenge. Here, a nigrocin peptide, QUB-1973, belonging to the brevinin superfamily, was identified in the skin secretions of Chinese Yunnanfu frogs, Odorrana andersonii. The bio-synthetic precursor sequence of QUB-1973 was first obtained via ‘shotgun’ molecular cloning from the skin secretion-derived cDNA library. The mature peptide (GLLSGVLGVGKKIVCGLSGLC) was then identified by characterising the cleavage site at the N terminus (the common convertase cleavage site, a pair of basic amino acids -Lys-Arg-) of the pro-peptide, along with sequence alignments with other known nigrocin peptides. Thereafter, QUB-1973 was synthesised by solid-phase peptide synthesis (SPPS). The synthetic peptide was then verified and purified by use of MALDI-TOF mass spectrometry and reverse-phase HPLC, respectively. The purified peptide was used for assessing antimicrobial, anticancer and haemolytic activities. Compared with most structurally similar peptides, QUB-1973 showed potent antibacterial activity against S. aureus with a TI value of 123.1 calculated by the MIC value against S. aureus (4 µM) and HC50 value (492.4 µM) for horse red blood cells. Also, MIC values against E. coli and C. albicans were 16 µM and 64 µM respectively. The antiproliferative activity of QUB-1973 against the lung cancer cells was 100 µM with IC50 at 56.12µM. Further investigations of QUB-1973 should be performed to exploit this peptide as a potential drug for related diseases like skin infections or sepsis caused by S. aureus.

Thesis embargoed until 31 December 2027

Date of Award	Dec 2022
Original language	English
Awarding Institution	Queen's University Belfast
Supervisor	Mei Zhou (Supervisor), Tianbao Chen (Supervisor) & Xiaoling Chen (Supervisor)