Discovery and functional evaluation of a host defense peptide from Rana amurensis

Abstract

Due to the drug-resistant bacterial infections have become a global medical problem, antimicrobial peptides (AMPs) are considered as a new possibility to replace traditional antibiotics. Host-defense peptides in amphibians skins with various biological activities are a rich source for discovering new AMPs. This thesis amid to discover and functionally study a new AMP from the skin secretions of Rana amurensis. A cDNA encoding a new ranatuerin precursor was successfully established through molecular cloning and Sanger sequencing, and the mature peptide sequence of the active form, QUB-2566 (GVLKGVGKNVSGSLLHQLKCLISGGC), was deduced from the cloned cDNA. Thereafter, the corresponding synthetic peptide was obtained by solid-phase Fmoc synthesis, and its antibacterial activity, antiproliferative activity and haemolytic activity were tested. QUB-2566 was found to inhibit the growth of S. aureus and E. coli from a peptide concentration of 1µM; however, it required higher peptide concentration to completely inhibit the growth of these bacteria. Interesting, this peptide exhibited better bactericidal effect against E.coli (MBC=32 μM) than grampositive bacterium (S.aureus) (MBC=128 μM). Moreover, this peptide had less potency against C.albicans (MIC=512μM), along with low haemolytic activity (HC50< 512 μM). Also, peptide QUB-2566 had a weak antiproliferative effect on lung cancer cells H838. Altogether, this peptide may become a lead compound for new antimicrobial drug development because of its potent antibacterial potency against E.coli and low haemolytic activity.

Date of Award	Dec 2020
Original language	English
Awarding Institution	Queen's University Belfast
Supervisor	Lei Wang (Supervisor) & Mei Zhou (Supervisor)