Identification, structural characterisation, and bioactivity studies of antimicrobial peptides from skin secretions of ranidae frogs

Abstract

Antimicrobial peptides (AMPs) have been considered potential alternatives to traditional antibiotics. To discover more AMPs that can be developed into clinical drugs, Brevinin-2GUb, Temporin-SHf and QUB-1841, extracted from the skin secretion of Hylarana guentheri, Pelophylax saharica and Pelophylax kl. esculentus, respectively, were selected as the main subjects of the project. Some rational designs were made on these peptides based on diverse principles and the assays of identification, structure characterisation and bioactivities were conducted on them and their derivatives. 
The Rana box has little influence on the antimicrobial activity of Brevinin-2GUb and its core structure is the 1st to 19th residues at the N-terminal region. The introduction of Arginine at the N-terminal end of Temporin-SHf can facilitate the peptide to penetrate the bacterial membrane, while the branched analogues cannot enhance its bioactivities possibly due to the overlapping of the high percentage of hydrophobic residues. The introduction of D-amino acids can reduce the haemolysis activity of QUB-1841, but the analogues still have no effect on gram-negative bacteria. The replacements with Lysine can provide it with more potent and broad-spectrum antimicrobial activity and the haemolysis can be undermined as well. The optimal number of charges for QUB-1841 is three. The positions of the substitution are also critical and it is better to make modifications on the polar face.

The three analogues, tB2U-6K, 3R-T-SHf and QUB-1841-3K, display potent and broad-spectrum antimicrobial activities in vitro and in vivo, high selectivity, low possibility to induce resistance and excellent stability, which makes them potential for clinical use.

Thesis embargoed until 31 July 2027.

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