Analysis of the structure-activity relationships of ranatuerin-5M7 (RT5M7) analogues generated by ‘Rana box’ splicing

Abstract

Bacterial resistance, especially in Gram-negative bacteria, has limited the application of many traditional antibiotics. In addition, bacterial infections are one of the most common complications during cancer treatment, and the annual mortality rate and side effects of cancer treatments have created an urgent need to find new alternative therapeutic agents. Fortunately, substances with both high anti-cancer and anti-bacterial activities and low toxic side effects, such as peptides, have been discovered. Amphibian skin secretions provide a rich source of peptides.

In this project, a new peptide, ranatuerin-5M7 (RT5M7), was first isolated and identified from the skin secretion of Rana catesbeiana frogs. Rana catesbeiana frogs were discovered to possess various bioactive peptides with a characteristic structure known as the 'Rana box.' RT5M7, identified in this study, showed no significant antibacterial or anticancer activity during the initial screening. Therefore, the approach of grafting modified peptides with the 'Rana box' structure was applied. This thesis involved the design and grafting of different 'Rana box' structures onto RT5M7, followed by a study of the physicochemical properties and structures of the resulting analogues. Importantly, the selected 'Rana box' structures for grafting were sourced from peptides with inherent activity advantages.

The parent peptide and all analogues underwent basic screening for antibacterial and anticancer activities. Compared to the parent peptide RT5M7, all modified peptides exhibited reduced inhibition concentrations against certain bacteria, with the most significant improvement observed against Escherichia coli (E. coli). This improvement might be correlated with the increased charge and helical structure of the modified peptides. Additionally, some modified peptides displayed inhibitory
activity against cancer cell proliferation. A series of experiments were conducted to explore in-depth, the mechanisms behind the antibacterial and anticancer properties of the most promising analogues, along with their structure/activity relationships.

Thesis is embargoed until 31 July 2029.

Date of Award	Jul 2024
Original language	English
Awarding Institution	Queen's University Belfast
Supervisor	Tianbao Chen (Supervisor) & Lei Wang (Supervisor)