Identification and functional study of a bioactive peptide, QUB-2315, from the skin secretion of Litoria caerulea

Frogs contain many bioactive molecules in their skin secretions, some of which are peptides with antimicrobial activity. In this study, peptide QUB-2315, identified in the dorsal skin secretion of the Australian green tree frog, Litoria caerulea, by molecular techniques and which belongs to the caerin family, was studied.

A cDNA library was constructed by isolating the skin secretion poly-A mRNA and 'shotgun' cloning through which the amino acid sequence of QUB-2315 was obtained. QUB-2315 had no significant effect on Staphylococcus aureus (a Gram-positive bacterium) and Candida albicans (a yeast) and was only effective against Escherichia coli (a Gram-negative bacterium) at a concentration of 512 μM. Meanwhile, QUB-2315 was found to have no significant inhibitory effect on the proliferation of human lung adenocarcinoma cells NCI-H838, but it showed haemolytic activity (around 20% haemolysis) at 512 μM. Although the antibacterial and anticancer effects of QUB-2315 were not apparent, it has research value through potential, targeted modification of its primary structure.<br><br><i>Thesis embargoed until 31 December 2027</i>