Identification and functional study of a bioactive peptide QUB-2007 from the skin secretion of the bicolour tree-frog Phyllomedusa bicolor

In this thesis, QUB-2007, a peptide belonging to the Phylloseptin family of the Dermaseptin superfamily, was derived from the skin secretion of Phyllomedusa bicolor. The peptide sequence was obtained by molecular cloning through constructing a cDNA library with isolated mRNA from frog skin secretion.

The peptide was synthesised by solid phase peptide synthesis, purified using reversed-phase high performance liquid chromatography and structurally-confirmed by MALDI-TOF MS. In broth microdilution assays, QUB-2007 showed antimicrobial activities against the Gram-negative bacterium, Escherichia coli (E. coli ATCC CRM 8739), and the yeast, Candida albicans (C. albicans ATCC CRM 10231) at concentration of 32 μM, and the Gram-positive bacterium, Staphylococcus aureus (S. aureus ATCC CRM6538) at a concentration of 8 μM. In terms of MTT anticancer cell proliferation assays, QUB-2007 was shown to have anticancer activities against HCI-H838 lung cancer cells at a concentration of 10-4 M. With regard to haemolysis, QUB-2007 was haemolytic at concentrations of 32 μM could be 15%.<br><br>In conclusion, QUB-2007 has potential to be a drug, but its haemolytic activity is a big obstacle.