Identification and activity assessment of a bioactive peptide QUB-2642 from the skin secretion of The American Bullfrog (Rana catesbeiana)

Amongst antimicrobial peptides widespread in different classes of life, those derived from amphibians have been receiving special research attention since the last century. Secreted by the granular glands located in amphibian skin, a wide range of cationic peptides were found to display potent antimicrobial activities and provide an effective defence against different microorganism infections.

Herein, a bioactive natural peptide QUB-2642 (SMFSVLKNLGKVGLGFVACKVSKQC), identified as an analogue belonging to ranatuerin-1 family, was discovered in the skin secretions of The American Bullfrog (Rana catesbeiana) by ‘shotgun’ cloning. Using synthetic peptides, subsequent antimicrobial and haemolysis assays demonstrated that QUB-2642 had strong inhibitory activity against bacterial strains Staphylococcus aureus (MIC = 8 µM) and Escherichia coli (MIC = 8 µM) as well as weak inhibitory activity against fungal strain Candida albicans (MIC = 64 µM) without significant haemolytic effect (HC50 >512 µM) upon horse erythrocytes.