Identification and bioactivity evaluation of a novel peptide from the skin secretion of Pelophylax kl. esculentus
Species of frogs and toads have proven to be a rich source of drugs and contain various components with potential biological activities, especially in their skin or skin secretions. Among these, peptides are found with broad-spectrum antibacterial and antifungal activities, as well as anticancer properties. It is generally assumed that these cationic, amphipathic and α-helical peptides constitute a part of the innate immune system that protects the animal from invasion by pathogenic microorganisms. In this thesis, a novel peptide (QUB-1342) was discovered in the skin secretion of the European edible frog, Pelophylax kl. esculentus. The precursor structure was found through applying a “shotgun” cloning method, and subsequently translating the cDNA to deduce the mature peptide sequence: FLPIVTGLLSGLL-NH2. From comparison with the sequences of known AMPs, QUB-1342 was classified as a temporin family member. The peptide was chemically-synthesised using solid phase chemistry and afterwards, its molecular mass and purity were confirmed by MALDI-TOF mass spectrometry and reverse phase HPLC. In pharmacological assays, QUB-1342 displayed a weak activity against S. aureus, with an MIC=64μM. It did not show any haemolytic effects at the concentrations employed. Further investigations are underway to seek more functions of the peptide and to examine the relationship between its structure and activity, and also to develop novel candidate drugs for the clinic.
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