Molecular characterization and bioactivity evaluation of two novel bombinin peptides from the skin secretion of Oriental fire-bellied toad, Bombina orientalis

Following the exploration of biochemicals in amphibian defensive skin secretion, great attention has been focused on the novel bioactive peptides with unique molecular structures and complicated features and functions. In this study, the skin secretion of Oriental fire-bellied toad, Bombina orientalis, was acquired to search peptides with therapeutic potential. Using "shotgun" cloning technique, a full-length peptide precursor co-encoding two novel bombinin peptides was cloned from the skin secretion-derived cDNA library of B. orientalis. The deduced peptides were identified as one bombinin-like peptide (BLP) (GIGSAILSAGKSIIKGLAKGLAEHF-NH2) and one bombinin H-type peptide (BH) (IIGPVLGLVGKALGGLL-NH2). The primary structures of both peptides were confirmed through reverse-phase HPLC fractionation and mass spectrometry. Secondary structural prediction revealed Bombinin-BO1 and Bombinin H-BO1 adopted alpha-helical structural features. In addition, the two peptides exhibited broad-spectrum antimicrobial effect against Gram-positive and Gram-negative bacteria and yeast. Meanwhile, the anticancer activity assay indicated both peptides exerted significant anticancer effects against human hepatoma cell lines tested (Hep G2/SK-HEP-1/Huh7). The peptides reported here for the first time may represent novel lead compounds for the design/development of new therapeutics for human infection and neoplastic disease.