Characteristics of cathelicidin-Bg, a novel gene expressed in the ear-side gland of Bufo gargarizans.

The traditional Chinese medicine Chan Su (toad venom) comprises dried secretions of the ear-side gland of Bufo gargarizans. Chan Su is known for its small molecular components, which include telocinobufagin, marinobufagin, and bufalin, while in other amphibians, studies mainly focus on peptide components. Until recently, no genes expressed in the ear-side gland of B. gargarizans gland had been cloned. In this study, cathelicidin-Bg, a coding sequence of anti-microbial peptide (AMP), was cloned. The predicted amino acid sequence of cathelicidin-Bg was very similar to that from other amphibians, with a 34-amino acid mature peptide predicted in the C-terminus. The functions of this mature peptide were verified by microbe and tumor cell inhibition assays. Our results showed that the mature peptide of cathelicidin-Bg could inhibit the proliferation of Staphylococcus aureus and Pseudomonas aeruginosa. The mature peptide was also shown to selectively inhibit tumor cells. These results indicate that the identified coding sequence represents an active peptide of Chan Su.