An atypical member of the brevinin-1 family of antimicrobial peptides isolated from the skin of the European frog Rana dalmatina

A single peptide with antimicrobial activity was extracted from the skin of the European agile frog (R. dalmatina). The primary structure of this 17 amino-acid-residue peptide (ILPLLLGKVVCAITKKC) does not immediately suggest membership of any of the previously described families of antimicrobial peptides from ranid frogs. However, if it is assumed that the peptide has undergone several residue deletions during the course of speciation, it shows sequence similarity with peptides belonging to the widely distributed brevinin-1 family, particularly those isolated from the related species Rana temporaria. The minimum inhibitory concentration of the peptide, termed brevinin-1Da, against the Gram-positive bacterium Staphylococcus aureus was 7 μM and against the Gram-negative bacterium Escherichia coli was 30 μM.