Peptides with antimicrobial activity of the brevinin-1 family isolated from skin secretions of the southern leopard frog, Rana sphenocephala

Three peptides with growth-inhibitory activity towards the Gram-negative bacterium Eschericia coli were isolated from electrically stimulated secretions from the skin of the southern leopard frog, Rana sphenocephala. Structural characterization demonstrated that the peptides [brevinin-1Sa, minimum inhibitory concentration (MIC) = 55 mu M; brevinin-1Sb, MIC = 17 mu M; brevinin-1Sc, MIC = 14 mu M] represent new members of the brevinin-1 family of antimicrobial peptides, previously isolated from several other species of frogs of the genus Rana. Their high concentration in skin secretions and extreme variability in amino acid sequence suggest that the brevinin-1 family of peptides may be of value as molecular markers for the identification and taxonomic classification of Ranid frogs.