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 ba cterium Eschericia coli were isolated from electrically stimulated secretio ns from the skin of the southern leopard frog, Rana sphenocephala. Structur al characterization demonstrated that the peptides [brevinin-1Sa, minimum i nhibitory concentration (MIC) = 55 mu M; brevinin-1Sb, MIC = 17 mu M; brevi nin-1Sc, MIC = 14 mu M] represent new members of the brevinin-1 family of a ntimicrobial peptides, previously isolated from several other species of fr ogs of the genus Rana. Their high concentration in skin secretions and extr eme variability in amino acid sequence suggest that the brevinin-1 family o f peptides may be of value as molecular markers for the identification and taxonomic classification of Ranid frogs.