Purification and characterization of antimicrobial peptides from the skin of the North American green frog Rana clamitans

Ten peptides with differential growth-inhibitory activity against the Gram- positive bacterium, Staphylococcus aureus, the Gram-negative bacterium, Esc herichia coli, and the yeast Candida albicans were isolated from an extract of the skin of a North American frog, the green frog Rana clamitans. Ranat uerin-1C (SMLSVLKNLGKVGLGLVACKINKQC), ranalexin-1Ca (FLGGLMKAFPALICAVTKKC), ranalexin-1Cb (FLGGLMKAFPAIICAVTKKC), ranatuerin-2Ca (GLFLDTLKGAAKDVAGKLLE GLKCKIAGC KP), and ranatuerin-2Cb (GLFLDTLKGLAGKLLQGLKCIKAGCKP), are member s of three previously characterized families of antimicrobial peptides, fir st identified in the North American bullfrog Rana catesbeiana. In addition, five structurally related peptides (temporin-1Ca, -1Cb, -1Cc, -1Cd, and -1 Ce), comprising 13 amino acid residues and containing a C-terminally alpha- amidated residue, belong to the temporin family first identified in the Eur opean common frog Rana temporaria. Peptides belonging to the brevinin-1, br evinin-2, esculentin-1, and esculentin-2 families, previously isolated from the skins of Asian and European Ranid frogs, were not identified in the ex tract. The data support the hypothesis that the distribution and amino acid sequences of the skin antimicrobial peptides are valuable tools in the ide ntification and classification of Ranid frogs. (C) 2000 Elsevier Science In c. All rights reserved.