Peptides with antimicrobial activity from four different families isolatedfrom the skins of the North American frogs Rana luteiventris, Rana berlandieri and Rana pipiens

The skins of frogs of the genus Rana synthesize a complex array of antimicr obial peptides that may be grouped into eight families on the basis of stru ctural similarity. A total of 24 peptides with differential growth-inhibito ry activity towards the Gram-positive bacterium Staphylococcus aureus, the Gram-negative bacterium Escherichia coli and the yeast Candida albicans wer e isolated from extracts of the skins of three closely related North Americ an frogs, Rana luteiventris (spotted frog), Rana berlandieri (Rio Grande le opard frog) and Rana pipiens (Northern leopard frog). Structural characteri zation of the antimicrobial peptides demonstrated that they belonged to fou r of the known families: the brevinin-1 family, first identified in skin of the Asian frog Rana porosa brevipoda; the esculentin-2 family, first ident ified in the European frog Rana esculenta; the ranatuerin-2 family, first i dentified in the North American bullfrog Rana catesbeiana; and the temporin family, first identified in the European frog Rana temporaria. Peptides be longing to the brevinin-2, ranalexin, esculentin-1 and ranatuerin-1 familie s were not identified in the extracts. Despite the close phylogenetic relat ionship between the various species of Ranid frogs, the distribution and am ino-acid sequences of the antimicrobial peptides produced by each species a re highly variable and species-specific, suggesting that they may be valuab le in taxonomic classification and molecular phylogenetic analysis.