Antimicrobial peptides from the skin of a Korean frog, Rana rugosa.

Six antimicrobial peptides, named gaegurins, were isolated from the skin of a Korean frog, Rana rugosa, and their amino acid sequences were determined by automated Edman degradation. All peptides contain two invariant cysteine residues, one at their C-terminus and the second at the seventh position from the C-terminus. The heptapeptides containing these two cysteine residues, which we designate 'Rana boxes', are conserved in the antimicrobial peptides derived from other Rana species. Each peptide manifested a broad spectrum of antimicrobial activity against Gram positive and Gram negative bacteria, fungi and protozoa with slightly different specific activities. All gaegurins manifest very little or no hemolytic activity. These properties provide the potential for application of these peptides to effective therapeutic agents for control of pathogenic microorganisms.