Novel Peptides from Skins of Amphibians Showed Broad-Spectrum Antimicrobial Activities

Peptide agents are often considered as potential biomaterials for developing new drugs that can overcome the rising resistance of pathogenic micro-organisms to classic antibiotic treatments. One key source of peptide agents is amphibian skin, as they provide a great deal of naturally occurring antimicrobial peptide (AMP) templates awaiting further exploitation and utilization. In this study, 12 novel AMPs from the skins of 3 ranid frogs, Rana limnocharis, R. exilispinosa, and Amolops afghanus, were identified using a 5' PCR primer. A total of 11 AMPs exhibited similarities with currently known AMP families, including brevinin-1, brevinin-2, esculentin-1, and nigrocin, besides, one AMP, named as Limnochariin, represented a novel AMP family. All 12 AMPs contain a C-terminus cyclic motif and most of them show obvious antimicrobial activities against 18 standard and clinically isolated strains of bacteria, including 4 Gram-positive bacteria, 11 Gram-negative bacteria, and 3 fungus. These findings provide helpful insight that will be useful in the design of anti-infective peptide agents.