Gene-encoded peptide antibiotics represent fascinating molecules for the development of new antimicrobials
with a new mode of action: and one of the richest sources is amphibian skin. In particular, the skin of the fire-bellied toad
Bombina genus contains mildly cationic antimicrobial peptides (AMPs), named bombinins H, with attractive properties.
Indeed, some members of this peptide family coexist in skin secretions as isomers in which a single D-amino acid (alloisoleucine
or leucine) is incorporated as a result of a post-translational modification of the respective gene-encoded Lamino
acid. Here, a brief overview of the genes coding for these peptides, their spectrum of antimicrobial activities,
mechanism of action and interactions with biological or model membranes is reported. Remarkably, a single D-amino acid
substitution represents a unique approach developed by Nature not only to modulate the peptide stability in vivo, but also
to confer the all-L peptide and its diastereomer distinctive biological features. Overall, such findings should assist in the
generation of new peptide-based anti-infective agents, which are urgently needed because of the growing emergence of
microbial strains resistant to conventional antimicrobials.
Keywords: Amphibian skin, antimicrobial peptides, bombinins, D-amino acid, innate immunity, membrane-permeabilization.
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