Antimicrobial peptides (AMPs), such as cecropin A, are key components of the innate immune system.  AMPs provide defense by folding into and disrupting cell membranes of invading pathogens, yet do not target host eukaryotic cells.  In contrast, peptide toxins such as melittin are potent against all cell types.  A cecropin-melittin hybrid peptide (CM15) improves upon the antimicrobial activity of cecropin without displaying hemolytic properties.  Here,  we report fluorescence and UV resonance Raman results of melittin, cecropin, and CM15 to elucidate potencies for membrane disruption, local environment of the single, critical tryptophan residue, and backbone structure of peptides in lipid environments that mimic eukaryotic and prokaryotic membranes.  These data suggest that deep insertion of the peptide is characteristic of toxins whereas AMPs localize to the lipid head group region.  Additionally, the spectroscopic and computational findings indicate that secondary structure may not be essential for membrane disruption.  These results suggest new models may be required to describe peptide-membrane interactions.

Spectroscopic and computational studies of α-helical membrane-disrupting peptides

243rd National Meeting (2012)

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