Journal
BIOPHYSICAL JOURNAL
Volume 91, Issue 1, Pages 206-216Publisher
CELL PRESS
DOI: 10.1529/biophysj.105.073890
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Funding
- NIAID NIH HHS [R01 AI054515, AI054515] Funding Source: Medline
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The mechanism of membrane interaction of two amphipathic antimicrobial peptides, MSI-78 and MSI-594, derived from magainin-2 and melittin, is presented. Both the peptides show excellent antimicrobial activity. The 8-anilinonaphthalene-1-sulfonic acid uptake experiment using Escherichia coli cells suggests that the outer membrane permeabilization is mainly due to electrostatic interactions. The interaction of MSI-78 and MSI-594 with lipid membranes was studied using P-31 and H-2 solid-state NMR, circular dichroism, and differential scanning calorimetry techniques. The binding of MSI-78 and MSI-594 to the lipid membrane is associated with a random coil to alpha-helix structural transition. MSI-78 and MSI-594 also induce the release of entrapped dye from POPC/ POPG (3: 1) vesicles. Measurement of the phase-transition temperature of peptide-DiPoPE dispersions shows that both MSI-78 and MSI-594 repress the lamellar-to-inverted hexagonal phase transition by inducing positive curvature strain. N-15 NMR data suggest that both the peptides are oriented nearly perpendicular to the bilayer normal, which infers that the peptides most likely do not function via a barrel-stave mechanism of membrane-disruption. Data obtained from P-31 NMR measurements using peptide-incorporated POPC and POPG oriented lamellar bilayers show a disorder in the orientation of lipids up to a peptide/lipid ratio of 1: 20, and the formation of nonbilayer structures at peptide/lipid ratio > 1:8. H-2-NMR experiments with selectively deuterated lipids reveal peptide-induced disorder in the methylene units of the lipid acyl chains. These results are discussed in light of lipid-peptide interactions leading to the disruption of membrane via either a carpet or a toroidal-type mechanism.
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