We addressed the onset of synergistic activity of the two well-studied antimicrobial peptides magainin 2 (MG2a) and PGLa using lipid-only mimics of Gram-negative cytoplasmic membranes. Specifically, we coupled a joint analysis of small-angle x-ray and neutron scattering experiments on fully hydrated lipid vesicles in the presence of MG2a and L18W-PGLa to all-atom and coarse-grained molecular dynamics simulations. In agreement with previous studies, both peptides, as well as their equimolar mixture, were found to remain upon adsorption in a surface-aligned topology and to induce significant membrane perturbation, as evidenced by membrane thinning and hydrocarbon order parameter changes in the vicinity of the inserted peptide. These effects were particularly pronounced for the so-called synergistic mixture of 1:1 (mol/mol) L18W-PGLa/MG2a and cannot be accounted for by a linear combination of the membrane perturbations of two peptides individually. Our data are consistent with the formation of parallel heterodimers at concentrations below a synergistic increase of dye leakage from vesicles. Our simulations further show that the heterodimers interact via salt bridges and hydrophobic forces, which apparently makes them more stable than putatively formed antiparallel L18W-PGLa and MG2a homodimers. Moreover, dimerization of L18W-PGLa and MG2a leads to a relocation of the peptides within the lipid headgroup region as compared to the individual peptides. The early onset of dimerization of L18W-PGLa and MG2a at low peptide concentrations consequently appears to be key to their synergistic dye-releasing activity from lipid vesicles at high concentrations.

• MeSH
• buněčná membrána metabolismus   MeSH
• dimerizace MeSH
• fosfatidylethanolaminy MeSH
• fosfatidylglyceroly MeSH
• kationické antimikrobiální peptidy metabolismus   MeSH
• lipidové dvojvrstvy chemie   MeSH
• lipidy chemie   MeSH
• magaininy metabolismus   MeSH
• simulace molekulární dynamiky MeSH
• teplota MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• 1-palmitoyl-2-oleoylphosphatidylethanolamine MeSH Prohlížeč
• 1,2-dioleoyl-sn-glycero-3-phosphoglycerol MeSH Prohlížeč
• fosfatidylethanolaminy MeSH
• fosfatidylglyceroly MeSH
• kationické antimikrobiální peptidy MeSH
• lipidové dvojvrstvy MeSH
• lipidy MeSH
• magaininy MeSH
• peptide-Gly-Leu-amide MeSH Prohlížeč

Mixtures of the frog peptides magainin 2 and PGLa are well-known for their pronounced synergistic killing of Gram-negative bacteria. We aimed to gain insight into the underlying biophysical mechanism by interrogating the permeabilizing efficacies of the peptides as a function of stored membrane curvature strain. For Gram-negative bacterial-inner-membrane mimics, synergism was only observed when the anionic bilayers exhibited significant negative intrinsic curvatures imposed by monounsaturated phosphatidylethanolamine. In contrast, the peptides and their mixtures did not exhibit significant activities in charge-neutral mammalian mimics, including those with negative curvature, which is consistent with the requirement of charge-mediated peptide binding to the membrane. Our experimental findings are supported by computer simulations showing a significant decrease of the peptide-insertion free energy in membranes upon shifting intrinsic curvatures toward more positive values. The physiological relevance of our model studies is corroborated by a remarkable agreement with the peptide's synergistic activity in Escherichia coli. We propose that synergism is related to a lowering of a membrane-curvature-strain-mediated free-energy barrier by PGLa that assists membrane insertion of magainin 2, and not by strict pairwise interactions of the two peptides as suggested previously.

• MeSH
• antibakteriální látky chemie   farmakologie   MeSH
• biomechanika účinky léků   MeSH
• buněčná membrána účinky léků   metabolismus   MeSH
• Escherichia coli cytologie   účinky léků   MeSH
• magaininy chemie   farmakologie   MeSH
• mechanický stres * MeSH
• multimerizace proteinu MeSH
• sekvence aminokyselin MeSH
• synergismus léků MeSH
• termodynamika MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• antibakteriální látky MeSH
• magaininy MeSH