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Binding and insertion of alpha-helical anti-microbial peptides in POPC bilayers studied by molecular dynamics
Senthil K Kandasamy1, Ronald G Larson
1Department of Chemical Engineering, The University of Michigan, Ann Arbor, MI 48109-2036, USA.
Abstract:
We have performed molecular dynamics simulations of the interactions of two alpha-helical anti-microbial peptides, magainin2 and its synthetic analog of MSI-78, with palmitoyl-oleoyl-phosphatidylcholine (POPC) lipid bilayers. We used various initial positions and orientations of the peptide with respect to the lipid bilayer, including a surface-bound state parallel to the interface, a trans-membrane state, and a partially inserted state. Our 20 ns long simulations show that both magainin2 and MSI-78 are most stable in the lipid environment, with the peptide destabilized to different extents in both aqueous and lipid/water interfacial environments. We found that there are strong specific interactions between the lysine residues of the peptides and the lipid head-group regions. MSI-78, owing to its large number of lysines, shows better binding characteristics and overall stability when compared to magainin2. We also find that both peptides destabilize the bilayer environment, as observed by the increase in lipid tail disorder and the induction of local curvature on the lipid head-groups by the peptides. From all the simulations, we conclude that the hydrogen bonding interactions between the lysines of the peptides and the oxygens of the polar lipid head-groups are the strongest and determine the overall peptide binding characteristics to the lipids.
Insights
Antimicrobial peptides magainin 2 and MSI-78 are most stable within lipid bilayers, with MSI-78 showing superior binding due to more lysine residues. These peptides disrupt lipid bilayers by increasing tail disorder and head-group curvature.
Area of Science:
- Biophysics
- Computational Chemistry
- Molecular Biology
Background:
- Antimicrobial peptides (AMPs) are crucial in innate immunity.
- Understanding AMP-lipid interactions is key to developing new therapeutics.
- Magainin 2 and its analog MSI-78 are model alpha-helical AMPs.
Purpose of the Study:
- To investigate the molecular dynamics of magainin 2 and MSI-78 interacting with palmitoyl-oleoyl-phosphatidylcholine (POPC) lipid bilayers.
- To determine the preferred binding modes and stability of these peptides within different membrane environments.
- To elucidate the role of specific residues, particularly lysine, in peptide-lipid interactions.
Main Methods:
- Molecular dynamics (MD) simulations.
- Simulations of peptides in various initial positions and orientations relative to POPC bilayers.
- Analysis of peptide stability, lipid tail disorder, and head-group curvature.
Main Results:
- Both magainin 2 and MSI-78 exhibit greatest stability within the POPC lipid bilayer environment.
- MSI-78 demonstrates enhanced binding affinity and stability compared to magainin 2, attributed to its higher lysine content.
- Peptides induce destabilization of the lipid bilayer, evidenced by increased lipid tail disorder and local head-group curvature.
Conclusions:
- Specific interactions, primarily hydrogen bonding between peptide lysine residues and lipid head-groups, govern peptide-lipid binding.
- The lysine-rich MSI-78 peptide exhibits superior binding characteristics and stability.
- Antimicrobial peptides significantly alter lipid bilayer structure and dynamics.
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