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Published on: April 5, 2018
Lipid Headgroup Charge Controls Melittin Oligomerization in Membranes: Implications in Membrane Lysis
Sreetama Pal1,2,3, Hirak Chakraborty1,4, Amitabha Chattopadhyay1,2
1CSIR-Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500 007, India.
Abstract:
Melittin, a hemolytic peptide present in bee venom, represents one of the most well-studied amphipathic antimicrobial peptides, particularly in terms of its membrane interaction and activity. Nevertheless, no consensus exists on the oligomeric state of membrane-bound melittin. We previously reported on the differential microenvironments experienced by melittin in zwitterionic and negatively charged phospholipid membranes. In this work, we explore the role of negatively charged lipids in the oligomerization of membrane-bound melittin (labeled with 7-nitrobenz-2-oxa-1,3-diazol-4-yl (NBD)) utilizing a quantitative photobleaching homo-FRET assay. Our results show that the presence of negatively charged lipids decreases melittin oligomeric size to ∼50% of that observed in zwitterionic membranes. This is possibly due to differential energetics of binding of the peptide monomer to membranes of different compositions and could explain the reduced lytic activity yet tighter binding of melittin in negatively charged membranes. These results constitute one of the first experimental observations on the role of phospholipid headgroup charge in the oligomerization of melittin in membranes and is relevant in light of previous apparently contradictory reports on oligomerization of membrane-bound melittin. Our results highlight the synergistic interplay of peptide-membrane binding events and peptide oligomerization in modulating the organization, dynamics, and function of amphipathic α-helical peptides.
Insights
Negatively charged lipids reduce the size of melittin oligomers on membranes by about 50%. This finding helps explain melittin
Area of Science:
- Biochemistry
- Biophysics
- Membrane Biology
Background:
- Melittin, an amphipathic peptide from bee venom, is extensively studied for its membrane interactions and antimicrobial activity.
- The oligomeric state of membrane-bound melittin remains debated, with previous studies showing differential behavior in various membrane environments.
Purpose of the Study:
- To investigate the influence of negatively charged lipids on the oligomerization of membrane-bound melittin.
- To elucidate the role of phospholipid headgroup charge in melittin's aggregation state and membrane activity.
Main Methods:
- Utilized a quantitative photobleaching homo-Förster resonance energy transfer (FRET) assay.
- Employed melittin labeled with 7-nitrobenz-2-oxa-1,3-diazol-4-yl (NBD) to monitor oligomerization.
- Compared melittin behavior in zwitterionic versus negatively charged phospholipid membranes.
Main Results:
- Negatively charged lipids significantly decrease the oligomeric size of membrane-bound melittin by approximately 50% compared to zwitterionic membranes.
- This reduction in oligomer size correlates with tighter binding and reduced lytic activity in negatively charged membranes.
- Suggests differential binding energetics of melittin monomers contribute to observed oligomerization changes.
Conclusions:
- Phospholipid headgroup charge plays a crucial role in modulating the oligomerization of melittin within membranes.
- Findings reconcile previous contradictory reports on melittin oligomerization and highlight the interplay between peptide binding and aggregation.
- Provides insights into how peptide-membrane interactions influence the organization, dynamics, and function of amphipathic peptides.
