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Ca(2+) bridging of apposed phospholipid bilayers
Zeena K Issa1, Charles W Manke, Bhanu P Jena
1Department of Chemical Engineering and Materials Science, Wayne State University, Detroit, Michigan 48202, USA.
The Journal of Physical Chemistry. B
|September 15, 2010
Summary
Calcium (Ca2+) ions facilitate lipid vesicle fusion by forming anhydrous complexes between bilayers, driving them into close contact and causing dehydration. This process differs significantly from sodium (Na+) ion interactions.
Area of Science:
- Biophysics
- Computational Chemistry
- Membrane Biology
Background:
- Lipid vesicle fusion is a critical process in cellular functions.
- Understanding the role of divalent cations like calcium (Ca2+) in membrane fusion is essential.
Purpose of the Study:
- To elucidate the mechanism of Ca2+-induced fusion of lipid vesicles.
- To investigate the interactions of Ca2+ with lipid bilayers at a molecular level.
Main Methods:
- Molecular dynamics simulations were employed.
- Simulations were performed in the isobaric-isothermal ensemble.
- Interactions of Ca2+ with apposed lipid bilayers were analyzed.
Main Results:
- A Ca2+-phospholipid "anhydrous complex" formed between apposed bilayers.
- Ca2+ binding induced close contact (<4 Å) and dehydration of bilayers.
- Water displacement from phospholipid head groups was observed.
- Dehydration led to ordering of phospholipid tails, with partial disruption by Ca2+-phospholipid bridges.
- In contrast, Na+ ions showed complexation only within single bilayers.
Conclusions:
- Ca2+ ions play a unique role in promoting lipid bilayer proximity and dehydration, distinct from Na+.
- The formation of anhydrous complexes and subsequent dehydration are key steps in Ca2+-induced membrane fusion.
- These findings provide molecular insights into cation-mediated membrane dynamics.
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