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Annular anionic lipids stabilize the integrin αIIbβ3 transmembrane complex.
Thomas Schmidt1, Jae-Eun Suk1, Feng Ye2
1From the Department of Biochemistry & Molecular Biology and Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California 90033 and.
The Journal of Biological Chemistry
|January 31, 2015
Summary
Anionic lipids stabilize membrane proteins like integrin αIIbβ3, even when competing for binding sites. This lipid-induced stability is crucial for membrane protein function and regulation.
Area of Science:
- Membrane biophysics
- Protein-lipid interactions
- Structural biology
Background:
- Cationic residues on membrane proteins interact with anionic lipids to determine protein topology.
- Anionic lipids are primarily located in the intracellular leaflet of cell membranes.
- The integrin αIIbβ3 transmembrane (TM) complex is stabilized by specific protein-protein interactions.
Purpose of the Study:
- To investigate the influence of anionic lipids on the stability of the integrin αIIbβ3 TM complex.
- To understand how anionic lipids affect the electrostatic interactions within the TM complex.
- To elucidate the role of lipid headgroup structure and accessibility in TM complex stabilization.
Main Methods:
- Computational modeling and simulations to analyze protein-lipid interactions.
- Free energy calculations to quantify TM complex stability.
- Analysis of lipid headgroup accessibility and protein-lipid contacts.
Main Results:
- Anionic lipids compete with the αIIb(Arg(995))-β3(Asp(723)) interaction but do not reduce its contribution to TM complex stability.
- Anionic lipids stabilize the αIIbβ3 TM complex by 0.50 ± 0.02 kcal/mol in a headgroup structure-dependent manner.
- This stabilization is significant compared to the destabilization required for integrin receptor activation (1.5 ± 0.2 kcal/mol).
Conclusions:
- Anionic lipids can stabilize membrane proteins by influencing TM helix-helix interactions through physical membrane characteristics and specific protein-lipid contacts.
- Despite competing for binding sites, anionic lipids enhance TM complex stability, leaving membrane-proximal electrostatic interactions intact.
- Lipid composition plays a critical role in regulating TM complex stability and, consequently, membrane protein function.
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