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Elastic properties of polyunsaturated phosphatidylethanolamines influence rhodopsin function
Walter E Teague1, Olivier Soubias, Horia Petrache
1Laboratory of Membrane Biochemistry and Biophysics, NIAAA, NIH, Bethesda, MD 20892, USA.
Faraday Discussions
|June 29, 2013
Summary
Polyunsaturated phosphatidylethanolamines (PE) in membranes promote metarhodopsin-II formation. This process is quantitatively linked to the elastic properties of PEs, specifically their negative curvature elastic stress.
Area of Science:
- Biochemistry
- Biophysics
- Membrane Biology
Background:
- Polyunsaturated phosphatidylethanolamines (PE) are crucial membrane components.
- Metarhodopsin-II (M(II)) is a key photointermediate of bovine rhodopsin that activates transducin.
- The role of membrane lipid elasticity in M(II) formation is not fully understood.
Purpose of the Study:
- To investigate the quantitative link between the elastic properties of polyunsaturated phosphatidylethanolamines (PE) and metarhodopsin-II (M(II)) formation.
- To determine how PE curvature elasticity influences rhodopsin photointermediate equilibrium.
Main Methods:
- Investigated the curvature elasticity of lipid monolayers of specific polyunsaturated PEs (18:0-22:6(n-3)PE, 18:0-22:5(n)-6PE) and a model lipid (18:1(n-9)-18:1(n-9)PE) in the inverse hexagonal phase.
- Measured spontaneous radii of curvature for the lipid monolayers.
Main Results:
- All investigated PE lipids formed monolayers with low spontaneous radii of curvature (26-28 angstroms).
- These PEs generate significant negative curvature elastic stress in membranes.
- This stress shifts the rhodopsin photointermediate equilibrium towards M(II) formation.
Conclusions:
- The elastic properties of polyunsaturated PEs, particularly negative curvature elastic stress, are quantitatively linked to M(II) formation.
- Membrane lipid composition significantly impacts the activation state of rhodopsin.
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