The effect of vitamin E on the structure of membrane lipid assemblies.
The effects of vitamin E on the activity of membrane-dependent enzymes suggest that it acts indirectly by modifying some properties of the lipid host. The effects of alpha-tocopherol (alpha-T) and alpha-tocopherol hemisuccinate (alpha-THS) on phospholipid monolayer structure, curvature, and bending elasticity were examined using X-ray diffraction and the osmotic stress method. These ligands were mixed with the hexagonal phase-forming lipid, dioleoylphosphatidylethanolamine (DOPE). Increasing levels up to 50 mol% alpha-T in DOPE in excess water result in a systematic decrease in the lattice dimension. Analysis of the structural changes imposed by alpha-T shows that it contributes a spontaneous radius of curvature of -13.7 A. This unusually negative value is comparable to diacylglycerols. alpha-T does not affect the bending elasticity of these monolayers. alpha-THS in its charged form decreases membrane curvature, but in its undissociated neutral form has a qualitatively similar but reduced effect on monolayer curvature, as does alpha-T. We discuss these results in terms of the local stresses such ligands would produce in the vicinity of a membrane protein, and how one might expect proteins to respond to such stress.
Bradford
A
A
Department of Biological Sciences, Brock University, St. Catharines, Ontario, Canada L2S 3A1.
Atkinson
J
J
Fuller
N
N
Rand
R P
RP
D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D004548:Elasticity; D008024:Ligands; D008563:Membrane Lipids / Q000737:chemistry* / Q000378:metabolism; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism; D008968:Molecular Conformation; D009997:Osmotic Pressure; D010714:Phosphatidylethanolamines / Q000737:chemistry; D010743:Phospholipids / Q000737:chemistry / Q000378:metabolism; D014810:Vitamin E / Q000031:analogs & derivatives* / Q000378:metabolism; D014867:Water / Q000737:chemistry; D014961:X-Ray Diffraction
D008024:Ligands; D008563:Membrane Lipids; D008565:Membrane Proteins; D010714:Phosphatidylethanolamines; D010743:Phospholipids; D014867:Water; D014810:Vitamin E; C094877:dioleoyl phosphatidylethanolamine