Spin label saturation transfer EPR determinations of the stoichiometry and selectivity of lipid-protein interactions in the gel phase.
Lipid-protein interactions with the myelin proteolipid protein incorporated in the gel phase of dimyristoylphosphatidylcholine bilayers have been studied by saturation transfer EPR spectroscopy of spin-labelled phospholipids. The integrated intensities of the saturation transfer EPR spectra from spin-labelled phosphatidylcholine are linearly dependent on the protein/lipid ratio, and correspond to a fixed stoichiometry of approximately 11 lipids per monomer associated with the protein in the gel phase. The normalized saturation transfer intensities of spin-labelled phosphatidic acid, on the other hand, display a non-linear dependence on the protein/lipid ratio that can be described well by a selectivity for interaction with the protein in the gel phase with an average association constant relative to phosphatidylcholine of approx. 5.2. These values for the stoichiometry and selectivity of lipid-protein interaction in the lipid gel phase obtained from saturation transfer EPR spectroscopy are comparable to those found previously in fluid phase lipids by conventional EPR spectroscopy.
Max-Planck-Institut für biophysikalische Chemie, Abteilung Spektroskopie, Göttingen, Germany.
L I
LI
Horváth
P J
PJ
Brophy
D
D
Marsh
D004134:Dimyristoylphosphatidylcholine; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods; D005782:Gels; D008055:Lipids / Q000737:chemistry*; D010712:Phosphatidic Acids / Q000737:chemistry; D011506:Proteins / Q000737:chemistry*; D011510:Proteolipids / Q000737:chemistry; D013113:Spin Labels
D005782:Gels; D008055:Lipids; D010712:Phosphatidic Acids; D011506:Proteins; D011510:Proteolipids; D013113:Spin Labels; D004134:Dimyristoylphosphatidylcholine