Stoichiometry and specificity of lipid-protein interaction with myelin proteolipid protein studied by spin-label electron spin resonance

Abstract
The interaction of spin-labeled lipids with the [bovine spinal cord] myelin proteolipid apoprotein in complexes with dimyristoylphosphatidylcholine or varying lipid/protein ratios was studied with ESR spectroscopy. A 1st shell of .apprx. 10 lipids/25,000-dalton protein is motionally restricted by the protein interface. This stoichiometry is consistent with a hexameric arrangement of the protein in the membrane. A selectivity of the various spin-labeled lipids for the motionally restricted component at the protein interface is found in the order stearic acid > phosphatidic acid > cardiolipin .gtorsim. phosphatidylserine > phosphatidylglycerol .apprxeq. phosphatidylcholine > phosphatidylethanolamine > androstanol .gtorsim. cholestane.