MOLECULAR-INTERACTIONS OF THE MAJOR MYELIN GLYCOSPHINGOLIPIDS AND MYELIN BASIC-PROTEIN IN MODEL MEMBRANES

The molecular organization, interactions, phase state and membrane-mem brane interactions of model membranes containing cerebroside (GalCer), sulfatide (Sulf) and myelin basic protein (MBP) were investigated. Su lf shows a larger cross-sectional area than GalCer, in keeping with th e lateral electrostatic repulsions in the negatively charged polar hea d group. The interactions of GalCer with different phospholipids are s imilar while those with Sulf depend on the phosphoryl choline moiety i n the phospholipid. MBP induces a decrease of the phase transition tem perature in both lipids but with Sulf this occurs at lower proportions of MBP. In mixtures of Sulf with phosphatidylcholine MBP induces phas e separation among Sulf-rich and PC-rich domains. Extensive apposition of bilayers containing Sulf is induced by MBP while GalCer interferes with this process. Few membrane interactions proceed to bilayer mergi ng or whole bilayer fusion and the glycosphingolipids help preserve th e membrane integrity.