Interactions of Lipids with Proteins of Myelin and its Associated Cytoskeleton

Myelin is composed of lipids and proteins whose mutual interactions and associations with the underlying cytoskeleton determine the macroscopic structure of the membrane. The cytoskeletal matrix isolated from rat brain myelin has been characterized further by sucrose-density-gradient centrifugation. The major interactions that the proteins will have with membrane lipids might be expected to be hydrophobic in nature. The increased affinity of proteolipid protein for phosphatidylserine compared to phosphatidylcholine is entirely due to electrostatic interactions at the bilayer surface. Important clues to the mechanism of myelin basic protein (MBP) binding and how it might cause the cytoplasmic surfaces of the oligodendrocyte plasma membrane to adhere have come from a detailed analysis of MBP interactions with lipid. Binding of MBP to dimyristoylphosphatidylglycerol bilayers is saturable and can be detected by the inclusion of spin-labeled phosphatidylglycerol in the bilayer.