ABSTRACT
The myelin membrane is a lipoprotein structure with a special membrane composition in which the lipids are more abundant than the proteins. Freeze-fracture technique has visualized intramembrane particles and thrown light upon the properties of the proteins penetrating the myelin membrane. The myelin membrane has a buoyant density corresponding to 0.5 to 0.8 M sucrose, lower than that of other membranes and subcellular particles with the exception of synaptic vesicles. By means of zonal sucrose gradient centrifugation, myelin-like membranes have been shown to distribute in a bell-shaped mode through the gradient. The formation of myelin is a complicated process involving the assembly of more than five different structural proteins with cholesterol, phospho-, and glycolipids. The decreased protein synthesis mainly concerns internal proteins of the myelin membrane which are incorporated into the myelin membrane in a complex manner and which need extra energy for transportation of the premyelin membranes to the myelination zone.
