Acylation of myelin proteolipid protein in subcellular fractions of rat brainstem

The acylation of myelin proteolipid protein (PLP) and intermediate protein (IP) was investigated in an in vitro system of tissue slices prepared from actively myelinating rat brainstem. The incorporation of ³H]palmitate into the proteins in nine subcellular fractions including myelin and other cellular membranes which are actively involved in the synthesis and intracellular transport of the proteins was measured. More than 80% of ³H]palmitate-labeled proteins were recovered in myelin. The incorporation was highest in the heavy myelin and lowest in the light myelin subfraction. Appreciable acylation was also detected in the myelin-like fraction. On the other hand, the remaining fractions comprising a variety of endo- and ectomembranes, which harbored over 90% of newly synthesized PLP and IP as seen from ³H]leucine labeling showed practically no ³H]palmitate incorporation. The results indicate that the acylation of PLP and IP is a late event in their posttranslational processing and occurs only at their entry into the myelin sheath.