INCORPORATION OF [H-3]LEUCINE INTO 3 SUBFRACTIONS OF MYELIN IN MURINE MYELIN DYSGENESIS - QUAKING MUTANT

Radioactively labeled myelin subfractions were isolated from mouse brain with the use of nonradioactive rat brain myelin as a carrier. The distribution of myelin proteins in each of the 3 subfractions was determined by calculating the relative dye binding capacity of individual proteins on Fast Green stained gels. The basis proteins were most heavily concentrated in light myelin, comprising 40% of the total dye binding capacity of that fraction, whereas the high molecular weight proteins were concentrated in heavy myelin, where they comprised 38% of the total. Proteolipid protein accounted for 20-30% of the dye binding capacity measured in the 3 subfractions of myelin. Any differences in the relative distribution of proteins in Quaking myelin subfractions were not detected. Despite the elevation of total brain radioactivity, Quaking mice incorporated only 11.8 and 31.9% of that in control mice into the light and medium subfractions of myelin, respectively. Quaking mice appeared to synthesize heavy myelin at near-normal (82.9%) levels.