Protein Heterogeneity in Rat CNS Myelin Subfractions
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Microsomal fraction-free myelin from forebrain and spinal cord of young and mature rats, when subjected to hypo-osmotic shock and slow speed centrifugation, yielded a myelin pellet and a supernatant fraction (SN 4). Fraction SN 4 consisted of small vesicular profiles in which the major myelin proteins were reduced whereas high molecular weight material such as Wolfgram protein, myelin-associated glycoprotein and CNP were substantially increased over myelin. A close correlation of the SN 4 fraction to the myelin-like fraction of Davison and coworkers was suggested.
The myelin pellets were subfractioned on zonal sucrose gradients to yield bell-shaped particle distributions. Besides shifts in densities of the maxima between myelin of young and mature forebrain and spinal cord, a decrease was observed from the light to the heavy gradient end in basic proteins, and an increase in Wolfgram protein and other high molecular weight proteins. Proteolipid protein took an intermediate position. Light fractions from adult spinal cord displayed CNP activities below those of the total homogenate. This result, together with the very high CNP activities in fraction SN 4 casts some doubt on CNP being a marker for compact myelin; rather it appears that CNP is a marker for the process of myelin formation.
KeywordsSpinal Cord Myelin Protein High Molecular Weight Protein Proteolipid Protein Total Homogenate
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- 2.Agrawal, H.C., Banik, N.L., Bone, S., Davison, A.N., Mitchell, R.F. and Spohn, M., The identity of myelin-like fraction isolated from developing brain, Biochem. J. 120 (1970) 635–642.Google Scholar
- 18.McIntyre, R.J., Quarles, R.H., Webster, H. deF. and Brady, R.O., Isolation and characterization of myelin-related membranes, Trans. Am. Soc. Neurochem. 8 (1977) 159.Google Scholar
- 21.Mokrasch, L.C., Biophysical chemistry and dynamics of myelin, in Myelin (L.C. Mokrasch, R.S. Bear and F.O. Schmitt, eds.) Neurosciences Res. Progr. Bull. 9 (1971) 452–506.Google Scholar
- 22.Moore, W.J., Smith, R. and Chapman, B.E., Conformation and function of myelin basic proteins, Trans. Am. Soc. Neurochem. 8 (1977) 67.Google Scholar
- 23.Morell, P., Greenfield, S., Costantino-Ceccarini, E. and Wisniewski, H., Changes in the protein composition of mouse brain myelin during development, J. Neurochem. 19 (1972) 2545–2554.Google Scholar
- 29.Quarles, R.H., The biochemical and morphological heterogeneity of myelin and myelin-related membranes, in Biochemistry of Brain (S. Kumar, ed.) Pergamon Press Ltd., in press.Google Scholar
- 30.Sabri, M.I., Tremblay, C., Banik, N.L., Scott, T., Gohil, K. and Davison, A.N., Biochemical and morphological changes in the subcellular fractions during myelination of rat brain, Biochem. Soc. Trans. (London) 3 (1975) 275–276.Google Scholar
- 37.Waehneldt, T.V., Matthieu, J.-M. and Neuhoff, V., Characteriza- tion of a myelin-related fraction (SN 4) isolated from rat forebrain at two developmental stages, Brain Res., in press.Google Scholar
- 39.Zgorzalewicz, B., Neuhoff, V. and Waehneldt, T.V., Rat myelin proteins. Compositional changes in various regions of the nervous system during ontogenetic development, Neurobiology 4 (1974) 265–276.Google Scholar