EFFECT OF PROTEOLYTIC ATTACK ON THE STRUCTURE OF CNS MYELIN MEMBRANE

Rat CNS myelin particles have been incubated with trypin and acetyltrypsin under conditions which ensured a selective and substantial removal of the basic proteins leaving acidic Wolfgram and proteolipid proteins. Some trypsin became associated with the basic protein denuded pellet while no attachment of acetyltrypsin was observed. The removal of basic proteins ‘solubilized’ some myelin and produced a lighter ‘fluff’ layer on top of the myelin pellet, but this amounted to no more than 10 per cent of the total myelin lamellae. Electron microscopy indicated a more dense-straining interperiod line in a small percentage of lamellae which otherwise remained normal. Selective extraction of complex lipids with solvents of increasing polarity, nuclear magnetic resonance spectra and X-ray diffraction patterns showed no significant changes on removing basic proteins from myelin. The results are interpreted as suggesting that the basic proteins are not uniformly distributed in myelin but preferentially located in the outside layers of the myelin sheath and that they play little part in stabilizing the bulk of the myelin membrane structure.