PROTEIN COMPOSITION OF MYELIN OF THE PERIPHERAL NERVOUS SYSTEM

Abstract— Myelin was purified from the peripheral nervous system (PNS) of several species. The protein composition of these preparations was examined by discontinuous polyacrylamide gel electrophoresis in buffers containing sodium lauryl sulphate. Proteins characteristic of all samples include, in order of increasing mobility: a series of high molecular weight proteins, the major peripheral nerve protein (P₀), two uncharacterized proteins, and two basic proteins (P₁ and P₂). Quantitative results, obtained by densitometry of gels stained with Fast Green showed differences in protein distribution, both between species, and from different types of nerves obtained from the same animal. The relative amounts of P₁ and P₂ proteins were the most variable; e.g. myelin from guinea-pig sciatic nerve had little or no P₂ protein, whereas 15 per cent of the myelin protein of beef posterior intradural root was Pz protein. P₀, P₁ and P₂ proteins from rabbit sciatic nerve and P₀ and P₂ proteins from beef dorsal and ventral intradural roots were purified and their amino acid compositions were determined. Our results indicated that the P₁ protein is very similar in size and amino acid composition to the basic protein of central nervous system myelin, whereas the P₀ and P₂ proteins are unique to the PNS.