Binding of protein SCP to myelin, its identity with protein P2. A simple method of protein P2 isolation

Protein SCP is found in myelin of spinal cord and spinal roots. It is shown that its amount accounts for 12% of the total protein content in myelin of spinal roots and only for 2% in myelin of spinal cord. Almost all the studied protein is extracted from myelin with 0.1 M NaCl (80-90%). The absolute identity of protens SCP and P2 is established using the cross reaction immunodiffusion with monospecific antisera. It is shown that- N-terminal amino acid in protein SCP, like in protein P2 is blocked. On the basis of the data obtained a conclusion is made that protein P2 is not an integral protein of myelin. However, myelin is capable under conditions of a nonionic medium of binding protein which then may be easily extracted by increasing the medium ionic strength. This gave reasons to propose a method for protein P2 isolation from myelin using 0.15 M NaCl with the subsequent purification by means of Sephadex G-50 gelfiltration.