THE ISOLATION AND CHARACTERIZATION OF AN ACID-SOLUBLE PROTEIN FROM MYELIN

Abstract

Myelin was isolated from central white matter of beef and human brains. It contained less than 0.1% ribonucleic acid, less than 0.03% deoxyribonucleic acid, and no glycolipid N-acetylneurammic acid. The preparation was 96% soluble in chloroform–methanol. Most of the insoluble material was sucrose. The myelin contained 19.6% protein, 17.4% cholesterol, 36.1% phospholipid, and 23.6% galactolipid. A protein extracted from the myelin preparation with cold 0.2 N sulfuric acid gave a single sedimenting boundary in the Spinco model E analytical ultracentrifuge. In 8 M urea–formate starch gels (pH 3.4) it migrated as a single band toward the cathode. Amino acid analysis revealed that the protein contained more than 20% dibasic amino acids, but little methionine and no cystine. It was rapidly hydrolyzed by trypsin. The molecular weight was estimated at 10,000. When injected intradermally into guinea pigs, in suspension in Freund's adjuvant, it caused weight loss, a flaccid paralysis, occasional convulsions, and death, a pattern characteristic of experimental allergic encephalomyelitis. Evidence is cited for the presence of at least one other protein in purified myelin.