Isolation and Characterization of an Active Fragment from Enzymatic Degradation of Encephalitogenic Protein

Abstract

Abstract The encephalitogenic protein isolated from spinal cord was hydrolyzed with an acid proteinase, also of neural origin. The 5-hour digestion mixture had encephalitogenic activity, although no trace of the substrate could be detected by electrophoresis on polyacrylamide gel. The active fragment was isolated from the enzymatic mixture by repeated gel filtration on Sephadex G-75 and by chromatography on carboxymethyl cellulose. It was homogeneous by the criteria of ultracentrifugation, polyacrylamide gel electrophoresis, and end group analyses. Characterization of the active fragment was carried out in comparison with the encephalitogenic protein. This included determination of the amino acid composition, minimum molecular weight, sedimentation, peptide mapping, and amino- and carboxyl-terminal group analyses. It was concluded that the active fragment is a polypeptide with approximately half the molecular size of encephalitogenic protein, derived entirely from the carboxyl terminus of the encephalitogen. It was active at the same level as the parent compound.