Abstract
A highly immunogenic spinal cord protein (SCP) has been extracted from bovine spinal cord (BSC) with 0.1 M sodium chloride. Immunodiffusion analyses of the subcellular fractions of BSC homogenates separated by differential centrifugation revealed that the antigen was located in the soluble fraction. SCP occurs in bovine peripheral nerve but has not been detected in extracts of other bovine organs and has a regional distribution in the bovine central nervous system (CNS); it composes about 5% of the total protein of extracts of BSC but accounts for only 0.2% of the total protein of extracts of cerebral white matter. SCP is distributed in similar fashion in the CNS of the human, rat and rabbit.
Immunoelectrophoretic analyses revealed that SCP occurred in two molecular forms having the electrophoretic mobilities of a β1 globulin (β1-SCP) and a γ globulin (γ-SCP) respectively. The more basic form of the antigen also existed as a peptide which was separated from the other proteins by filtering BSC extracts through dialysis tubing. Similar amounts of the peptide were obtained when BSC was homogenized and extracted in the presence of cupric ions to inhibit protease activity. About 6% of the total SCP activity was found in the peptide form. The molecular forms of the antigen retained by dialysis tubing, β1-SCP and γ-SCP, were estimated by gel filtration chromatography to have molecular weights of 18,000 and 12,000 respectively. The SCP peptide had a molecular size approaching 5000.
β1-SCP that was purified by batch absorption of bovine cord extracts with DEAE Sephadex A-50 and CM-cellulose chromatography formed one band when analyzed by polyacrylamide gel electrophoresis at pH 8.9. Although β1-SCP is not an acidic protein, the dicarboxylic amino acids, glutamic and aspartic, comprise 20% of the total amino acid content.
Footnotes
This work was supported by grants from the Multiple Sclerosis Society of Canada and the Medical Research Council of Canada. Parts of this work were presented at the meeting of the Federation of American Societies for Experimental Biology, Chicago, Ill., April, 1971, and the American Society for Neurochemistry, Seattle, Wash., March, 1972. This work is from a thesis submitted by Sui-Lan Yo to the Faculty of Graduate Studies and Research of McGill University in Partial fulfillment of the requirements of the degree of Doctor of Philosophy.
