| Popis: |
The single tryptophan residue of the basic A1 protein from bovine and human central nervous system myelin was selectively modified to the oxindole derivative with a mild oxidizing reagent BNPS-skatole, a bromine adduct of 2-(2-nitrophenylsulfenyl)-3-methylindole. Quantitative oxidation of the tryptophan residue was shown by several methods. Following reduction, no other residue appeared to be modified. The oxidized A1 protein showed the same encephalitogenic activity, antigenic specificity, and delayed-type skin reactivity as the unmodified A1 protein, thus demonstrating that position 2 of the indole ring is not critical for induction of experimental allergic encephalomyelitis in guinea pigs. Under stronger conditions, BNPS-skatole cleaved the COOH-tryptophanyl bond, giving two peptides (L and T) in 38% yield. Although Peptides L and T were comparatively nonencephalitogenic (1 to 2% of the A1 protein), Peptide L retained nearly full reactivity against sheep antibody to the A1 protein in the passive hemagglutination inhibition test. Peptide T, the 54-residue COOH-terminal segment of the A1 protein, was considered unreactive. It was concluded that the portion of the A1 molecule which contains the antigenic determinants for humoral antibody, the 116 residues of the NH2-terminal region, is distinct from the major encephalitogenic site (9-residue tryptophan region). Both Peptides L and T, in nonencephalitogenic doses, induce the formation of sensitized cells, as shown by positive reactions in the delayed-type skin test in guinea pigs. It appears, therefore, that no strict correlation exists between the encephalitogenic and delayed hypersensitive responses to certain peptide regions of the A1 protein. |
