Allergic encephalomyelitis. Oxidation and cleavage of the single tryptophan residue of the A1 protein from bovine and human myelin.
Allergic encephalomyelitis. Oxidation and cleavage of the single tryptophan residue of the A1 protein from bovine and human myelin.
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过敏性脑脊髓炎。
DOI：
10.1016/s0021-9258(18)62241-0
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发表时间：
1971
期刊：
影响因子：
--
通讯作者：
E. Eylar
中科院分区：
文献类型：
--
作者：
P. Burnett;E. Eylar
用温和的氧化剂BNPS-skatole选择性地将牛和人中枢神经系统髓鞘碱性A1蛋白的单一色氨酸残基修饰成氧吲哚衍生物。用几种方法对色氨酸残基进行了定量氧化。在还原之后，似乎没有其他残基被修改。氧化后的A1蛋白表现出与未经修饰的A1蛋白相同的致脑活性、抗原特异性和迟发性皮肤反应性，这表明吲哚环的第2位对于诱发豚鼠实验性变态反应性脑脊髓炎并不是关键的。在更强的条件下，BNPS-skatole裂解了羧基-色氨酸键，以38%的产率得到了两个肽(L和T)。虽然L和T是相对无脑性的(A1蛋白的1%~2%)，但在被动血凝抑制试验中，L与羊的A1蛋白抗体保持了几乎完全的反应活性。肽T是A1蛋白的54个残基的COOH末端片段，被认为是无反应的。结论：A1分子中含有体液抗体抗原决定簇的部分，即NH2末端的116个残基，与主要的脑源性部位(9个色氨酸残基)是不同的。非致脑剂量的L和T均能诱导致敏细胞的形成，豚鼠迟发型皮肤试验呈阳性反应。因此，似乎对A1蛋白某些肽段的脑源性和迟发性超敏反应之间没有严格的相关性。
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.