Modifications of transthyretin in amyloid fibrils: analysis of amyloid from homozygous and heterozygous individuals with the Met30 mutation.
Modifications of transthyretin in amyloid fibrils: analysis of amyloid from homozygous and heterozygous individuals with the Met30 mutation.
复制标题
淀粉样原纤维中运甲状腺素蛋白的修饰：对具有 Met30 突变的纯合子和杂合子个体的淀粉样蛋白进行分析。
作者：
C. Thylén;J. Wahlqvist;E. Haettner;O. Sandgren;G. Holmgren;E. Lundgren
在玻璃体中发现FAP I（家族性淀粉样变性多神经病变，转甲状腺素TTRMet30）与淀粉样蛋白沉积纯合的个体，使我们获得了一种缺乏野生型转甲状腺素和污染蛋白的独特物质。淀粉样蛋白TTR可以通过几种方式进行修饰。除了全长蛋白及其二聚体形式外，还通过SDS - PAGE和蛋白测序鉴定了两个较小的条带。其中一个对应于从Thr49氨基酸开始的肽，另一个是以3:1的比例从位置1和3开始的两个肽的混合物。随着TTR二聚体数量的减少，单体数量增加，所得单体可用于羧甲基化。此外，包括Cys10在内的小波段的迁移率随着还原而增加。这种半胱氨酸似乎参与了完整TTR分子之间和小片段之间的链间二硫桥。在杂合纤维材料中发现了相同的模式，尽管发现了较少数量的截断肽。在杂合子中，正常和突变的TTR均可形成原纤维。讨论了我们的结果对淀粉样蛋白形成的意义。
The finding of individuals homozygous for FAP I (familial amyloidotic polyneuropathy, transthyretin TTRMet30) with amyloid deposits in the vitreous body, gave us access to a unique material lacking wild type transthyretin and contaminating proteins. Amyloid TTR is modified in several ways. Besides the full‐length protein and its dimer form, two smaller bands were identified by SDS‐PAGE and protein sequencing. One corresponded to a peptide starting at amino acid Thr49, the other was a mixture of two peptides starting at positions 1 and 3 in a 3:1 ratio. Upon reduction the amount of the TTR dimer decreased, the monomer amount increased, and the resulting monomers became available for carboxymethylation. Moreover, the mobility of the small band, which includes Cys10, increased upon reduction. This cysteine seemed to be involved in an interchain disulfide bridge both between intact TTR molecules and between small fragments. The same pattern was found in heterozygous fibril material although smaller amounts of the truncated peptides were found. Fibrils were formed both from normal and mutated TTR in heterozygotes. The significance of our results for amyloid formation is discussed.