The intrachain disulfide bond of beta(2)-microglobulin is not essential for the immunoglobulin fold at neutral pH, but is essential for amyloid fibril formation at acidic pH.
The intrachain disulfide bond of beta(2)-microglobulin is not essential for the immunoglobulin fold at neutral pH, but is essential for amyloid fibril formation at acidic pH.
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β(2)-微球蛋白的链内二硫键对于中性 pH 下的免疫球蛋白折叠不是必需的，但对于酸性 pH 下淀粉样原纤维的形成是必需的。
DOI：
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发表时间：
2002
期刊：
影响因子：
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通讯作者：
Y. Goto
中科院分区：
文献类型：
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作者：
Y. Ohhashi;Y. Hagihara;G. Kozhukh;M. Hoshino;K. Hasegawa;I. Yamaguchi;H. Naiki;Y. Goto
β(2)-微球蛋白 (beta2M) 是 I 型主要组织相容性复合物的轻链，是透析相关淀粉样原纤维的主要成分。天然状态下的 beta2M 具有典型的免疫球蛋白折叠，带有隐藏的链内二硫键。通过环糊精、色氨酸荧光和一维核磁共振研究了链内二硫键还原的重组β2M的构象和稳定性。在没有变性剂的情况下，在 pH 8.5 下，还原的 beta2M 的构象与完整蛋白质的构象相似，除非硫醇基团被修饰。然而，通过盐酸胍的变性测量，二硫键的还原降低了稳定性。使用超声处理的淀粉样蛋白原纤维作为种子，通过延伸反应，完整的 beta2M 在 pH 2.5 下形成淀粉样蛋白原纤维。在相同条件下，还原的β2M不会形成典型的淀粉样原纤维，尽管它竞争性地抑制原纤维延伸，这表明二硫键定义的构象对于β2M的淀粉样原纤维形成很重要。
beta(2)-Microglobulin (beta2M), the light chain of the type I major histocompatibility complex, is a major component of dialysis-related amyloid fibrils. beta2M in the native state has a typical immunoglobulin fold with a buried intrachain disulfide bond. The conformation and stability of recombinant beta2M in which the intrachain disulfide bond was reduced were studied by CD, tryptophan fluorescence, and one-dimensional NMR. The conformation of the reduced beta2M in the absence of denaturant at pH 8.5 was similar to that of the intact protein unless the thiol groups were modified. However, reduction of the disulfide bond decreased the stability as measured by denaturation in guanidine hydrochloride. Intact beta2M formed amyloid fibrils at pH 2.5 by extension reaction using sonicated amyloid fibrils as seeds. Under the same conditions, reduced beta2M did not form typical amyloid fibrils, although it inhibited fibril extension competitively, suggesting that the conformation defined by the disulfide bond is important for amyloid fibril formation of beta2M.