Hayano T, Inaka K, Otsu M, Taniyama Y, Miki K, Matsushima M, Kikuchi M
Protein Engineering Research Institute, Osaka, Japan.
FEBS Lett. 1993 Aug 9;328(1-2):203-8. doi: 10.1016/0014-5793(93)80993-5.
A mutant human lysozyme, designated as C77A-a, in which glutathione is bound to Cys95, has been shown to mimic an intermediate in the formation of a disulfide bond during folding of human (h)-lysozyme. Protein disulfide isomerase (PDI), which is believed to catalyze disulfide bond formation and associated protein folding in the endoplasmic reticulum, attacked the glutathionylated h-lysozyme C77A-a to dissociate the glutathione molecule. Structural analyses showed that the protein is folded and that the structure around the disulfide bond, buried in a hydrophobic core, between the protein and the bound glutathione is fairly rigid. Thioredoxin, which has higher reducing activity of protein disulfides than PDI, catalyzed the reduction with lower efficiency. These results strongly suggest that PDI can catalyze the disulfide formation in intermediates with compact structure like the native states in the later step of in vivo protein folding.
一种名为C77A-a的突变型人溶菌酶，其中谷胱甘肽与半胱氨酸95结合，已被证明在人（h）-溶菌酶折叠过程中模拟二硫键形成的中间体。蛋白质二硫键异构酶（PDI）被认为在内质网中催化二硫键形成及相关的蛋白质折叠，它攻击谷胱甘肽化的h-溶菌酶C77A-a以解离谷胱甘肽分子。结构分析表明该蛋白质已折叠，并且位于蛋白质与结合的谷胱甘肽之间、埋于疏水核心中的二硫键周围结构相当刚性。硫氧还蛋白对蛋白质二硫键的还原活性高于PDI，但其催化还原的效率较低。这些结果有力地表明，PDI能够在体内蛋白质折叠后期，催化具有紧凑结构（如天然状态）的中间体中的二硫键形成。
