Laboissiere M C, Sturley S L, Raines R T
Department of Biochemistry, University of Wisconsin, Madison 53706-1569, USA.
J Biol Chem. 1995 Nov 24;270(47):28006-9. doi: 10.1074/jbc.270.47.28006.
Protein-disulfide isomerase (PDI) is an abundant protein of the endoplasmic reticulum that catalyzes dithiol oxidation and disulfide bond reduction and isomerization using the active site CGHC. Haploid pdi1 delta Saccharomyces cerevisiae are inviable, but can be complemented with either a wild-type rat PDI gene or a mutant gene coding for CGHS PDI (shufflease). In contrast, pdi1 delta yeast cannot be complemented with a gene coding for SGHC PDI. In vitro, shufflease is an efficient catalyst for the isomerization of existing disulfide bonds but not for dithiol oxidation or disulfide bond reduction. SGHC PDI catalyzes none of these processes. These results indicate that in vivo protein folding pathways contain intermediates with non-native disulfide bonds, and that the essential role of PDI is to unscramble these intermediates.
蛋白质二硫键异构酶（PDI）是内质网中一种丰富的蛋白质，它利用活性位点CGHC催化二硫醇氧化、二硫键还原和异构化。单倍体pdi1δ酿酒酵母无法存活，但可以用野生型大鼠PDI基因或编码CGHS PDI（shufflease）的突变基因进行互补。相比之下，pdi1δ酵母不能用编码SGHC PDI的基因进行互补。在体外，shufflease是现有二硫键异构化的有效催化剂，但不是二硫醇氧化或二硫键还原的有效催化剂。SGHC PDI不能催化这些过程中的任何一个。这些结果表明，体内蛋白质折叠途径包含具有非天然二硫键的中间体，并且PDI的重要作用是解开这些中间体。
