Sakurai Yasuyuki, Anzai Itsuki, Furukawa Yoshiaki
From the Laboratory for Mechanistic Chemistry of Biomolecules, Department of Chemistry, Keio University, Yokohama, Kanagawa 223-8522 Japan.
From the Laboratory for Mechanistic Chemistry of Biomolecules, Department of Chemistry, Keio University, Yokohama, Kanagawa 223-8522 Japan
J Biol Chem. 2014 Jul 18;289(29):20139-49. doi: 10.1074/jbc.M114.567677. Epub 2014 Jun 10.
Enzymatic activation of Cu,Zn-superoxide dismutase (SOD1) requires not only binding of a catalytic copper ion but also formation of an intramolecular disulfide bond. Indeed, the disulfide bond is completely conserved among all species possessing SOD1; however, it remains obscure how disulfide formation controls the enzymatic activity of SOD1. Here, we show that disulfide formation is a primary event in the folding process of prokaryotic SOD1 (SodC) localized to the periplasmic space. Escherichia coli SodC was found to attain β-sheet structure upon formation of the disulfide bond, whereas disulfide-reduced SodC assumed little secondary structure even in the presence of copper and zinc ions. Moreover, reduction of the disulfide bond made SodC highly susceptible to proteolytic degradation. We thus propose that the thiol-disulfide status in SodC controls the intracellular stability of this antioxidant enzyme and that the oxidizing environment of the periplasm is required for the enzymatic activation of SodC.
铜锌超氧化物歧化酶（SOD1）的酶促活化不仅需要催化铜离子的结合，还需要分子内二硫键的形成。事实上，在所有拥有SOD1的物种中，二硫键都是完全保守的；然而，二硫键的形成如何控制SOD1的酶活性仍不清楚。在这里，我们表明二硫键的形成是定位于周质空间的原核SOD1（SodC）折叠过程中的一个主要事件。发现大肠杆菌SodC在形成二硫键后获得β-折叠结构，而二硫键还原的SodC即使在存在铜离子和锌离子的情况下也几乎没有二级结构。此外，二硫键的还原使SodC极易受到蛋白水解降解。因此，我们提出SodC中的硫醇-二硫键状态控制着这种抗氧化酶的细胞内稳定性，并且周质的氧化环境是SodC酶促活化所必需的。
