Laboratório de Bioquímica e Biofísica, Instituto Butantan, São Paulo, Brasil.
Antioxid Redox Signal. 2012 Jun 1;16(11):1183-94. doi: 10.1089/ars.2011.4210. Epub 2012 Mar 6.
The proteasome is the primary contributor in intracellular proteolysis. Oxidized or unstructured proteins can be degraded via a ubiquitin- and ATP-independent process by the free 20S proteasome (20SPT). The mechanism by which these proteins enter the catalytic chamber is not understood thus far, although the 20SPT gating conformation is considered to be an important barrier to allowing proteins free entrance. We have previously shown that S-glutathiolation of the 20SPT is a post-translational modification affecting the proteasomal activities.
The goal of this work was to investigate the mechanism that regulates 20SPT activity, which includes the identification of the Cys residues prone to S-glutathiolation.
Modulation of 20SPT activity by proteasome gating is at least partially due to the S-glutathiolation of specific Cys residues. The gate was open when the 20SPT was S-glutathiolated, whereas following treatment with high concentrations of dithiothreitol, the gate was closed. S-glutathiolated 20SPT was more effective at degrading both oxidized and partially unfolded proteins than its reduced form. Only 2 out of 28 Cys were observed to be S-glutathiolated in the proteasomal α5 subunit of yeast cells grown to the stationary phase in glucose-containing medium.
We demonstrate a redox post-translational regulatory mechanism controlling 20SPT activity.
S-glutathiolation is a post-translational modification that triggers gate opening and thereby activates the proteolytic activities of free 20SPT. This process appears to be an important regulatory mechanism to intensify the removal of oxidized or unstructured proteins in stressful situations by a process independent of ubiquitination and ATP consumption. Antioxid. Redox Signal. 16, 1183-1194.
蛋白酶体是细胞内蛋白水解的主要贡献者。氧化或无结构的蛋白质可以通过无泛素和 ATP 依赖过程被游离的 20S 蛋白酶体（20SPT）降解。这些蛋白质进入催化腔的机制目前尚不清楚，尽管 20SPT 门控构象被认为是阻止蛋白质自由进入的重要障碍。我们之前已经表明，20SPT 的 S-谷胱甘肽化是一种影响蛋白酶体活性的翻译后修饰。
这项工作的目的是研究调节 20SPT 活性的机制，包括鉴定易发生 S-谷胱甘肽化的 Cys 残基。
蛋白酶体门控对 20SPT 活性的调节至少部分是由于特定 Cys 残基的 S-谷胱甘肽化。当 20SPT 发生 S-谷胱甘肽化时，门是打开的，而在用高浓度二硫苏糖醇处理后，门是关闭的。与还原形式相比，S-谷胱甘肽化的 20SPT 更有效地降解氧化和部分展开的蛋白质。在含有葡萄糖的培养基中生长至静止期的酵母细胞的蛋白酶体 α5 亚基中，只有 28 个 Cys 中的 2 个被观察到发生 S-谷胱甘肽化。
我们展示了一种控制 20SPT 活性的氧化还原后翻译调节机制。
S-谷胱甘肽化是一种翻译后修饰，它触发门的打开，从而激活游离 20SPT 的蛋白水解活性。这一过程似乎是一种重要的调节机制，可以在应激情况下通过一个独立于泛素化和 ATP 消耗的过程来加强对氧化或无结构蛋白质的清除。抗氧化。氧化还原信号。16,1183-1194。
