Trotter Eleanor W, Grant Chris M
The Faculty of Life Sciences, The University of Manchester, Manchester M60 1QD, United Kingdom.
Eukaryot Cell. 2005 Feb;4(2):392-400. doi: 10.1128/EC.4.2.392-400.2005.
Thioredoxins are small, highly conserved oxidoreductases which are required to maintain the redox homeostasis of the cell. Saccharomyces cerevisiae contains a cytoplasmic thioredoxin system (TRX1, TRX2, and TRR1) as well as a complete mitochondrial thioredoxin system, comprising a thioredoxin (TRX3) and a thioredoxin reductase (TRR2). In the present study we have analyzed the functional overlap between the two systems. By constructing mutant strains with deletions of both the mitochondrial and cytoplasmic systems (trr1 trr2 and trx1 trx2 trx3), we show that cells can survive in the absence of both systems. Analysis of the redox state of the cytoplasmic thioredoxins reveals that they are maintained independently of the mitochondrial system. Similarly, analysis of the redox state of Trx3 reveals that it is maintained in the reduced form in wild-type cells and in mutants lacking components of the cytoplasmic thioredoxin system (trx1 trx2 or trr1). Surprisingly, the redox state of Trx3 is also unaffected by the loss of the mitochondrial thioredoxin reductase (trr2) and is largely maintained in the reduced form unless cells are exposed to an oxidative stress. Since glutathione reductase (Glr1) has been shown to colocalize to the cytoplasm and mitochondria, we examined whether loss of GLR1 influences the redox state of Trx3. During normal growth conditions, deletion of TRR2 and GLR1 was found to result in partial oxidation of Trx3, indicating that both Trr2 and Glr1 are required to maintain the redox state of Trx3. The oxidation of Trx3 in this double mutant is even more pronounced during oxidative stress or respiratory growth conditions. Taken together, these data indicate that Glr1 and Trr2 have an overlapping function in the mitochondria.
硫氧还蛋白是一类小型的、高度保守的氧化还原酶，对于维持细胞的氧化还原稳态至关重要。酿酒酵母含有一个细胞质硫氧还蛋白系统（TRX1、TRX2和TRR1）以及一个完整的线粒体硫氧还蛋白系统，该系统由一个硫氧还蛋白（TRX3）和一个硫氧还蛋白还原酶（TRR2）组成。在本研究中，我们分析了这两个系统之间的功能重叠情况。通过构建线粒体和细胞质系统均缺失的突变菌株（trr1 trr2和trx1 trx2 trx3），我们发现细胞在两个系统均缺失的情况下仍能存活。对细胞质硫氧还蛋白氧化还原状态的分析表明，它们的维持独立于线粒体系统。同样，对Trx3氧化还原状态的分析表明，在野生型细胞以及缺乏细胞质硫氧还蛋白系统组分（trx1 trx2或trr1）的突变体中，Trx3以还原形式存在。令人惊讶的是，Trx3的氧化还原状态也不受线粒体硫氧还蛋白还原酶缺失（trr2）的影响，并且除非细胞受到氧化应激，否则Trx3在很大程度上保持还原形式。由于谷胱甘肽还原酶（Glr1）已被证明定位于细胞质和线粒体，我们研究了GLR1的缺失是否会影响Trx3的氧化还原状态。在正常生长条件下，发现TRR2和GLR1的缺失会导致Trx3部分氧化，表明Trr2和Glr1对于维持Trx3的氧化还原状态均是必需 的。在氧化应激或呼吸生长条件下，该双突变体中Trx3的氧化更为明显。综上所述，这些数据表明Glr1和Trr2在线粒体中具有重叠功能。
