The L-Cysteine/L-Cystine Shuttle System Provides Reducing Equivalents to the Periplasm in Escherichia coli
The L-Cysteine/L-Cystine Shuttle System Provides Reducing Equivalents to the Periplasm in Escherichia coli
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DOI：
10.1074/jbc.m109.081356
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发表时间：
2010-06-04
影响因子：
4.8
通讯作者：
Takagi, Hiroshi
中科院分区：
文献类型：
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作者：
Ohtsu, Iwao;Wiriyathanawudhiwong, Natthawut;Takagi, Hiroshi
细胞内的硫醇，如L-半胱氨酸和谷胱甘肽，在细胞过程的调节中起着关键作用。大肠杆菌有多个L-半胱氨酸转运体，它们将L-半胱氨酸从细胞质输出到周质中。然而，L-半胱氨酸在周质中的作用仍不清楚。在这里，我们证明了L-半胱氨酸转运体YdeD是大肠杆菌细胞对过氧化氢耐受所必需的。我们还提供了证据表明，L-半胱氨酸是L-半胱氨酸被过氧化氢氧化的产物，通过依赖于胞质周膜上的L-半胱氨酸结合蛋白FliY的方式被重新输入细胞质。值得注意的是，这种参与氧化的L半胱氨酸循环的蛋白质，也被发现对这种有机体的过氧化氢抗性很重要。此外，我们对相关基因转录的分析表明，编码FliY和YdeD的基因的转录高度受过氧化氢的诱导，而不是由L-半胱氨酸诱导。这些发现导致我们提出，可诱导的L-半胱氨酸/L-半胱氨酸穿梭系统通过在大肠杆菌中提供与周质相同的还原等价物，在氧化应激耐受中发挥重要作用。
Intracellular thiols like L-cysteine and glutathione play a critical role in the regulation of cellular processes. Escherichia coli has multiple L-cysteine transporters, which export L-cysteine from the cytoplasm into the periplasm. However, the role of L-cysteine in the periplasm remains unknown. Here we show that an L-cysteine transporter, YdeD, is required for the tolerance of E. coli cells to hydrogen peroxide. We also present evidence that L-cystine, a product from the oxidation of L-cysteine by hydrogen peroxide, is imported back into the cytoplasm in a manner dependent on FliY, the periplasmic L-cystine-binding protein. Remarkably, this protein, which is involved in the recycling of the oxidized L-cysteine, is also found to be important for the hydrogen peroxide resistance of this organism. Furthermore, our analysis of the transcription of relevant genes revealed that the transcription of genes encoding FliY and YdeD is highly induced by hydrogen peroxide rather than by L-cysteine. These findings led us to propose that the inducible L-cysteine/L-cystine shuttle system plays an important role in oxidative stress tolerance through providing a reducing equivalent to the periplasm in E. coli.