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首页> 外文期刊>Journal of bacteriology >Role of the Tat Transport System in Nitrous Oxide Reductase Translocation and Cytochrome cd 1 Biosynthesis inPseudomonas stutzeri
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Role of the Tat Transport System in Nitrous Oxide Reductase Translocation and Cytochrome cd 1 Biosynthesis inPseudomonas stutzeri

机译:Tat转运系统在斯氏假单胞菌中一氧化二氮还原酶易位和细胞色素cd 1生物合成中的作用

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By transforming N2O to N2, the multicopper enzyme nitrous oxide reductase provides a periplasmic electron sink for a respiratory chain that is part of denitrification. The signal sequence of the enzyme carries the heptameric twin-arginine consensus motif characteristic of the Tat pathway. We have identifiedtat genes of Pseudomonas stutzeri and functionally analyzed the unlinked tatC andtatE loci. A tatC mutant retained N2O reductase in the cytoplasm in the unprocessed form and lacking the metal cofactors. This is contrary to viewing the Tat system as specific only for fully assembled proteins. A C618V exchange in the electron transfer center CuA rendered the enzyme largely incompetent for transport. The location of the mutation in the C-terminal domain of N2O reductase implies that the Tat system acts on a completely synthesized protein and is sensitive to a late structural variation in folding. By generating a tatEmutant and a reductase-overproducing strain, we show a function for TatE in N2O reductase translocation. Further, we have found that the Tat and Sec pathways have to cooperate to produce a functional nitrite reductase system. The cytochrome cd 1nitrite reductase was found in the periplasm of thetatC mutant, suggesting export by the Sec pathway; however, the enzyme lacked the heme D1 macrocycle. The NirD protein as part of a complex required for heme D1 synthesis or processing carries a putative Tat signal peptide. Since NO reduction was also inhibited in the tatC mutant, the Tat protein translocation system is necessary in multiple ways for establishing anaerobic nitrite denitrification.
机译:通过将N 2 O转换为N 2 ,多铜酶一氧化二氮还原酶为呼吸链提供了周质电子吸收体,这是反硝化的一部分。该酶的信号序列带有Tat途径的七聚体双精氨酸共有基序。我们已经鉴定了斯图氏假单胞菌的 tat 基因,并在功能上分析了未连接的 tatC tatE 基因座。 tatC 突变体在细胞质中保留了未加工形式的N 2 O还原酶,并且缺乏金属辅因子。这与将Tat系统视为仅对完全组装的蛋白质具有特异性是相反的。电子转移中心Cu A 中的C618V交换使得该酶在运输中非常不称职。突变在N 2 O还原酶C末端结构域中的位置表明Tat系统作用于完全合成的蛋白质,并且对后期折叠中的结构变异敏感。通过生成一个 tatE 突变体和一个还原酶高产菌株,我们展示了TatE在N 2 O还原酶易位中的功能。此外,我们发现,Tat和Sec途径必须协同产生功能性亚硝酸还原酶系统。在 tatC 突变体的周质中发现了细胞色素 cd 1 亚硝酸盐还原酶,表明通过Sec途径输出。然而,该酶缺乏血红素D 1 大环。 NirD蛋白是血红素D 1 合成或加工所需复合物的一部分,带有一个假定的Tat信号肽。由于NO的还原也被抑制在 tatC 突变体中,因此Tat蛋白易位系统对于建立厌氧亚硝酸盐反硝化作用有多种作用。

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