Maximal expression of membrane-bound nitrate reductase in Paracoccus is induced by nitrate via a third FNR-like regulator named NarR
Maximal expression of membrane-bound nitrate reductase in Paracoccus is induced by nitrate via a third FNR-like regulator named NarR
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DOI：
10.1128/jb.183.12.3606-3613.2001
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发表时间：
2001-06-01
影响因子：
3.2
通讯作者：
Moir, JW
中科院分区：
文献类型：
--
作者：
Wood, NJ;Alizadeh, T;Moir, JW
呼吸还原硝酸盐为亚硝酸盐是导致硝酸盐从土壤中流失的反硝化过程中的第一个关键步骤。在泛食副金枪鱼中，催化这一反应的酶系统由narKGHJI基因簇编码。在有硝酸盐存在的厌氧条件下，该簇的表达最高。Nark的上游是narr，这是一种编码FNR转录激活因子家族成员的基因。NARR的转录与其他划桨基因不同。突变分析表明，NARR是膜结合硝酸还原酶基因最高表达所必需的，而NARK没有与反硝化相关的其他调节功能，NARR被证明需要硝酸盐和/或亚硝酸盐来激活基因表达。该蛋白的N-末端区域缺乏半胱氨酸残基，而半胱氨酸残基是在FNR家族的其他一些成员中形成氧敏感的铁-硫簇所必需的。此外，NarR缺乏参与该家族与RNA聚合酶的sigma(70)亚单位相互作用的关键残基，表明使用了不同的机制来促进转录。在脱氮副球藻中也发现了NARR，这表明本种至少包含三个FNR同源物。
Respiratory reduction of nitrate to nitrite is the first key step in the denitrification process that leads to nitrate loss from soils. In Paracoccus pantohophus, the enzyme system that catalyzes this reaction is encoded by the narKGHJI gene cluster. Expression of this cluster is maximal under anaerobic conditions in the presence of nitrate. Upstream from narK is narR, a gene encoding a member of the FNR family of transcriptional activators. narR is transcribed divergently from the other oar genes. Mutational analysis reveals that NarR is required for maximal expression of the membrane-bound nitrate reductase genes and narK but has no other regulatory function related to denitrification, NarR is shown to require nitrate and/or nitrite is order to activate gene expression. The N-terminal region of the protein lacks the cysteine residues that are required for formation of an oxygen-sensitive iron-sulfur cluster in some other members of the FNR family. Also, NarR lacks a crucial residue involved in interactions of this family of regulators with the sigma (70) subunit of RNA polymerase, indicating that a different mechanism is used to promote transcription. narR is also found in Paracoccus denitrificans, indicating that this species contains at least three FNR homologues.