The signal transduction protein GlnK is required for NifL-dependent nitrogen control of nif gene expression in Klebsiella pneumoniae
The signal transduction protein GlnK is required for NifL-dependent nitrogen control of nif gene expression in Klebsiella pneumoniae
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DOI：
10.1128/jb.181.4.1156-1162.1999
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发表时间：
1999-02-01
影响因子：
3.2
通讯作者：
Merrick, M
中科院分区：
文献类型：
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作者：
Jack, R;De Zamaroczy, M;Merrick, M
在肺炎克雷伯菌中，固氮（nif）基因的转录通过nifA和nifA基因产物的协调活动来调节，以响应分子氧或固定氮的可用性。NifA是一种nif特异性转录激活因子，其活性可通过与NifL的相互作用而被抑制。NifL的氮控制发生在两个层面：nifLA操纵子的转录受全局ntr系统的调控，NifL的抑制活性受未知因素对固定氮的响应控制。肺炎克雷伯菌合成两种p - ii样信号转导蛋白，GlnB，我们之前已经证明不参与NifL对固定氮的反应，以及最近鉴定的蛋白GlnK，我们现在克隆了肺炎克雷伯菌GlnK基因，研究了其表达，并表明GlnK的零突变阻止NifL对缺乏固定氮的反应，即减轻对NifA活性的抑制。因此，GlnK似乎直接或间接地参与了肺炎克雷伯菌中nif基因表达的nif依赖调控。比较6种变形菌的GlnB和GlnK氨基酸序列，鉴定出5个残基（残基3、5、52、54和64），用于区分GlnB和GlnK蛋白。
In Klebsiella pneumoniae, transcription of the nitrogen fixation (nif) genes is regulated in response to molecular oxygen or availability of fixed nitrogen by the coordinated activities of the nifA and nifA gene products. NifA is a nif-specific transcriptional activator, the activity of which is inhibited by intellection with NifL,. Nitrogen control of NifL occurs at two levels: transcription of the nifLA operon is regulated by the global ntr system, and the inhibitory activity of NifL is controlled in response to fixed nitrogen by an unknown factor. K. pneumoniae synthesizes two P-II-like signal transduction proteins, GlnB, which we have previously shown not to be involved in the response of NifL to fixed nitrogen, and the recently identified protein GlnK, We have now cloned the K. pneumoniae glnK gene, studied its expression, and shown that a null mutation in glnK prevents NifL from responding to the absence of fixed nitrogen, i.e., from relieving the inhibition of NifA activity. Hence, GlnK appears to be involved, directly or indirectly, in NifL-dependent regulation of nif gene expression in K. pneumoniae. Comparison of the GlnB and GlnK amino acid sequences from six species of proteobacteria identifies five residues (residues 3, 5, 52, 54, and 64) which serve to distinguish the GlnB and GlnK proteins.