The nif gene operon of the methanogenic archaeon Methanococcus maripaludis
The nif gene operon of the methanogenic archaeon Methanococcus maripaludis
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DOI：
10.1128/jb.180.6.1504-1511.1998
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发表时间：
1998-03-01
影响因子：
3.2
通讯作者：
Leigh, JA
中科院分区：
文献类型：
--
作者：
Kessler, PS;Blank, C;Leigh, JA
固氮作用发生在两个领域，微生物和细菌，我们已经确定了一个nif（固氮）基因簇的产甲烷古菌Methanococcus maripaludis。序列分析显示8个基因，6个与已知的nif基因序列相似，2个与glnB序列相似。基因顺序，nifH，ORF 105（类似于glnB），ORF 121（类似于glnB），nifD，nifK，nifE，nifN和nifX，是相同的，部分在其他固氮产甲烷菌中发现的，除了存在的glnB样基因，也类似于在细菌的许多成员中发现的顺序。利用转座子插入突变，我们确定固氮所需的一个8-kb区域对应于nif基因簇，北方分析显示存在单个7.6-kb的nif mRNA转录物或10个较小的mRNA种类，其含有大转录物的部分。转座子插入的极性效应表明，所有这些mRNA都来自单个启动子区域，其中转录起始于nifH 5'的80 bp。nif基因簇的独特特征包括在单个操纵子中存在六个主要的nif基因，两个glnB样基因在簇内的位置，该簇与可能存在于基因组中的任何其他nif基因的明显物理分离、mRNA的片段化模式以及通过先前描述的抑制机制对表达的调节。我们的研究和其他产甲烷古菌报告多个mRNA产生的基因簇，只有一个假定的启动子序列表明，转录后的mRNA加工可能是一个常见的发生在产甲烷菌。
Nitrogen fixation occurs in two domains, Archaea and Bacteria, We have characterized a nif (nitrogen fixation) gene cluster in the methanogenic archaeon Methanococcus maripaludis. Sequence analysis revealed eight genes, six with sequence similarity to known nif genes and two with sequence similarity to glnB. The gene order, nifH, ORF105 (similar to glnB), ORF121 (similar to glnB), nifD, nifK, nifE, nifN, and nifX, was the same as that found in part in other diazotrophic methanogens and except for the presence of the glnB-like genes, also resembled the order found in many members of the Bacteria. Using transposon insertion mutagenesis, we determined that an 8-kb region required for nitrogen fixation corresponded to the nif gene cluster, Northern analysis revealed the presence of either a single 7.6-kb nif mRNA transcript or 10 smaller mRNA species containing portions of the large transcript. Polar effects of transposon insertions demonstrated that all of these mRNAs arose from a single promoter region, where transcription initiated 80 hp 5' to nifH, Distinctive features of the nif gene cluster include the presence of the six primary nif genes in a single operon, the placement of the two glnB-like genes within the cluster, the apparent physical separation of the cluster from any other nif genes that might he in the genome, the fragmentation pattern of the mRNA, and the regulation of expression by a repression mechanism described previously. Our study and others with methanogenic archaea reporting multiple mRNAs arising from gene clusters with only a single putative promoter sequence suggest that mRNA processing following transcription may be a common occurrence in methanogens.