Transcriptional regulation of nitrogen fixation by molybdenum in Azotobacter vinelandii
Transcriptional regulation of nitrogen fixation by molybdenum in Azotobacter vinelandii
复制标题
维氏固氮菌中钼固氮的转录调控
作者：
M. Jacobson;R. Premakumar;P. Bishop
在重氮菌棕色固氮菌中发现了与nifH同源的多个基因组区域。NifHDK基因簇位于12.8kb的XhoI片段和另外两个XhoI片段(7.4和8.4kb)上，与nifH特异的DNA模板杂交，但7.4和8.4kb的片段不与nifD或nifK特异的DNA探针杂交。在体内，nifHDK基因簇的转录是氨抗性的，需要去阻抑介质中至少50 nM的钼存在。从nifHDK基因簇转录出三种mRNA，一个4.2kb的转录本与nifH、nifD和nifK特异的DNA模板同源，一个2.6kb的转录本与nifH和nifD特异的DNA模板同源，以及一个1.2kb的转录本仅与nifH特异的DNA模板同源。在nifHDK缺失突变体CA11中，没有产生nifHDK特异的转录本，该菌株不能在无N的Na2MoO4浓度为50 nM或更高的条件下生长。然而，当钼浓度在25 nM或更低时，在无氮条件下才能生长。在此条件下，观察到两个nifH同源(但不是nifD或nifK同源)转录本(1.2和1.8kb)。推测这些基因是从基因组中存在的额外的nifH-同源序列转录而来的。这些结果与棕色拟青霉中存在两个受钼在转录水平上调控的氮固定系统相一致。
Multiple genomic regions homologous to nifH were found in the diazotroph Azotobacter vinelandii. The nifHDK gene cluster, located on a 12.8-kilobase (kb) XhoI fragment and two additional XhoI fragments (7.4 and 8.4 kb) hybridized to a nifH-specific DNA template but the 7.4- and 8.4-kb fragments did not hybridize to nifD- or nifK-specific DNA probes. In vivo transcription of the nifHDK gene cluster was ammonia-repressible and required the presence of at least 50 nM molybdenum in the derepression medium. Three mRNA species were transcribed from the nifHDK gene cluster, a 4.2-kb transcript homologous to nifH-, nifD-, and nifK-specific DNA templates, a 2.6-kb transcript homologous to nifH- and nifD-specific DNA templates, and a 1.2-kb transcript homologous only to the nifH-specific DNA template. In strain CA11, a nifHDK deletion mutant, the nifHDK-specific transcripts were not produced and the strain was unable to grow in N-free medium in the presence of Na2MoO4 at concentrations of 50 nM or higher. However, at concentrations of 25 nM Mo or less, growth occurred in N-free medium. Under these conditions two nifH-homologous (but not nifD- or nifK-homologous) transcripts were observed (1.2 and 1.8 kb). Presumably these were transcribed from the additional nifH-homologous sequences present in the genome. These results are consistent with the existence of two N2 fixation systems in A. vinelandii which are regulated by molybdenum at the level of transcription.
蓝藻鱼腥藻 7120 固氮基因的分离和物理作图。
DOI：
--
发表时间：
1982
期刊：
The Journal of biological chemistry
影响因子：
--
作者：
Rice,D;Mazur,BJ;Haselkorn,R
通讯作者：
Haselkorn,R
无需使用 RNase，即可快速、简单地去除质粒 DNA 中的污染 RNA。
影响因子：
2.9
作者：
Norgard,MV
通讯作者：
Norgard,MV