A novel NO-responding regulator controls the reduction of nitric oxide in Ralstonia eutropha
A novel NO-responding regulator controls the reduction of nitric oxide in Ralstonia eutropha
复制标题
DOI：
10.1046/j.1365-2958.2000.02157.x
复制
发表时间：
2000-11-01
影响因子：
3.6
通讯作者：
Friedrich, B
中科院分区：
文献类型：
--
作者：
Pohlmann, A;Cramm, R;Friedrich, B
富营养化Ralstonia eutropha H16通过两种功能相同的单组分膜结合NO还原酶（NorB1和NorB2）介导一氧化氮（NO）还原为一氧化二氮（N2O）。该反应被整合到反硝化途径中，该途径涉及将硝酸盐连续还原为二氮。norB1基因通过位于norA1上游的sigma (54) （RpoN）依赖启动子与norA1共转录。借助norA1'-lacZ转录融合和调控突变体的产生，研究人员发现，norB1基因的转录需要一个功能性rpoN基因和调控因子NorR， NorR是NtrC应答调控因子家族的新成员。调节基因与norAB相邻，是发散转录的，存在于大质粒pHG1 （norR1）和染色体（norR2）上的两个拷贝。NorR的转录激活响应NO的可用性。一个亚硝酸盐还原酶缺陷突变体不能内源性产生NO，其norA1表达减少70%。硝普钠的加入诱导了norA1'-lacZ的转录。NorR1 n端受体结构域的截断中断了NO信号转导，导致norA1'-lacZ的本构性表达。结果表明，NorR控制着真菌素中NO的还原转化。在监管层面上，该反应与脱硝链中独立于NorR的其他氮氧化物还原步骤没有严格协调。
Ralstonia eutropha H16 mediates the reduction of nitric oxide (NO) to nitrous oxide (N2O) with two isofunctional single component membrane-bound NO reductases (NorB1 and NorB2). This reaction is integrated into the denitrification pathway that involves the successive reduction of nitrate to dinitrogen. The norB1 gene is co-transcribed with norA1 from a sigma (54) (RpoN)-dependent promoter, located upstream of norA1. With the aid of norA1'-lacZ transcriptional fusions and the generation of regulatory mutants, it was shown that norB1 gene transcription requires a functional rpoN gene and the regulator NorR, a novel member of the NtrC family of response regulators. The regulator gene maps adjacent to norAB, is divergently transcribed and present in two copies on the megaplasmid pHG1 (norR1) and the chromosome (norR2). Transcription activation by NorR responds to the availability of NO. A nitrite reductase-deficient mutant that is incapable of producing NO endogenously, showed a 70% decrease of norA1 expression. Addition of the NO-donating agent sodium nitroprusside caused induction of norA1'-lacZ transcription. Truncation of the N-terminal receiver domain of NorR1 interrupted the NO signal transduction and led to a constitutive expression of norA1'-lacZ. The results indicate that NorR controls the reductive conversion of NO in R. eutropha. This reaction is not strictly co-ordinated on the regulatory level with the other nitrogen oxide-reducing steps of the denitrification chain that are independent of NorR.