Tosques I E, Kwiatkowski A V, Shi J, Shapleigh J P
Section of Microbiology, Cornell University, Ithaca, New York 14853, USA.
J Bacteriol. 1997 Feb;179(4):1090-5. doi: 10.1128/jb.179.4.1090-1095.1997.
Nitrite reductase catalyzes the reduction of nitrite to nitric oxide, the first step in denitrification to produce a gaseous product. We have cloned the gene nirK, which encodes the copper-type nitrite reductase from a denitrifying variant of Rhodobacter sphaeroides, strain 2.4.3. The deduced open reading frame has significant identity with other copper-type nitrite reductases. Analysis of the promoter region shows that transcription initiates 31 bases upstream of the translation start codon. The transcription initiation site is 43.5 bases downstream of a putative binding site for a transcriptional activator. Maximal expression of a nirK-lacZ construct in 2.4.3 requires both a low level of oxygen and the presence of a nitrogen oxide. nirK-lacZ expression was severely impaired in a nitrite reductase-deficient strain of 2.4.3. This suggests that nirK expression is dependent on nitrite reduction. The inability of microaerobically grown nitrite reductase-deficient cells to induce nirK-lacZ expression above basal levels in medium unamended with nitrate demonstrates that changes in oxygen concentrations are not sufficient to modulate nirK expression.
亚硝酸还原酶催化将亚硝酸盐还原为一氧化氮，这是反硝化作用产生气态产物的第一步。我们已经克隆了nirK基因，它编码来自球形红杆菌2.4.3反硝化变体的铜型亚硝酸还原酶。推导的开放阅读框与其他铜型亚硝酸还原酶具有显著的同源性。对启动子区域的分析表明，转录起始于翻译起始密码子上游31个碱基处。转录起始位点位于假定的转录激活因子结合位点下游43.5个碱基处。nirK-lacZ构建体在2.4.3中的最大表达需要低水平的氧气和氮氧化物的存在。nirK-lacZ表达在2.4.3的亚硝酸还原酶缺陷菌株中严重受损。这表明nirK表达依赖于亚硝酸盐还原。在未添加硝酸盐的培养基中，微需氧生长的亚硝酸还原酶缺陷细胞无法将nirK-lacZ表达诱导至基础水平以上，这表明氧气浓度的变化不足以调节nirK表达。
