Sidoti C, Harwood G, Ackerman R, Coppard J, Merrick M
AFRC IPSR Nitrogen Fixation Laboratory, University of Sussex, Brighton, UK.
Arch Microbiol. 1993;159(3):276-81. doi: 10.1007/BF00248484.
The nifL gene product of Klebsiella pneumoniae inhibits the activity of the positive activator protein NifA in response to increased levels either of fixed nitrogen or of oxygen in the medium. In order to demonstrate that the responses to these two effectors are discrete we have subjected nifL to hydroxylamine mutagenesis and isolated nifL mutants that are impaired in their ability to respond to oxygen but not to fixed nitrogen. Two such mutations were sequenced and shown to be single base pair changes located in different parts of nifL. The amino acid sequence of NifL shows limited homology to the histidine protein kinases which comprise the sensing component of bacterial two-component regulatory systems. In the light of the location of one of the oxygen-insensitive mutations (Leu294Phe) we have reassessed this homology and we suggest that the Gln273-Leu317 region of NifL may facilitate interactions between NifL and NifA.
肺炎克雷伯菌的nifL基因产物会响应培养基中固定氮或氧气水平的升高，抑制正激活蛋白NifA的活性。为了证明对这两种效应物的反应是不相关的，我们对nifL进行了羟胺诱变，并分离出了nifL突变体，这些突变体对氧气的反应能力受损，但对固定氮的反应能力不受影响。对其中两个这样的突变进行了测序，结果表明它们是位于nifL不同部位的单碱基对变化。NifL的氨基酸序列与构成细菌双组分调节系统传感成分的组氨酸蛋白激酶具有有限的同源性。鉴于其中一个对氧气不敏感的突变（Leu294Phe）的位置，我们重新评估了这种同源性，并认为NifL的Gln273-Leu317区域可能促进NifL与NifA之间的相互作用。
