Drummond M H, Wootton J C
AFRC Unit of Nitrogen Fixation, University of Sussex, Brighton, UK.
Mol Microbiol. 1987 Jul;1(1):37-44. doi: 10.1111/j.1365-2958.1987.tb00524.x.
We present the nucleotide sequence of K. pneumoniae nifL, which negatively regulates nif transcription in response to oxygen and fixed nitrogen. It shows partial sequence homology to the general nitrogen regulatory proteins NtrB of K. pneumoniae and Bradyrhizobium parasponiae. This homology is weaker than that shown between the NifA and NtrC activator components of the nif and general nitrogen control systems. The N-terminal section of the NifL protein includes a structural duplication sharing sequence homology with part of NtrB, and a region containing a cysteine pair which might be implicated in redox control Unlike NtrB, NifL appears to lack a DNA-binding motif, consistent with evidence that NifL represses by interacting directly with NifA. The C-terminal section of NifL shows clear homology to NtrB and to a family of proteins involved in transcriptional control or chemotaxis, each of which probably interacts with a member of the family of regulatory proteins showing homology to NtrC.
我们展示了肺炎克雷伯菌nifL的核苷酸序列，它可响应氧气和固定氮对nif转录进行负调控。它与肺炎克雷伯菌和副慢生根瘤菌的一般氮调节蛋白NtrB具有部分序列同源性。这种同源性比nif和一般氮控制系统的NifA和NtrC激活成分之间的同源性弱。NifL蛋白的N端部分包括一个与NtrB部分具有序列同源性的结构重复，以及一个含有半胱氨酸对的区域，这可能与氧化还原控制有关。与NtrB不同，NifL似乎缺乏DNA结合基序，这与NifL通过直接与NifA相互作用进行抑制的证据一致。NifL的C端部分与NtrB以及参与转录控制或趋化作用的一类蛋白质具有明显的同源性，其中每一种可能都与显示出与NtrC同源性的调节蛋白家族的一个成员相互作用。
