Identification of Rhodospirillum rubrum GlnB variants that are altered in their ability to interact with different targets in response to nitrogen status signals.
Identification of Rhodospirillum rubrum GlnB variants that are altered in their ability to interact with different targets in response to nitrogen status signals.
复制标题
鉴定红色红螺菌 GlnB 变体，这些变体响应氮状态信号而改变与不同靶标相互作用的能力。
DOI：
10.1128/jb.188.5.1866-1874.2006
复制
发表时间：
2006
影响因子：
3.2
通讯作者：
Roberts,GaryP
中科院分区：
文献类型：
--
作者：
Zhu,Yu;Conrad,MaryC;Zhang,Yaoping;Roberts,GaryP
InRhodospirillum rubrum, NifA, the transcriptional activator for thenifgenes, is posttranslationally activated only by the uridylylated form of GlnB, one of three PIIhomologs in the organism. We have used the yeast two-hybrid system to detect variants of GlnB that interact better with NifA than does wild-type GlnB. When examined for physiological effects inR. rubrum, these GlnB* variants activated NifA in the presence of NH4+, which normally blocks NifA activation completely, and in the absence of GlnD, whose uridylylation of GlnB is also normally essential for NifA activation. When these variants were tested in the two-hybrid system for their interaction with NtrB, a receptor that should interact with the nonuridylylated form of GlnB, they were uniformly weaker than wild-type GlnB in that interaction. When expressed inR. rubrumeither as single-copy integrants or on multiple-copy plasmids, these variants were also dramatically altered in terms of their ability to regulate several other receptors involved in nitrogen metabolism, including GlnE, NtrB/NtrC, and DRAT (dinitrogenase reductase ADP-ribosyl transferase)-DRAG (dinitrogenase reductase-activating glycohydrolase). The consistent pattern throughout is that these GlnB variants partially mimic the uridylylated form of wild-type GlnB, even under nitrogen-excess conditions and in strains lacking GlnD. The results suggest that the role of uridylylation of GlnB is primarily to shift the equilibrium of GlnB from a “nitrogen-sufficient” form to a “nitrogen-deficient” form, each of which interacts with different but overlapping receptor proteins in the cell. These GlnB variants apparently shift that equilibrium through direct structural changes.
