InterPro domain: IPR002187
General Information
- Identifier IPR002187
- Description Nitrogen regulatory protein PII
- Number of genes 116
- Gene duplication stats Loading...
- Associated GO terms GO:0006808 GO:0030234
Abstract
In Gram-negative bacteria, the activity and concentration of glutamine synthetase (GS) is regulated in response to nitrogen source availability. PII, a tetrameric protein encoded by the glnB gene, is a component of the adenylation cascade involved in the regulation of GS activity [ 1 ]. In nitrogen-limiting conditions, when the ratio of glutamine to 2-ketoglutarate decreases, P-II is uridylylated on a tyrosine residue to form P-II-UMP. P-II-UMP allows the deadenylation of GS, thus activating the enzyme. Conversely, in nitrogen excess, P-II-UMP is deuridylated and then promotes the adenylation of GS. P-II also indirectly controls the transcription of the GS gene (glnA) by preventing NR-II (ntrB) to phosphorylate NR-I (ntrC) which is the transcriptional activator of glnA. Once P-II is uridylylated, these events are reversed.
P-II is a protein of about 110 amino acid residues extremely well conserved. The tyrosine which is uridylated is located in the central part of the protein. In cyanobacteria, P-II seems to be phosphorylated on a serine residue rather than being uridylated. In methanogenic archaebacteria, the nitrogenase iron protein gene (nifH) is followed by two open reading frames highly similar to the eubacterial P-II protein [ 2 ]. These proteins could be involved in the regulation of nitrogen fixation. In the red alga, Porphyra purpurea, there is a glnB homologue encoded in the chloroplast genome.
Other proteins highly similar to glnB are:
- Bacillus subtilis protein nrgB [ 3 ].
- Escherichia coli hypothetical protein ybaI [ 4 ].
- GlnK from Archaea and bacteria, an homologue of GlnB protein, which regulates ammonium transport (Amt) proteins [ 5 , 6 ]
1. Characterization of three different nitrogen-regulated promoter regions for the expression of glnB and glnA in Azospirillum brasilense. Mol. Gen. Genet. 224, 421-30
2. Nucleotide sequence of nifH regions from Methanobacterium ivanovii and Methanosarcina barkeri 227 and characterization of glnB-like genes. Res. Microbiol. 142, 5-12
3. The nitrogen-regulated Bacillus subtilis nrgAB operon encodes a membrane protein and a protein highly similar to the Escherichia coli glnB-encoded PII protein. J. Bacteriol. 176, 108-14
4. Cloning and organization of the abc and mdl genes of Escherichia coli: relationship to eukaryotic multidrug resistance. Gene 136, 231-6
5. Mechanism of disruption of the Amt-GlnK complex by P(II)-mediated sensing of 2-oxoglutarate. PLoS ONE 6, e26327
6. Structure of GlnK1 with bound effectors indicates regulatory mechanism for ammonia uptake. EMBO J. 26, 589-99