|PROSITE documentation PDOC00439 [for PROSITE entry PS00496]|
P-II family proteins are regulators of nitrogen metabolism, with a length of ~110 amino acid residues, found throughout the bacteria and most archaea. P-II proteins sense cellular 2-oxoglutarate as an indicator for nitrogen limitation and bind and respond to ATP. The family is named after the P-II protein (gene glnB), a bacterial protein important for the control of glutamine synthetase [1,2,3]. 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 glutamine synthetase (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. The tyrosine which is uridylated is located in the T-loop in the central part of the protein.
Not all P-II family proteins have this site for sensing cellular glutamine . In cyanobacteria, P-II seems to be phosphorylated on a serine residue rather than being uridylated. It has a different set of interacting proteins.
In methanogenic archaebacteria, the nitrogenase iron protein gene (nifH) is followed by two open reading frames highly similar to the eubacterial P-II protein . These proteins could be involved in the regulation of nitrogen fixation.
In the red alga, Porphyra purpurea, there is a glnB homolog encoded in the chloroplast genome.
Other proteins highly similar to glnB are:
We developed two signature patterns for P-II protein. The first one is a conserved stretch (in eubacteria) of six residues which contains the uridylated tyrosine, the other is derived from a conserved region in the C-terminal part of the P-II protein. We also developed a profile that covers the whole P-II protein.Last update:
December 2007 / Text revised; profile added.
PROSITE methods (with tools and information) covered by this documentation:
|Title||Regulation of transcription of the glnALG operon of Escherichia coli by protein phosphorylation.|
|2||Authors||Holtel A. Merrick M.|
|Title||Identification of the Klebsiella pneumoniae glnB gene: nucleotide sequence of wild-type and mutant alleles.|
|Source||Mol. Gen. Genet. 215:134-138(1988).|
|3||Authors||Cheah E. Carr P.D. Suffolk P.M. Vasudevan S.G. Dixon N.E. Ollis D.L.|
|Title||Structure of the Escherichia coli signal transducing protein PII.|
|4||Authors||Leigh J.A. Dodsworth J.A.|
|Title||Nitrogen regulation in bacteria and archaea.|
|Source||Annu. Rev. Microbiol. 61:349-377(2007).|
|5||Authors||Sibold L. Henriquet M. Possot O. Aubert J.-P.|
|Title||Nucleotide sequence of nifH regions from Methanobacterium ivanovii and Methanosarcina barkeri 227 and characterization of glnB-like genes.|
|Source||Res. Microbiol. 142:5-12(1991).|
|6||Authors||Wray L.V. Jr. Atkinson M.R. Fisher S.H.|
|Title||The nitrogen-regulated Bacillus subtilis nrgAB operon encodes a membrane protein and a protein highly similar to the Escherichia coli glnB-encoded PII protein.|
|Source||J. Bacteriol. 176:108-114(1994).|
|7||Authors||Allikmets R. Gerrard B.C. Court D. Dean M.|
|Title||Cloning and organization of the abc and mdl genes of Escherichia coli: relationship to eukaryotic multidrug resistance.|
|8||Authors||Mizuno Y. Berenger B. Moorhead G.B. Ng K.K.|
|Title||Crystal structure of Arabidopsis PII reveals novel structural elements unique to plants.|