Conserved Site

Nitrogen regulatory protein PII, conserved site (IPR017918)

Short name: N-reg_PII_CS


The P-II protein (gene glnB) is a bacterial protein important for the control of glutamine synthetase [PMID: 2574599, PMID: 2907369, PMID: 7866749]. 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.

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 the red alga, Porphyra purpurea, there is a glnB homologue encoded in the chloroplast genome. Other proteins highly similar to glnB include Bacillus subtilis protein nrgB [PMID: 8282685]; and Escherichia coli hypothetical protein ybaI [PMID: 7904973].

This entry represents a conserved site in the C-terminal region of the P-II protein.

GO terms

Biological Process

GO:0006808 regulation of nitrogen utilization

Molecular Function

GO:0030234 enzyme regulator activity

Cellular Component

No terms assigned in this category.

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.
PROSITE patterns