| Type: | PTM | Name: | Nitrogen regulatory protein P-II, urydylation site |
| Description: | The P-II protein (gene glnB) is a bacterial protein important for the control of glutamine synthetase [, , ]. 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 subtilisprotein nrgB []; and Escherichia colihypothetical protein ybaI [].This entry represents a conserved stretch (in eubacteria) of six residues which contains the uridylated tyrosine. | Short Name: | N-reg_PII_urydylation_site |
