title: Crystal structure of the C-terminal domain of the two-component system transmitter protein nitrogen regulator II (NRII; NtrB), regulator of nitrogen assimilation in Escherichia coli.
abstract: The kinase/phosphatase nitrogen regulator II (NRII, NtrB) is a member of the transmitter protein family of conserved two-component signal transduction systems. The kinase activity of NRII brings about the phosphorylation of the transcription factor nitrogen regulator I (NRI, NtrC), causing the activation of Ntr gene transcription. The phosphatase activity of NRII results in the inactivation of NRI-P. The activities of NRII are regulated by the signal transduction protein encoded by glnB, PII protein, which upon binding to NRII inhibits the kinase and activates the phosphatase activity. The C-terminal ATP-binding domain of NRII is required for both the kinase and phosphatase activities and contains the PII binding site. Here, we present the crystal structure of the C-terminal domain of a mutant form of NRII, NRII-Y302N, at 1.6 A resolution and compare this structure to the analogous domains of other two-component system transmitter proteins. While the C-terminal domain of NRII shares the general tertiary structure seen in CheA, PhoQ, and EnvZ transmitter proteins, it contains a distinct beta-hairpin projection that is absent in these related proteins. This projection is near the site of a well-characterized mutation that reduces the binding of PII and near other less-characterized mutations that affect the phosphatase activity of NRII. Sequence alignment suggests that the beta-hairpin projection is present in NRII proteins from various organisms, and absent in other transmitter proteins from Escherichia coliK-12. This unique structural element in the NRII C-terminal domain may play a role in binding PII or in intramolecular signal transduction.
authors.affiliation: Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, Michigan 48109-0606, USA.
authors.forename: Yuanda
authors.initials: Y
authors.lastname: Song
authors.forename: Daniel
authors.initials: D
authors.lastname: Peisach
authors.forename: Augen A
authors.initials: AA
authors.lastname: Pioszak
authors.forename: Zhaohui
authors.initials: Z
authors.lastname: Xu
authors.forename: Alexander J
authors.initials: AJ
authors.lastname: Ninfa
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D018360:Crystallography, X-Ray; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D051922:PII Nitrogen Regulatory Proteins; D010749:Phosphoprotein Phosphatases / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D011487:Protein Conformation; D011494:Protein Kinases / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D012995:Solubility; D013329:Structure-Activity Relationship
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D051922:PII Nitrogen Regulatory Proteins; C404143:PIID regulatory protein, Bacteria; D000255:Adenosine Triphosphate; D011494:Protein Kinases; C055699:protein kinase-phosphatase NTRB; D010749:Phosphoprotein Phosphatases