title: Structure of the Escherichia coli signal transducing protein PII.
abstract: BACKGROUND
  In Gram-negative proteobacteria, the nitrogen level in the cell is reflected by the uridylylation status of a key signal transducing protein, PII. PII modulates the activity of glutamine synthetase (GS) through its interaction with adenylyl transferase and it represses the expression of GS by acting in concert with nitrogen regulatory protein II.
  
  
  RESULTS
  The three-dimensional structure of the Escherichia coli PII trimer has been determined at 2.7 A resolution. PII shows a low level of structural similarity to a broad family of alpha/beta proteins and contains a double beta alpha beta motif. The PII trimer contains three beta-sheets, each of which is composed of strands from each of the three monomers. These are surrounded by six alpha-helices.
  
  
  CONCLUSIONS
  The structure of PII suggests potential regions of interaction with other proteins and serves as an initial step in understanding its signal transducing role in nitrogen regulation.
authors.affiliation: Centre for Molecular Structure and Function, Research School of Chemistry, Australian National University, Canberra.
authors.forename: E
authors.initials: E
authors.lastname: Cheah
authors.forename: P D
authors.initials: PD
authors.lastname: Carr
authors.forename: P M
authors.initials: PM
authors.lastname: Suffolk
authors.forename: S G
authors.initials: SG
authors.lastname: Vasudevan
authors.forename: N E
authors.initials: NE
authors.lastname: Dixon
authors.forename: D L
authors.initials: DL
authors.lastname: Ollis
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics; D017124:Conserved Sequence; D004563:Electrochemistry; D004926:Escherichia coli / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D005974:Glutamate-Ammonia Ligase / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D015394:Molecular Structure; D009713:Nucleotidyltransferases / Q000378:metabolism; D051922:PII Nitrogen Regulatory Proteins; D011487:Protein Conformation; D017510:Protein Folding; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction
chemical_list: D001426:Bacterial Proteins; D051922:PII Nitrogen Regulatory Proteins; C404143:PIID regulatory protein, Bacteria; D009713:Nucleotidyltransferases; C022515:regulatory protein uridylyltransferase; D005974:Glutamate-Ammonia Ligase