title: The role of the T-loop of the signal transducing protein PII from Escherichia coli.
abstract: The 3D structure of PII, the central protein that controls the level of transcription and the enzymatic activity of glutamine synthetase in enteric bacteria revealed that residues 37-55 form the "T' loop, part of which protrudes from the core of the protein. Within this loop are the only two tyrosine residues that occur in the polypeptide, and one of them, Tyr-51, has been shown by chemical modification studies to be the site of uridylylation. Since tyrosine at position 46 is conserved in all known PII proteins, oligonucleotide directed mutagenesis was used to investigate the role of the two residues. Changing Tyr-51 to phenylalanine or serine abolished uridylylation. Altering tyrosine at position 46 to phenylalanine affected the rate of uridylylation of the protein. This latter mutation does not alter the structure of PII but the reduction in the uridylylation efficiency suggests a role for this residue in recognition and binding of the sensor enzyme uridylyl transferase.
authors.affiliation: Department of Biochemistry and Molecular Biology, School of Molecular Sciences, James Cook University, Townsville, Qld, Australia.
authors.forename: R
authors.initials: R
authors.lastname: Jaggi
authors.forename: W
authors.initials: W
authors.lastname: Ybarlucea
authors.forename: E
authors.initials: E
authors.lastname: Cheah
authors.forename: P D
authors.initials: PD
authors.lastname: Carr
authors.forename: K J
authors.initials: KJ
authors.lastname: Edwards
authors.forename: D L
authors.initials: DL
authors.lastname: Ollis
authors.forename: S G
authors.initials: SG
authors.lastname: Vasudevan
mesh_terms: D000595:Amino Acid Sequence; D001419:Bacteria / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism*; D001483:Base Sequence; D018360:Crystallography, X-Ray; D017931:DNA Primers; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D007700:Kinetics; D046911:Macromolecular Substances; D008961:Models, Structural; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D051922:PII Nitrogen Regulatory Proteins; D010649:Phenylalanine; D010957:Plasmids; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D012694:Serine; D015398:Signal Transduction; D012984:Software; D014443:Tyrosine; D006599:UDPglucose-Hexose-1-Phosphate Uridylyltransferase / Q000378:metabolism; D014529:Uridine
chemical_list: D001426:Bacterial Proteins; D017931:DNA Primers; D046911:Macromolecular Substances; D051922:PII Nitrogen Regulatory Proteins; D011994:Recombinant Proteins; D014443:Tyrosine; D012694:Serine; D010649:Phenylalanine; C404143:PIID regulatory protein, Bacteria; D006599:UDPglucose-Hexose-1-Phosphate Uridylyltransferase; D014529:Uridine