title: Steric hindrance regulation of the Pseudomonas aeruginosa amidase operon.
abstract: Expression of the amidase operon of Pseudomonas aeruginosa is controlled by AmiC, the ligand sensor and negative regulator, and AmiR the transcription antitermination factor activator. We have titrated out AmiC repression activity in vivo by increased AmiR production in trans and shown AmiC regulation of the antitermination activity of AmiR by a steric hindrance mechanism. In the presence of the co-repressor butyramide we have isolated a stable AmiC.AmiR complex. Addition of the inducing ligand acetamide to the complex trips the molecular switch, causing complex dissociation and release of AmiR. The AmiC.AmiR butyramide complex exhibits acetamide-dependent, sequence-specific RNA binding activity and a K(d) of 1.0 nm has been calculated for the AmiR.RNA interaction. The results show that amidase operon expression is controlled by a novel type of signal transduction system in which activity of a site-specific RNA binding activator is regulated via a sequestration mechanism.
authors.affiliation: Department of Biochemistry and Molecular Biology, University College London, Gower St., London WC1E 6BT, United Kingdom. R.Norman@icrf.icnet.uk
authors.forename: R A
authors.initials: RA
authors.lastname: Norman
authors.forename: C L
authors.initials: CL
authors.lastname: Poh
authors.forename: L H
authors.initials: LH
authors.lastname: Pearl
authors.forename: B P
authors.initials: BP
authors.lastname: O'Hara
authors.forename: R E
authors.initials: RE
authors.lastname: Drew
mesh_terms: D000081:Acetamides / Q000378:metabolism; D000577:Amides / Q000378:metabolism; D000581:Amidohydrolases / Q000235:genetics*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001665:Binding Sites; D015964:Gene Expression Regulation, Bacterial; D015971:Gene Expression Regulation, Enzymologic; D008968:Molecular Conformation; D009690:Nucleic Acid Conformation; D009876:Operon; D010442:Peptide Chain Initiation, Translational; D033902:Periplasmic Binding Proteins; D011485:Protein Binding; D011550:Pseudomonas aeruginosa / Q000235:genetics*; D011994:Recombinant Proteins / Q000378:metabolism; D015398:Signal Transduction
chemical_list: D000081:Acetamides; D000577:Amides; D001426:Bacterial Proteins; D033902:Periplasmic Binding Proteins; D011994:Recombinant Proteins; C070135:AmiC protein, Pseudomonas aeruginosa; C030686:acetamide; C006866:butyramide; D000581:Amidohydrolases; C019665:amidase