title: Crystal structure and induction mechanism of AmiC-AmiR: a ligand-regulated transcription antitermination complex.
abstract: Inducible expression of the aliphatic amidase operon in Pseudomonas aeruginosa is controlled by an antitermination mechanism which allows production of the full-length transcript only in the presence of small-molecule inducers, such as acetamide. Ligand-regulated antitermination is provided by AmiC, the ligand-sensitive negative regulator, and AmiR, the RNA-binding positive regulator. Under non-inducing or repressing growth conditions, AmiC and AmiR form a complex in which the activity of AmiR is silenced. The crystal structure of the AmiC-AmiR complex identifies AmiR as a new and highly unusual member of the response-regulator family of bacterial signal transduction proteins, regulated by sequestration rather than phosphorylation. Comparison with the structure of free AmiC reveals the subtle mechanism of ligand-induced release of AmiR.
authors.affiliation: Centre for Structural Biology, Institute of Cancer Research, Chester Beatty Laboratories, 237 Fulham Road, London SW3 6JB, UK.
authors.forename: B P
authors.initials: BP
authors.lastname: O'Hara
authors.forename: R A
authors.initials: RA
authors.lastname: Norman
authors.forename: P T
authors.initials: PT
authors.lastname: Wan
authors.forename: S M
authors.initials: SM
authors.lastname: Roe
authors.forename: T E
authors.initials: TE
authors.lastname: Barrett
authors.forename: R E
authors.initials: RE
authors.lastname: Drew
authors.forename: L H
authors.initials: LH
authors.lastname: Pearl
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics; D003001:Cloning, Molecular; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D008969:Molecular Sequence Data; D033902:Periplasmic Binding Proteins; D011487:Protein Conformation; D013728:Terminator Regions, Genetic; D014158:Transcription, Genetic
chemical_list: D001426:Bacterial Proteins; D033902:Periplasmic Binding Proteins; C070135:AmiC protein, Pseudomonas aeruginosa