title: AccR is a master regulator involved in carbon catabolite repression of the anaerobic catabolism of aromatic compounds in Azoarcus sp. CIB.
abstract: Here we characterized the first known transcriptional regulator that accounts for carbon catabolite repression (CCR) control of the anaerobic catabolism of aromatic compounds in bacteria. The AccR response regulator of Azoarcus sp. CIB controls succinate-responsive CCR of the central pathways for the anaerobic catabolism of aromatics by this strain. Phosphorylation of AccR to AccR-P triggers a monomer-to-dimer transition as well as the ability to bind to the target promoter and causes repression both in vivo and in vitro. Substitution of the Asp(60) phosphorylation target residue of the N-terminal receiver motif of AccR to a phosphomimic Glu residue generates a constitutively active derivative that behaves as a superrepressor of the target genes. AccR-P binds in vitro to a conserved inverted repeat (ATGCA-N6-TGCAT) present at two different locations within the PN promoter of the bzd genes for anaerobic benzoate degradation. Because the DNA binding-proficient C-terminal domain of AccR is monomeric, we propose an activation mechanism in which phosphorylation of Asp(60) of AccR alleviates interdomain repression mediated by the N-terminal domain. The presence of AccR-like proteins encoded in the genomes of other β-proteobacteria of the Azoarcus/Thauera group further suggests that AccR constitutes a master regulator that controls anaerobic CCR in these bacteria.
authors.affiliation: From the Department of Environmental Biology, Centro de Investigaciones Biológicas-Consejo Superior de Investigaciones Científicas, Ramiro de Maeztu 9, 28040 Madrid, Spain and.
authors.forename: J Andrés
authors.initials: JA
authors.lastname: Valderrama
authors.forename: Victoria
authors.initials: V
authors.lastname: Shingler
authors.forename: Manuel
authors.initials: M
authors.lastname: Carmona
authors.forename: Eduardo
authors.initials: E
authors.lastname: Díaz
mesh_terms: D019943:Amino Acid Substitution; D000693:Anaerobiosis / Q000502:physiology; D020627:Azoarcus / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001565:Benzoates / Q000378:metabolism*; D057465:Catabolite Repression / Q000502:physiology*; D020125:Mutation, Missense; D020218:Response Elements / Q000502:physiology*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D001565:Benzoates; D014157:Transcription Factors
keywords: Anaerobic Degradation; Azoarcus; Bacterial Transcription; Carbon Catabolite Repression; Gene Regulation; Microbiology; Protein-DNA Interaction; Signal Transduction; Transcription Regulation