title: 3-phenylpropionate catabolism and the Escherichia coli oxidative stress response.
abstract: Cells have devised a variety of protection systems against the toxic effects of dioxygen. Dioxygenases are part of this defence mechanism. In Escherichia coli, the positive regulator HcaR, a member of the LysR family of regulators, controls expression of the neighbouring genes, hcaA1, hcaA2, hcaC, hcaB and hcaD, coding for the 3-phenylpropionate dioxygenase complex and 3-phenylpropionate-2',3'-dihydrodiol dehydrogenase, that oxidizes 3-phenylpropionate to 3-(2,3-dihydroxyphenyl) propionate. Differences between expression of hcaR and expression of its target, hcaA, suggest that HcaR is involved in control of other cellular processes or that other regulatory proteins modulate hcaA expression. Protein expression profiling was used to identify other HcaR targets. Two-dimensional gel electrophoresis was used to compare the proteomes of wild-type E. coli and strains in which hcaR was disrupted. Several polypeptides whose production was up- or downregulated in the hcaR mutant were involved in the oxidative stress response. Subsequent experiments demonstrated that hcaR disruption was involved in regulation of genes involved in the oxidative stress response. Modification of the stress response also occurred in an hcaA1A2CD mutant strain. Using gel retardation, the HcaR binding site was estimated to be located about -70 to -55 bp upstream of the hcaA transcription start site. The expression of hcaR was repressed in the absence of oxygen by the ArcA/ArcB two-component system.
authors.affiliation: Unité de Génétique des Génomes Bactériens, Département de Structure et dynamique des génomes, Institut Pasteur, 28 rue du Dr. Roux, 75724 Paris cedex 15, France.
authors.forename: Evelyne
authors.initials: E
authors.lastname: Turlin
authors.forename: Odile
authors.initials: O
authors.lastname: Sismeiro
authors.forename: Jean Pierre
authors.initials: JP
authors.lastname: Le Caer
authors.forename: Valérie
authors.initials: V
authors.lastname: Labas
authors.forename: Antoine
authors.initials: A
authors.lastname: Danchin
authors.forename: Francis
authors.initials: F
authors.lastname: Biville
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D004269:DNA, Bacterial / Q000235:genetics; D049308:Dioxygenases / Q000378:metabolism*; D015180:Electrophoresis, Gel, Two-Dimensional; D024202:Electrophoretic Mobility Shift Assay; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D018384:Oxidative Stress / Q000502:physiology*; D010666:Phenylpropionates / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
chemical_list: D004269:DNA, Bacterial; D010666:Phenylpropionates; C035253:3-phenylpropionic acid; D049308:Dioxygenases