title: 3-Hydroxyphenylpropionate and phenylpropionate are synergistic activators of the MhpR transcriptional regulator from Escherichia coli.
abstract: The degradation of the aromatic compound phenylpropionate (PP) in Escherichia coli K-12 requires the activation of two different catabolic pathways coded by the hca and the mhp gene clusters involved in the mineralization of PP and 3-hydroxyphenylpropionate (3HPP), respectively. The compound 3-(2,3-dihydroxyphenyl)propionate (DHPP) is a common intermediate of both pathways which must be cleaved by the MhpB dioxygenase before entering into the primary cell metabolism. Therefore, the degradation of PP has to be controlled by both its specific regulator (HcaR) but also by the MhpR regulator of the mhp cluster. We have demonstrated that 3HPP and DHPP are the true and best activators of MhpR, whereas PP only induces no response. However, in vivo and in vitro transcription experiments have demonstrated that PP activates the MhpR regulator synergistically with the true inducers, representing the first case of such a peculiar synergistic effect described for a bacterial regulator. The three compounds enhanced the interaction of MhpR with its DNA operator in electrophoretic mobility shift assays. Inducer binding to MhpR is detected by circular dichroism and fluorescence spectroscopies. Fluorescence quenching measurements have revealed that the true inducers (3HPP and DHPP) and PP bind with similar affinities and independently to MhpR. This type of dual-metabolite synergy provides great potential for a rapid modulation of gene expression and represents an important feature of transcriptional control. The mhp regulatory system is an example of the high complexity achievable in prokaryotes.
authors.affiliation: Departamento de Microbiología Molecular, Spain.
authors.forename: Isabel
authors.initials: I
authors.lastname: Manso
authors.forename: Begoña
authors.initials: B
authors.lastname: Torres
authors.forename: José Manuel
authors.initials: JM
authors.lastname: Andreu
authors.forename: Margarita
authors.initials: M
authors.lastname: Menéndez
authors.forename: Germán
authors.initials: G
authors.lastname: Rivas
authors.forename: Carlos
authors.initials: C
authors.lastname: Alfonso
authors.forename: Eduardo
authors.initials: E
authors.lastname: Díaz
authors.forename: José Luis
authors.initials: JL
authors.lastname: García
authors.forename: Beatriz
authors.initials: B
authors.lastname: Galán
mesh_terms: D002942:Circular Dichroism; D016000:Cluster Analysis; D049308:Dioxygenases / Q000378:metabolism / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D004926:Escherichia coli / Q000378:metabolism / Q000502:physiology*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D008024:Ligands; D008954:Models, Biological; D008956:Models, Chemical; D008957:Models, Genetic; D005810:Multigene Family; D010666:Phenylpropionates / Q000378:metabolism*; D013050:Spectrometry, Fluorescence / Q000379:methods; D014158:Transcription, Genetic
chemical_list: D029968:Escherichia coli Proteins; D008024:Ligands; D010666:Phenylpropionates; D049308:Dioxygenases; C083582:3-carboxyethylcatechol 2,3-dioxygenase