Dataset Information

HbpR, a new member of the XylR/DmpR subclass within the NtrC family of bacterial transcriptional activators, regulates expression of 2-hydroxybiphenyl metabolism in Pseudomonas azelaica HBP1.

ABSTRACT: The regulation of 2-hydroxybiphenyl and 2,2'-dihydroxybiphenyl degradation in Pseudomonas azelaica is mediated by the regulatory gene, hbpR. The hbpR gene encodes a 63-kDa protein belonging to the NtrC family of prokaryotic transcriptional activators and having the highest homology to members of the XylR/DmpR subclass. Disruption of the hbpR gene in P. azelaica and complementation in trans showed that the HbpR protein was the key regulator for 2-hydroxybiphenyl metabolism. Induction experiments with P. azelaica and Escherichia coli containing luxAB-based transcriptional fusions revealed that HbpR activates transcription from a promoter (P(hbpC)) in front of the first gene for 2-hydroxybiphenyl degradation, hbpC, and that 2-hydroxybiphenyl itself is the direct effector for HbpR-mediated activation. Of several compounds tested, only the pathway substrates 2-hydroxybiphenyl and 2,2'-dihydroxybiphenyl and structural analogs like 2-aminobiphenyl and 2-hydroxybiphenylmethane were effectors for HbpR activation. HbpR is therefore, to our knowledge, the first regulator of the XylR/DmpR class that recognizes biaromatic but not monoaromatic structures. Analysis of a spontaneously occurring mutant, P. azelaica HBP1 Prp, which can grow with the non-wild-type effector 2-propylphenol, revealed a single mutation in the hbpR gene (T613C) leading to a Trp-->Arg substitution at amino acid residue 205. P. azelaica HBP1 derivative strains without a functional hbpR gene constitutively expressed the genes for 2-hydroxybiphenyl degradation when complemented in trans with the hbpR-T613C gene. This suggests the importance of this residue, which is conserved among all members of the XylR/DmpR subclass, for interdomain repression.

SUBMITTER: Jaspers MC

PROVIDER: S-EPMC94290 | biostudies-literature | 2000 Jan

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

HbpR, a new member of the XylR/DmpR subclass within the NtrC family of bacterial transcriptional activators, regulates expression of 2-hydroxybiphenyl metabolism in Pseudomonas azelaica HBP1.

Jaspers M C MC Suske W A WA Schmid A A Goslings D A DA Kohler H P HP van der Meer J R JR

Journal of bacteriology 20000101 2

The regulation of 2-hydroxybiphenyl and 2,2'-dihydroxybiphenyl degradation in Pseudomonas azelaica is mediated by the regulatory gene, hbpR. The hbpR gene encodes a 63-kDa protein belonging to the NtrC family of prokaryotic transcriptional activators and having the highest homology to members of the XylR/DmpR subclass. Disruption of the hbpR gene in P. azelaica and complementation in trans showed that the HbpR protein was the key regulator for 2-hydroxybiphenyl metabolism. Induction experiments ...[more]

PMID: 10629187

Similar Datasets

Project description:We have isolated a recombinant phage antibody (Phab) that binds a distinct epitope of the subclass of the sigma(54)-dependent prokaryotic enhancer-binding proteins that respond directly to aromatic effectors, e.g., those that activate biodegradative operons of Pseudomonas spp. The DNA segments encoding the variable (V) domains of the immunoglobulins expressed by mice immunized with the C-terminal half of TouR (TouRDeltaA) of Pseudomonas stutzeri OX1 were amplified and rearranged in vitro as single-chain Fv (scFv) genes. An scFv library was thereby constructed, expressed in an M13 display system, and subjected to a panning procedure with TouR. One clone (named B7) was selected with high affinity for TouR and XylR (the regulator of the upper TOL operon of the pWW0 plasmid). The epitope recognized by this Phab was mapped to the peptide TPRAQATLLRVL, which seems to be characteristic of the group of enhancer-binding proteins to which TouR and XylR belong and which is located adjacent to the Walker B motif of the proteins. The Phab B7 was instrumental in measuring directly the intracellular levels of XylR expressed from its natural promoter in monocopy gene dosage in Pseudomonas putida under various conditions. Growth stage, the physical form of the protein produced (XylR or XylRDeltaA), and the presence or absence of aromatic inducers in the medium influenced the intracellular pool of these molecules. XylR oscillated from a minimum of approximately 30 molecules (monomers) per cell during exponential phase to approximately140 molecules per cell at stationary phase. Activation of XylR by aromatic inducers decreased the intracellular concentration of the regulator. The levels of the constitutively active variant of XylR named XylRDeltaA were higher, fluctuating between approximately 90 and approximately 570 molecules per cell, depending on the growth stage. These results are compatible with the present model of transcriptional autoregulation of XylR and suggest the existence of mechanisms controlling the stability of XylR protein in vivo.

Dataset Information

HbpR, a new member of the XylR/DmpR subclass within the NtrC family of bacterial transcriptional activators, regulates expression of 2-hydroxybiphenyl metabolism in Pseudomonas azelaica HBP1.

Publications

HbpR, a new member of the XylR/DmpR subclass within the NtrC family of bacterial transcriptional activators, regulates expression of 2-hydroxybiphenyl metabolism in Pseudomonas azelaica HBP1.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets