Role of <scp>PdxR</scp> in the activation of vitamin <scp>B</scp>6 biosynthesis in <scp>L</scp>isteria monocytogenes

Belitsky, Boris R.

doi:10.1111/mmi.12618

Cited by 38 publications

(73 citation statements)

References 42 publications

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“…In addition, members of the MocR family have a highly conserved aspartate (class I) aminotransferase domain at their C terminus, which can bind pyridoxal 5=-phosphate (PLP) as a cofactor (3,5,13,14). PLP, alone or with other small molecules, proved to modulate the DNA-binding activities of MocR family regulators (5,(13)(14)(15)(16). Since the putative PLP-binding site is highly conserved in EhuR (data not shown), we analyzed EhuR-mediated mobility shifts in the presence of PLP as well as ectoine, DABA (a catabolic end product), and aspartate (Fig.…”

Section: Resultsmentioning

confidence: 99%

“…PdxR, another MocR protein, directly activates the divergently transcribed pdxST operon (which is responsible for the de novo synthesis of PLP) and serves as a negative autoregulator in Corynebacterium glutamicum, Listeria monocytogenes, and Bacillus clausii. PLP decreases the activation activity and increases the repression activity of PdxR (5,7,14,15). Still another MocR family member, TauR, was found to activate taurine-dependent tpa expression (6).…”

Section: Discussionmentioning

confidence: 99%

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Negative Regulation of Ectoine Uptake and Catabolism in Sinorhizobium meliloti: Characterization of the EhuR Gene

Cai

Zhang

et al. 2017

J Bacteriol

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Ectoine has osmoprotective effects on Sinorhizobium meliloti that differ from its effects in other bacteria. Ectoine does not accumulate in S. meliloti cells; instead, it is degraded. The products of the ehuABCD-eutABCDE operon were previously discovered to be responsible for the uptake and catabolism of ectoine in S. meliloti. However, the mechanism by which ectoine is involved in the regulation of the ehuABCD-eutABCDE operon remains unclear. The ehuR gene, which is upstream of and oriented in the same direction as the ehuABCD-eutABCDE operon, encodes a member of the MocR/GntR family of transcriptional regulators. Quantitative reverse transcription-PCR and promoter-lacZ reporter fusion experiments revealed that EhuR represses transcription of the ehuABCD-eutABCDE operon, but this repression is inhibited in the presence of ectoine. Electrophoretic mobility shift assays and DNase I footprinting assays revealed that EhuR bound specifically to the DNA regions overlapping the Ϫ35 region of the ehuA promoter and the ϩ1 region of the ehuR promoter. Surface plasmon resonance assays further demonstrated direct interactions between EhuR and the two promoters, although EhuR was found to have higher affinity for the ehuA promoter than for the ehuR promoter. In vitro, DNA binding by EhuR could be directly inhibited by a degradation product of ectoine. Our work demonstrates that EhuR is an important negative transcriptional regulator involved in the regulation of ectoine uptake and catabolism and is likely regulated by one or more end products of ectoine catabolism.IMPORTANCE Sinorhizobium meliloti is an important soil bacterium that displays symbiotic interactions with legume hosts. Ectoine serves as a key osmoprotectant for S. meliloti. However, ectoine does not accumulate in the cells; rather, it is degraded. In this study, we characterized the transcriptional regulation of the operon responsible for ectoine uptake and catabolism in S. meliloti. We identified and characterized the transcription repressor EhuR, which is the first MocR/GntR family member found to be involved in the regulation of compatible solute uptake and catabolism. More importantly, we demonstrated for the first time that an ectoine catabolic end product could modulate EhuR DNA-binding activity. Therefore, this work provides new insights into the unique mechanism of ectoine-induced osmoprotection in S. meliloti.KEYWORDS Sinorhizobium meliloti, EhuR, MocR, ectoine, transcriptional regulator S inorhizobium meliloti is a soil bacterium that can be found either free-living or on the roots of leguminous plants. The ability to adapt to changes in the osmolality of the external soil environment is of vital importance for the growth and survival of soil bacteria, and ectoine serves as a key osmoprotectant for S. meliloti (1). Unlike many other bacteria, however, S. meliloti does not produce ectoine. Therefore, other soil

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Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Negative Regulation of Ectoine Uptake and Catabolism in Sinorhizobium meliloti: Characterization of the EhuR Gene

Cai

Zhang

et al. 2017

J Bacteriol

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“…arrangement of two direct repeats and one inverted repeat is very similar to the pdxR-pdxST promoter region of C. glutamicum [10]. On the other hand, the promoter region in L. monocytogenes [12], although having two direct repeats and one inverted repeat, shows a different arrangement of these recognition elements (Fig. 7).…”

mentioning

confidence: 91%

“…Despite the importance of vitamin B 6 metabolism, only a few studies have focused on the regulation of vitamin B 6 biosynthesis and recycling [8] and, in particular, very little is known about the regulation of gene expression. Recently, the role of the transcriptional regulator PdxR in the expression of pdxST genes was analyzed in Corynebacterium glutamicum [10], Streptococcus pneumoniae [11] and Listeria monocytogenes [12]. These studies demonstrated that, in these organisms, PdxR acts as an activator of pdxST transcription and, at the same time, as an autorepressor of its own pdxR gene.…”

Section: Introductionmentioning

confidence: 99%

“…7). In the model proposed for L. monocytogenes [12], PdxR binds to DNA inverted repeats in its dimeric form, whether or not PLP is bound to the transcriptional activator. In this model, the distance between the recognized DNA sequences (corresponding to one helix turn) is not compatible with a closed GabR-like conformation of PdxR, in which the HTH domains are separated by a distance corresponding to three DNA helix turns.…”

Section: Proposed Molecular Mechanism For Bcpdxrmentioning

confidence: 99%

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Molecular mechanism of PdxR – a transcriptional activator involved in the regulation of vitamin B₆ biosynthesis in the probiotic bacterium Bacillus clausii

et al. 2015

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Pyridoxal 5′‐phosphate (PLP), the well‐known active form of vitamin B6, is an essential enzyme cofactor involved in a large number of metabolic processes. PLP levels need to be finely tuned in response to cell requirements; however, little is known about the regulation of PLP biosynthesis and recycling pathways. The transcriptional regulator PdxR activates transcription of the pdxST genes encoding PLP synthase. It is characterized by an N‐terminal helix‐turn‐helix motif that binds DNA and an effector‐binding C‐terminal domain homologous to PLP‐dependent enzymes. Although it is known that PLP acts as an anti‐activator, the mechanism of action of PdxR is unknown. In the present study, we analyzed the biochemical and DNA‐binding properties of PdxR from the probiotic Bacillus clausii. Spectroscopic measurements showed that PLP is the only B6 vitamer that acts as an effector molecule of PdxR. Binding of PLP to PdxR determines a protein conformational change, as detected by gel filtration chromatography and limited proteolysis experiments. We showed that two direct repeats and one inverted repeat are present in the DNA promoter region and PdxR is able to bind DNA fragments containing any combination of two of them. However, when PLP binds to PdxR, it modifies the DNA‐binding properties of the protein, making it selective for inverted repeats. A molecular mechanism is proposed in which the two different DNA binding modalities of PdxR determined by the presence or absence of PLP are responsible for the control of pdxST transcription.

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Underground metabolism facilitates the evolution of novel pathways for vitamin B6 biosynthesis

Richts

Commichau

2021

Appl Microbiol Biotechnol

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The term vitamin B6 is a designation for the vitamers pyridoxal, pyridoxamine, pyridoxine and the respective phosphate esters pyridoxal-5′-phosphate (PLP), pyridoxamine-5′-phosphate and pyridoxine-5′-phosphate. Animals and humans are unable to synthesise vitamin B6. These organisms have to take up vitamin B6 with their diet. Therefore, vitamin B6 is of commercial interest as a food additive and for applications in the pharmaceutical industry. As yet, two naturally occurring routes for de novo synthesis of PLP are known. Both routes have been genetically engineered to obtain bacteria overproducing vitamin B6. Still, major genetic engineering efforts using the existing pathways are required for developing fermentation processes that could outcompete the chemical synthesis of vitamin B6. Recent suppressor screens using mutants of the Gram-negative and Gram-positive model bacteria Escherichia coli and Bacillus subtilis, respectively, carrying mutations in the native pathways or heterologous genes uncovered novel routes for PLP biosynthesis. These pathways consist of promiscuous enzymes and enzymes that are already involved in vitamin B6 biosynthesis. Thus, E. coli and B. subtilis contain multiple promiscuous enzymes causing a so-called underground metabolism allowing the bacteria to bypass disrupted vitamin B6 biosynthetic pathways. The suppressor screens also show the genomic plasticity of the bacteria to suppress a genetic lesion. We discuss the potential of the serendipitous pathways to serve as a starting point for the development of bacteria overproducing vitamin B6. Key points • Known vitamin B6 routes have been genetically engineered. • Underground metabolism facilitates the emergence of novel vitamin B6 biosynthetic pathways. • These pathways may be suitable to engineer bacteria overproducing vitamin B6.

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Role of PdxR in the activation of vitamin B₆ biosynthesis in Listeria monocytogenes

Cited by 38 publications

References 42 publications

Negative Regulation of Ectoine Uptake and Catabolism in Sinorhizobium meliloti: Characterization of the EhuR Gene

Negative Regulation of Ectoine Uptake and Catabolism in Sinorhizobium meliloti: Characterization of the EhuR Gene

Molecular mechanism of PdxR – a transcriptional activator involved in the regulation of vitamin B₆ biosynthesis in the probiotic bacterium Bacillus clausii

Underground metabolism facilitates the evolution of novel pathways for vitamin B6 biosynthesis

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Role of PdxR in the activation of vitamin B6 biosynthesis in Listeria monocytogenes

Cited by 38 publications

References 42 publications

Negative Regulation of Ectoine Uptake and Catabolism in Sinorhizobium meliloti: Characterization of the EhuR Gene

Negative Regulation of Ectoine Uptake and Catabolism in Sinorhizobium meliloti: Characterization of the EhuR Gene

Molecular mechanism of PdxR – a transcriptional activator involved in the regulation of vitamin B6 biosynthesis in the probiotic bacterium Bacillus clausii

Underground metabolism facilitates the evolution of novel pathways for vitamin B6 biosynthesis

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Role of PdxR in the activation of vitamin B₆ biosynthesis in Listeria monocytogenes

Molecular mechanism of PdxR – a transcriptional activator involved in the regulation of vitamin B₆ biosynthesis in the probiotic bacterium Bacillus clausii