Growing Repertoire of AraC/XylS Activators

Egan, Susan M.

doi:10.1128/jb.184.20.5529-5532.2002

Cited by 127 publications

(158 citation statements)

References 46 publications

(40 reference statements)

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“…In each case the positive regulator has been shown to require two binding sites, one located upstream and one downstream of the promoter (Jordi et al, 1992;Murphree et al, 1997). The requirement for the downstream site has never been explained adequately (Egan, 2002) and it is tempting to speculate that it is involved in the establishment of an Rns-or CfaD-mediated bridge that protects the promoter from incursion by H-NS.…”

Section: The Leuo Protein: Setting Boundariesmentioning

confidence: 99%

Anti-silencing: overcoming H-NS-mediated repression of transcription in Gram-negative enteric bacteria

2008

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Section: The Leuo Protein: Setting Boundariesmentioning

confidence: 99%

Anti-silencing: overcoming H-NS-mediated repression of transcription in Gram-negative enteric bacteria

2008

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“…2). AraCfamily transcription regulators generally function as dimers to either activate or repress transcription at a given locus (57,58). The AraC family members canonically regulate genes involved in metabolism (e.g., AraC and XylS for regulation of arabinose and xylene/benzoate metabolism, respectively [59,60]) and/or virulence (61) (e.g., ExsA regulation of type III secretion in P. aeruginosa [62] and ToxT regulation of cholera toxin and the toxincoregulated pilus in Vibrio cholerae [63]).…”

Section: Choline and Gb Import Versus De Novo Synthesismentioning

confidence: 99%

Homeostasis and Catabolism of Choline and Glycine Betaine: Lessons from Pseudomonas aeruginosa

Wargo

2013

Appl Environ Microbiol

155

121

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Most sequenced bacteria possess mechanisms to import choline and glycine betaine (GB) into the cytoplasm. The primary role of choline in bacteria appears to be as the precursor to GB, and GB is thought to primarily act as a potent osmoprotectant. Choline and GB may play accessory roles in shaping microbial communities, based on their limited availability and ability to enhance survival under stress conditions. Choline and GB enrichment near eukaryotes suggests a role in the chemical relationships between these two kingdoms, and some of these interactions have been experimentally demonstrated. While many bacteria can convert choline to GB for osmoprotection, a variety of soil-and water-dwelling bacteria have catabolic pathways for the multistep conversion of choline, via GB, to glycine and can thereby use choline and GB as sole sources of carbon and nitrogen. In these choline catabolizers, the GB intermediate represents a metabolic decision point to determine whether GB is catabolized or stored as an osmo-and stress protectant. This minireview focuses on this decision point in Pseudomonas aeruginosa, which aerobically catabolizes choline and can use GB as an osmoprotectant and a nutrient source. P. aeruginosa is an experimentally tractable and ecologically relevant model to study the regulatory pathways controlling choline and GB homeostasis in choline-catabolizing bacteria. The study of P. aeruginosa associations with eukaryotes and other bacteria also makes this a powerful model to study the impact of choline and GB, and their associated regulatory and catabolic pathways, on host-microbe and microbe-microbe relationships.

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“…Like ExsA, they often possess an additional N-terminal domain that may carry dimerization determinants and/or ligand-binding property capable of modulating their activity (14,15). Interestingly, although the ligands are usually small molecules (for instance, arabinose for AraC and 3-methyl benzoate for XylS), some AraC/XylS members involved in virulence, and more particularly in T3SS, are regulated positively or negatively through interactions with protein ligands (16).…”

mentioning

confidence: 99%

Anti-activator ExsD Forms a 1:1 Complex with ExsA to Inhibit Transcription of Type III Secretion Operons

Thibault

Faudry

Ebel

et al. 2009

Journal of Biological Chemistry

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The ExsA protein is a Pseudomonas aeruginosa transcriptional regulator of the AraC/XylS family that is responsible for activating the type III secretion system operons upon host cell contact. Its activity is known to be controlled in vivo through interaction with its negative regulator ExsD. Using a heterologous expression system, we demonstrated that ExsD is sufficient to inhibit the transcriptional activity of ExsA. Gel shift assays with ExsA-and ExsD-containing cytosolic extracts revealed that ExsD does not block DNA target sites but affects the DNA binding activity of the transcriptional activator. The ExsA-ExsD complex was purified after coproduction of the two partners in Escherichia coli. Size exclusion chromatography and ultracentrifugation analysis revealed a homogeneous complex with a 1:1 ratio. When in interaction with ExsD, ExsA is not able to bind to its specific target any longer, as evidenced by gel shift assays. Size exclusion chromatography further showed a partial dissociation of the complex in the presence of a specific DNA sequence. A model of the molecular inhibitory role of ExsD toward ExsA is proposed, in which, under noninducing conditions, the anti-activator ExsD sequesters ExsA and hinders its binding to DNA sites, preventing the transcription of type III secretion genes.

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Growing Repertoire of AraC/XylS Activators

Cited by 127 publications

References 46 publications

Anti-silencing: overcoming H-NS-mediated repression of transcription in Gram-negative enteric bacteria

Anti-silencing: overcoming H-NS-mediated repression of transcription in Gram-negative enteric bacteria

Homeostasis and Catabolism of Choline and Glycine Betaine: Lessons from Pseudomonas aeruginosa

Anti-activator ExsD Forms a 1:1 Complex with ExsA to Inhibit Transcription of Type III Secretion Operons

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