PMID:21542860

Citation	Morgan, SJ, Felek, S, Gadwal, S, Koropatkin, NM, Perry, JW, Bryson, AB and Krukonis, ES (2011) The two faces of ToxR: activator of ompU, co-regulator of toxT in Vibrio cholerae. Mol. Microbiol. 81:113-28
Abstract	ToxR of Vibrio cholerae directly activates the ompU promoter, but requires a second activator, TcpP to activate the toxT promoter. ompU encodes a porin, while toxT encodes the transcription factor, ToxT, which activates V. cholerae virulence genes including cholera toxin and the toxin co-regulated pilus. Using an ompU-sacB transcriptional fusion, toxR mutant alleles were identified that encode ToxR molecules defective for ompU promoter activation. Many toxR mutants defective for ompU activation affected residues involved in DNA binding. Mutants defective for ompU activation were also tested for activation of the toxT promoter. ToxR-F69A and ToxR-V71A, both in the α-loop of ToxR, were preferentially defective for ompU activation, with ToxR-V71A nearly completely defective. Six mutants from the ompU-sacB selection showed more dramatic defects in toxT activation than ompU activation. All but one of the affected residues map to the wing domain of the winged helix-turn-helix of ToxR. Some ToxR mutants preferentially affecting toxT activation had partial DNA-binding defects, and one mutant, ToxR-P101L, had altered interactions with TcpP. These data suggest that while certain residues in the α-loop of ToxR are utilized to activate the ompU promoter, the wing domain of ToxR contributes to both promoter binding and ToxR/TcpP interaction facilitating toxT activation.
Links	PubMed PMC3124598 Online version:10.1111/j.1365-2958.2011.07681.x
Keywords	Adhesins, Bacterial/genetics; Adhesins, Bacterial/metabolism; Bacterial Proteins/genetics; Bacterial Proteins/metabolism; DNA, Bacterial/metabolism; DNA-Binding Proteins/genetics; DNA-Binding Proteins/metabolism; Electrophoretic Mobility Shift Assay; Gene Expression Regulation, Bacterial; Helix-Turn-Helix Motifs; Models, Biological; Models, Molecular; Mutant Proteins/genetics; Mutant Proteins/metabolism; Promoter Regions, Genetic; Protein Binding; Protein Conformation; Transcription Factors/genetics; Transcription Factors/metabolism; Vibrio cholerae/genetics; Vibrio cholerae/physiology
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
VIBCH:TOXR	enables	GO:0000156: phosphorelay response regulator activity	ECO:0000314: direct assay evidence used in manual assertion		F		Seeded From UniProt	complete
VIBCH:TOXR		GO:0000156: two-component response regulator activity	ECO:0000314:		F		figure 1, This suggests the ToxR-V71A mutation affects a region of ToxR that is especially important for ToxR to directly activate the ompU promoter, but less critical when ToxR plays an accessory role with TcpP to activate the toxT promoter figure 3. Gel-shift assays to assess promoter recognition by various ToxR mutant proteins identified in a random mutagenesis ompU-sacB selection strategy.	complete CACAO 4012

References

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