The AraC transcriptional activators

The AraC family of bacterial transcriptional activators regulate diverse genetic systems. Recent X-ray diffraction studies show that the monomeric MarA and Rob activators bind to their asymmetric degenerate DNA sites via two different helix-turn-helix elements. Activation by MarA, SoxS or Rob requir...

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Bibliographic Details
Published in:Current Opinion in Microbiology 2001-04, Vol.4 (2), p.132-137
Main Authors: Martin, Robert G, Rosner, Judah L
Format: Article
Language:English
Subjects:
AraC
AraC protein
Bacteriology
Binding Sites
Biological and medical sciences
crystal structure
Crystallography, X-Ray
DNA binding sites
DNA-Directed RNA Polymerases - metabolism
Escherichia coli
Fundamental and applied biological sciences. Psychology
Genes, araC
Genetics
Helix-Turn-Helix Motifs
Host parasite relation
pathogenicity
HTH
Invertebrates
Microbiology
Nemathelminthia. Plathelmintha
promoter
Promoter Regions, Genetic
Protein Conformation
regulation
RNA polymerase
rns promoter
Transcription activation
Transcription Factors - chemistry
Transcription Factors - physiology
Transcription, Genetic
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Summary:The AraC family of bacterial transcriptional activators regulate diverse genetic systems. Recent X-ray diffraction studies show that the monomeric MarA and Rob activators bind to their asymmetric degenerate DNA sites via two different helix-turn-helix elements. Activation by MarA, SoxS or Rob requires a particular orientation of the asymmetric binding sequence (and hence the activator), depending on its distance from the –10 RNAP signal. Genetic studies are beginning to clarify how the activators interact with RNAP. Growing evidence suggests that for the sugar metabolism activators, multiple binding sites upstream of the promoter anchor the activator in a repressing or nonactivating configuration. By interaction with the sugar and/or CRP, the activator is allosterically altered so it can bind a new set of sites that enable it to activate the promoter. Surprisingly, the virulence activator, Rns, must bind to both upstream and downstream sites in order to activate the rns promoter.
ISSN:1369-5274
1879-0364
DOI:10.1016/S1369-5274(00)00178-8