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The AraC transcriptional activators.
1Laboratory of Molecular Biology, National Institute of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892-0560, USA. rgmartin@helix.nih.gov
Current Opinion in Microbiology
|April 3, 2001
Summary
Bacterial AraC transcriptional activators use helix-turn-helix elements to bind DNA. Sugar metabolism activators require allosteric changes for activation, while virulence activators bind both upstream and downstream DNA sites.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- The AraC family of bacterial transcriptional activators controls various genetic systems.
- Structural studies reveal MarA and Rob activators bind asymmetric DNA sites using helix-turn-helix motifs.
Purpose of the Study:
- To elucidate the mechanisms of transcriptional activation by AraC family proteins.
- To understand the role of DNA binding orientation and interactions with RNA polymerase (RNAP).
Main Methods:
- X-ray diffraction studies to determine protein-DNA complex structures.
- Genetic analyses to investigate activator-RNAP interactions and DNA binding requirements.
Main Results:
- Activator binding orientation is crucial and depends on DNA site proximity to the -10 RNAP signal.
- Sugar metabolism activators undergo allosteric changes upon sugar/CRP interaction to bind activating sites.
- The virulence activator Rns requires binding to both upstream and downstream sites for rns promoter activation.
Conclusions:
- AraC activators exhibit diverse DNA binding and activation strategies.
- Allosteric regulation and multi-site DNA interactions are key to controlling gene expression in bacteria.