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Published on: October 31, 2013
Interaction of Bacillus subtilis CodY with GTP
Luke D Handke1, Robert P Shivers, Abraham L Sonenshein
1Department of Molecular Biology and Microbiology, Tufts University School of Medicine, 136 Harrison Avenue, Boston, MA 02111, USA.
Bacillus subtilis adaptation relies on CodY, a protein regulated by GTP and branched-chain amino acids (BCAAs). CodY specifically binds GTP, enhancing its DNA affinity without hydrolysis, especially when BCAAs are also present.
Area of Science:
- Microbiology
- Molecular Biology
- Biochemistry
Background:
- Bacillus subtilis utilizes adaptive mechanisms for nutrient availability, primarily regulated by the CodY protein.
- CodY's DNA-binding activity is modulated by effectors: GTP and branched-chain amino acids (BCAAs).
- Nutrient limitation depletes effectors, releasing CodY-mediated repression of adaptive genes.
Purpose of the Study:
- To investigate the interaction between CodY and GTP in vitro.
- To elucidate the role of GTP hydrolysis in CodY-dependent gene regulation.
- To understand the combined effect of GTP and BCAAs on CodY's DNA-binding affinity.
Main Methods:
- DNase I footprinting assays to determine CodY-GTP binding affinity.
- Testing specificity of CodY interaction with various nucleotides.
- In vitro transcription assays to assess CodY's regulatory activity.
Main Results:
- CodY exhibits millimolar affinity for GTP.
- CodY specifically interacts with GTP and dGTP, but not other tested nucleotides like ppGpp or pppGpp.
- Non-hydrolyzable GTP analogs activate CodY binding, indicating hydrolysis is not required.
- GTP and BCAAs act additively to enhance CodY's DNA-binding affinity.
- Transcriptional repression is stronger with both GTP and BCAAs present.
Conclusions:
- CodY's interaction with GTP is specific and enhances its affinity for target genes.
- GTP-dependent activation of CodY is independent of GTP hydrolysis.
- The presence of BCAAs further augments CodY's DNA-binding affinity, highlighting a synergistic regulatory mechanism.
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