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Bacillus subtilis glnR mutants defective in regulation
1Center of Marine Biotechnology, University of Maryland Biotechnology Institute, Baltimore 21202, USA.
Gene
|August 8, 1995
Summary
Bacillus subtilis GlnR repressor controls nitrogen assimilation. Mutations in the putative helix-turn-helix motif and C-terminus reveal critical residues for GlnR DNA binding and effector interaction.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- The Bacillus subtilis glnR gene encodes the GlnR repressor, a key regulator of nitrogen assimilation.
- GlnR controls the transcription of the glnRA operon in response to environmental nitrogen availability.
Purpose of the Study:
- To investigate the functional domains of the GlnR repressor involved in regulating gene expression.
- To identify specific amino acid residues critical for GlnR's DNA binding and regulatory activity.
Main Methods:
- Site-directed mutagenesis and random mutagenesis were employed to generate glnR mutants.
- Analysis of mutant phenotypes under varying nitrogen conditions.
- Identification of mutations affecting GlnR repressor function.
Main Results:
- Mutations at Leu77 and Ala80 within the putative helix-turn-helix (HTH) motif disrupted GlnR's ability to repress transcription under nitrogen excess.
- Alteration of Gly72 also impacted regulation, suggesting its role in DNA binding.
- Truncation mutations in the C-terminal region (residues 110, 116, 123, 129) resulted in constitutive repression.
- Substitution of Asp129 with Asn abolished repression, indicating its involvement in effector interaction or modification.
Conclusions:
- The HTH motif region (aa 59-83) and the C-terminal region of GlnR are crucial for its regulatory function.
- Specific residues, including Asp129, are involved in sensing effector molecules or post-translational modifications.
- These findings provide insights into the mechanism of nitrogen regulation by GlnR in Bacillus subtilis.