Recombinant Bacillus subtilis HTH-type transcriptional repressor glcR (glcR)
Description
Introduction to GlcR
The HTH-type transcriptional repressor GlcR is a regulatory protein in Bacillus subtilis that governs carbon catabolite repression (CCR), a process enabling preferential utilization of energetically favorable carbon sources like glucose. GlcR specifically represses catabolic operons when glucose is available, optimizing metabolic efficiency . Recombinant GlcR refers to the protein produced via heterologous expression systems (e.g., E. coli or yeast), enabling detailed biochemical and structural studies .
Functional Role in Carbon Catabolite Repression
GlcR works synergistically with CcpA (catabolite control protein A) to mediate CCR. Key mechanisms include:
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Repression of non-glucose pathways: Silences operons like lev (levanase), sacPA (sucrose utilization), and bglPH (β-glucosidase) in the presence of glucose .
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Regulation of glucose transport: Loss of GlcR function disrupts glucose uptake and ptsG (glucose-specific PTS transporter) expression .
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Cross-talk with other regulators: Mutations in glcR enhance galactose utilization by alleviating repression of the Leloir pathway, as shown in evolved B. subtilis strains .
Recombinant Production and Applications
Recombinant GlcR is produced using plasmid-based systems. Key advances include:
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Heterologous expression: Optimized in E. coli or yeast for high-yield soluble protein .
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Industrial relevance: Engineered B. subtilis strains with glcR mutations show improved galactose metabolism for biotechnological applications (e.g., enzyme production) .
Table 2: Key Mutations and Phenotypic Effects8
| Mutation | Gene | Effect on Metabolism |
|---|---|---|
| SNP1 | araR | Enhanced galactose uptake |
| SNP2 | glcR | Derepression of galactose utilization pathways |
Research Findings
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Glucose transport deficiency: glcR mutants exhibit reduced glucose uptake, linking its role to PTS transporter regulation .
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Evolutionary engineering: Adaptive laboratory evolution (ALE) of B. subtilis identified glcR nonsense mutations that enhance galactose conversion rates by 10-fold .
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Metabolite interplay: GlcR activity is modulated by glycolytic intermediates, though direct ligand interactions remain under investigation .
Future Directions
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Structural studies: Elucidate GlcR-DNA/ligand binding dynamics via cryo-EM or X-ray crystallography.
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Synthetic biology: Engineer glcR variants for fine-tuned metabolic control in industrial strains.
Product Specs
Target Background
KEGG: bsu:BSU36300
STRING: 224308.Bsubs1_010100019626
