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The MocR/GabR Ectoine and Hydroxyectoine Catabolism Regulator EnuR: Inducer and DNA Binding
Lucas Hermann1,2, Felix Dempwolff3, Wieland Steinchen3
1Faculty of Biology, Philipps-University Marburg, Marburg, Germany.
Frontiers in Microbiology
|January 10, 2022
Summary
Bacterial regulators like EnuR control nutrient utilization. This study reveals EnuR
Area of Science:
- Microbiology and Molecular Biology
- Biochemistry
- Bacterial Physiology
Background:
- Compatible solutes ectoine and 5-hydroxyectoine serve as osmostress protectants and nutrients for bacteria.
- Bacterial catabolism of ectoines is often regulated by genes associated with transcriptional repressors like EnuR.
- EnuR belongs to the MocR/GabR sub-family of GntR-type transcription factors.
Purpose of the Study:
- To elucidate the regulatory mechanism of ectoine and 5-hydroxyectoine utilization by the marine bacterium *Ruegeria pomeroyi*.
- To characterize the structure, cofactor binding, and DNA-binding properties of the EnuR repressor.
- To understand the interaction between EnuR, its inducers, and the target promoter.
Main Methods:
- Protein purification and characterization of EnuR from *Ruegeria pomeroyi*.
- Mass spectrometry to identify cofactor attachment and interaction sites.
- Enzyme assays and binding studies to determine inducer and DNA affinities.
- Bioinformatic analysis including evolutionary conservation and structural modeling.
- Site-directed mutagenesis and docking experiments.
Main Results:
- EnuR dimerization is mediated by its aminotransferase domain, which binds pyridoxal-5'-phosphate (PLP) cofactor.
- PLP covalently attaches to Lys302 and interacts with inducer molecules alpha-acetyldiaminobutyric acid (alpha-ADABA) and hydroxy-alpha-acetyldiaminobutyric acid (hydroxy-alpha-ADABA).
- EnuR binds these inducers with low micro-molar affinity and binds to the promoter DNA with micro-molar affinity.
- Structural modeling and docking reveal inducer interaction within the PLP binding cavity.
Conclusions:
- EnuR functions as a repressor, binding to the promoter of ectoine/5-hydroxyectoine utilization genes.
- The binding of alpha-ADABA and hydroxy-alpha-ADABA to EnuR is crucial for regulating gene expression in response to nutrient availability.
- This study provides a regulatory model for bacterial adaptation to environmental ectoines and their subsequent catabolism.
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