Journal: Nat Commun / Year: 2022 Title: A nucleotide-sensing oligomerization mechanism that controls NrdR-dependent transcription of ribonucleotide reductases. Authors: Inna Rozman Grinberg / Markel Martínez-Carranza / Ornella Bimai / Ghada Nouaïria / Saher Shahid / Daniel Lundin / Derek T Logan / Britt-Marie Sjöberg / Pål Stenmark / Abstract: Ribonucleotide reductase (RNR) is an essential enzyme that catalyzes the synthesis of DNA building blocks in virtually all living cells. NrdR, an RNR-specific repressor, controls the transcription of ...Ribonucleotide reductase (RNR) is an essential enzyme that catalyzes the synthesis of DNA building blocks in virtually all living cells. NrdR, an RNR-specific repressor, controls the transcription of RNR genes and, often, its own, in most bacteria and some archaea. NrdR senses the concentration of nucleotides through its ATP-cone, an evolutionarily mobile domain that also regulates the enzymatic activity of many RNRs, while a Zn-ribbon domain mediates binding to NrdR boxes upstream of and overlapping the transcription start site of RNR genes. Here, we combine biochemical and cryo-EM studies of NrdR from Streptomyces coelicolor to show, at atomic resolution, how NrdR binds to DNA. The suggested mechanism involves an initial dodecamer loaded with two ATP molecules that cannot bind to DNA. When dATP concentrations increase, an octamer forms that is loaded with one molecule each of dATP and ATP per monomer. A tetramer derived from this octamer then binds to DNA and represses transcription of RNR. In many bacteria - including well-known pathogens such as Mycobacterium tuberculosis - NrdR simultaneously controls multiple RNRs and hence DNA synthesis, making it an excellent target for novel antibiotics development.
Name: ZINC ION / type: ligand / ID: 3 / Number of copies: 12 / Formula: ZN
Molecular weight
Theoretical: 65.409 Da
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Experimental details
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Structure determination
Method
cryo EM
Processing
single particle reconstruction
Aggregation state
particle
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Sample preparation
Concentration
0.4 mg/mL
Buffer
pH: 8
Grid
Model: Quantifoil R1.2/1.3 / Material: GOLD / Mesh: 300 / Support film - Material: GRAPHENE OXIDE / Support film - topology: CONTINUOUS / Pretreatment - Type: GLOW DISCHARGE
Vitrification
Cryogen name: ETHANE / Chamber humidity: 100 % / Chamber temperature: 298 K / Instrument: FEI VITROBOT MARK IV
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Electron microscopy
Microscope
TFS KRIOS
Image recording
Film or detector model: FEI FALCON III (4k x 4k) / Detector mode: COUNTING / Number grids imaged: 2 / Number real images: 6317 / Average electron dose: 50.0 e/Å2
Electron beam
Acceleration voltage: 300 kV / Electron source: FIELD EMISSION GUN
Electron optics
Illumination mode: OTHER / Imaging mode: BRIGHT FIELD
Experimental equipment
Model: Titan Krios / Image courtesy: FEI Company
+
Image processing
Startup model
Type of model: NONE
Final reconstruction
Number classes used: 1 / Applied symmetry - Point group: D3 (2x3 fold dihedral) / Resolution.type: BY AUTHOR / Resolution: 2.96 Å / Resolution method: FSC 0.143 CUT-OFF / Software - Name: cryoSPARC (ver. 3.1) / Number images used: 922502
Initial angle assignment
Type: MAXIMUM LIKELIHOOD / Software - Name: cryoSPARC (ver. 3.1)
Final angle assignment
Type: MAXIMUM LIKELIHOOD / Software - Name: cryoSPARC (ver. 3.1)
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