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Hofmann L, Mandato A, Saxena S, Ruthstein S. The use of EPR spectroscopy to study transcription mechanisms. Biophys Rev 2022; 14:1141-1159. [PMID: 36345280 PMCID: PMC9636360 DOI: 10.1007/s12551-022-01004-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2022] [Accepted: 09/26/2022] [Indexed: 02/08/2023] Open
Abstract
Electron paramagnetic resonance (EPR) spectroscopy has become a promising structural biology tool to resolve complex and dynamic biological mechanisms in-vitro and in-cell. Here, we focus on the advantages of continuous wave (CW) and pulsed EPR distance measurements to resolve transcription processes and protein-DNA interaction. The wide range of spin-labeling approaches that can be used to follow structural changes in both protein and DNA render EPR a powerful method to study protein-DNA interactions and structure-function relationships in other macromolecular complexes. EPR-derived data goes well beyond static structural information and thus serves as the method of choice if dynamic insight is needed. Herein, we describe the conceptual details of the theory and the methodology and illustrate the use of EPR to study the protein-DNA interaction of the copper-sensitive transcription factor, CueR.
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Affiliation(s)
- L. Hofmann
- Department of Chemistry and the Institute of Nanotechnology and Advanced Materials, Bar Ilan University, Ramat-Gan, Israel
| | - A. Mandato
- Department of Chemistry, University of Pittsburgh, Pittsburgh, PA USA
| | - S. Saxena
- Department of Chemistry, University of Pittsburgh, Pittsburgh, PA USA
| | - S. Ruthstein
- Department of Chemistry and the Institute of Nanotechnology and Advanced Materials, Bar Ilan University, Ramat-Gan, Israel
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2
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Balogh RK, Németh E, Jones NC, Hoffmann SV, Jancsó A, Gyurcsik B. A study on the secondary structure of the metalloregulatory protein CueR: effect of pH, metal ions and DNA. Eur Biophys J 2021; 50:491-500. [PMID: 33907862 DOI: 10.1007/s00249-021-01539-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/23/2020] [Revised: 01/13/2021] [Accepted: 04/14/2021] [Indexed: 11/30/2022]
Abstract
The response of CueR towards environmental changes in solution was investigated. CueR is a bacterial metal ion selective transcriptional metalloregulator protein, which controls the concentration of copper ions in the cell. Although several articles have been devoted to the discussion of the structural and functional features of this protein, CueR has not previously been extensively characterized in solution. Here, we studied the effect of change in pH, temperature, and the presence of specific or non-specific binding partners on the secondary structure of CueR with circular dichroism (CD) spectroscopy. A rather peculiar reversible pH-dependent secondary structure transformation was observed, elucidated and supplemented with pKa estimation by PROPKA and CpHMD simulations suggesting an important role of His(76) and His(94) in this process. CD experiments revealed that the presence of DNA prevents this structural switch, suggesting that DNA locks CueR in the α-helical-rich form. In contrast to the non-cognate metal ions HgII, CdII and ZnII, the presence of the cognate AgI ion affects the secondary structure of CueR, most probably by stabilizing the metal ion and DNA-binding domains of the protein.
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Affiliation(s)
- Ria K Balogh
- Department of Inorganic and Analytical Chemistry, University of Szeged, Dóm tér 7, Szeged, 6720, Hungary
| | - Eszter Németh
- Department of Inorganic and Analytical Chemistry, University of Szeged, Dóm tér 7, Szeged, 6720, Hungary.,Institute of Enzymology, Genome Stability Research Group, Research Centre for Natural Sciences, Magyar tudósok körútja 2, Budapest, 1117, Hungary
| | - Nykola C Jones
- ISA, Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, 8000, Aarhus C, Denmark
| | - Søren Vrønning Hoffmann
- ISA, Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, 8000, Aarhus C, Denmark
| | - Attila Jancsó
- Department of Inorganic and Analytical Chemistry, University of Szeged, Dóm tér 7, Szeged, 6720, Hungary
| | - Béla Gyurcsik
- Department of Inorganic and Analytical Chemistry, University of Szeged, Dóm tér 7, Szeged, 6720, Hungary.
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Baya G, Muhindi S, Ngendahimana V, Caguiat J. Potential Whole-Cell Biosensors for Detection of Metal Using MerR Family Proteins from Enterobacter sp. YSU and Stenotrophomonas maltophilia OR02. Micromachines (Basel) 2021; 12:mi12020142. [PMID: 33572806 PMCID: PMC7911910 DOI: 10.3390/mi12020142] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/07/2021] [Revised: 01/24/2021] [Accepted: 01/27/2021] [Indexed: 01/15/2023]
Abstract
Cell-based biosensors harness a cell's ability to respond to the environment by repurposing its sensing mechanisms. MerR family proteins are activator/repressor switches that regulate the expression of bacterial metal resistance genes and have been used in metal biosensors. Upon metal binding, a conformational change switches gene expression from off to on. The genomes of the multimetal resistant bacterial strains, Stenotrophomonas maltophilia Oak Ridge strain 02 (S. maltophilia 02) and Enterobacter sp. YSU, were recently sequenced. Sequence analysis and gene cloning identified three mercury resistance operons and three MerR switches in these strains. Transposon mutagenesis and sequence analysis identified Enterobacter sp. YSU zinc and copper resistance operons, which appear to be regulated by the protein switches, ZntR and CueR, respectively. Sequence analysis and reverse transcriptase polymerase chain reaction (RT-PCR) showed that a CueR switch appears to activate a S. maltophilia 02 copper transport gene in the presence of CuSO4 and HAuCl4·3H2O. In previous studies, genetic engineering replaced metal resistance genes with the reporter genes for β-galactosidase, luciferase or the green fluorescence protein (GFP). These produce a color change of a reagent, produce light, or fluoresce in the presence of ultraviolet (UV) light, respectively. Coupling these discovered operons with reporter genes has the potential to create whole-cell biosensors for HgCl2, ZnCl2, CuSO4 and HAuCl4·3H2O.
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Affiliation(s)
- Georgina Baya
- Department of Biological and Chemical Sciences, Youngstown State University, Youngstown, OH 44555, USA;
| | - Stephen Muhindi
- Department of Biological Sciences, University of Toledo, Toledo, OH 43606, USA;
| | - Valentine Ngendahimana
- Biology Department, Lone Star College-CyFair, 9191 Barker Cypress Rd, Cypress, TX 77433, USA;
| | - Jonathan Caguiat
- Department of Biological and Chemical Sciences, Youngstown State University, Youngstown, OH 44555, USA;
- Correspondence: ; Tel.: +1-330-941-2063
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Pavlin M, Qasem Z, Sameach H, Gevorkyan-Airapetov L, Ritacco I, Ruthstein S, Magistrato A. Unraveling the Impact of Cysteine-to-Serine Mutations on the Structural and Functional Properties of Cu(I)-Binding Proteins. Int J Mol Sci 2019; 20:E3462. [PMID: 31337158 PMCID: PMC6679193 DOI: 10.3390/ijms20143462] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2019] [Revised: 07/09/2019] [Accepted: 07/11/2019] [Indexed: 02/03/2023] Open
Abstract
Appropriate maintenance of Cu(I) homeostasis is an essential requirement for proper cell function because its misregulation induces the onset of major human diseases and mortality. For this reason, several research efforts have been devoted to dissecting the inner working mechanism of Cu(I)-binding proteins and transporters. A commonly adopted strategy relies on mutations of cysteine residues, for which Cu(I) has an exquisite complementarity, to serines. Nevertheless, in spite of the similarity between these two amino acids, the structural and functional impact of serine mutations on Cu(I)-binding biomolecules remains unclear. Here, we applied various biochemical and biophysical methods, together with all-atom simulations, to investigate the effect of these mutations on the stability, structure, and aggregation propensity of Cu(I)-binding proteins, as well as their interaction with specific partner proteins. Among Cu(I)-binding biomolecules, we focused on the eukaryotic Atox1-ATP7B system, and the prokaryotic CueR metalloregulator. Our results reveal that proteins containing cysteine-to-serine mutations can still bind Cu(I) ions; however, this alters their stability and aggregation propensity. These results contribute to deciphering the critical biological principles underlying the regulatory mechanism of the in-cell Cu(I) concentration, and provide a basis for interpreting future studies that will take advantage of cysteine-to-serine mutations in Cu(I)-binding systems.
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Affiliation(s)
- Matic Pavlin
- CNR-IOM at SISSA, via Bonomea 265, 34135 Trieste, Italy
| | - Zena Qasem
- Department of Chemistry, Faculty of Exact Sciences, Bar Ilan University, Ramat-Gan 5290002, Israel
| | - Hila Sameach
- Department of Chemistry, Faculty of Exact Sciences, Bar Ilan University, Ramat-Gan 5290002, Israel
| | - Lada Gevorkyan-Airapetov
- Department of Chemistry, Faculty of Exact Sciences, Bar Ilan University, Ramat-Gan 5290002, Israel
| | - Ida Ritacco
- CNR-IOM at SISSA, via Bonomea 265, 34135 Trieste, Italy
| | - Sharon Ruthstein
- Department of Chemistry, Faculty of Exact Sciences, Bar Ilan University, Ramat-Gan 5290002, Israel.
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Sameach H, Narunsky A, Azoulay-Ginsburg S, Gevorkyan-Aiapetov L, Zehavi Y, Moskovitz Y, Juven-Gershon T, Ben-Tal N, Ruthstein S. Structural and Dynamics Characterization of the MerR Family Metalloregulator CueR in its Repression and Activation States. Structure 2017; 25:988-996.e3. [PMID: 28578875 DOI: 10.1016/j.str.2017.05.004] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2017] [Revised: 04/12/2017] [Accepted: 05/05/2017] [Indexed: 10/19/2022]
Abstract
CueR (Cu export regulator) is a metalloregulator protein that "senses" Cu(I) ions with very high affinity, thereby stimulating DNA binding and the transcription activation of two other metalloregulator proteins. The crystal structures of CueR when unbound or bound to DNA and a metal ion are very similar to each other, and the role of CueR and Cu(I) in initiating the transcription has not been fully understood yet. Using double electron-electron resonance (DEER) measurements and structure modeling, we investigate the conformational changes that CueR undergoes upon binding Cu(I) and DNA in solution. We observe three distinct conformations, corresponding to apo-CueR, DNA-bound CueR in the absence of Cu(I) (the "repression" state), and CueR-Cu(I)-DNA (the "activation" state). We propose a detailed structural mechanism underlying CueR's regulation of the transcription process. The mechanism explicitly shows the dependence of CueR activity on copper, thereby revealing the important negative feedback mechanism essential for regulating the intracellular copper concentration.
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Affiliation(s)
- Hila Sameach
- The Chemistry Department, Faculty of Exact Sciences, Bar Ilan University, Ramat-Gan 5290002, Israel
| | - Aya Narunsky
- Department of Biochemistry and Molecular Biochemistry, George S. Wise Faculty of Life sciences, Tel Aviv University, Ramat Aviv 69978, Israel
| | - Salome Azoulay-Ginsburg
- The Chemistry Department, Faculty of Exact Sciences, Bar Ilan University, Ramat-Gan 5290002, Israel
| | - Lada Gevorkyan-Aiapetov
- The Chemistry Department, Faculty of Exact Sciences, Bar Ilan University, Ramat-Gan 5290002, Israel
| | - Yonathan Zehavi
- The Mina and Everard Goodman Faculty of Life Sciences, Bar Ilan University, Ramat-Gan 5290002, Israel
| | - Yoni Moskovitz
- The Chemistry Department, Faculty of Exact Sciences, Bar Ilan University, Ramat-Gan 5290002, Israel
| | - Tamar Juven-Gershon
- The Mina and Everard Goodman Faculty of Life Sciences, Bar Ilan University, Ramat-Gan 5290002, Israel
| | - Nir Ben-Tal
- Department of Biochemistry and Molecular Biochemistry, George S. Wise Faculty of Life sciences, Tel Aviv University, Ramat Aviv 69978, Israel
| | - Sharon Ruthstein
- The Chemistry Department, Faculty of Exact Sciences, Bar Ilan University, Ramat-Gan 5290002, Israel.
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Bittner LM, Kraus A, Schäkermann S, Narberhaus F. The Copper Efflux Regulator CueR Is Subject to ATP-Dependent Proteolysis in Escherichia coli. Front Mol Biosci 2017; 4:9. [PMID: 28293558 PMCID: PMC5329002 DOI: 10.3389/fmolb.2017.00009] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2016] [Accepted: 02/13/2017] [Indexed: 11/13/2022] Open
Abstract
The trace element copper serves as cofactor for many enzymes but is toxic at elevated concentrations. In bacteria, the intracellular copper level is maintained by copper efflux systems including the Cue system controlled by the transcription factor CueR. CueR, a member of the MerR family, forms homodimers, and binds monovalent copper ions with high affinity. It activates transcription of the copper tolerance genes copA and cueO via a conserved DNA-distortion mechanism. The mechanism how CueR-induced transcription is turned off is not fully understood. Here, we report that Escherichia coli CueR is prone to proteolysis by the AAA+ proteases Lon, ClpXP, and ClpAP. Using a set of CueR variants, we show that CueR degradation is not altered by mutations affecting copper binding, dimerization or DNA binding of CueR, but requires an accessible C terminus. Except for a twofold stabilization shortly after a copper pulse, proteolysis of CueR is largely copper-independent. Our results suggest that ATP-dependent proteolysis contributes to copper homeostasis in E. coli by turnover of CueR, probably to allow steady monitoring of changes of the intracellular copper level and shut-off of CueR-dependent transcription.
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