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Augustine J, Baksh KA, Prosser RS, Zamble DB. Insights into the Allosteric Response to Acidity by the Helicobacter pylori NikR Transcription Factor. Biochemistry 2023; 62:3265-3275. [PMID: 37917856 DOI: 10.1021/acs.biochem.3c00356] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2023]
Abstract
Helicobacter pylori NikR (HpNikR) is a nickel-responsive transcription factor that regulates genes involved in nickel homeostasis, which is essential for the survival of this pathogen within the acidic human stomach. HpNikR also responds to drops in pH and regulates genes controlling acid acclimation of the bacteria, independently of nickel. We previously showed that nickel binding biases the conformational ensemble of HpNikR to the more DNA-binding competent states via an allosteric network of residues encompassing the nickel binding sites and the interface between the metal- and DNA-binding domains. Here, we examine how acidity promotes this response using 19F-NMR, mutagenesis, and DNA-binding studies. 19F-NMR revealed that a drop in pH from 7.6 to 6.0 does little to shift the conformational ensemble of HpNikR to the DNA binding-compatible cis conformer. Nevertheless, DNA-binding affinities of apo-HpNikR at pH 6.0 and Ni(II)-HpNikR at pH 7.6 are comparable for the ureA promoter. Histidine residues of the nickel binding sites were shown to be important for pH-dependent DNA binding and thus likely impart positive charge to the protein, initiating long-range electrostatic interactions with DNA that induce DNA complexation. The results point to a different DNA-binding mechanism in response to acidity compared to the conformational selection mechanism in response to nickel and overall provide new insights into the influence of pH on HpNikR activity, which contributes to H. pylori viability.
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Affiliation(s)
- Jerry Augustine
- Department of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada
| | - Karina A Baksh
- Department of Biochemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Robert Scott Prosser
- Department of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada
- Department of Biochemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Deborah B Zamble
- Department of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada
- Department of Biochemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada
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2
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Cao K, Li S, Wang Y, Hu H, Xiang S, Zhang Q, Liu Y. Cellular uptake of nickel by NikR is regulated by phase separation. Cell Rep 2023; 42:112518. [PMID: 37210726 DOI: 10.1016/j.celrep.2023.112518] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2022] [Revised: 02/02/2023] [Accepted: 05/01/2023] [Indexed: 05/23/2023] Open
Abstract
Bacterial cells were long thought to be "bags of enzymes" with minimal internal structures. In recent years, membrane-less organelles formed by liquid-liquid phase separation (LLPS) of proteins or nucleic acids have been found to be involved in many important biological processes, although most of them were studied on eukaryotic cells. Here, we report that NikR, a bacterial nickel-responsive regulatory protein, exhibits LLPS both in solution and inside cells. Analyses of cellular nickel uptake and cell growth of E. coli confirm that LLPS enhances the regulatory function of NikR, while disruption of LLPS in cells promotes the expression of nickel transporter (nik) genes, which are negatively regulated by NikR. Mechanistic study shows that Ni(II) ions induces the accumulation of nik promoter DNA into the condensates formed by NikR. This result suggests that the formation of membrane-less compartments can be a regulatory mechanism of metal transporter proteins in bacterial cells.
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Affiliation(s)
- Kaiming Cao
- College of Chemistry and Environmental Engineering, College of Physics and Optoelectronic Engineering, Shenzhen University, Shenzhen 518060, China; Department of Chemistry, University of Science and Technology of China, Hefei 230026, China
| | - Shixuan Li
- Department of Chemistry, University of Science and Technology of China, Hefei 230026, China
| | - Yu Wang
- Department of Chemistry, University of Science and Technology of China, Hefei 230026, China
| | - Hongze Hu
- Department of Chemistry, University of Science and Technology of China, Hefei 230026, China
| | - Sijia Xiang
- Department of Chemistry, University of Science and Technology of China, Hefei 230026, China
| | - Qianling Zhang
- College of Chemistry and Environmental Engineering, College of Physics and Optoelectronic Engineering, Shenzhen University, Shenzhen 518060, China.
| | - Yangzhong Liu
- Department of Chemistry, University of Science and Technology of China, Hefei 230026, China.
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3
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Baksh KA, Augustine J, Sljoka A, Prosser RS, Zamble DB. Mechanistic insights into the nickel-dependent allosteric response of the Helicobacter pylori NikR transcription factor. J Biol Chem 2022; 299:102785. [PMID: 36502919 PMCID: PMC9860126 DOI: 10.1016/j.jbc.2022.102785] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2022] [Revised: 11/30/2022] [Accepted: 12/03/2022] [Indexed: 12/13/2022] Open
Abstract
In Helicobacter pylori, the nickel-responsive NikR transcription factor plays a key role in regulating intracellular nickel concentrations, which is an essential process for survival of this pathogen in the acidic human stomach. Nickel binding to H. pylori NikR (HpNikR) allosterically activates DNA binding to target promoters encoding genes involved in nickel homeostasis and acid adaptation, to either activate or repress their transcription. We previously showed that HpNikR adopts an equilibrium between an open conformation and DNA-binding competent cis and trans states. Nickel binding slows down conformational exchange between these states and shifts the equilibrium toward the binding-competent states. The protein then becomes stabilized in a cis conformation upon binding the ureA promoter. Here, we investigate how nickel binding creates this response and how it is transmitted to the DNA-binding domains. Through mutagenesis, DNA-binding studies, and computational methods, the allosteric response to nickel was found to be propagated from the nickel-binding sites to the DNA-binding domains via the β-sheets of the metal-binding domain and a network of residues at the inter-domain interface. Our computational results suggest that nickel binding increases protein rigidity to slow down the conformational exchange. A thymine base in the ureA promoter sequence, known to be critical for high affinity DNA binding by HpNikR, was also found to be important for the allosteric response, while a modified version of this promoter further highlighted the importance of the DNA sequence in modulating the response. Collectively, our results provide insights into regulation of a key protein for H. pylori survival.
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Affiliation(s)
- Karina A. Baksh
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
| | - Jerry Augustine
- Department of Chemistry, University of Toronto, Toronto, Ontario, Canada
| | - Adnan Sljoka
- RIKEN Center for Advanced Intelligence Project, RIKEN, Chuo-ku, Tokyo, Japan,For correspondence: R. Scott Prosser; Adnan Sljoka
| | - R. Scott Prosser
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada,Department of Chemistry, University of Toronto, Toronto, Ontario, Canada,For correspondence: R. Scott Prosser; Adnan Sljoka
| | - Deborah B. Zamble
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada,Department of Chemistry, University of Toronto, Toronto, Ontario, Canada
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4
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Baksh KA, Pichugin D, Prosser RS, Zamble DB. Allosteric regulation of the nickel-responsive NikR transcription factor from Helicobacter pylori. J Biol Chem 2021; 296:100069. [PMID: 33199369 PMCID: PMC7949043 DOI: 10.1074/jbc.ra120.015459] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2020] [Revised: 11/08/2020] [Accepted: 11/15/2020] [Indexed: 12/20/2022] Open
Abstract
Nickel is essential for the survival of the pathogenic bacteria Helicobacter pylori in the fluctuating pH of the human stomach. Due to its inherent toxicity and limited availability, nickel homeostasis is maintained through a network of pathways that are coordinated by the nickel-responsive transcription factor NikR. Nickel binding to H. pylori NikR (HpNikR) induces an allosteric response favoring a conformation that can bind specific DNA motifs, thereby serving to either activate or repress transcription of specific genes involved in nickel homeostasis and acid adaptation. Here, we examine how nickel induces this response using 19F-NMR, which reveals conformational and dynamic changes associated with nickel-activated DNA complex formation. HpNikR adopts an equilibrium between an open state and DNA-binding competent states regardless of nickel binding, but a higher level of dynamics is observed in the absence of metal. Nickel binding shifts the equilibrium toward the binding-competent states and decreases the mobility of the DNA-binding domains. The nickel-bound protein is then able to adopt a single conformation upon binding a target DNA promoter. Zinc, which does not promote high-affinity DNA binding, is unable to induce the same allosteric response as nickel. We propose that the allosteric mechanism of nickel-activated DNA binding by HpNikR is driven by conformational selection.
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Affiliation(s)
- Karina A Baksh
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
| | - Dmitry Pichugin
- Department of Chemistry, University of Toronto, Toronto, Ontario, Canada
| | - Robert Scott Prosser
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada; Department of Chemistry, University of Toronto, Toronto, Ontario, Canada.
| | - Deborah B Zamble
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada; Department of Chemistry, University of Toronto, Toronto, Ontario, Canada
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5
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Jankovics H, Kovacs B, Saftics A, Gerecsei T, Tóth É, Szekacs I, Vonderviszt F, Horvath R. Grating-coupled interferometry reveals binding kinetics and affinities of Ni ions to genetically engineered protein layers. Sci Rep 2020; 10:22253. [PMID: 33335217 PMCID: PMC7746762 DOI: 10.1038/s41598-020-79226-w] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2020] [Accepted: 12/03/2020] [Indexed: 12/18/2022] Open
Abstract
Reliable measurement of the binding kinetics of low molecular weight analytes to their targets is still a challenging task. Often, the introduction of labels is simply impossible in such measurements, and the application of label-free methods is the only reliable choice. By measuring the binding kinetics of Ni(II) ions to genetically modified flagellin layers, we demonstrate that: (1) Grating-Coupled Interferometry (GCI) is well suited to resolve the binding of ions, even at very low protein immobilization levels; (2) it supplies high quality kinetic data from which the number and strength of available binding sites can be determined, and (3) the rate constants of the binding events can also be obtained with high accuracy. Experiments were performed using a flagellin variant incorporating the C-terminal domain of the nickel-responsive transcription factor NikR. GCI results were compared to affinity data from titration calorimetry. We found that besides the low-affinity binding sites characterized by a micromolar dissociation constant (Kd), tetrameric FliC-NikRC molecules possess high-affinity binding sites with Kd values in the nanomolar range. GCI enabled us to obtain real-time kinetic data for the specific binding of an analyte with molar mass as low as 59 Da, even at signals lower than 1 pg/mm2.
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Affiliation(s)
- Hajnalka Jankovics
- Bio-Nanosystems Laboratory, Research Institute of Biomolecular and Chemical Engineering, University of Pannonia, Egyetem u. 10, Veszprém, Hungary
| | - Boglarka Kovacs
- Nanobiosensorics Laboratory, Institute of Technical Physics and Materials Science, Centre for Energy Research, Konkoly-Thege Miklós út 29-33, Budapest, Hungary
| | - Andras Saftics
- Nanobiosensorics Laboratory, Institute of Technical Physics and Materials Science, Centre for Energy Research, Konkoly-Thege Miklós út 29-33, Budapest, Hungary
| | - Tamas Gerecsei
- Nanobiosensorics Laboratory, Institute of Technical Physics and Materials Science, Centre for Energy Research, Konkoly-Thege Miklós út 29-33, Budapest, Hungary
| | - Éva Tóth
- Bio-Nanosystems Laboratory, Research Institute of Biomolecular and Chemical Engineering, University of Pannonia, Egyetem u. 10, Veszprém, Hungary
| | - Inna Szekacs
- Nanobiosensorics Laboratory, Institute of Technical Physics and Materials Science, Centre for Energy Research, Konkoly-Thege Miklós út 29-33, Budapest, Hungary
| | - Ferenc Vonderviszt
- Bio-Nanosystems Laboratory, Research Institute of Biomolecular and Chemical Engineering, University of Pannonia, Egyetem u. 10, Veszprém, Hungary
- Nanobiosensorics Laboratory, Institute of Technical Physics and Materials Science, Centre for Energy Research, Konkoly-Thege Miklós út 29-33, Budapest, Hungary
| | - Robert Horvath
- Nanobiosensorics Laboratory, Institute of Technical Physics and Materials Science, Centre for Energy Research, Konkoly-Thege Miklós út 29-33, Budapest, Hungary.
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6
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Abstract
Nickel is essential for the survival of many pathogenic bacteria. E. coli and H. pylori require nickel for [NiFe]-hydrogenases. H. pylori also requires nickel for urease. At high concentrations nickel can be toxic to the cell, therefore, nickel concentrations are tightly regulated. Metalloregulators help to maintain nickel concentration in the cell by regulating the expression of the genes associated with nickel import and export. Nickel import into the cell, delivery of nickel to target proteins, and export of nickel from the cell is a very intricate and well-choreographed process. The delivery of nickel to [NiFe]-hydrogenase and urease is complex and involves several chaperones and accessory proteins. A combination of biochemical, crystallographic, and spectroscopic techniques has been utilized to study the structures of these proteins, as well as protein-protein interactions resulting in an expansion of our knowledge regarding how these proteins sense and bind nickel. In this review, recent advances in the field will be discussed, focusing on the metal site structures of nickel bound to metalloregulators and chaperones.
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7
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Handing KB, Niedzialkowska E, Shabalin IG, Kuhn ML, Zheng H, Minor W. Characterizing metal-binding sites in proteins with X-ray crystallography. Nat Protoc 2018; 13:1062-1090. [PMID: 29674755 PMCID: PMC6235626 DOI: 10.1038/nprot.2018.018] [Citation(s) in RCA: 65] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Metals have crucial roles in many physiological, pathological, toxicological, pharmaceutical, and diagnostic processes. Proper handling of metal-containing macromolecule samples for structural studies is not trivial, and failure to handle them properly is often a source of irreproducibility caused by issues such as pH changes, incorporation of unexpected metals, or oxidization/reduction of the metal. This protocol outlines the guidelines and best practices for characterizing metal-binding sites in protein structures and alerts experimenters to potential pitfalls during the preparation and handling of metal-containing protein samples for X-ray crystallography studies. The protocol features strategies for controlling the sample pH and the metal oxidation state, recording X-ray fluorescence (XRF) spectra, and collecting diffraction data sets above and below the corresponding metal absorption edges. This protocol should allow experimenters to gather sufficient evidence to unambiguously determine the identity and location of the metal of interest, as well as to accurately characterize the coordinating ligands in the metal binding environment within the protein. Meticulous handling of metal-containing macromolecule samples as described in this protocol should enhance experimental reproducibility in biomedical sciences, especially in X-ray macromolecular crystallography. For most samples, the protocol can be completed within a period of 7-190 d, most of which (2-180 d) is devoted to growing the crystal. The protocol should be readily understandable to structural biologists, particularly protein crystallographers with an intermediate level of experience.
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Affiliation(s)
- Katarzyna B Handing
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, Virginia, USA
- Center for Structural Genomics of Infectious Diseases (CSGID), University of Virginia, Charlottesville, Virginia, USA
| | - Ewa Niedzialkowska
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, Virginia, USA
- Center for Structural Genomics of Infectious Diseases (CSGID), University of Virginia, Charlottesville, Virginia, USA
- Jerzy Haber Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences, Krakow, Poland
| | - Ivan G Shabalin
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, Virginia, USA
- Center for Structural Genomics of Infectious Diseases (CSGID), University of Virginia, Charlottesville, Virginia, USA
| | - Misty L Kuhn
- Department of Chemistry and Biochemistry, San Francisco State University, San Francisco, California, USA
| | - Heping Zheng
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, Virginia, USA
- Center for Structural Genomics of Infectious Diseases (CSGID), University of Virginia, Charlottesville, Virginia, USA
| | - Wladek Minor
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, Virginia, USA
- Center for Structural Genomics of Infectious Diseases (CSGID), University of Virginia, Charlottesville, Virginia, USA
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8
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Abstract
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Metal ions and metallocofactors play important
roles in a broad
range of biochemical reactions. Accordingly, it has been estimated
that as much as 25–50% of the proteome uses transition metal
ions to carry out a variety of essential functions. The metal ions
incorporated within metalloproteins fulfill functional roles based
on chemical properties, the diversity of which arises as transition
metals can adopt different redox states and geometries, dictated by
the identity of the metal and the protein environment. The coupling
of a metal ion with an organic framework in metallocofactors, such
as heme and cobalamin, further expands the chemical functionality
of metals in biology. The three-dimensional visualization of metal
ions and complex metallocofactors within a protein scaffold is often
a starting point for enzymology, highlighting the importance of structural
characterization of metalloproteins. Metalloprotein crystallography,
however, presents a number of implicit challenges including correctly
incorporating the relevant metal or metallocofactor, maintaining the
proper environment for the protein to be purified and crystallized
(including providing anaerobic, cold, or aphotic environments), and
being mindful of the possibility of X-ray induced damage to the proteins
or incorporated metal ions. Nevertheless, the incorporated metals
or metallocofactors also present unique advantages in metalloprotein
crystallography. The significant resonance that metals undergo with
X-ray photons at wavelengths used for protein crystallography and
the rich electronic properties of metals, which provide intense and
spectroscopically unique signatures, allow a metalloprotein crystallographer
to use anomalous dispersion to determine phases for structure solution
and to use simultaneous or parallel spectroscopic techniques on single
crystals. These properties, coupled with the improved brightness of
beamlines, the ability to tune the wavelength of the X-ray beam, the
availability of advanced detectors, and the incorporation of spectroscopic
equipment at a number of synchrotron beamlines, have yielded exciting
developments in metalloprotein structure determination. Here we will
present results on the advantageous uses of metals in metalloprotein
crystallography, including using metallocofactors to obtain phasing
information, using K-edge X-ray absorption spectroscopy to identify
metals coordinated in metalloprotein crystals, and using UV–vis
spectroscopy on crystals to probe the enzymatic activity of the crystallized
protein.
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Affiliation(s)
- Sarah E. J. Bowman
- Department
of Chemistry, ‡Department of Biology, and §Howard Hughes Medical Institute, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
| | - Jennifer Bridwell-Rabb
- Department
of Chemistry, ‡Department of Biology, and §Howard Hughes Medical Institute, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
| | - Catherine L. Drennan
- Department
of Chemistry, ‡Department of Biology, and §Howard Hughes Medical Institute, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
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9
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Abstract
In Escherichia coli, hydrogen metabolism plays a prominent role in anaerobic physiology. The genome contains the capability to produce and assemble up to four [NiFe]-hydrogenases, each of which are known, or predicted, to contribute to different aspects of cellular metabolism. In recent years, there have been major advances in the understanding of the structure, function, and roles of the E. coli [NiFe]-hydrogenases. The membrane-bound, periplasmically oriented, respiratory Hyd-1 isoenzyme has become one of the most important paradigm systems for understanding an important class of oxygen-tolerant enzymes, as well as providing key information on the mechanism of hydrogen activation per se. The membrane-bound, periplasmically oriented, Hyd-2 isoenzyme has emerged as an unusual, bidirectional redox valve able to link hydrogen oxidation to quinone reduction during anaerobic respiration, or to allow disposal of excess reducing equivalents as hydrogen gas. The membrane-bound, cytoplasmically oriented, Hyd-3 isoenzyme is part of the formate hydrogenlyase complex, which acts to detoxify excess formic acid under anaerobic fermentative conditions and is geared towards hydrogen production under those conditions. Sequence identity between some Hyd-3 subunits and those of the respiratory NADH dehydrogenases has led to hypotheses that the activity of this isoenzyme may be tightly coupled to the formation of transmembrane ion gradients. Finally, the E. coli genome encodes a homologue of Hyd-3, termed Hyd-4, however strong evidence for a physiological role for E. coli Hyd-4 remains elusive. In this review, the versatile hydrogen metabolism of E. coli will be discussed and the roles and potential applications of the spectrum of different types of [NiFe]-hydrogenases available will be explored.
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10
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Sanyal R, Zhang X, Chakraborty P, Giri S, Chattopadhyay SK, Zhao C, Das D. Role of solvent in the phosphatase activity of a dinuclear nickel(ii) complex of a Schiff base ligand: mechanistic interpretation by DFT studies. NEW J CHEM 2016. [DOI: 10.1039/c6nj01043a] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A biomimetic metallohydrolase has been synthesized and its catalytic mechanism and the related solvent effect were elucidated using theoretical modeling.
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Affiliation(s)
- Ria Sanyal
- Department of Chemistry
- University of Calcutta
- Kolkata – 700 009
- India
| | - Xuepeng Zhang
- School of Chemistry and Chemical Engineering
- Sun Yat-Sen University
- Guangzhou 510275
- P. R. China
| | | | - Sanjib Giri
- Department of Chemistry
- University of Calcutta
- Kolkata – 700 009
- India
| | | | - Cunyuan Zhao
- School of Chemistry and Chemical Engineering
- Sun Yat-Sen University
- Guangzhou 510275
- P. R. China
| | - Debasis Das
- Department of Chemistry
- University of Calcutta
- Kolkata – 700 009
- India
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11
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Mazzei L, Dobrovolska O, Musiani F, Zambelli B, Ciurli S. On the interaction of Helicobacter pylori NikR, a Ni(II)-responsive transcription factor, with the urease operator: in solution and in silico studies. J Biol Inorg Chem 2015. [PMID: 26204982 DOI: 10.1007/s00775-015-1284-0] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Helicobacter pylori (Hp) is a carcinogen that relies on Ni(II) to survive in the extreme pH conditions of the human guts. The regulation of genes coding for Ni(II) enzymes and proteins is effected by the nickel-responsive transcription factor NikR, composed of a DNA-binding domain (DBD) and a metal-binding domain (MBD). The scope of this study is to obtain the molecular details of the HpNikR interaction with the urease operator OP ureA , in solution. The size of the full-length protein prevents the characterization of the HpNikR-OP ureA interaction using NMR. We thus investigated the two separate domains of HpNikR. The conservation of their oligomeric state was established by multiple-angle light scattering. Isothermal calorimetric titrations indicated that the thermodynamics of Ni(II) binding to the isolated MBD is independent of the presence of the adjacent DBDs. The NMR spectra of the isolated DBD support considerable conservation of its structural properties. The spectral perturbations induced on the DBD by OP ureA provided information useful to calculate a structural model of the HpNikR-OP ureA complex using a docking computational protocol. The NMR assignment of the residues involved in the protein-DNA interaction represents a starting point for the development of drugs potentially able to eradicate H. pylori infections. All evidences so far collected, in this and previous studies, consistently indicate that binding of Ni(II) to the MBD increases the HpNikR-DNA affinity by modulating the dynamic, and not the structural, properties of the protein, suggesting that the formation of a stable complex relies upon an induced fit mechanism.
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Affiliation(s)
- Luca Mazzei
- Laboratory of Bioinorganic Chemistry, Department of Pharmacy and Biotechnology, University of Bologna, Bologna, 40127, Italy
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12
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Lu M, Jiang YL, Wang S, Jin H, Zhang RG, Virolle MJ, Chen Y, Zhou CZ. Streptomyces coelicolor SCO4226 is a nickel binding protein. PLoS One 2014; 9:e109660. [PMID: 25285530 PMCID: PMC4186839 DOI: 10.1371/journal.pone.0109660] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2014] [Accepted: 09/03/2014] [Indexed: 12/03/2022] Open
Abstract
The open reading frame SCO4226 of Streptomyces coelicolor A3(2) encodes an 82-residue hypothetical protein. Biochemical assays revealed that each SCO4226 dimer binds four nickel ions. To decipher the molecular function, we solved the crystal structures of SCO4226 in both apo- and nickel-bound (Ni-SCO4226) forms at 1.30 and 2.04 Å resolution, respectively. Each subunit of SCO4226 dimer adopts a canonical ferredoxin-like fold with five β-strands flanked by two α-helices. In the structure of Ni-SCO4226, four nickel ions are coordinated at the surface of the dimer. Further biochemical assays suggested that the binding of Ni2+ triggers the self-aggregation of SCO4226 in vitro. In addition, RT-qPCR assays demonstrated that the expression of SCO4226 gene in S. coelicolor is specifically up-regulated by the addition of Ni2+, but not other divalent ions such as Cu2+, Mn2+ or Co2+. All these results suggested that SCO4226 acts as a nickel binding protein, probably required for nickel sequestration and/or detoxification.
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Affiliation(s)
- Mo Lu
- Hefei National Laboratory for Physical Sciences at the Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, People's Republic of China
- Department of Biology, South University of Sciences and Technology of China, Shenzhen, Guangdong, People's Republic of China
| | - Yong-Liang Jiang
- Hefei National Laboratory for Physical Sciences at the Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, People's Republic of China
- * E-mail: (YLJ); (CZZ)
| | - Shu Wang
- Hefei National Laboratory for Physical Sciences at the Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, People's Republic of China
| | - Hua Jin
- Hefei National Laboratory for Physical Sciences at the Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, People's Republic of China
| | - Rong-Guang Zhang
- Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Marie-Joelle Virolle
- Institut de Génétique et Microbiologie, UMR8621 CNRS Université Paris Sud, Orsay, France
| | - Yuxing Chen
- Hefei National Laboratory for Physical Sciences at the Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, People's Republic of China
| | - Cong-Zhao Zhou
- Hefei National Laboratory for Physical Sciences at the Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, People's Republic of China
- * E-mail: (YLJ); (CZZ)
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13
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Chivers PT. Cobalt and Nickel. BINDING, TRANSPORT AND STORAGE OF METAL IONS IN BIOLOGICAL CELLS 2014. [DOI: 10.1039/9781849739979-00381] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Cobalt and nickel play key roles in biological systems as cofactors in a small number of important enzymes. The majority of these are found in microbes. Evidence for direct roles for Ni(II) and Co(II) enzymes in higher organisms is limited, with the exception of the well-known requirement for the cobalt-containing vitamin B12 cofactor and the Ni-dependent urease in plants. Nonetheless, nickel in particular plays a key role in human health because of its essential role in microbes that inhabit various growth niches within the body. These roles can be beneficial, as can be seen with the anaerobic production and consumption of H2 in the digestive tract by bacteria and archaea that results in increased yields of short-chain fatty acids. In other cases, nickel has an established role in the establishment of pathogenic infection (Helicobacter pylori urease and colonization of the stomach). The synthesis of Co- and Ni-containing enzymes requires metal import from the extracellular milieu followed by the targeting of these metals to the appropriate protein and enzymes involved in metallocluster or cofactor biosynthesis. These metals are toxic in excess so their levels must be regulated carefully. This complex pathway of metalloenzyme synthesis and intracellular homeostasis requires proteins that can specifically recognize these metals in a hierarchical manner. This chapter focuses on quantitative and structural details of the cobalt and nickel binding sites in transport, trafficking and regulatory proteins involved in cobalt and nickel metabolism in microbes.
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Affiliation(s)
- Peter T. Chivers
- Department of Chemistry, School of Biological and Biomedical Sciences, and Biophysical Sciences Institute, Durham University Durham UK
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14
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15
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Higgins KA, Carr CE, Maroney MJ. Specific metal recognition in nickel trafficking. Biochemistry 2012; 51:7816-32. [PMID: 22970729 DOI: 10.1021/bi300981m] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Nickel is an essential metal for a number of bacterial species that have developed systems for acquiring, delivering, and incorporating the metal into target enzymes and controlling the levels of nickel in cells to prevent toxic effects. As with other transition metals, these trafficking systems must be able to distinguish between the desired metal and other transition metal ions with similar physical and chemical properties. Because there are few enzymes (targets) that require nickel for activity (e.g., Escherichia coli transports nickel for hydrogenases made under anaerobic conditions, and Helicobacter pylori requires nickel for hydrogenase and urease that are essential for acid viability), the "traffic pattern" for nickel is relatively simple, and nickel trafficking therefore presents an opportunity to examine a system for the mechanisms that are used to distinguish nickel from other metals. In this review, we describe the details known for examples of uptake permeases, metallochaperones and proteins involved in metallocenter assembly, and nickel metalloregulators. We also illustrate a variety of mechanisms, including molecular recognition in the case of NikA protein and examples of allosteric regulation for HypA, NikR, and RcnR, employed to generate specific biological responses to nickel ions.
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Affiliation(s)
- Khadine A Higgins
- Department of Chemistry, University of Massachusetts, Amherst, Massachusetts 01003, USA
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16
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Krecisz S, Jones MD, Zamble DB. Nonspecific interactions between Escherichia coli NikR and DNA are critical for nickel-activated DNA binding. Biochemistry 2012; 51:7873-9. [PMID: 22971172 DOI: 10.1021/bi300510z] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The Escherichia coli transcription factor NikR is responsible for nickel-mediated repression of the operon encoding the Nik uptake transporter. The crystal structure of Ni(II)-NikR bound to the nik operator sequence revealed that residues in the loop preceding helix α3 in the metal-binding domain, which becomes structurally ordered upon stoichiometric nickel binding, interact with the DNA backbone. Here, we show that mutating both of these residues that make the nonspecific contacts, K64 and R65, abolishes DNA binding in vitro and nickel-responsive transcriptional repression of the nik promoter in vivo. In contrast, mutation of Q118, which forms a bridge between R65 and a potassium site, does not impact the activities of NikR. These data support the model that the nonspecific interactions between the metal-binding domain of the protein and the DNA phosphodiester backbone are critical for the Ni(II)-responsive activity of E. coli NikR.
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Affiliation(s)
- Sandra Krecisz
- Department of Chemistry, University of Toronto, Toronto, Ontario, Canada M5S 3H6
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17
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Guerra AJ, Giedroc DP. Metal site occupancy and allosteric switching in bacterial metal sensor proteins. Arch Biochem Biophys 2012; 519:210-22. [PMID: 22178748 PMCID: PMC3312040 DOI: 10.1016/j.abb.2011.11.021] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2011] [Revised: 11/23/2011] [Accepted: 11/29/2011] [Indexed: 12/22/2022]
Abstract
All prokaryotes encode a panel of metal sensor or metalloregulatory proteins that govern the expression of genes that allows an organism to quickly adapt to toxicity or deprivation of both biologically essential transition metal ions, e.g., Zn, Cu, Fe, and heavy metal pollutants. As such, metal sensor proteins can be considered arbiters of intracellular transition metal bioavailability and thus potentially control the metallation state of the metalloproteins in the cell. Metal sensor proteins are specialized allosteric proteins that regulate transcription as a result direct binding of one or two cognate metal ions, to the exclusion of all others. In most cases, the binding of the cognate metal ion induces a structural change in a protein oligomer that either activates or inhibits operator DNA binding. A quantitative measure of the degree to which a particular metal drives metalloregulation of operator DNA-binding is the allosteric coupling free energy, ΔGc. In this review, we summarize recent work directed toward understanding metal occupancy and metal selectivity of these allosteric switches in selected families of metal sensor proteins and examine the structural origins of ΔGc in the functional context a thermodynamic "set-point" model of intracellular metal homeostasis.
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Affiliation(s)
- Alfredo J. Guerra
- Department of Chemistry, Indiana University, 212 S. Hawthorne Drive, Bloomington, IN USA 47405-7102
| | - David P. Giedroc
- Department of Chemistry, Indiana University, 212 S. Hawthorne Drive, Bloomington, IN USA 47405-7102
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Benini S, Cianci M, Ciurli S. Holo-Ni2+ Helicobacter pylori NikR contains four square-planar nickel-binding sites at physiological pH. Dalton Trans 2011; 40:7831-3. [PMID: 21725560 DOI: 10.1039/c1dt11107h] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The crystal structure of Helicobacter pylori holo-NikR, a Ni(2+)-dependent transcription factor, determined at pH 7.3, shows four square-planar nickel-binding sites, involving one cysteinate and three histidine ligands. This observation reconciles previous inconsistencies among calorimetric data, structural information at non-physiological pH, and computational studies.
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Affiliation(s)
- Stefano Benini
- Faculty of Science and Technology, Free University of Bolzano, 39100, Bolzano, Italy.
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Abstract
Both the essentiality and toxicity of transition metals are exploited as part of mammalian immune defenses against bacterial infection. Salmonella serovars continue to cause serious medical and veterinary problems worldwide and detecting deficiency and excess of different metal ions (such as copper, iron, zinc, manganese, nickel, and cobalt) is fundamental to their virulence. This involves multiple DNA-binding metal-responsive transcription factors that discriminate between elements and trigger expression of genes that mediate appropriate responses to metal fluxes. This review focuses on the metal stresses encountered by Salmonella during infection and the roles of the different metal-sensing regulatory proteins and their target genes in adapting to these changing metal levels. Current knowledge regarding the mechanisms of metal-regulated gene expression and the structural features of sensory metal binding sites are described. In addition, the principles governing the ability of the different sensors to detect specific metals within a cell to control cytosolic metal levels are also discussed. These proteins represent potential targets for the development of new therapeutic approaches.
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Phillips CM, Stultz CM, Drennan CL. Searching for the Nik operon: how a ligand-responsive transcription factor hunts for its DNA binding site. Biochemistry 2010; 49:7757-63. [PMID: 20712334 PMCID: PMC2934762 DOI: 10.1021/bi100947k] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
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Transcription factors regulate a wide variety of genes in the cell and play a crucial role in maintaining cellular homeostasis. A major unresolved issue is how transcription factors find their specific DNA binding sequence in the vast expanse of the cell and how they do so at rates that appear faster than the diffusion limit. Here, we relate an atomic-detail model that has been developed to describe the transcription factor NikR’s mechanism of DNA binding to the broader theories of how transcription factors find their binding sites on DNA. NikR is the nickel regulatory transcription factor for many bacteria, and NikR from Escherichia coli is one of the best studied ligand-mediated transcription factors. For the E. coli NikR protein, there is a wide variety of structural, biochemical, and computational studies that provide significant insight into the NikR−DNA binding mechanism. We find that the two models, the atomic-level model for E. coli NikR and the cellular model for transcription factors in general, are in agreement, and the details laid out by the NikR system may lend additional credence to the current models for transcription factors searching for DNA.
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Affiliation(s)
- Christine M Phillips
- Department of Chemistry, Massachusetts Institute of Technology,Cambridge, Massachusetts 02139, USA
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