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Cho HL, Gullett KL, Fout AR. Synthesis and characterization of tetrapodal nickel complexes with adaptable ligand binding geometries. Chem Commun (Camb) 2024. [PMID: 39229921 DOI: 10.1039/d4cc03186e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/05/2024]
Abstract
This study explores the versatile binding properties of a tetrapodal ligand framework with nickel, demonstrating significant ligand fluxionality through the interconversions of several complexes. Kinetic studies using UV-vis and NMR techniques underscore the pivotal role of solvent coordination in initiating these dynamic processes. A unique reverse-dative Ni → Ag interaction provides another approach in modifying nickel's geometry.
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Affiliation(s)
- Hsien-Liang Cho
- Department of Chemistry, Texas A&M University, College Station, Texas 77843, USA.
| | - Kelly L Gullett
- School of Chemical Sciences, University of Illinois at Urbana-Champaign, 600 S. Mathews Ave., Urbana, Illinois 61801, USA
| | - Alison R Fout
- Department of Chemistry, Texas A&M University, College Station, Texas 77843, USA.
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2
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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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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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Baksh KA, Zamble DB. Allosteric control of metal-responsive transcriptional regulators in bacteria. J Biol Chem 2020; 295:1673-1684. [PMID: 31857375 PMCID: PMC7008368 DOI: 10.1074/jbc.rev119.011444] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Many transition metals are essential trace nutrients for living organisms, but they are also cytotoxic in high concentrations. Bacteria maintain the delicate balance between metal starvation and toxicity through a complex network of metal homeostasis pathways. These systems are coordinated by the activities of metal-responsive transcription factors-also known as metal-sensor proteins or metalloregulators-that are tuned to sense the bioavailability of specific metals in the cell in order to regulate the expression of genes encoding proteins that contribute to metal homeostasis. Metal binding to a metalloregulator allosterically influences its ability to bind specific DNA sequences through a variety of intricate mechanisms that lie on a continuum between large conformational changes and subtle changes in internal dynamics. This review summarizes recent advances in our understanding of how metal sensor proteins respond to intracellular metal concentrations. In particular, we highlight the allosteric mechanisms used for metal-responsive regulation of several prokaryotic single-component metalloregulators, and we briefly discuss current open questions of how metalloregulators function in bacterial cells. Understanding the regulation and function of metal-responsive transcription factors is a fundamental aspect of metallobiochemistry and is important for gaining insights into bacterial growth and virulence.
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Affiliation(s)
- Karina A Baksh
- Department of Biochemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Deborah B Zamble
- Department of Biochemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada; Department of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada.
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Lacasse MJ, Sebastiampillai S, Côté JP, Hodkinson N, Brown ED, Zamble DB. A whole-cell, high-throughput hydrogenase assay to identify factors that modulate [NiFe]-hydrogenase activity. J Biol Chem 2019; 294:15373-15385. [PMID: 31455635 DOI: 10.1074/jbc.ra119.008101] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2019] [Revised: 08/08/2019] [Indexed: 12/25/2022] Open
Abstract
[NiFe]-hydrogenases have attracted attention as potential therapeutic targets or components of a hydrogen-based economy. [NiFe]-hydrogenase production is a complicated process that requires many associated accessory proteins that supply the requisite cofactors and substrates. Current methods for measuring hydrogenase activity have low throughput and often require specialized conditions and reagents. In this work, we developed a whole-cell high-throughput hydrogenase assay based on the colorimetric reduction of benzyl viologen to explore the biological networks of these enzymes in Escherichia coli We utilized this assay to screen the Keio collection, a set of nonlethal single-gene knockouts in E. coli BW25113. The results of this screen highlighted the assay's specificity and revealed known components of the intricate network of systems that underwrite [NiFe]-hydrogenase activity, including nickel homeostasis and formate dehydrogenase activities as well as molybdopterin and selenocysteine biosynthetic pathways. The screen also helped identify several new genetic components that modulate hydrogenase activity. We examined one E. coli strain with undetectable hydrogenase activity in more detail (ΔeutK), finding that nickel delivery to the enzyme active site was completely abrogated, and tracked this effect to an ancillary and unannotated lack of the fumarate and nitrate reduction (FNR) anaerobic regulatory protein. Collectively, these results demonstrate that the whole-cell assay developed here can be used to uncover new information about bacterial [NiFe]-hydrogenase production and to probe the cellular components of microbial nickel homeostasis.
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Affiliation(s)
- Michael J Lacasse
- Department of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada
| | | | - Jean-Philippe Côté
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario L8N 3Z5, Canada.,Michael G. DeGroote Institute of Infectious Disease Research, McMaster University, Hamilton, Ontario L8N 3Z5, Canada
| | - Nicholas Hodkinson
- Department of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada
| | - Eric D Brown
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario L8N 3Z5, Canada.,Michael G. DeGroote Institute of Infectious Disease Research, McMaster University, Hamilton, Ontario L8N 3Z5, 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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6
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Metallochaperones and metalloregulation in bacteria. Essays Biochem 2017; 61:177-200. [PMID: 28487396 DOI: 10.1042/ebc20160076] [Citation(s) in RCA: 66] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2016] [Revised: 02/23/2017] [Accepted: 02/27/2017] [Indexed: 12/21/2022]
Abstract
Bacterial transition metal homoeostasis or simply 'metallostasis' describes the process by which cells control the intracellular availability of functionally required metal cofactors, from manganese (Mn) to zinc (Zn), avoiding both metal deprivation and toxicity. Metallostasis is an emerging aspect of the vertebrate host-pathogen interface that is defined by a 'tug-of-war' for biologically essential metals and provides the motivation for much recent work in this area. The host employs a number of strategies to starve the microbial pathogen of essential metals, while for others attempts to limit bacterial infections by leveraging highly competitive metals. Bacteria must be capable of adapting to these efforts to remodel the transition metal landscape and employ highly specialized metal sensing transcriptional regulators, termed metalloregulatory proteins,and metallochaperones, that allocate metals to specific destinations, to mediate this adaptive response. In this essay, we discuss recent progress in our understanding of the structural mechanisms and metal specificity of this adaptive response, focusing on energy-requiring metallochaperones that play roles in the metallocofactor active site assembly in metalloenzymes and metallosensors, which govern the systems-level response to metal limitation and intoxication.
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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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Musiani F, Zambelli B, Bazzani M, Mazzei L, Ciurli S. Nickel-responsive transcriptional regulators. Metallomics 2015; 7:1305-18. [DOI: 10.1039/c5mt00072f] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The structural features, metal coordination modes and metal binding thermodynamics of known Ni(ii)-dependent transcriptional regulators are highlighted and discussed.
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Affiliation(s)
- Francesco Musiani
- Laboratory of Bioinorganic Chemistry
- Department of Pharmacy and Biotechnology
- University of Bologna
- 40127 Bologna, Italy
| | - Barbara Zambelli
- Laboratory of Bioinorganic Chemistry
- Department of Pharmacy and Biotechnology
- University of Bologna
- 40127 Bologna, Italy
| | - Micaela Bazzani
- Laboratory of Bioinorganic Chemistry
- Department of Pharmacy and Biotechnology
- University of Bologna
- 40127 Bologna, Italy
| | - Luca Mazzei
- Laboratory of Bioinorganic Chemistry
- Department of Pharmacy and Biotechnology
- University of Bologna
- 40127 Bologna, Italy
| | - Stefano Ciurli
- Laboratory of Bioinorganic Chemistry
- Department of Pharmacy and Biotechnology
- University of Bologna
- 40127 Bologna, Italy
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Tan BG, Vijgenboom E, Worrall JAR. Conformational and thermodynamic hallmarks of DNA operator site specificity in the copper sensitive operon repressor from Streptomyces lividans. Nucleic Acids Res 2013; 42:1326-40. [PMID: 24121681 PMCID: PMC3902906 DOI: 10.1093/nar/gkt902] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Metal ion homeostasis in bacteria relies on metalloregulatory proteins to upregulate metal resistance genes and enable the organism to preclude metal toxicity. The copper sensitive operon repressor (CsoR) family is widely distributed in bacteria and controls the expression of copper efflux systems. CsoR operator sites consist of G-tract containing pseudopalindromes of which the mechanism of operator binding is poorly understood. Here, we use a structurally characterized CsoR from Streptomyces lividans (CsoRSl) together with three specific operator targets to reveal the salient features pertaining to the mechanism of DNA binding. We reveal that CsoRSl binds to its operator site through a 2-fold axis of symmetry centred on a conserved 5′-TAC/GTA-3′ inverted repeat. Operator recognition is stringently dependent not only on electropositive residues but also on a conserved polar glutamine residue. Thermodynamic and circular dichroic signatures of the CsoRSl–DNA interaction suggest selectivity towards the A-DNA-like topology of the G-tracts at the operator site. Such properties are enhanced on protein binding thus enabling the symmetrical binding of two CsoRSl tetramers. Finally, differential binding modes may exist in operator sites having more than one 5′-TAC/GTA-3′ inverted repeat with implications in vivo for a mechanism of modular control.
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Affiliation(s)
- Benedict G Tan
- School of Biological Science, University of Essex, Wivenhoe Park, Colchester, CO4 3SQ, UK and Molecular Biotechnology, Institute of Biology Leiden, Sylvius Laboratory, Leiden University, PO Box 9505, 2300 RA Leiden, The Netherlands
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