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Pierro A, Tamburrini KC, Leguenno H, Gerbaud G, Etienne E, Guigliarelli B, Belle V, Zambelli B, Mileo E. In-cell investigation of the conformational landscape of the GTPase UreG by SDSL-EPR. iScience 2023; 26:107855. [PMID: 37766968 PMCID: PMC10520941 DOI: 10.1016/j.isci.2023.107855] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2023] [Revised: 07/07/2023] [Accepted: 09/06/2023] [Indexed: 09/29/2023] Open
Abstract
UreG is a cytosolic GTPase involved in the maturation network of urease, an Ni-containing bacterial enzyme. Previous investigations in vitro showed that UreG features a flexible tertiary organization, making this protein the first enzyme discovered to be intrinsically disordered. To determine whether this heterogeneous behavior is maintained in the protein natural environment, UreG structural dynamics was investigated directly in intact bacteria by in-cell EPR. This approach, based on site-directed spin labeling coupled to electron paramagnetic resonance (SDSL-EPR) spectroscopy, enables the study of proteins in their native environment. The results show that UreG maintains heterogeneous structural landscape in-cell, existing in a conformational ensemble of two major conformers, showing either random coil-like or compact properties. These data support the physiological relevance of the intrinsically disordered nature of UreG and indicates a role of protein flexibility for this specific enzyme, possibly related to the regulation of promiscuous protein interactions for metal ion delivery.
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Affiliation(s)
- Annalisa Pierro
- Aix Marseille Univ, CNRS, BIP, IMM, 13009 Marseille, France
- Department of Chemistry, University of Konstanz, Universitätsstraße 10, 78457 Konstanz, Germany
| | - Ketty Concetta Tamburrini
- Aix Marseille Univ, CNRS, AFMB, 13009 Marseille, France
- INRAE, Aix Marseille Univ, BBF, 13009 Marseille, France
| | - Hugo Leguenno
- Aix Marseille Univ, CNRS, IMM, Microscopy Core Facility, 13009 Marseille, France
| | | | | | | | - Valérie Belle
- Aix Marseille Univ, CNRS, BIP, IMM, 13009 Marseille, France
| | - Barbara Zambelli
- Laboratory of Bioinorganic Chemistry, Department of Pharmacy and Biotechnology, University of Bologna, 40127 Bologna, Italy
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2
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Xia X. Multiple regulatory mechanisms for pH homeostasis in the gastric pathogen, Helicobacter pylori. ADVANCES IN GENETICS 2022; 109:39-69. [PMID: 36334916 DOI: 10.1016/bs.adgen.2022.07.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Acid-resistance in gastric pathogen Helicobacter pylori requires the coordination of four essential processes to regulate urease activity. Firstly, urease expression above a base level needs to be finely tuned at different ambient pH. Secondly, as nickel is needed to activate urease, nickel homeostasis needs to be maintained by proteins that import and export nickel ions, and sequester, store and release nickel when needed. Thirdly, urease accessary proteins that activate urease activity by nickel insertion need to be expressed. Finally, a reliable source of urea needs to be maintained by both intrinsic and extrinsic sources of urea. Two-component systems (arsRS and flgRS), as well as a nickel response regulator (NikR), sense the change in pH and act on a variety of genes to accomplish the function of acid resistance without causing cellular overalkalization and nickel toxicity. Nickel storage proteins also feature built-in switches to store nickel at neutral pH and release nickel at low pH. This review summarizes the current status of H. pylori research and highlights a number of hypotheses that need to be tested.
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Affiliation(s)
- Xuhua Xia
- Department of Biology, University of Ottawa, Ottawa, Canada; Ottawa Institute of Systems Biology, Ottawa, Canada.
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3
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Abstract
Hydrogenases and ureases play vital metabolic functions in all three domains of life. However, nickel ions are cytotoxic because they can inactivate enzymes that require less competitive ions (e.g. Mg2+) in the Irving-Williams series to function. Life has evolved elegant mechanisms to solve the problem of delivering the toxic metal to the active site of nickel-containing enzymes inside the cells. Here, we review our current understanding of nickel trafficking along the hydrogenase and urease maturation pathways. Metallochaperones and accessory proteins (SlyD, HypA, HypB, UreD, UreE, UreF, and UreG) form specific protein complexes to allow the transfer of nickel from one protein to another without releasing the toxic metal into the cytoplasm. The role of SlyD is not fully understood, but it can interact with and transfer its nickel to HypB. In the hydrogenase maturation pathway, nickel is transferred from HypB to HypA, which can then deliver its nickel to the hydrogenase large subunit precursor. In Helicobacter pylori, the urease maturation pathway receives its nickel from HypA of the hydrogenase maturation pathway via the formation of a HypA/UreE2 complex. Guanosine triphosphate (GTP) binding promotes the formation of a UreE2G2 complex, where UreG receives a nickel from UreE. In the final step of the urease maturation, nickel/GTP-bound UreG forms an activation complex with UreF, UreD, and apo-urease. Upon GTP hydrolysis, nickel is released from UreG to the urease. Finally, some common themes learned from the hydrogenase-urease maturation pathway are discussed.
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Affiliation(s)
- Ka Lung Tsang
- School of Life Sciences, Centre for Protein Science and Crystallography, State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Shatin, Hong Kong, China
| | - Kam-Bo Wong
- School of Life Sciences, Centre for Protein Science and Crystallography, State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Shatin, Hong Kong, China
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4
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Masetti M, Bertazzo M, Recanatini M, Ciurli S, Musiani F. Probing the transport of Ni(II) ions through the internal tunnels of the Helicobacter pylori UreDFG multimeric protein complex. J Inorg Biochem 2021; 223:111554. [PMID: 34325209 DOI: 10.1016/j.jinorgbio.2021.111554] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2021] [Revised: 07/08/2021] [Accepted: 07/16/2021] [Indexed: 11/19/2022]
Abstract
The survival of several pathogenic bacteria, such as Helicobacter pylori (Hp), relies on the activity of the nickel-dependent enzyme urease. Nickel insertion into urease is mediated by a multimeric chaperone complex (HpUreDFG) that is responsible for the transport of Ni(II) from a conserved metal binding motif located in the UreG dimer (CPH motif) to the catalytic site of the enzyme. The X-ray structure of HpUreDFG revealed the presence of water-filled tunnels that were proposed as a route for Ni(II) translocation. Here, we probe the transport of Ni(II) through the internal tunnels of HpUreDFG, from the CPH motif to the external surface of the complex, using microsecond-long enhanced molecular dynamics simulations. The results suggest a "bucket-brigade" mechanism whereby Ni(II) can be transported through a series of stations found along these internal pathways.
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Affiliation(s)
- Matteo Masetti
- Laboratory of Computational Medicinal Chemistry, Department of Pharmacy and Biotechnology, Alma Mater Studiorum - University of Bologna, via Belmeloro 6, I-40126 Bologna, Italy.
| | - Martina Bertazzo
- Laboratory of Computational Medicinal Chemistry, Department of Pharmacy and Biotechnology, Alma Mater Studiorum - University of Bologna, via Belmeloro 6, I-40126 Bologna, Italy; Computational Sciences, Istituto Italiano di Tecnologia, via Morego 30, I-16163 Genova, Italy
| | - Maurizio Recanatini
- Laboratory of Computational Medicinal Chemistry, Department of Pharmacy and Biotechnology, Alma Mater Studiorum - University of Bologna, via Belmeloro 6, I-40126 Bologna, Italy
| | - Stefano Ciurli
- Laboratory of Bioinorganic Chemistry, Department of Pharmacy and Biotechnology, Alma Mater Studiorum - University of Bologna, viale G. Fanin 40, I-40127 Bologna, Italy.
| | - Francesco Musiani
- Laboratory of Bioinorganic Chemistry, Department of Pharmacy and Biotechnology, Alma Mater Studiorum - University of Bologna, viale G. Fanin 40, I-40127 Bologna, Italy.
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5
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Nickel as a virulence factor in the Class I bacterial carcinogen, Helicobacter pylori. Semin Cancer Biol 2021; 76:143-155. [PMID: 33865991 DOI: 10.1016/j.semcancer.2021.04.009] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2021] [Accepted: 04/12/2021] [Indexed: 01/16/2023]
Abstract
Helicobacter pylori is a human bacterial pathogen that causes peptic ulcers and has been designated a Class I carcinogen by the International Agency for Research on Cancer (IARC). Its ability to survive in the acid environment of the stomach, to colonize the stomach mucosa, and to cause cancer, are linked to two enzymes that require nickel-urease and hydrogenase. Thus, nickel is an important virulence factor and the proteins involved in nickel trafficking are potential antibiotic targets. This review summarizes the nickel biochemistry of H. pylori with a focus on the roles of nickel in virulence, nickel homeostasis, maturation of urease and hydrogenase, and the unique nickel trafficking that occurs between the hydrogenase maturation pathway and urease nickel incorporation that is mediated by the metallochaperone HypA and its partner, HypB.
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6
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Zhang X, Zhao S, He Y, Zheng N, Yan X, Wang J. Substitution of residues in UreG to investigate UreE interactions and nickel binding in a predominant urease gene cluster from the ruminal metagenome. Int J Biol Macromol 2020; 161:1591-1601. [PMID: 32755703 DOI: 10.1016/j.ijbiomac.2020.07.260] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2020] [Revised: 07/17/2020] [Accepted: 07/20/2020] [Indexed: 11/17/2022]
Abstract
Microbial ureases catalyze the hydrolysis of urea to ammonia, and inhibition of these enzymes in rumen has the potential to improve urea utilization efficiency and reduce urinary nitrogen excretion. Urease activity is catalyzed by a protein complex encoded by a gene cluster, and its accessory proteins (especially UreE and UreG) play important roles in transferring nickel to the active site for urease maturation. In this study, a predominant urease gene cluster (5290 bp) from the ruminal microbial metagenome was identified. Isothermal titration calorimetry (ITC) and analytical ultracentrifugation (AUC) analyses showed that the reaction of identified UreE with UreG was endothermic, and was dominated by a hydrophobic interaction, in which each UreE dimer bound 2 M equivalents of UreG monomer to form a UreE2-2UreG complex. Mutagenesis analyses showed that the UreG residues Glu-23, Asp-41, Glu-46, Glu-66, Cys-70, His-72, Asp-78, and Asp-118 were involved in the GTPase activity of UreG. Furthermore, variants of Cys-70 and His-72 involved in CPH motif of UreG, as well as the nearby Glu-66 and Asp-78, not only prevented interactions with UreE, but also prevented nickel binding. These data provide additional information regarding UreG residues that may be targeted for the design of new urease inhibitors.
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Affiliation(s)
- Xiaoyin Zhang
- State Key Laboratory of Animal Nutrition, Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing, China; College of Animal Science and Technology, Huazhong Agricultural University, Wuhan, China
| | - Shengguo Zhao
- State Key Laboratory of Animal Nutrition, Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Yue He
- State Key Laboratory of Animal Nutrition, Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Nan Zheng
- State Key Laboratory of Animal Nutrition, Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Xianghua Yan
- College of Animal Science and Technology, Huazhong Agricultural University, Wuhan, China
| | - Jiaqi Wang
- State Key Laboratory of Animal Nutrition, Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing, China; College of Animal Science and Technology, Huazhong Agricultural University, Wuhan, China.
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7
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Pierro A, Etienne E, Gerbaud G, Guigliarelli B, Ciurli S, Belle V, Zambelli B, Mileo E. Nickel and GTP Modulate Helicobacter pylori UreG Structural Flexibility. Biomolecules 2020; 10:E1062. [PMID: 32708696 PMCID: PMC7408563 DOI: 10.3390/biom10071062] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2020] [Revised: 06/25/2020] [Accepted: 07/10/2020] [Indexed: 12/14/2022] Open
Abstract
UreG is a P-loop GTP hydrolase involved in the maturation of nickel-containing urease, an essential enzyme found in plants, fungi, bacteria, and archaea. This protein couples the hydrolysis of GTP to the delivery of Ni(II) into the active site of apo-urease, interacting with other urease chaperones in a multi-protein complex necessary for enzyme activation. Whereas the conformation of Helicobacter pylori (Hp) UreG was solved by crystallography when it is in complex with two other chaperones, in solution the protein was found in a disordered and flexible form, defining it as an intrinsically disordered enzyme and indicating that the well-folded structure found in the crystal state does not fully reflect the behavior of the protein in solution. Here, isothermal titration calorimetry and site-directed spin labeling coupled to electron paramagnetic spectroscopy were successfully combined to investigate HpUreG structural dynamics in solution and the effect of Ni(II) and GTP on protein mobility. The results demonstrate that, although the protein maintains a flexible behavior in the metal and nucleotide bound forms, concomitant addition of Ni(II) and GTP exerts a structural change through the crosstalk of different protein regions.
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Affiliation(s)
- Annalisa Pierro
- Aix Marseille Univ, CNRS, BIP, Bioénergétique et Ingénierie des Protéines, IMM, Marseille, France; (A.P.); (E.E.); (G.G.); (B.G.); (V.B.)
| | - Emilien Etienne
- Aix Marseille Univ, CNRS, BIP, Bioénergétique et Ingénierie des Protéines, IMM, Marseille, France; (A.P.); (E.E.); (G.G.); (B.G.); (V.B.)
| | - Guillaume Gerbaud
- Aix Marseille Univ, CNRS, BIP, Bioénergétique et Ingénierie des Protéines, IMM, Marseille, France; (A.P.); (E.E.); (G.G.); (B.G.); (V.B.)
| | - Bruno Guigliarelli
- Aix Marseille Univ, CNRS, BIP, Bioénergétique et Ingénierie des Protéines, IMM, Marseille, France; (A.P.); (E.E.); (G.G.); (B.G.); (V.B.)
| | - Stefano Ciurli
- Laboratory of Bioinorganic Chemistry, Department of Pharmacy and Biotechnology, University of Bologna, 40127 Bologna, Italy;
| | - Valérie Belle
- Aix Marseille Univ, CNRS, BIP, Bioénergétique et Ingénierie des Protéines, IMM, Marseille, France; (A.P.); (E.E.); (G.G.); (B.G.); (V.B.)
| | - Barbara Zambelli
- Laboratory of Bioinorganic Chemistry, Department of Pharmacy and Biotechnology, University of Bologna, 40127 Bologna, Italy;
| | - Elisabetta Mileo
- Aix Marseille Univ, CNRS, BIP, Bioénergétique et Ingénierie des Protéines, IMM, Marseille, France; (A.P.); (E.E.); (G.G.); (B.G.); (V.B.)
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8
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Targeting the Protein Tunnels of the Urease Accessory Complex: A Theoretical Investigation. Molecules 2020; 25:molecules25122911. [PMID: 32599898 PMCID: PMC7355429 DOI: 10.3390/molecules25122911] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2020] [Revised: 06/19/2020] [Accepted: 06/22/2020] [Indexed: 12/13/2022] Open
Abstract
Urease is a nickel-containing enzyme that is essential for the survival of several and often deadly pathogenic bacterial strains, including Helicobacter pylori. Notwithstanding several attempts, the development of direct urease inhibitors without side effects for the human host remains, to date, elusive. The recently solved X-ray structure of the HpUreDFG accessory complex involved in the activation of urease opens new perspectives for structure-based drug discovery. In particular, the quaternary assembly and the presence of internal tunnels for nickel translocation offer an intriguing possibility to target the HpUreDFG complex in the search of indirect urease inhibitors. In this work, we adopted a theoretical framework to investigate such a hypothesis. Specifically, we searched for putative binding sites located at the protein–protein interfaces on the HpUreDFG complex, and we challenged their druggability through structure-based virtual screening. We show that, by virtue of the presence of tunnels, some protein–protein interfaces on the HpUreDFG complex are intrinsically well suited for hosting small molecules, and, as such, they possess good potential for future drug design endeavors.
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9
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Zambelli B, Mazzei L, Ciurli S. Intrinsic disorder in the nickel-dependent urease network. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2020; 174:307-330. [DOI: 10.1016/bs.pmbts.2020.05.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
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10
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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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11
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Abstract
Maturation of urease involves post-translational insertion of nickel ions to form an active site with a carbamylated lysine ligand and is assisted by urease accessory proteins UreD, UreE, UreF and UreG. Here, we review our current understandings on how these urease accessory proteins facilitate the urease maturation. The urease maturation pathway involves the transfer of Ni2+ from UreE → UreG → UreF/UreD → urease. To avoid the release of the toxic metal to the cytoplasm, Ni2+ is transferred from one urease accessory protein to another through specific protein–protein interactions. One central theme depicts the role of guanosine triphosphate (GTP) binding/hydrolysis in regulating the binding/release of nickel ions and the formation of the protein complexes. The urease and [NiFe]-hydrogenase maturation pathways cross-talk with each other as UreE receives Ni2+ from hydrogenase maturation factor HypA. Finally, the druggability of the urease maturation pathway is reviewed.
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Marinoni C, Ribaldone DG, Rosso C, Astegiano M, Caviglia GP. Diagnosis of Helicobacter pylori infection: a look into molecular aspects of urea breath test. MINERVA BIOTECNOL 2019. [DOI: 10.23736/s1120-4826.19.02555-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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13
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Fagoonee S, Pellicano R. Helicobacter pylori: molecular basis for colonization and survival in gastric environment and resistance to antibiotics. A short review. Infect Dis (Lond) 2019; 51:399-408. [PMID: 30907202 DOI: 10.1080/23744235.2019.1588472] [Citation(s) in RCA: 65] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Helicobacter pylori is a human-specific pathogen with a strict tropism for the gastric mucosa. This bacterium infects around half of the world population and is the main responsible for gastritis, peptic ulcer and, in some cases, for the pathogenesis of gastric cancer. Nevertheless, disease development in infected subjects depends not only on the bacterium, but also on the host genetic predisposition and on environmental factors. The fascinating question of how the bacterium can survive in the gastric environment has stimulated research in this field. It is now clear that H. pylori is able to colonize and adhere to the gastric epithelium through several mechanisms, including the breakdown of urea with production of the cell-toxic ammonia. The resulting raise in pH neutralizes acidity of the stomach, thereby allowing the bacterium to safely cross the mucus layer to the epithelial surface. Current challenges regard understanding the mechanisms of antibiotic resistance and how to overcome it. Lately, an increasing H. pylori resistance rate to antibiotics has been reported and several molecular bases for this phenomenon described. In this review, we highlight the current knowledge on mechanisms supporting H. pylori resistance to gastric environment and to therapy.
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Affiliation(s)
- Sharmila Fagoonee
- a Institute for Biostructure and Bioimaging (CNR) c/o Molecular Biotechnology Center , Turin , Italy
| | - Rinaldo Pellicano
- b Unit of Gastroenterology , Molinette-SGAS Hospital , Turin , Italy
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14
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Gamov GA, Zavalishin MN, Khokhlova AY, Gashnikova AV, Aleksandriiskii VV, Sharnin VA. Complexation between nickel(II), cobalt(III) and hydrazones derived from pyridoxal 5′-phosphate and hydrazides of 2-,3-,4-pyridinecarboxylic acids in aqueous solution. J COORD CHEM 2018. [DOI: 10.1080/00958972.2018.1512708] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Affiliation(s)
- G. A. Gamov
- Ivanovo State University of Chemistry and Technology, Ivanovo, Russia
| | - M. N. Zavalishin
- Ivanovo State University of Chemistry and Technology, Ivanovo, Russia
| | - A. Y. Khokhlova
- Ivanovo State University of Chemistry and Technology, Ivanovo, Russia
| | - A. V. Gashnikova
- Ivanovo State University of Chemistry and Technology, Ivanovo, Russia
| | - V. V. Aleksandriiskii
- Ivanovo State University of Chemistry and Technology, Ivanovo, Russia
- G.A. Krestov Institute of Solution Chemistry, Russian Academy of Sciences, Ivanovo, Russia
| | - V. A. Sharnin
- Ivanovo State University of Chemistry and Technology, Ivanovo, Russia
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15
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Tarsia C, Danielli A, Florini F, Cinelli P, Ciurli S, Zambelli B. Targeting Helicobacter pylori urease activity and maturation: In-cell high-throughput approach for drug discovery. Biochim Biophys Acta Gen Subj 2018; 1862:2245-2253. [PMID: 30048738 DOI: 10.1016/j.bbagen.2018.07.020] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2018] [Revised: 07/12/2018] [Accepted: 07/18/2018] [Indexed: 02/07/2023]
Abstract
BACKGROUND Helicobacter pylori is a bacterium strongly associated with gastric cancer. It thrives in the acidic environment of the gastric niche of large portions of the human population using a unique adaptive mechanism that involves the catalytic activity of the nickel-dependent enzyme urease. Targeting urease represents a key strategy for drug design and H. pylori eradication. METHOD Here, we describe a novel method to screen, directly in the cellular environment, urease inhibitors. A ureolytic Escherichia coli strain was engineered by cloning the entire urease operon in an expression plasmid and used to test in-cell urease inhibition with a high-throughput colorimetric assay. A two-plasmid system was further developed to evaluate the ability of small peptides to block the protein interactions that lead to urease maturation. RESULTS The developed assay is a robust cellular model to test, directly in the cell environment, urease inhibitors. The efficacy of a co-expressed peptide to affect the interaction between UreF and UreD, two accessory proteins necessary for urease activation, was observed. This event involves a process that occurs through folding upon binding, pointing to the importance of intrinsically disordered hot spots in protein interfaces. CONCLUSIONS The developed system allows the concomitant screening of a large number of drug candidates that interfere with the urease activity both at the level of the enzyme catalysis and maturation. GENERAL SIGNIFICANCE As inhibition of urease has the potential of being a global antibacterial strategy for a large number of infections, this work paves the way for the development of new candidates for antibacterial drugs.
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Affiliation(s)
- Cinzia Tarsia
- Department of Pharmacy and Biotechnology, University of Bologna, Viale G. Fanin 40, 40127 Bologna, Italy
| | - Alberto Danielli
- Department of Pharmacy and Biotechnology, University of Bologna, Viale G. Fanin 40, 40127 Bologna, Italy
| | - Francesca Florini
- Department of Pharmacy and Biotechnology, University of Bologna, Viale G. Fanin 40, 40127 Bologna, Italy
| | - Paolo Cinelli
- Department of Pharmacy and Biotechnology, University of Bologna, Viale G. Fanin 40, 40127 Bologna, Italy
| | - Stefano Ciurli
- Department of Pharmacy and Biotechnology, University of Bologna, Viale G. Fanin 40, 40127 Bologna, Italy
| | - Barbara Zambelli
- Department of Pharmacy and Biotechnology, University of Bologna, Viale G. Fanin 40, 40127 Bologna, Italy.
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16
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Hu HQ, Huang HT, Maroney MJ. The Helicobacter pylori HypA·UreE 2 Complex Contains a Novel High-Affinity Ni(II)-Binding Site. Biochemistry 2018; 57:2932-2942. [PMID: 29708738 DOI: 10.1021/acs.biochem.8b00127] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Helicobacter pylori is a human pathogen that colonizes the stomach, is the major cause of ulcers, and has been associated with stomach cancers. To survive in the acidic environment of the stomach, H. pylori uses urease, a nickel-dependent enzyme, to produce ammonia for maintenance of cellular pH. The bacteria produce apo-urease in large quantities and activate it by incorporating nickel under acid shock conditions. Urease nickel incorporation requires the urease-specific metallochaperone UreE and the (UreFGH)2 maturation complex. In addition, the H. pylori nickel urease maturation pathway recruits accessory proteins from the [NiFe] hydrogenase maturation pathway, namely, HypA and HypB. HypA and UreE dimers (UreE2) are known to form a protein complex, the role of which in urease maturation is largely unknown. Herein, we examine the nickel-binding properties and protein-protein interactions of HypA and UreE2 using isothermal titration calorimetry and fluorometric methods under neutral and acidic pH conditions to gain insight into the roles played by HypA in urease maturation. The results reveal that HypA and UreE2 form a stable complex with micromolar affinity that protects UreE from hydrolytic degradation. The HypA·UreE2 complex contains a unique high-affinity (nanomolar) Ni2+-binding site that is maintained under conditions designed to mimic acid shock (pH 6.3). The data are interpreted in terms of a proposed mechanism wherein HypA and UreE2 act as co-metallochaperones that target the delivery of Ni2+ to apo-urease with high fidelity.
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17
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Structural insights into how GTP-dependent conformational changes in a metallochaperone UreG facilitate urease maturation. Proc Natl Acad Sci U S A 2017; 114:E10890-E10898. [PMID: 29203664 DOI: 10.1073/pnas.1712658114] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The ability of metallochaperones to allosterically regulate the binding/release of metal ions and to switch protein-binding partners along the metal delivery pathway is essential to the metallation of the metalloenzymes. Urease, catalyzing the hydrolysis of urea into ammonia and carbon dioxide, contains two nickel ions bound by a carbamylated lysine in its active site. Delivery of nickel ions for urease maturation is dependent on GTP hydrolysis and is assisted by four urease accessory proteins UreE, UreF, UreG, and UreH(UreD). Here, we determined the crystal structure of the UreG dimer from Klebsiella pneumoniae in complex with nickel and GMPPNP, a nonhydrolyzable analog of GTP. Comparison with the structure of the GDP-bound Helicobacter pylori UreG (HpUreG) in the UreG2F2H2 complex reveals large conformational changes in the G2 region and residues near the 66CPH68 metal-binding motif. Upon GTP binding, the side chains of Cys66 and His68 from each of the UreG protomers rotate toward each other to coordinate a nickel ion in a square-planar geometry. Mutagenesis studies on HpUreG support the conformational changes induced by GTP binding as essential to dimerization of UreG, GTPase activity, in vitro urease activation, and the switching of UreG from the UreG2F2H2 complex to form the UreE2G2 complex with the UreE dimer. The nickel-charged UreE dimer, providing the sole source of nickel, and the UreG2F2H2 complex could activate urease in vitro in the presence of GTP. Based on our results, we propose a mechanism of how conformational changes of UreG during the GTP hydrolysis/binding cycle facilitate urease maturation.
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Lai YT, Yang Y, Hu L, Cheng T, Chang YY, Koohi-Moghadam M, Wang Y, Xia J, Wang J, Li H, Sun H. Integration of fluorescence imaging with proteomics enables visualization and identification of metallo-proteomes in living cells. Metallomics 2017; 9:38-47. [PMID: 27830853 DOI: 10.1039/c6mt00169f] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Metalloproteins account for nearly one-third of proteins in proteomes. To date, the identification of metalloproteins relies mainly on protein purification and the subsequent characterization of bound metals, which often leads to losses of metal ions bound weakly and transiently. Herein, we developed a strategy to visualize and subsequently identify endogenous metalloproteins and metal-binding proteins in living cells via integration of fluorescence imaging with proteomics. We synthesized a "metal-tunable" fluorescent probe (denoted as Mn+-TRACER) that rapidly enters cells to target proteins with 4-40 fold fluorescence enhancements. By using Ni2+-TRACER as an example, we demonstrate the feasibility of tracking Ni2+-binding proteins in vitro, while cellular small molecules exhibit negligible interference on the labeling. We identified 44 Ni2+-binding proteins from microbes using Helicobacter pylori as a showcase. We further applied Cu2+-TRACER to mammalian cells and found 54 Cu2+-binding proteins. The strategy we report here provides a great opportunity to track various endogenous metallo-proteomes and to mine potential targets of metallodrugs.
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Affiliation(s)
- Yau-Tsz Lai
- Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong SAR, P. R. China.
| | - Ya Yang
- Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong SAR, P. R. China.
| | - Ligang Hu
- Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong SAR, P. R. China.
| | - Tianfan Cheng
- Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong SAR, P. R. China.
| | - Yuen-Yan Chang
- Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong SAR, P. R. China.
| | - Mohamad Koohi-Moghadam
- Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong SAR, P. R. China.
| | - Yuchuan Wang
- MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, School of Chemistry and Chemical Engineering, Sun Yat-sen University, Guangzhou, P. R. China
| | - Jiang Xia
- Department of Chemistry, The Chinese University of Hong Kong, Hong Kong, P. R. China
| | - Junwen Wang
- Center for Individualized Medicine & Department of Health Sciences Research, Mayo Clinic, Scottsdale, AZ 85259 USA and Department of Biomedical Informatics, Arizona State University, Scottsdale, AZ 85259 USA
| | - Hongyan Li
- Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong SAR, P. R. China.
| | - Hongzhe Sun
- Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong SAR, P. R. China.
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Myrach T, Zhu A, Witte CP. The assembly of the plant urease activation complex and the essential role of the urease accessory protein G (UreG) in delivery of nickel to urease. J Biol Chem 2017; 292:14556-14565. [PMID: 28710280 PMCID: PMC5582847 DOI: 10.1074/jbc.m117.780403] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2017] [Revised: 07/11/2017] [Indexed: 12/24/2022] Open
Abstract
Urease is a ubiquitous nickel metalloenzyme. In plants, its activation requires three urease accessory proteins (UAPs), UreD, UreF, and UreG. In bacteria, the UAPs interact with urease and facilitate activation, which involves the channeling of two nickel ions into the active site. So far this process has not been investigated in eukaryotes. Using affinity pulldowns of Strep-tagged UAPs from Arabidopsis and rice transiently expressed in planta, we demonstrate that a urease-UreD-UreF-UreG complex exists in plants and show its stepwise assembly. UreG is crucial for nickel delivery because UreG-dependent urease activation in vitro was observed only with UreG obtained from nickel-sufficient plants. This activation competence could not be generated in vitro by incubation of UreG with nickel, bicarbonate, and GTP. Compared with their bacterial orthologs, plant UreGs possess an N-terminal extension containing a His- and Asp/Glu-rich hypervariable region followed by a highly conserved sequence comprising two potential HXH metal-binding sites. Complementing the ureG-1 mutant of Arabidopsis with N-terminal deletion variants of UreG demonstrated that the hypervariable region has a minor impact on activation efficiency, whereas the conserved region up to the first HXH motif is highly beneficial and up to the second HXH motif strictly required for activation. We also show that urease reaches its full activity several days after nickel becomes available in the leaves, indicating that urease activation is limited by nickel accessibility in vivo Our data uncover the crucial role of UreG for nickel delivery during eukaryotic urease activation, inciting further investigations of the details of this process.
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Affiliation(s)
- Till Myrach
- From the Freie Universität Berlin, Dahlem Centre of Plant Sciences, Department of Plant Biochemistry, Königin-Luise-Strasse 12-16, 14195 Berlin, Germany and
| | - Anting Zhu
- Leibniz Universität Hannover, Institute of Plant Nutrition, Molecular Nutrition and Biochemistry of Plants, Herrenhäuser Strasse 2, 30419 Hannover, Germany
| | - Claus-Peter Witte
- Leibniz Universität Hannover, Institute of Plant Nutrition, Molecular Nutrition and Biochemistry of Plants, Herrenhäuser Strasse 2, 30419 Hannover, Germany
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Selleck C, Guddat LW, Ollis DL, Schenk G, Pedroso MM. High resolution crystal structure of a fluoride-inhibited organophosphate-degrading metallohydrolase. J Inorg Biochem 2017; 177:287-290. [PMID: 28673485 DOI: 10.1016/j.jinorgbio.2017.06.013] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2017] [Revised: 05/16/2017] [Accepted: 06/22/2017] [Indexed: 11/17/2022]
Abstract
Metal ion-dependent, organophosphate-degrading enzymes (OP hydrolases) have received increasing attention due to their ability to degrade and thus detoxify commonly used pesticides and nerve agents such as sarin and VX. These enzymes thus garner strong potential as bioremediators. The OP hydrolase from Agrobacterium radiobacter (OpdA) is one of the most efficient members of this group of enzymes. Previous studies have indicated that the choice of the hydrolysis-initiating nucleophile may depend on the pH of the reaction, with a metal ion-bridging hydroxide being preferred at lower pH (i.e. pH≤8.5), and a terminally coordinated hydroxide at higher pH (i.e. pH>9.0). Furthermore, fluoride was shown to be a potent inhibitor of the reaction, but only at low pH. Here, the crystal structure (1.3Å, pH6) of OpdA in presence of fluoride is described. While the first coordination sphere in the active site displays minimal changes in the presence of fluoride, the hydrogen bonding network that connects the dimetallic metal center to the substrate binding pocket is disrupted. Thus, the structure of fluoride-inhibited OpdA demonstrates the significance of this hydrogen bond network in controlling the mechanism and function of this enzyme.
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Affiliation(s)
- Christopher Selleck
- School of Chemistry and Molecular Biosciences, The University of Queensland, St. Lucia, Queensland 4072, Australia
| | - Luke W Guddat
- School of Chemistry and Molecular Biosciences, The University of Queensland, St. Lucia, Queensland 4072, Australia
| | - David L Ollis
- Research School of Chemistry, Australian National University, Canberra, ACT 0200, Australia
| | - Gerhard Schenk
- School of Chemistry and Molecular Biosciences, The University of Queensland, St. Lucia, Queensland 4072, Australia.
| | - Marcelo Monteiro Pedroso
- School of Chemistry and Molecular Biosciences, The University of Queensland, St. Lucia, Queensland 4072, Australia.
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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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Musiani F, Gioia D, Masetti M, Falchi F, Cavalli A, Recanatini M, Ciurli S. Protein Tunnels: The Case of Urease Accessory Proteins. J Chem Theory Comput 2017; 13:2322-2331. [PMID: 28379694 DOI: 10.1021/acs.jctc.7b00042] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Transition metals are both essential micronutrients and limited in environmental availability. The Ni(II)-dependent urease protein, the most efficient enzyme known to date, is a paradigm for studying the strategies that cells use to handle an essential, yet toxic, metal ion. Urease is a virulence factor of several human pathogens, in addition to decreasing the efficiency of soil organic nitrogen fertilization. Ni(II) insertion in the urease active site is performed through the action of three essential accessory proteins: UreD, UreF, and UreG. The crystal structure of the UreD-UreF-UreG complex from the human pathogen Helicobacter pylori (HpUreDFG) revealed the presence of tunnels that cross the entire length of both UreF and UreD, potentially able to deliver Ni(II) ions from UreG to apo-urease. Atomistic molecular dynamics simulations performed on the HpUreDFG complex in explicit solvent and at physiological ionic conditions demonstrate the stability of these protein tunnels in solution and provide insights on the trafficking of water molecules inside the tunnels. The presence of different alternative routes across the identified tunnels for Ni(II) ions, water molecules, and carbonate ions, all involved in urease activation, is highlighted here, and their potential role in the urease activation mechanism is discussed.
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Affiliation(s)
- Francesco Musiani
- Laboratory of Bioinorganic Chemistry, Department of Pharmacy and Biotechnology, University of Bologna , Viale G. Fanin 40, I-40127 Bologna, Italy
| | - Dario Gioia
- Laboratory of Computational Medicinal Chemistry, Department of Pharmacy and Biotechnology, University of Bologna , Via Belmeloro 6, I-40126 Bologna, Italy
| | - Matteo Masetti
- Laboratory of Computational Medicinal Chemistry, Department of Pharmacy and Biotechnology, University of Bologna , Via Belmeloro 6, I-40126 Bologna, Italy
| | - Federico Falchi
- Compunet, Istituto Italiano di Tecnologia , Via Morego 30, I-16163 Genova, Italy
| | - Andrea Cavalli
- Laboratory of Computational Medicinal Chemistry, Department of Pharmacy and Biotechnology, University of Bologna , Via Belmeloro 6, I-40126 Bologna, Italy.,Compunet, Istituto Italiano di Tecnologia , Via Morego 30, I-16163 Genova, Italy
| | - Maurizio Recanatini
- Laboratory of Computational Medicinal Chemistry, Department of Pharmacy and Biotechnology, University of Bologna , Via Belmeloro 6, I-40126 Bologna, Italy
| | - Stefano Ciurli
- Laboratory of Bioinorganic Chemistry, Department of Pharmacy and Biotechnology, University of Bologna , Viale G. Fanin 40, I-40127 Bologna, Italy
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Xia W, Li H, Sun H. Nickel Metallochaperones: Structure, Function, and Nickel-Binding Properties. THE BIOLOGICAL CHEMISTRY OF NICKEL 2017. [DOI: 10.1039/9781788010580-00284] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Nickel-containing enzymes catalyze a series of important biochemical processes in both prokaryotes and eukaryotes. The maturation of the enzymes requires the proper assembly of the nickel-containing active sites, which involves a battery of nickel metallochaperones that exert metal delivery and storage functions. “Cross-talk” also exists between different nickel enzyme maturation processes. This chapter summarizes the updated knowledge about the nickel chaperones based on biochemical and structural biology research, and discusses the possible nickel delivery mechanisms.
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Affiliation(s)
- Wei Xia
- MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, School of Chemistry Sun Yat-sen University Guangzhou 510275 China
| | - Hongyan Li
- Department of Chemistry, The University of Hong Kong Hong Kong SAR China
| | - Hongzhe Sun
- MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, School of Chemistry Sun Yat-sen University Guangzhou 510275 China
- Department of Chemistry, The University of Hong Kong Hong Kong SAR China
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Gao B, Chi L, Mahbub R, Bian X, Tu P, Ru H, Lu K. Multi-Omics Reveals that Lead Exposure Disturbs Gut Microbiome Development, Key Metabolites, and Metabolic Pathways. Chem Res Toxicol 2017; 30:996-1005. [PMID: 28234468 DOI: 10.1021/acs.chemrestox.6b00401] [Citation(s) in RCA: 119] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Lead exposure remains a global public health issue, and the recent Flint water crisis has renewed public concern about lead toxicity. The toxicity of lead has been well established in a variety of systems and organs. The gut microbiome has been shown to be highly involved in many critical physiological processes, including food digestion, immune system development, and metabolic homeostasis. However, despite the key role of the gut microbiome in human health, the functional impact of lead exposure on the gut microbiome has not been studied. The aim of this study is to define gut microbiome toxicity induced by lead exposure in C57BL/6 mice using multiomics approaches, including 16S rRNA sequencing, whole genome metagenomics sequencing, and gas chromatography-mass spectrometry (GC-MS) metabolomics. 16S rRNA sequencing revealed that lead exposure altered the gut microbiome trajectory and phylogenetic diversity. Metagenomics sequencing and metabolomics profiling showed that numerous metabolic pathways, including vitamin E, bile acids, nitrogen metabolism, energy metabolism, oxidative stress, and the defense/detoxification mechanism, were significantly disturbed by lead exposure. These perturbed molecules and pathways may have important implications for lead toxicity in the host. Taken together, these results demonstrated that lead exposure not only altered the gut microbiome community structures/diversity but also greatly affected metabolic functions, leading to gut microbiome toxicity.
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Affiliation(s)
- Bei Gao
- Department of Environmental Health Science, University of Georgia , Athens, Georgia 30602, United States
| | - Liang Chi
- Department of Environmental Sciences and Engineering, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina 27599, United States
| | - Ridwan Mahbub
- Department of Environmental Health Science, University of Georgia , Athens, Georgia 30602, United States
| | - Xiaoming Bian
- Department of Environmental Health Science, University of Georgia , Athens, Georgia 30602, United States
| | - Pengcheng Tu
- Department of Environmental Sciences and Engineering, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina 27599, United States
| | - Hongyu Ru
- Department of Population Health and Pathobiology, North Carolina State University , Raleigh, North Carolina 27607, United States
| | - Kun Lu
- Department of Environmental Sciences and Engineering, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina 27599, United States
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Hu HQ, Johnson RC, Merrell DS, Maroney MJ. Nickel Ligation of the N-Terminal Amine of HypA Is Required for Urease Maturation in Helicobacter pylori. Biochemistry 2017; 56:1105-1116. [PMID: 28177601 DOI: 10.1021/acs.biochem.6b00912] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The human pathogen Helicobacter pylori requires nickel for colonization of the acidic environment of the stomach. HypA, a Ni metallochaperone that is typically associated with hydrogenase maturation, is also required for urease maturation and acid survival of H. pylori. There are two proposed Ni site structures for HypA; one is a paramagnetic six-coordinate site characterized by X-ray absorption spectroscopy (XAS) in unmodified HypA, while another is a diamagnetic four-coordinate planar site characterized by solution nuclear magnetic resonance in an N-terminally modified HypA construct. To determine the role of the N-terminal amine in Ni binding of HypA, an N-terminal extension variant, L2*-HypA, in which a leucine residue was inserted into the second position of the amino acid sequence in the proposed Ni-binding motif, was characterized in vitro and in vivo. Structural characterization of the Ni site using XAS showed a coordination change from six-coordinate in wild-type HypA (WT-HypA) to five-coordinate pyramidal in L2*-HypA, which was accompanied by the loss of two N/O donor protein ligands and the addition of an exogenous bromide ligand from the buffer. The magnetic properties of the Ni sites in WT-HypA compared to those of the Ni sites in L2*-HypA confirmed that a spin-state change from high to low spin accompanied this change in structure. The L2*-HypA H. pylori strain was shown to be acid sensitive and deficient in urease activity in vivo. In vitro characterization showed that L2*-HypA did not disrupt the HypA-UreE interaction that is essential for urease maturation but was at least 20-fold weaker in Ni binding than WT-HypA. Characterization of the L2*-HypA variant clearly demonstrates that the N-terminal amine of HypA is involved in proper Ni coordination and is necessary for urease activity and acid survival.
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Affiliation(s)
- Heidi Q Hu
- Department of Chemistry and Program of Molecular and Cellular Biology, University of Massachusetts Amherst , Amherst, Massachusetts 01003, United States
| | - Ryan C Johnson
- Microbiology and Immunology, Uniformed Services University of the Health Sciences , Bethesda, Maryland 20814, United States
| | - D Scott Merrell
- Microbiology and Immunology, Uniformed Services University of the Health Sciences , Bethesda, Maryland 20814, United States
| | - Michael J Maroney
- Department of Chemistry and Program of Molecular and Cellular Biology, University of Massachusetts Amherst , Amherst, Massachusetts 01003, United States
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Non-thiolate ligation of nickel by nucleotide-free UreG of Klebsiella aerogenes. J Biol Inorg Chem 2016; 22:497-503. [PMID: 28004186 DOI: 10.1007/s00775-016-1429-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2016] [Accepted: 12/08/2016] [Indexed: 10/20/2022]
Abstract
Nickel-dependent ureases are activated by a multiprotein complex that includes the GTPase UreG. Prior studies showed that nucleotide-free UreG from Klebsiella aerogenes is monomeric and binds one nickel or zinc ion with near-equivalent affinity using an undefined binding site, whereas nucleotide-free UreG from Helicobacter pylori selectively binds one zinc ion per dimer via a universally conserved Cys-Pro-His motif in each protomer. Iodoacetamide-treated K. aerogenes UreG was nearly unaffected in nickel binding compared to non-treated sample, suggesting the absence of thiolate ligands to the metal. X-ray absorption spectroscopy of nickel-bound UreG showed the metal possessed four-coordinate geometry with all O/N donor ligands including one imidazole, thus confirming the absence of thiolate ligation. The nickel site in Strep-tag II-modified protein possessed six-coordinate geometry, again with all O/N donor ligands, but now including two or three imidazoles. An identical site was noted for the Strep-tag II-modified H74A variant, substituted in the Cys-Pro-His motif, ruling out coordination by this His residue. These results are consistent with metal binding to both His6 and a His residue of the fusion peptide in Strep-tagged K. aerogenes UreG. We conclude that the nickel- and zinc-binding site in nucleotide-free K. aerogenes UreG is distinct from that of nucleotide-free H. pylori UreG and does not involve the Cys-Pro-His motif. Further, we show the Strep-tag II can perturb metal coordination of this protein.
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Nutrition and Helicobacter pylori: Host Diet and Nutritional Immunity Influence Bacterial Virulence and Disease Outcome. Gastroenterol Res Pract 2016; 2016:3019362. [PMID: 27688750 PMCID: PMC5027306 DOI: 10.1155/2016/3019362] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/29/2016] [Accepted: 08/03/2016] [Indexed: 12/19/2022] Open
Abstract
Helicobacter pylori colonizes the stomachs of greater than 50% of the world's human population making it arguably one of the most successful bacterial pathogens. Chronic H. pylori colonization results in gastritis in nearly all patients; however in a subset of people, persistent infection with H. pylori is associated with an increased risk for more severe disease outcomes including B-cell lymphoma of mucosal-associated lymphoid tissue (MALT lymphoma) and invasive adenocarcinoma. Research aimed at elucidating determinants that mediate disease progression has revealed genetic differences in both humans and H. pylori which increase the risk for developing gastric cancer. Furthermore, host diet and nutrition status have been shown to influence H. pylori-associated disease outcomes. In this review we will discuss how H. pylori is able to create a replicative niche within the hostile host environment by subverting and modifying the host-generated immune response as well as successfully competing for limited nutrients such as transition metals by deploying an arsenal of metal acquisition proteins and virulence factors. Lastly, we will discuss how micronutrient availability or alterations in the gastric microbiome may exacerbate negative disease outcomes associated with H. pylori colonization.
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Vinella D, Fischer F, Vorontsov E, Gallaud J, Malosse C, Michel V, Cavazza C, Robbe-Saule M, Richaud P, Chamot-Rooke J, Brochier-Armanet C, De Reuse H. Evolution of Helicobacter: Acquisition by Gastric Species of Two Histidine-Rich Proteins Essential for Colonization. PLoS Pathog 2015; 11:e1005312. [PMID: 26641249 PMCID: PMC4671568 DOI: 10.1371/journal.ppat.1005312] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2015] [Accepted: 11/05/2015] [Indexed: 02/07/2023] Open
Abstract
Metal acquisition and intracellular trafficking are crucial for all cells and metal ions have been recognized as virulence determinants in bacterial pathogens. Virulence of the human gastric pathogen Helicobacter pylori is dependent on nickel, cofactor of two enzymes essential for in vivo colonization, urease and [NiFe] hydrogenase. We found that two small paralogous nickel-binding proteins with high content in Histidine (Hpn and Hpn-2) play a central role in maintaining non-toxic intracellular nickel content and in controlling its intracellular trafficking. Measurements of metal resistance, intracellular nickel contents, urease activities and interactomic analysis were performed. We observed that Hpn acts as a nickel-sequestration protein, while Hpn-2 is not. In vivo, Hpn and Hpn-2 form homo-multimers, interact with each other, Hpn interacts with the UreA urease subunit while Hpn and Hpn-2 interact with the HypAB hydrogenase maturation proteins. In addition, Hpn-2 is directly or indirectly restricting urease activity while Hpn is required for full urease activation. Based on these data, we present a model where Hpn and Hpn-2 participate in a common pathway of controlled nickel transfer to urease. Using bioinformatics and top-down proteomics to identify the predicted proteins, we established that Hpn-2 is only expressed by H. pylori and its closely related species Helicobacter acinonychis. Hpn was detected in every gastric Helicobacter species tested and is absent from the enterohepatic Helicobacter species. Our phylogenomic analysis revealed that Hpn acquisition was concomitant with the specialization of Helicobacter to colonization of the gastric environment and the duplication at the origin of hpn-2 occurred in the common ancestor of H. pylori and H. acinonychis. Finally, Hpn and Hpn-2 were found to be required for colonization of the mouse model by H. pylori. Our data show that during evolution of the Helicobacter genus, acquisition of Hpn and Hpn-2 by gastric Helicobacter species constituted a decisive evolutionary event to allow Helicobacter to colonize the hostile gastric environment, in which no other bacteria persistently thrives. This acquisition was key for the emergence of one of the most successful bacterial pathogens, H. pylori. Helicobacter pylori is a bacterium that persistently colonizes the stomach of half of the human population. Infection by H. pylori is associated with gastritis, peptic ulcer disease and adenocarcinoma. To resist gastric acidity and proliferate in the stomach, H. pylori relies on urease, an enzyme that contains a nickel-metallocenter at its active site. Thus, nickel is a virulence determinant for H. pylori. Our aim is to characterize how H. pylori controls the intracellular nickel concentration to avoid toxicity, which protein partners are involved, and how they impact urease activity and virulence. We characterized two H. pylori proteins, Hpn and Hpn-2 that are rich in Histidine residues. We demonstrated that Hpn is involved in nickel sequestration, that the two proteins interact with each other and that their combined activities participate in a nickel transfer pathway to urease. Hpn is only expressed in gastric Helicobacter species able to colonize the stomach and Hpn-2 is restricted to the H. pylori and its close relative H. acinonychis. We found that both proteins are essential for colonization of a mouse model by H. pylori. We conclude that during evolution, the acquisition of Hpn and Hpn-2 by gastric Helicobacter species was decisive for their capacity to colonize the stomach.
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Affiliation(s)
- Daniel Vinella
- Institut Pasteur, Département de Microbiologie, Unité Pathogenèse de Helicobacter, ERL CNRS 3526, Paris, France
| | - Frédéric Fischer
- Institut Pasteur, Département de Microbiologie, Unité Pathogenèse de Helicobacter, ERL CNRS 3526, Paris, France
| | - Egor Vorontsov
- Institut Pasteur, Département de Biologie Structurale et Chimie, Unité Spectrométrie de Masse Structurale et Protéomique, CNRS UMR 3528, Paris, France
| | - Julien Gallaud
- Institut Pasteur, Département de Microbiologie, Unité Pathogenèse de Helicobacter, ERL CNRS 3526, Paris, France
- Université Paris Diderot, Sorbonne Paris Cité, Cellule Pasteur, Paris, France
| | - Christian Malosse
- Institut Pasteur, Département de Biologie Structurale et Chimie, Unité Spectrométrie de Masse Structurale et Protéomique, CNRS UMR 3528, Paris, France
| | - Valérie Michel
- Institut Pasteur, Département de Microbiologie, Unité Pathogenèse de Helicobacter, ERL CNRS 3526, Paris, France
| | | | - Marie Robbe-Saule
- Institut Pasteur, Département de Microbiologie, Unité Pathogenèse de Helicobacter, ERL CNRS 3526, Paris, France
| | - Pierre Richaud
- CEA, DSV, IBEB, SBVME and CNRS, UMR 7265 Biol Veget & Microbiol Environ, Saint-Paul-lez-Durance, France and Aix Marseille Université, BVME UMR7265, Marseille, France
| | - Julia Chamot-Rooke
- Institut Pasteur, Département de Biologie Structurale et Chimie, Unité Spectrométrie de Masse Structurale et Protéomique, CNRS UMR 3528, Paris, France
| | - Céline Brochier-Armanet
- Université de Lyon, Université Lyon 1, CNRS, UMR5558, Laboratoire de Biométrie et Biologie Evolutive, Villeurbanne, France
| | - Hilde De Reuse
- Institut Pasteur, Département de Microbiologie, Unité Pathogenèse de Helicobacter, ERL CNRS 3526, Paris, France
- * E-mail:
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30
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Farrugia MA, Wang B, Feig M, Hausinger RP. Mutational and Computational Evidence That a Nickel-Transfer Tunnel in UreD Is Used for Activation of Klebsiella aerogenes Urease. Biochemistry 2015; 54:6392-401. [PMID: 26401965 DOI: 10.1021/acs.biochem.5b00942] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Nickel-containing urease from Klebsiella aerogenes requires four accessory proteins for proper active site metalation. The metallochaperone UreE delivers nickel to UreG, a GTPase that forms a UreD/UreF/UreG complex, which binds to urease apoprotein via UreD. Prior in silico analysis of the homologous, structurally characterized UreH/UreF/UreG complex from Helicobacter pylori identified a water tunnel originating at a likely nickel-binding motif in UreG, passing through UreF, and exiting UreH, suggestive of a role for the channel in providing the metal to urease apoprotein for its activation; however, no experimental support was reported for the significance of this tunnel. Here, specific variants were designed to disrupt a comparable 34.6 Å predicted internal tunnel, alternative channels, and surface sites for UreD. Cells producing a set of tunnel-disrupting variants of UreD exhibited greatly reduced urease specific activities, whereas other mutants had no appreciable effect on activity. Affinity pull-down studies of cell-free extracts from tunnel-disrupting mutant cultures showed no loss of UreD interactions with urease or UreF/UreG. The nickel contents of urease samples enriched from activity-deficient cultures were decreased, while zinc and iron incorporation increased. Molecular dynamics simulations revealed size restrictions in the internal channels of the UreD variants. These findings support the role of a molecular tunnel in UreD as a direct facilitator of nickel transfer into urease, illustrating a new paradigm in active site metallocenter assembly.
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Affiliation(s)
- Mark A Farrugia
- Department of Biochemistry and Molecular Biology, ‡Department of Chemistry, and §Department of Microbiology and Molecular Genetics, Michigan State University , East Lansing, Michigan 48824, United States
| | - Beibei Wang
- Department of Biochemistry and Molecular Biology, ‡Department of Chemistry, and §Department of Microbiology and Molecular Genetics, Michigan State University , East Lansing, Michigan 48824, United States
| | - Michael Feig
- Department of Biochemistry and Molecular Biology, ‡Department of Chemistry, and §Department of Microbiology and Molecular Genetics, Michigan State University , East Lansing, Michigan 48824, United States
| | - Robert P Hausinger
- Department of Biochemistry and Molecular Biology, ‡Department of Chemistry, and §Department of Microbiology and Molecular Genetics, Michigan State University , East Lansing, Michigan 48824, United States
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31
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Musiani F, Ciurli S. Evolution of Macromolecular Docking Techniques: The Case Study of Nickel and Iron Metabolism in Pathogenic Bacteria. Molecules 2015; 20:14265-92. [PMID: 26251891 PMCID: PMC6332059 DOI: 10.3390/molecules200814265] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2015] [Revised: 07/23/2015] [Accepted: 07/28/2015] [Indexed: 11/24/2022] Open
Abstract
The interaction between macromolecules is a fundamental aspect of most biological processes. The computational techniques used to study protein-protein and protein-nucleic acid interactions have evolved in the last few years because of the development of new algorithms that allow the a priori incorporation, in the docking process, of experimentally derived information, together with the possibility of accounting for the flexibility of the interacting molecules. Here we review the results and the evolution of the techniques used to study the interaction between metallo-proteins and DNA operators, all involved in the nickel and iron metabolism of pathogenic bacteria, focusing in particular on Helicobacter pylori (Hp). In the first part of the article we discuss the methods used to calculate the structure of complexes of proteins involved in the activation of the nickel-dependent enzyme urease. In the second part of the article, we concentrate on two applications of protein-DNA docking conducted on the transcription factors HpFur (ferric uptake regulator) and HpNikR (nickel regulator). In both cases we discuss the technical expedients used to take into account the conformational variability of the multi-domain proteins involved in the calculations.
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Affiliation(s)
- Francesco Musiani
- Laboratory of Bioinorganic Chemistry, Department of Pharmacy and Biotechnology, University of Bologna, Viale G. Fanin 40, Bologna I-40127, Italy.
| | - Stefano Ciurli
- Laboratory of Bioinorganic Chemistry, Department of Pharmacy and Biotechnology, University of Bologna, Viale G. Fanin 40, Bologna I-40127, Italy.
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32
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Yang X, Li H, Cheng T, Xia W, Lai YT, Sun H. Nickel translocation between metallochaperones HypA and UreE in Helicobacter pylori. Metallomics 2015; 6:1731-6. [PMID: 25010720 DOI: 10.1039/c4mt00134f] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Incorporation of nickel ions to the active sites of urease and hydrogenase is prerequisite for the appropriate functions of the metalloenzymes. Such a process requires the participation of several accessory proteins. Interestingly, some of them are shared by the two enzymes in their maturation processes. In this work, we characterized the molecular details of the interaction of metallochaperones UreE and HypA in Helicobacter pylori. We show by chemical cross-linking and static light scattering that the UreE dimer binds to HypA to form a hetero-complex i.e. HypA-(UreE)2. The dissociation constant (Kd) of the protein complex was determined by ITC to be 1 μM in the absence of nickel ions; whereas binding of Ni(2+) but not Zn(2+) to UreE resulted in ca. one fold decrease in the affinity. The putative interfaces on HypA unveiled by NMR chemical shift perturbation were found mainly at the nickel binding domain and in the cleft between α1 and β1/β6. We also identified that the C-domain of UreE, in particular the C-terminal residues of 158-170 are indispensable for the interaction of UreE and HypA. Such an interaction was also observed intracellularly by GFP-fragment reassembly assay. Moreover, we demonstrated using a fluorescent probe that nickel is transferred from HypA to UreE via the specific protein-protein interaction. Deletion of the C-terminus (residues 158-170) of UreE abolished nickel transfer and led to a significant decrease in urease activity. This study provides direct in vitro and in vivo evidence as well as molecular details of nickel translocation mediated by protein-protein interaction.
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Affiliation(s)
- Xinming Yang
- Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, P.R. China.
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33
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Miraula M, Ciurli S, Zambelli B. Intrinsic disorder and metal binding in UreG proteins from Archae hyperthermophiles: GTPase enzymes involved in the activation of Ni(II) dependent urease. J Biol Inorg Chem 2015; 20:739-55. [PMID: 25846143 DOI: 10.1007/s00775-015-1261-7] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2014] [Accepted: 03/20/2015] [Indexed: 02/03/2023]
Abstract
Urease is a Ni(II) enzyme present in every domain of life, in charge for nitrogen recycling through urea hydrolysis. Its activity requires the presence of two Ni(II) ions in the active site. These are delivered by the concerted action of four accessory proteins, named UreD, UreF, UreG and UreE. This process requires protein flexibility at different levels and some disorder-to-order transition events that coordinate the mechanism of protein-protein interaction. In particular, UreG, the GTPase in charge of nucleotide hydrolysis required for urease activation, presents a significant degree of intrinsic disorder, existing as a conformational ensemble featuring characteristics that recall a molten globule. Here, the folding properties of UreG were explored in Archaea hyperthermophiles, known to generally feature significantly low level of structural disorder in their proteome. UreG proteins from Methanocaldococcus jannaschii (Mj) and Metallosphaera sedula (Ms) were structurally and functionally analyzed by integrating circular dichroism, NMR, light scattering and enzymatic assays. Metal-binding properties were studied using isothermal titration calorimetry. The results indicate that, as the mesophilic counterparts, both proteins contain a significant amount of secondary structure but maintain a flexible fold and a low GTPase activity. As opposed to other UreGs, secondary structure is lost at high temperatures (68 and 75 °C, respectively) with an apparent two-state mechanism. Both proteins bind Zn(II) and Ni(II), with affinities two orders of magnitude higher for Zn(II) than for Ni(II). No major modifications of the average conformational ensemble are observed, but binding of Zn(II) yields a more compact dimeric form in MsUreG.
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Affiliation(s)
- Manfredi Miraula
- Laboratory of Bioinorganic Chemistry, Department of Pharmacy and Biotechnology, University of Bologna, Viale Giuseppe Fanin 40, 40127, Bologna, Italy
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Yang X, Li H, Lai TP, Sun H. UreE-UreG complex facilitates nickel transfer and preactivates GTPase of UreG in Helicobacter pylori. J Biol Chem 2015; 290:12474-85. [PMID: 25752610 DOI: 10.1074/jbc.m114.632364] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2014] [Indexed: 11/06/2022] Open
Abstract
The pathogenicity of Helicobacter pylori relies heavily on urease, which converts urea to ammonia to neutralize the stomach acid. Incorporation of Ni(2+) into the active site of urease requires a battery of chaperones. Both metallochaperones UreE and UreG play important roles in the urease activation. In this study, we demonstrate that, in the presence of GTP and Mg(2+), UreG binds Ni(2+) with an affinity (Kd) of ∼0.36 μm. The GTPase activity of Ni(2+)-UreG is stimulated by both K(+) (or NH4 (+)) and HCO3 (-) to a biologically relevant level, suggesting that K(+)/NH4 (+) and HCO3 (-) might serve as GTPase elements of UreG. We show that complexation of UreE and UreG results in two protein complexes, i.e. 2E-2G and 2E-G, with the former being formed only in the presence of both GTP and Mg(2+). Mutagenesis studies reveal that Arg-101 on UreE and Cys-66 on UreG are critical for stabilization of 2E-2G complex. Combined biophysical and bioassay studies show that the formation of 2E-2G complex not only facilitates nickel transfer from UreE to UreG, but also enhances the binding of GTP. This suggests that UreE might also serve as a structural scaffold for recruitment of GTP to UreG. Importantly, we demonstrate for the first time that UreE serves as a bridge to grasp Ni(2+) from HypA, subsequently donating it to UreG. The study expands our horizons on the molecular details of nickel translocation among metallochaperones UreE, UreG, and HypA, which further extends our knowledge on the urease maturation process.
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Affiliation(s)
- Xinming Yang
- From the Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, China
| | - Hongyan Li
- From the Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, China
| | - Tsz-Pui Lai
- From the Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, China
| | - Hongzhe Sun
- From the Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, China
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35
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The conformational response to Zn(II) and Ni(II) binding of Sporosarcina pasteurii UreG, an intrinsically disordered GTPase. J Biol Inorg Chem 2014; 19:1341-54. [PMID: 25200810 DOI: 10.1007/s00775-014-1191-9] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2014] [Accepted: 08/25/2014] [Indexed: 10/24/2022]
Abstract
Urease is an essential Ni(II) enzyme involved in the nitrogen metabolism of bacteria, plants and fungi. Ni(II) delivery into the enzyme active site requires the presence of four accessory proteins, named UreD, UreF, UreG and UreE, acting through a complex protein network regulated by metal binding and GTP hydrolysis. The GTPase activity is catalyzed by UreG, which couples this function to a non-enzymatic role as a molecular chaperone. This moonlighting activity is reflected in a flexible fold that makes UreG the first discovered intrinsically disordered enzyme. UreG binds Ni(II) and Zn(II),which in turn modulate the interactions with other urease chaperones. The aim of this study is to understand the structural implications of metal binding to Sporosarcina pasteurii UreG (SpUreG). A combination of light scattering, calorimetry, mass spectrometry, and NMR spectroscopy revealed that SpUreG exists in monomer-dimer equilibrium (K(d)= 45 µM), sampling three distinct folding populations with different degrees of compactness. Binding of Zn(II) ions, occurring in two distinct sites (K(d1) = 3 nM, K(d2) = 0.53 µM), shifts the protein conformational landscape toward the more compact population, while maintaining the overall protein structural plasticity. Differently, binding of Ni(II) ions occurs in three binding sites (K(d1(= 14 µM; K(d2) = 270 µM; K(d3)= 160 µM), with much weaker influence on the protein conformational equilibrium. These distinct conformational responses of SpUreG to Ni(II) and Zn(II) binding suggest that selective metal binding modulates protein plasticity, possibly having an impact on the protein-protein interactions and the enzymatic activity of UreG.
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36
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Merloni A, Dobrovolska O, Zambelli B, Agostini F, Bazzani M, Musiani F, Ciurli S. Molecular landscape of the interaction between the urease accessory proteins UreE and UreG. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2014; 1844:1662-74. [PMID: 24982029 DOI: 10.1016/j.bbapap.2014.06.016] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2014] [Revised: 06/12/2014] [Accepted: 06/19/2014] [Indexed: 01/07/2023]
Abstract
Urease, the most efficient enzyme so far discovered, depends on the presence of nickel ions in the catalytic site for its activity. The transformation of inactive apo-urease into active holo-urease requires the insertion of two Ni(II) ions in the substrate binding site, a process that involves the interaction of four accessory proteins named UreD, UreF, UreG and UreE. This study, carried out using calorimetric and NMR-based structural analysis, is focused on the interaction between UreE and UreG from Sporosarcina pasteurii, a highly ureolytic bacterium. Isothermal calorimetric protein-protein titrations revealed the occurrence of a binding event between SpUreE and SpUreG, entailing two independent steps with positive cooperativity (Kd1=42±9μM; Kd2=1.7±0.3μM). This was interpreted as indicating the formation of the (UreE)2(UreG)2 hetero-oligomer upon binding of two UreG monomers onto the pre-formed UreE dimer. The molecular details of this interaction were elucidated using high-resolution NMR spectroscopy. The occurrence of SpUreE chemical shift perturbations upon addition of SpUreG was investigated and analyzed to establish the protein-protein interaction site. The latter appears to involve the Ni(II) binding site as well as mobile portions on the C-terminal and the N-terminal domains. Docking calculations based on the information obtained from NMR provided a structural basis for the protein-protein contact site. The high sequence and structural similarity within these protein classes suggests a generality of the interaction mode among homologous proteins. The implications of these results on the molecular details of the urease activation process are considered and analyzed.
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Affiliation(s)
- Anna Merloni
- Laboratory of Bioinorganic Chemistry, Department of Pharmacy and Biotechnology, University of Bologna, Italy
| | - Olena Dobrovolska
- Laboratory of Bioinorganic Chemistry, Department of Pharmacy and Biotechnology, University of Bologna, Italy
| | - Barbara Zambelli
- Laboratory of Bioinorganic Chemistry, Department of Pharmacy and Biotechnology, University of Bologna, Italy
| | - Federico Agostini
- Laboratory of Bioinorganic Chemistry, Department of Pharmacy and Biotechnology, University of Bologna, Italy
| | - Micaela Bazzani
- Laboratory of Bioinorganic Chemistry, Department of Pharmacy and Biotechnology, University of Bologna, Italy
| | - Francesco Musiani
- Laboratory of Bioinorganic Chemistry, Department of Pharmacy and Biotechnology, University of Bologna, Italy
| | - Stefano Ciurli
- Laboratory of Bioinorganic Chemistry, Department of Pharmacy and Biotechnology, University of Bologna, Italy.
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37
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Zambelli B, Berardi A, Martin-Diaconescu V, Mazzei L, Musiani F, Maroney MJ, Ciurli S. Nickel binding properties of Helicobacter pylori UreF, an accessory protein in the nickel-based activation of urease. J Biol Inorg Chem 2014; 19:319-34. [PMID: 24292245 PMCID: PMC3943961 DOI: 10.1007/s00775-013-1068-3] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2013] [Accepted: 11/14/2013] [Indexed: 02/08/2023]
Abstract
Helicobacter pylori UreF (HpUreF) is involved in the insertion of Ni(2+) in the urease active site. The recombinant protein in solution is a dimer characterized by an extensive α-helical structure and a well-folded tertiary structure. HpUreF binds two Ni(2+) ions per dimer, with a micromolar dissociation constant, as shown by calorimetry. X-ray absorption spectroscopy indicated that the Ni(2+) ions reside in a five-coordinate pyramidal geometry comprising exclusively N/O-donor ligands derived from the protein, including one or two histidine imidazole and carboxylate ligands. Binding of Ni(2+) does not affect the solution properties of the protein. Mutation to alanine of His229 and/or Cys231, a pair of residues located on the protein surface that interact with H. pylori UreD, altered the affinity of the protein for Ni(2+). This result, complemented by the findings from X-ray absorption spectroscopy, indicates that the Ni(2+) binding site involves His229, and that Cys231 has an indirect structural role in metal binding. An in vivo assay of urease activation demonstrated that H229A HpUreF, C231A HpUreF, and H229/C231 HpUreF are significantly less competent in this process, suggesting a role for a Ni(2+) complex with UreF in urease maturation. This hypothesis was supported by calculations revealing the presence of a tunnel that joins the Cys-Pro-His metal binding site on UreG and an opening on the UreD surface, passing through UreF close to His229 and Cys231, in the structure of the H. pylori UreDFG complex. This tunnel could be used to transfer nickel into the urease active site during apoenzyme-to-holoenzyme activation.
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Affiliation(s)
- Barbara Zambelli
- Laboratory of Bioinorganic Chemistry, Department of Pharmacy and Biotechnology, University of Bologna, Viale G. Fanin 40, 40127 Bologna (Italy)
| | - Andrea Berardi
- Laboratory of Bioinorganic Chemistry, Department of Pharmacy and Biotechnology, University of Bologna, Viale G. Fanin 40, 40127 Bologna (Italy)
| | | | - Luca Mazzei
- Laboratory of Bioinorganic Chemistry, Department of Pharmacy and Biotechnology, University of Bologna, Viale G. Fanin 40, 40127 Bologna (Italy)
| | - Francesco Musiani
- Laboratory of Bioinorganic Chemistry, Department of Pharmacy and Biotechnology, University of Bologna, Viale G. Fanin 40, 40127 Bologna (Italy)
- International School for Advanced Studies (Sissa/ISAS), Trieste (Italy)
| | - Michael J. Maroney
- Department of Chemistry, University of Massachusetts, Amherst 01003, MA, USA
| | - Stefano Ciurli
- Laboratory of Bioinorganic Chemistry, Department of Pharmacy and Biotechnology, University of Bologna, Viale G. Fanin 40, 40127 Bologna (Italy)
- Center for Magnetic Resonance (CERM), University of Florence (Italy)
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Rowinska-Zyrek M, Zakrzewska-Czerwinska J, Zawilak-Pawlik A, Kozlowski H. Ni2+chemistry in pathogens – a possible target for eradication. Dalton Trans 2014; 43:8976-89. [DOI: 10.1039/c4dt00421c] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Nickel homeostasis inHelicobacter pyloriand potential histidine-rich binding sites from various bacterial and fungal pathogens are discussed.
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Affiliation(s)
| | - Jolanta Zakrzewska-Czerwinska
- Faculty of Biotechnology
- University of Wroclaw
- 50-383 Wroclaw, Poland
- Institute of Immunology and Experimental Therapy
- Polish Academy of Sciences
| | - Anna Zawilak-Pawlik
- Institute of Immunology and Experimental Therapy
- Polish Academy of Sciences
- Department of Microbiology
- 53-114 Wrocław, Poland
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39
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de Reuse H, Vinella D, Cavazza C. Common themes and unique proteins for the uptake and trafficking of nickel, a metal essential for the virulence of Helicobacter pylori. Front Cell Infect Microbiol 2013; 3:94. [PMID: 24367767 PMCID: PMC3856676 DOI: 10.3389/fcimb.2013.00094] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2013] [Accepted: 11/21/2013] [Indexed: 12/22/2022] Open
Abstract
Nickel is a virulence determinant for the human gastric pathogen Helicobacter pylori. Indeed, H. pylori possesses two nickel-enzymes that are essential for in vivo colonization, [NiFe] hydrogenase and urease, an abundant virulence factor that contains 24 nickel ions per active complex. Because of these two enzymes, survival of H. pylori relies on an important supply of nickel, implying a tight control of its distribution and storage. In this review, we will present the pathways of activation of the nickel enzymes as well as original mechanisms found in H. pylori for the uptake, trafficking and distribution of nickel between the two enzymes. These include (i) an outer-membrane nickel uptake system, the FrpB4 TonB-dependent transporter, (ii) overlapping protein complexes and interaction networks involved in nickel trafficking and distribution between urease and hydrogenase and, (iii) Helicobacter specific nickel-binding proteins that are involved in nickel storage and can play the role of metallo-chaperones. Finally, we will discuss the implication of the nickel trafficking partners in virulence and propose them as novel therapeutic targets for treatments against H. pylori infection.
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Affiliation(s)
- Hilde de Reuse
- Unité Pathogenèse de Helicobacter, Département de Microbiologie, Institut Pasteur, ERL CNRS 3526 Paris, France
| | - Daniel Vinella
- Unité Pathogenèse de Helicobacter, Département de Microbiologie, Institut Pasteur, ERL CNRS 3526 Paris, France
| | - Christine Cavazza
- Metalloproteins Group, Institut de Biologie Structurale Jean-Pierre Ebel, UMR 5075, CEA, CNRS, Université Joseph Fourier-Grenoble 1 Grenoble, France
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40
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Ge RG, Wang DX, Hao MC, Sun XS. Nickel trafficking system responsible for urease maturation in Helicobacter pylori. World J Gastroenterol 2013; 19:8211-8218. [PMID: 24363511 PMCID: PMC3857443 DOI: 10.3748/wjg.v19.i45.8211] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/06/2013] [Revised: 10/17/2013] [Accepted: 11/03/2013] [Indexed: 02/06/2023] Open
Abstract
Helicobacter pylori (H. pylori) is a common human pathogen responsible for various gastric diseases. This bacterium relies on the production of urease and hydrogenase to inhabit the acidic environment of the stomach. Nickel is an essential cofactor for urease and hydrogenase. H. pylori has to uptake sufficient nickel ions for the maturation of urease, and on the other way, to prevent the toxic effects of excessive nickel ions. Therefore, H. pylori has to strike a delicate balance between the import of nickel ions, its efficient intracellular storage, and delivery to nickel-dependent metalloenzymes when required. The assembly and maturation of the urease enzyme is a complex and timely ordered process, requiring various regulatory, uptake, chaperone and accessory proteins. In this review, we focus on several nickel trafficking proteins involved in urease maturation: NikR, NixA, HypAB, UreEFGH, HspA, Hpn and Hpnl. The work will deepen our understanding of how this pathogenic bacterium adapts to severe habitant environments in the host.
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Selectivity of Ni(II) and Zn(II) binding to Sporosarcina pasteurii UreE, a metallochaperone in the urease assembly: a calorimetric and crystallographic study. J Biol Inorg Chem 2013; 18:1005-17. [PMID: 24126709 DOI: 10.1007/s00775-013-1049-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2013] [Accepted: 09/13/2013] [Indexed: 10/26/2022]
Abstract
Urease is a nickel-dependent enzyme that plays a critical role in the biogeochemical nitrogen cycle by catalyzing the hydrolysis of urea to ammonia and carbamate. This enzyme, initially synthesized in the apo form, needs to be activated by incorporation of two nickel ions into the active site, a process driven by the dimeric metallochaperone UreE. Previous studies reported that this protein can bind different metal ions in vitro, beside the cognate Ni(II). This study explores the metal selectivity and affinity of UreE from Sporosarcina pasteurii (Sp, formerly known as Bacillus pasteurii) for cognate [Ni(II)] and noncognate [Zn(II)] metal ions. In particular, the thermodynamic parameters of SpUreE Ni(II) and Zn(II) binding have been determined using isothermal titration calorimetry. These experiments show that two Ni(II) ions bind to the protein dimer with positive cooperativity. The high-affinity site involves the conserved solvent-exposed His(100) and the C-terminal His(145), whereas the low-affinity site comprises also the C-terminal His(147). Zn(II) binding to the protein, occurring in the same protein regions and with similar affinity as compared to Ni(II), causes metal-driven dimerization of the protein dimer. The crystal structure of the protein obtained in the presence of equimolar amounts of both metal ions indicates that the high-affinity metal binding site binds Ni(II) preferentially over Zn(II). The ability of the protein to select Ni(II) over Zn(II) was confirmed by competition experiments in solution as well as by analysis of X-ray anomalous dispersion data. Overall, the thermodynamics and structural parameters that modulate the metal ion specificity of the different binding sites on the protein surface of SpUreE have been established.
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42
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Structure of UreG/UreF/UreH complex reveals how urease accessory proteins facilitate maturation of Helicobacter pylori urease. PLoS Biol 2013; 11:e1001678. [PMID: 24115911 PMCID: PMC3792862 DOI: 10.1371/journal.pbio.1001678] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2013] [Accepted: 08/29/2013] [Indexed: 11/19/2022] Open
Abstract
Structural and biochemical study of urease accessory protein complex provides mechanistic insights into the delivery of nickel to metalloenzyme urease, an enzyme enabling the survival of Helicobacter pylori in the human stomach. Urease is a metalloenzyme essential for the survival of Helicobacter pylori in acidic gastric environment. Maturation of urease involves carbamylation of Lys219 and insertion of two nickel ions at its active site. This process requires GTP hydrolysis and the formation of a preactivation complex consisting of apo-urease and urease accessory proteins UreF, UreH, and UreG. UreF and UreH form a complex to recruit UreG, which is a SIMIBI class GTPase, to the preactivation complex. We report here the crystal structure of the UreG/UreF/UreH complex, which illustrates how UreF and UreH facilitate dimerization of UreG, and assembles its metal binding site by juxtaposing two invariant Cys66-Pro67-His68 metal binding motif at the interface to form the (UreG/UreF/UreH)2 complex. Interaction studies revealed that addition of nickel and GTP to the UreG/UreF/UreH complex releases a UreG dimer that binds a nickel ion at the dimeric interface. Substitution of Cys66 and His68 with alanine abolishes the formation of the nickel-charged UreG dimer. This nickel-charged UreG dimer can activate urease in vitro in the presence of the UreF/UreH complex. Static light scattering and atomic absorption spectroscopy measurements demonstrated that the nickel-charged UreG dimer, upon GTP hydrolysis, reverts to its monomeric form and releases nickel to urease. Based on our results, we propose a mechanism on how urease accessory proteins facilitate maturation of urease. Catalytic activities of many important enzymes depend upon metal cofactors. Ensuring each enzyme acquires the proper type of metal cofactor is essential to life. One such example is urease, which is a nickel containing metalloenzyme catalyzing the hydrolysis of urea to ammonia. The survival of Helicobacter pylori, a stomach ulcer–causing pathogen, in the human stomach depends on the ammonia released to neutralize gastric acid. In this study, we revealed the detail mechanism of how urease accessory proteins UreF, UreH, and UreG cooperate to couple GTP hydrolysis to deliver nickel to urease. UreF/UreH complex interacts with two molecules of GTPase UreG and assembles a metal binding site located at the interface between two UreG molecules. Nickel can induce GTP-dependent dimerization of UreG. This nickel-carrying UreG dimer together with UreF, UreH, and urease assemble into a protein complex. Upon stimulation of UreG GTPase activity by bicarbonate, UreG hydrolyses GTP and releases nickel into urease. Other nickel-delivering NTPases share similar properties with UreG; therefore, the nickel delivery mechanism described here is likely universally shared among these proteins.
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Structure of the UreD-UreF-UreG-UreE complex in Helicobacter pylori: a model study. J Biol Inorg Chem 2013; 18:571-7. [PMID: 23661161 DOI: 10.1007/s00775-013-1002-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2013] [Accepted: 04/23/2013] [Indexed: 10/26/2022]
Abstract
The molecular details of the protein complex formed by UreD, UreF, UreG, and UreE, accessory proteins for urease activation in the carcinogenic bacterium Helicobacter pylori, have been elucidated using computational modeling. The calculated structure of the complex supports the hypothesis of UreF acting as a GTPase activation protein that facilitates GTP hydrolysis by UreG during urease maturation, and provides a rationale for the design of new drugs against infections by ureolytic bacterial pathogens.
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Musiani F, Ippoliti E, Micheletti C, Carloni P, Ciurli S. Conformational fluctuations of UreG, an intrinsically disordered enzyme. Biochemistry 2013; 52:2949-54. [PMID: 23560717 DOI: 10.1021/bi4001744] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
UreG proteins are small GTP binding (G) proteins that catalyze the hydrolysis of GTP necessary for the maturation of urease, a virulence factor in bacterial pathogenesis. UreG proteins are the first documented cases of intrinsically disordered enzymes. The comprehension of the dynamics of folding-unfolding events occurring in this protein could shed light on the enzymatic mechanism of UreG. Here, we used the recently developed replica exchange with solute tempering (REST2) computational methodology to explore the conformational space of UreG from Helicobacter pylori (HpUreG) and to identify its structural fluctuations. The same simulation and analysis protocol has been applied to HypB from Methanocaldococcus jannaschii (MjHypB), which is closely related to UreG in both sequence and function, even though it is not intrinsically disordered. A comparison of the two systems reveals that both HpUreG and MjHypB feature a substantial rigidity of the protein regions involved in catalysis, justifying its residual catalytic activity. On the other hand, HpUreG tends to unfold more than MjHypB in portions involved in protein-protein interactions with metallochaperones necessary for the formation of multiprotein complexes known to be involved in urease activation.
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Affiliation(s)
- Francesco Musiani
- Laboratory of Bioinorganic Chemistry, Department of Pharmacy and Biotechnology, University of Bologna, Bologna, Italy
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Abstract
Metalloenzymes often require elaborate metallocenter assembly systems to create functional active sites. The medically important dinuclear nickel enzyme urease provides an excellent model for studying metallocenter assembly. Nickel is inserted into the urease active site in a GTP-dependent process with the assistance of UreD/UreH, UreE, UreF, and UreG. These accessory proteins orchestrate apoprotein activation by delivering the appropriate metal, facilitating protein conformational changes, and possibly providing a requisite post-translational modification. The activation mechanism and roles of each accessory protein in urease maturation are the subject of ongoing studies, with the latest findings presented in this minireview.
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Affiliation(s)
- Mark A Farrugia
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824, USA
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Abstract
This review focuses on the impact of nickel on human health. In particular, the dual nature of nickel as an essential as well as toxic element in nature is described, and the main forms of nickel that can come in contact with living systems from natural sources and anthropogenic activities are discussed. Concomitantly, the main routes of nickel uptake and transport in humans are covered, and the potential dangers that nickel exposure can represent for health are described. In particular, the insurgence of nickel-derived allergies, nickel-induced carcinogenesis as well as infectious diseases caused by human pathogens that rely on nickel-based enzymes to colonize the host are reviewed at different levels, from their macroscopic aspects on human health to the molecular mechanisms underlying these points. Finally, the importance of nickel as a beneficial element for human health, especially being essential for microorganisms that colonize the human guts, is examined.
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Affiliation(s)
- Barbara Zambelli
- Laboratory of Bioinorganic Chemistry, Department of Pharmacy and Biotechnology, University of Bologna, Bologna, Italy,
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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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Benoit SL, McMurry JL, Hill SA, Maier RJ. Helicobacter pylori hydrogenase accessory protein HypA and urease accessory protein UreG compete with each other for UreE recognition. Biochim Biophys Acta Gen Subj 2012; 1820:1519-25. [PMID: 22698670 DOI: 10.1016/j.bbagen.2012.06.002] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2012] [Revised: 06/01/2012] [Accepted: 06/04/2012] [Indexed: 01/15/2023]
Abstract
BACKGROUND The gastric pathogen Helicobacter pylori relies on nickel-containing urease and hydrogenase enzymes in order to colonize the host. Incorporation of Ni(2+) into urease is essential for the function of the enzyme and requires the action of several accessory proteins, including the hydrogenase accessory proteins HypA and HypB and the urease accessory proteins UreE, UreF, UreG and UreH. METHODS Optical biosensing methods (biolayer interferometry and plasmon surface resonance) were used to screen for interactions between HypA, HypB, UreE and UreG. RESULTS Using both methods, affinity constants were found to be 5nM and 13nM for HypA-UreE and 8μM and 14μM for UreG-UreE. Neither Zn(2+) nor Ni(2+) had an effect on the kinetics or stability of the HypA-UreE complex. By contrast, addition of Zn(2+), but not Ni(2+), altered the kinetics and greatly increased the stability of the UreE-UreG complex, likely due in part to Zn(2+)-mediated oligomerization of UreE. Finally our results unambiguously show that HypA, UreE and UreG cannot form a heterotrimeric protein complex in vitro; instead, HypA and UreG compete with each other for UreE recognition. GENERAL SIGNIFICANCE Factors influencing the pathogen's nickel budget are important to understand pathogenesis and for future drug design.
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Affiliation(s)
- Stéphane L Benoit
- Department of Microbiology, University of Georgia, 805 Biological Sciences Bldg., Athens, GA, USA
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Crystallographic and X-ray absorption spectroscopic characterization of Helicobacter pylori UreE bound to Ni²⁺ and Zn²⁺ reveals a role for the disordered C-terminal arm in metal trafficking. Biochem J 2012; 441:1017-26. [PMID: 22010876 DOI: 10.1042/bj20111659] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The survival and growth of the pathogen Helicobacter pylori in the gastric acidic environment is ensured by the activity of urease, an enzyme containing two essential Ni²⁺ ions in the active site. The metallo-chaperone UreE facilitates in vivo Ni²⁺ insertion into the apoenzyme. Crystals of apo-HpUreE (H. pylori UreE) and its Ni⁺- and Zn⁺-bound forms were obtained from protein solutions in the absence and presence of the metal ions. The crystal structures of the homodimeric protein, determined at 2.00 Å (apo), 1.59 Å (Ni²⁺) and 2.52 Å (Zn²⁺) resolution, show the conserved proximal and solvent-exposed His¹⁰² residues from two adjacent monomers invariably involved in metal binding. The C-terminal regions of the apoprotein are disordered in the crystal, but acquire significant ordering in the presence of the metal ions due to the binding of His¹⁵². The analysis of X-ray absorption spectral data obtained using solutions of Ni²⁺- and Zn²⁺-bound HpUreE provided accurate information of the metal-ion environment in the absence of solid-state effects. These results reveal the role of the histidine residues at the protein C-terminus in metal-ion binding, and the mutual influence of protein framework and metal-ion stereo-electronic properties in establishing co-ordination number and geometry leading to metal selectivity.
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