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Rushworth DD, Schenkeveld WDC, Kumar N, Noël V, Dewulf J, van Helmond NAGM, Slomp CP, Lehmann MF, Kraemer SM. Solid phase speciation controls copper mobilisation from marine sediments by methanobactin. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 934:173046. [PMID: 38735326 DOI: 10.1016/j.scitotenv.2024.173046] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/06/2024] [Revised: 04/26/2024] [Accepted: 05/05/2024] [Indexed: 05/14/2024]
Abstract
Although marine environments represent huge reservoirs of the potent greenhouse gas methane, they currently contribute little to global net methane emissions. Most of the methane is oxidized by methanotrophs, minimizing escape to the atmosphere. Aerobic methanotrophs oxidize methane mostly via the copper (Cu)-bearing enzyme particulate methane monooxygenase (pMMO). Therefore, aerobic methane oxidation depends on sufficient Cu acquisition by methanotrophs. Because they require both oxygen and methane, aerobic methanotrophs reside at oxic-anoxic interfaces, often close to sulphidic zones where Cu bioavailability can be limited by poorly soluble Cu sulphide mineral phases. Under Cu-limiting conditions, certain aerobic methanotrophs exude Cu-binding ligands termed chalkophores, such as methanobactin (mb) exuded by Methylosinus trichosporium OB3b. Our main objective was to establish whether chalkophores can mobilise Cu from Cu sulphide-bearing marine sediments to enhance Cu bioavailability. Through a series of kinetic batch experiments, we investigated Cu mobilisation by mb from a set of well-characterized sulphidic marine sediments differing in sediment properties, including Cu content and phase distribution. Characterization of solid-phase Cu speciation included X-ray absorption spectroscopy and a targeted sequential extraction. Furthermore, in batch experiments, we investigated to what extent adsorption of metal-free mb and Cu-mb complexes to marine sediments constrains Cu mobilisation. Our results are the first to show that both solid phase Cu speciation and chalkophore adsorption can constrain methanotrophic Cu acquisition from marine sediments. Only for certain sediments did mb addition enhance dissolved Cu concentrations. Cu mobilisation by mb was not correlated to the total Cu content of the sediment, but was controlled by solid-phase Cu speciation. Cu was only mobilised from sediments containing a mono-Cu-sulphide (CuSx) phase. We also show that mb adsorption to sediments limits Cu acquisition by mb to less compact (surface) sediments. Therefore, in sulphidic sediments, mb-mediated Cu acquisition is presumably constrained to surface-sediment interfaces containing mono-Cu-sulphide phases.
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Affiliation(s)
- Danielle D Rushworth
- Centre for Microbiology and Environmental Systems Science, University of Vienna, Vienna, Austria; Environmental Sciences, Copernicus Institute of Sustainable Development, Utrecht University, Utrecht, Netherlands
| | - Walter D C Schenkeveld
- Soil Chemistry and Chemical Soil Quality, Environmental Sciences, Wageningen University, Wageningen, Netherlands.
| | - Naresh Kumar
- Soil Chemistry and Chemical Soil Quality, Environmental Sciences, Wageningen University, Wageningen, Netherlands.
| | - Vincent Noël
- Environmental Geochemistry Group at SLAC, Stanford Synchrotron Radiation Lightsource (SSRL), SLAC National Accelerator Laboratory, Menlo Park, USA
| | - Jannes Dewulf
- Environmental Sciences, Copernicus Institute of Sustainable Development, Utrecht University, Utrecht, Netherlands
| | - Niels A G M van Helmond
- Geochemistry, Department of Earth Sciences, Utrecht University, Utrecht, Netherlands; Department of Microbiology, Radboud Institute for Biological and Environmental Sciences, Radboud University, Nijmegen, Netherlands
| | - Caroline P Slomp
- Geochemistry, Department of Earth Sciences, Utrecht University, Utrecht, Netherlands; Department of Microbiology, Radboud Institute for Biological and Environmental Sciences, Radboud University, Nijmegen, Netherlands
| | - Moritz F Lehmann
- Department of Environmental Sciences, University of Basel, Basel, Switzerland
| | - Stephan M Kraemer
- Centre for Microbiology and Environmental Systems Science, University of Vienna, Vienna, Austria
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Singh R, Panghal A, Jadhav K, Thakur A, Verma RK, Singh C, Goyal M, Kumar J, Namdeo AG. Recent Advances in Targeting Transition Metals (Copper, Iron, and Zinc) in Alzheimer's Disease. Mol Neurobiol 2024:10.1007/s12035-024-04256-8. [PMID: 38809370 DOI: 10.1007/s12035-024-04256-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2024] [Accepted: 05/21/2024] [Indexed: 05/30/2024]
Abstract
Changes in the transition metal homeostasis in the brain are closely linked with Alzheimer's disease (AD), including intraneuronal iron accumulation and extracellular copper and zinc pooling in the amyloid plague. The brain copper, zinc, and iron surplus are commonly acknowledged characteristics of AD, despite disagreements among some. This has led to the theory that oxidative stress resulting from abnormal homeostasis of these transition metals may be a causative explanation behind AD. In the nervous system, the interaction of metals with proteins appears to be an essential variable in the development or suppression of neurodegeneration. Chelation treatment may be an option for treating neurodegeneration induced by transition metal ion dyshomeostasis. Some clinicians even recommend using chelating agents as an adjunct therapy for AD. The current review also looks at the therapeutic strategies that have been attempted, primarily with metal-chelating drugs. Metal buildup in the nervous system, as reported in the AD, could be the result of compensatory mechanisms designed to improve metal availability for physiological functions.
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Affiliation(s)
- Raghuraj Singh
- Pharmaceutical Nanotechnology Lab, Institutes of Nano Science and Technology (INST), Sector 81. Mohali, Punjab, 140306, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, Uttar Pradesh, 201002, India
| | - Archna Panghal
- Department of Pharmacology and Toxicology, Facility for Risk Assessment and Intervention Studies, National Institute of Pharmaceutical Education and Research, S.A.S Nagar, Punjab, India
| | - Krishna Jadhav
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, Uttar Pradesh, 201002, India
| | - Ashima Thakur
- Faculty of Pharmaceutical Sciences, ICFAI University, Baddi, Distt. Solan, Himachal Pradesh, 174103, India
| | - Rahul Kumar Verma
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, Uttar Pradesh, 201002, India
| | - Charan Singh
- Department of Pharmaceutical Sciences Hemwati, Nandan Bahuguna Garhwal University (A Central University), Srinagar, Dist. Garhwal (Uttarakhand), 246174, India
| | - Manoj Goyal
- Department of Pharmaceutical Sciences Hemwati, Nandan Bahuguna Garhwal University (A Central University), Srinagar, Dist. Garhwal (Uttarakhand), 246174, India
| | - Jayant Kumar
- Department of Pharmaceutical Sciences Hemwati, Nandan Bahuguna Garhwal University (A Central University), Srinagar, Dist. Garhwal (Uttarakhand), 246174, India.
| | - Ajay G Namdeo
- Department of Pharmaceutical Sciences Hemwati, Nandan Bahuguna Garhwal University (A Central University), Srinagar, Dist. Garhwal (Uttarakhand), 246174, India
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Peng W, Wang Z, Zhang Q, Yan S, Wang B. Unraveling the Valence State and Reactivity of Copper Centers in Membrane-Bound Particulate Methane Monooxygenase. J Am Chem Soc 2023; 145:25304-25317. [PMID: 37955571 DOI: 10.1021/jacs.3c08834] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2023]
Abstract
Particulate methane monooxygenase (pMMO) plays a critical role in catalyzing the conversion of methane to methanol, constituting the initial step in the C1 metabolic pathway within methanotrophic bacteria. However, the membrane-bound pMMO's structure and catalytic mechanism, notably the copper's valence state and genuine active site for methane oxidation, have remained elusive. Based on the recently characterized structure of membrane-bound pMMO, extensive computational studies were conducted to address these long-standing issues. A comprehensive analysis comparing the quantum mechanics/molecular mechanics (QM/MM) molecular dynamics (MD) simulated structures with cryo-EM data indicates that both the CuC and CuD sites tend to stay in the Cu(I) valence state within the membrane environment. Additionally, the concurrent presence of Cu(I) at both CuC and CuD sites leads to the significant reduction of the ligand-binding cavity situated between them, making it less likely to accommodate a reductant molecule such as durohydroquinone (DQH2). Subsequent QM/MM calculations reveal that the CuD(I) site is more reactive than the CuC(I) site in oxygen activation, en route to H2O2 formation and the generation of Cu(II)-O•- species. Finally, our simulations demonstrate that the natural reductant ubiquinol (CoQH2) assumes a productive binding conformation at the CuD(I) site but not at the CuC(I) site. This provides evidence that the true active site of membrane-bound pMMOs may be CuD rather than CuC. These findings clarify pMMO's catalytic mechanism and emphasize the membrane environment's pivotal role in modulating the coordination structure and the activity of copper centers within pMMO.
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Affiliation(s)
- Wei Peng
- State Key Laboratory of Physical Chemistry of Solid Surfaces and Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, College of Chemistry and Chemical Engineering and Innovation Laboratory for Sciences and Technologies of Energy Materials of Fujian Province (IKKEM), Xiamen University, Xiamen 361005, P. R. China
- Key Laboratory of Aerosol Chemistry and Physics, State Key Laboratory of Loess and Quaternary Geology (SKLLQG), Institute of Earth Environment, Chinese Academy of Sciences, Xi'an 710061, P. R. China
| | - Zikuan Wang
- Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, Mülheim an der Ruhr 45470, Germany
| | - Qiaoyu Zhang
- State Key Laboratory of Physical Chemistry of Solid Surfaces and Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, College of Chemistry and Chemical Engineering and Innovation Laboratory for Sciences and Technologies of Energy Materials of Fujian Province (IKKEM), Xiamen University, Xiamen 361005, P. R. China
| | - Shengheng Yan
- State Key Laboratory of Physical Chemistry of Solid Surfaces and Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, College of Chemistry and Chemical Engineering and Innovation Laboratory for Sciences and Technologies of Energy Materials of Fujian Province (IKKEM), Xiamen University, Xiamen 361005, P. R. China
| | - Binju Wang
- State Key Laboratory of Physical Chemistry of Solid Surfaces and Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, College of Chemistry and Chemical Engineering and Innovation Laboratory for Sciences and Technologies of Energy Materials of Fujian Province (IKKEM), Xiamen University, Xiamen 361005, P. R. China
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4
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Rushworth DD, Christl I, Kumar N, Hoffmann K, Kretzschmar R, Lehmann MF, Schenkeveld WDC, Kraemer SM. Copper mobilisation from Cu sulphide minerals by methanobactin: Effect of pH, oxygen and natural organic matter. GEOBIOLOGY 2022; 20:690-706. [PMID: 35716154 PMCID: PMC9544142 DOI: 10.1111/gbi.12505] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Revised: 05/03/2022] [Accepted: 05/24/2022] [Indexed: 06/15/2023]
Abstract
Aerobic methane oxidation (MOx) depends critically on the availability of copper (Cu) as a crucial component of the metal centre of particulate methane monooxygenase, one of the main enzymes involved in MOx. Some methanotrophs have developed Cu acquisition strategies, in which they exude Cu-binding ligands termed chalkophores under conditions of low Cu availability. A well-characterised chalkophore is methanobactin (mb), exuded by the microaerophilic methanotroph Methylosinus trichosporium OB3b. Aerobic methanotrophs generally reside close to environmental oxic-anoxic interfaces, where the formation of Cu sulphide phases can aggravate the limitation of bioavailable Cu due to their low solubility. The reactivity of chalkophores towards such Cu sulphide mineral phases has not yet been investigated. In this study, a combination of dissolution experiments and equilibrium modelling was used to examine the dissolution and solubility of bulk and nanoparticulate Cu sulphide minerals in the presence of mb as influenced by pH, oxygen and natural organic matter. In general, we show that mb is effective at increasing the dissolved Cu concentrations in the presence of a variety of Cu sulphide phases that may potentially limit Cu bioavailability. More Cu was mobilised per mole of mb from Cu sulphide nanoparticles compared with well-crystalline bulk covellite (CuS). In general, the efficacy of mb at mobilising Cu from Cu sulphides is pH-dependent. At lower pH, e.g. pH 5, mb was ineffective at solubilizing Cu. The presence of mb increased dissolved Cu concentrations between pH 7 and 8.5, where the solubility of all Cu sulphides is generally low, both in the presence and absence of oxygen. These results suggest that chalkophore-promoted Cu mobilisation from sulphide phases is an effective extracellular mechanism for increasing dissolved Cu concentrations at oxic-anoxic interfaces, particularly in the neutral to slightly alkaline pH range. This suggests that aerobic methanotrophs may be able to fulfil their Cu requirements via the exudation of mb in natural environments where the bioavailability of Cu is constrained by very stable Cu sulphide phases.
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Affiliation(s)
- Danielle D. Rushworth
- Centre for Microbiology and Environmental Systems ScienceUniversity of ViennaViennaAustria
| | - Iso Christl
- Soil ChemistryInstitute of Biogeochemistry and Pollutant Dynamics, ETHZurichSwitzerland
| | - Naresh Kumar
- Soil Chemistry and Chemical Soil Quality, Environmental SciencesWageningen UniversityWageningenThe Netherlands
| | - Kevin Hoffmann
- Soil ChemistryInstitute of Biogeochemistry and Pollutant Dynamics, ETHZurichSwitzerland
| | - Ruben Kretzschmar
- Soil ChemistryInstitute of Biogeochemistry and Pollutant Dynamics, ETHZurichSwitzerland
| | - Moritz F. Lehmann
- Department of Environmental GeosciencesUniversity of BaselBaselSwitzerland
| | - Walter D. C. Schenkeveld
- Soil Chemistry and Chemical Soil Quality, Environmental SciencesWageningen UniversityWageningenThe Netherlands
| | - Stephan M. Kraemer
- Centre for Microbiology and Environmental Systems ScienceUniversity of ViennaViennaAustria
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An Overview on Methanotrophs and the Role of Methylosinus trichosporium OB3b for Biotechnological Applications. BIOTECHNOL BIOPROC E 2022. [DOI: 10.1007/s12257-022-0046-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Fasae KD, Abolaji AO, Faloye TR, Odunsi AY, Oyetayo BO, Enya JI, Rotimi JA, Akinyemi RO, Whitworth AJ, Aschner M. Metallobiology and therapeutic chelation of biometals (copper, zinc and iron) in Alzheimer's disease: Limitations, and current and future perspectives. J Trace Elem Med Biol 2021; 67:126779. [PMID: 34034029 DOI: 10.1016/j.jtemb.2021.126779] [Citation(s) in RCA: 54] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/08/2020] [Revised: 04/03/2021] [Accepted: 05/10/2021] [Indexed: 02/08/2023]
Abstract
BACKGROUND Alzheimer's disease (AD) is the most prevalent cause of cognitive impairment and dementia worldwide. The pathobiology of the disease has been studied in the form of several hypotheses, ranging from oxidative stress, amyloid-beta (Aβ) aggregation, accumulation of tau forming neurofibrillary tangles (NFT) through metal dysregulation and homeostasis, dysfunction of the cholinergic system, and to inflammatory and autophagic mechanism. However, none of these hypotheses has led to confirmed diagnostics or approved cure for the disease. OBJECTIVE This review is aimed as a basic and an encyclopedic short course into metals in AD and discusses the advances in chelation strategies and developments adopted in the treatment of the disease. Since there is accumulating evidence of the role of both biometal dyshomeostasis (iron (Fe), copper (Cu), and zinc (Zn)) and metal-amyloid interactions that lead to the pathogenesis of AD, this review focuses on unraveling therapeutic chelation strategies that have been considered in the treatment of the disease, aiming to sequester free and protein-bound metal ions and reducing cerebral metal burden. Promising compounds possessing chemically modified moieties evolving as multi-target ligands used as anti-AD drug candidates are also covered. RESULTS AND CONCLUSION Several multidirectional and multifaceted studies on metal chelation therapeutics show the need for improved synthesis, screening, and analysis of compounds to be able to effectively present chelating anti-AD drugs. Most drug candidates studied have limitations in their physicochemical properties; some enhance redistribution of metal ions, while others indirectly activate signaling pathways in AD. The metal chelation process in vivo still needs to be established and the design of potential anti-AD compounds that bi-functionally sequester metal ions as well as inhibit the Aβ aggregation by competing with the metal ions and reducing metal-induced oxidative damage and neurotoxicity may signal a bright end in chelation-based therapeutics of AD.
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Affiliation(s)
- Kehinde D Fasae
- Department of Biochemistry, Molecular Drug Metabolism and Toxicology Unit, College of Medicine, University of Ibadan, Nigeria
| | - Amos O Abolaji
- Department of Biochemistry, Molecular Drug Metabolism and Toxicology Unit, College of Medicine, University of Ibadan, Nigeria.
| | - Tolulope R Faloye
- Department of Biochemistry, Molecular Drug Metabolism and Toxicology Unit, College of Medicine, University of Ibadan, Nigeria
| | - Atinuke Y Odunsi
- Department of Biochemistry, Molecular Drug Metabolism and Toxicology Unit, College of Medicine, University of Ibadan, Nigeria
| | - Bolaji O Oyetayo
- Department of Pharmacology and Therapeutics, Neuropharmacology Unit, College of Medicine, University of Ibadan, Nigeria
| | - Joseph I Enya
- Department of Anatomy, University of Ilorin, Kwara State, Nigeria
| | - Joshua A Rotimi
- Department of Biochemistry and Molecular Biology, Obafemi Awolowo University, Ile-Ife, Nigeria
| | - Rufus O Akinyemi
- Neuroscience and Ageing Research Unit, Institute for Advanced Medical Research and Training, College of Medicine, University of Ibadan, Ibadan, Oyo State, Nigeria
| | | | - Michael Aschner
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY, USA.
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Karthikeyan OP, Smith TJ, Dandare SU, Parwin KS, Singh H, Loh HX, Cunningham MR, Williams PN, Nichol T, Subramanian A, Ramasamy K, Kumaresan D. Metal(loid) speciation and transformation by aerobic methanotrophs. MICROBIOME 2021; 9:156. [PMID: 34229757 PMCID: PMC8262016 DOI: 10.1186/s40168-021-01112-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2021] [Accepted: 06/09/2021] [Indexed: 05/06/2023]
Abstract
Manufacturing and resource industries are the key drivers for economic growth with a huge environmental cost (e.g. discharge of industrial effluents and post-mining substrates). Pollutants from waste streams, either organic or inorganic (e.g. heavy metals), are prone to interact with their physical environment that not only affects the ecosystem health but also the livelihood of local communities. Unlike organic pollutants, heavy metals or trace metals (e.g. chromium, mercury) are non-biodegradable, bioaccumulate through food-web interactions and are likely to have a long-term impact on ecosystem health. Microorganisms provide varied ecosystem services including climate regulation, purification of groundwater, rehabilitation of contaminated sites by detoxifying pollutants. Recent studies have highlighted the potential of methanotrophs, a group of bacteria that can use methane as a sole carbon and energy source, to transform toxic metal (loids) such as chromium, mercury and selenium. In this review, we synthesise recent advances in the role of essential metals (e.g. copper) for methanotroph activity, uptake mechanisms alongside their potential to transform toxic heavy metal (loids). Case studies are presented on chromium, selenium and mercury pollution from the tanneries, coal burning and artisanal gold mining, respectively, which are particular problems in the developing economy that we propose may be suitable for remediation by methanotrophs. Video Abstract.
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Affiliation(s)
- Obulisamy Parthiba Karthikeyan
- School of Biological Sciences & Institute for Global Food Security, Queen’s University Belfast, 19 Chlorine Gardens, Belfast, UK
- Civil and Environmental Engineering, University of Michigan, Ann Arbor, MI USA
- Department of Engineering Technology, College of Technology, University of Houston, Houston, TX USA
| | - Thomas J. Smith
- Biomolecular Sciences Research Centre, Sheffield Hallam University, Sheffield, UK
| | - Shamsudeen Umar Dandare
- School of Biological Sciences & Institute for Global Food Security, Queen’s University Belfast, 19 Chlorine Gardens, Belfast, UK
| | - Kamaludeen Sara Parwin
- Department of Environmental Sciences, Tamil Nadu Agricultural University, Coimbatore, India
| | - Heetasmin Singh
- Department of Chemistry, University of Guyana, Georgetown, Guyana
| | - Hui Xin Loh
- School of Biological Sciences & Institute for Global Food Security, Queen’s University Belfast, 19 Chlorine Gardens, Belfast, UK
| | - Mark R Cunningham
- School of Biological Sciences & Institute for Global Food Security, Queen’s University Belfast, 19 Chlorine Gardens, Belfast, UK
| | - Paul Nicholas Williams
- School of Biological Sciences & Institute for Global Food Security, Queen’s University Belfast, 19 Chlorine Gardens, Belfast, UK
| | - Tim Nichol
- Biomolecular Sciences Research Centre, Sheffield Hallam University, Sheffield, UK
| | | | | | - Deepak Kumaresan
- School of Biological Sciences & Institute for Global Food Security, Queen’s University Belfast, 19 Chlorine Gardens, Belfast, UK
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Detoxification, Active Uptake, and Intracellular Accumulation of Chromium Species by a Methane-Oxidizing Bacterium. Appl Environ Microbiol 2021; 87:AEM.00947-20. [PMID: 33127813 PMCID: PMC7783347 DOI: 10.1128/aem.00947-20] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2020] [Accepted: 10/20/2020] [Indexed: 01/28/2023] Open
Abstract
M. capsulatus Bath is a well-characterized aerobic methane-oxidizing bacterium that has become a model system for biotechnological development of methanotrophs to perform useful reactions for environmental cleanup and for making valuable chemicals and biological products using methane gas. Interest in such technology has increased recently owing to increasing availability of low-cost methane from fossil and biological sources. Here, it is demonstrated that this versatile methanotroph can reduce the toxic contaminating heavy metal chromium(VI) to the less toxic form chromium(III) while accumulating the chromium(III) within the cells. This is expected to diminish the bioavailability of the chromium and make it less likely to be reoxidized to chromium(VI). Thus, M. capsulatus has the capacity to perform methane-driven remediation of chromium-contaminated water and other materials and to accumulate the chromium in the low-toxicity chromium(III) form within the cells. Despite the wide-ranging proscription of hexavalent chromium, chromium(VI) remains among the major polluting heavy metals worldwide. Aerobic methane-oxidizing bacteria are widespread environmental microorganisms that can perform diverse reactions using methane as the feedstock. The methanotroph Methylococcus capsulatus Bath, like many other microorganisms, detoxifies chromium(VI) by reduction to chromium(III). Here, the interaction of chromium species with M. capsulatus Bath was examined in detail by using a range of techniques. Cell fractionation and high-performance liquid chromatography–inductively coupled plasma mass spectrometry (HPLC–ICP-MS) indicated that externally provided chromium(VI) underwent reduction and was then taken up into the cytoplasmic and membranous fractions of the cells. This was confirmed by X-ray photoelectron spectroscopy (XPS) of intact cultures that indicated negligible chromium on the surfaces of or outside the cells. Distribution of chromium and other elements within intact and sectioned cells, as observed via transmission electron microscopy (TEM) combined with energy-dispersive X-ray spectroscopy (EDX) and electron energy loss spectroscopy (EELS), was consistent with the cytoplasm/membrane location of the chromium(III), possibly as chromium phosphate. The cells could also take up chromium(III) directly from the medium in a metabolism-dependent fashion and accumulate it. These results indicate a novel pattern of interaction with chromium species distinct from that observed previously with other microorganisms. They also suggest that M. capsulatus and similar methanotrophs may contribute directly to chromium(VI) reduction and accumulation in mixed communities of microorganisms that are able to perform methane-driven remediation of chromium(VI). IMPORTANCEM. capsulatus Bath is a well-characterized aerobic methane-oxidizing bacterium that has become a model system for biotechnological development of methanotrophs to perform useful reactions for environmental cleanup and for making valuable chemicals and biological products using methane gas. Interest in such technology has increased recently owing to increasing availability of low-cost methane from fossil and biological sources. Here, it is demonstrated that this versatile methanotroph can reduce the toxic contaminating heavy metal chromium(VI) to the less toxic form chromium(III) while accumulating the chromium(III) within the cells. This is expected to diminish the bioavailability of the chromium and make it less likely to be reoxidized to chromium(VI). Thus, M. capsulatus has the capacity to perform methane-driven remediation of chromium-contaminated water and other materials and to accumulate the chromium in the low-toxicity chromium(III) form within the cells.
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9
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Naizabekov S, Lee EY. Genome-Scale Metabolic Model Reconstruction and in Silico Investigations of Methane Metabolism in Methylosinus trichosporium OB3b. Microorganisms 2020; 8:microorganisms8030437. [PMID: 32244934 PMCID: PMC7144005 DOI: 10.3390/microorganisms8030437] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2020] [Revised: 03/16/2020] [Accepted: 03/19/2020] [Indexed: 01/09/2023] Open
Abstract
Methylosinus trichosporium OB3b is an obligate aerobic methane-utilizing alpha-proteobacterium. Since its isolation, M. trichosporium OB3b has been established as a model organism to study methane metabolism in type II methanotrophs. M. trichosporium OB3b utilizes soluble and particulate methane monooxygenase (sMMO and pMMO respectively) for methane oxidation. While the source of electrons is known for sMMO, there is less consensus regarding electron donor to pMMO. To investigate this and other questions regarding methane metabolism, the genome-scale metabolic model for M. trichosporium OB3b (model ID: iMsOB3b) was reconstructed. The model accurately predicted oxygen: methane molar uptake ratios and specific growth rates on nitrate-supplemented medium with methane as carbon and energy source. The redox-arm mechanism which links methane oxidation with complex I of electron transport chain has been found to be the most optimal mode of electron transfer. The model was also qualitatively validated on ammonium-supplemented medium indicating its potential to accurately predict methane metabolism in different environmental conditions. Finally, in silico investigations regarding flux distribution in central carbon metabolism of M. trichosporium OB3b were performed. Overall, iMsOB3b can be used as an organism-specific knowledgebase and a platform for hypothesis-driven theoretical investigations of methane metabolism.
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Yousef EN, Angel LA. Comparison of the pH-dependent formation of His and Cys heptapeptide complexes of nickel(II), copper(II), and zinc(II) as determined by ion mobility-mass spectrometry. JOURNAL OF MASS SPECTROMETRY : JMS 2020; 55:e4489. [PMID: 31881105 DOI: 10.1002/jms.4489] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/28/2019] [Revised: 12/05/2019] [Accepted: 12/13/2019] [Indexed: 06/10/2023]
Abstract
The analog methanobactin (amb) peptide with the sequence ac-His1 -Cys2 -Gly3 -Pro4 -Tyr5 -His6 -Cys7 (amb5A ) will bind the metal ions of zinc, nickel, and copper. To further understand how amb5A binds these metals, we have undertaken a series of studies of structurally related heptapeptides where one or two of the potential His or Cys binding sites have been replaced by Gly, or the C-terminus has been blocked by amidation. The studies were designed to compare how these metals bind to these sequences in different pH solutions of pH 4.2 to 10 and utilized native electrospray ionization (ESI) with ion mobility-mass spectrometry (IM-MS) which allows for the quantitative analysis of the charged species produced during the reactions. The native ESI conditions were chosen to conserve as much of the solution-phase behavior of the amb peptides as possible and an analysis of how the IM-MS results compare with the expected solution-phase behavior is discussed. The oligopeptides studied here have applications for tag-based protein purification methods, as therapeutics for diseases caused by elevated metal ion levels or as inhibitors for metal-protein enzymes such as matrix metalloproteinases.
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Affiliation(s)
- Enas N Yousef
- Department of Chemistry, Texas A&M University-Commerce, Commerce, Texas, 75428, USA
| | - Laurence A Angel
- Department of Chemistry, Texas A&M University-Commerce, Commerce, Texas, 75428, USA
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11
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Malik A, Angel LA, Spezia R, Hase WL. Collisional dynamics simulations revealing fragmentation properties of Zn(ii)-bound poly-peptide. Phys Chem Chem Phys 2020; 22:14551-14559. [DOI: 10.1039/d0cp02463e] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Collisional simulations show how peptide fragmentation is modified by the presence of Zn(ii).
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Affiliation(s)
- Abdul Malik
- Department of Chemistry and Biochemistry
- Texas Tech University
- Lubbock
- USA
| | | | - Riccardo Spezia
- Laboratoire de Chimie Théorique
- Sorbonne Université
- UMR 7616 CNRS
- 75005 Paris
- France
| | - William L. Hase
- Department of Chemistry and Biochemistry
- Texas Tech University
- Lubbock
- USA
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Si Z, Wang Y, Song X, Cao X, Zhang X, Sand W. Mechanism and performance of trace metal removal by continuous-flow constructed wetlands coupled with a micro-electric field. WATER RESEARCH 2019; 164:114937. [PMID: 31400593 DOI: 10.1016/j.watres.2019.114937] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2019] [Revised: 07/25/2019] [Accepted: 07/30/2019] [Indexed: 06/10/2023]
Abstract
Constructed wetlands coupled with a micro-electric field (CW-MEF) is a novel and efficient water treatment technology. The objective of this study was to investigate the mechanism and performance of trace metals (TMs) removal for CW-MEF systems during summer and winter. The mass distribution of TMs in plants and biofilms, physiological indices of wetland plants, and bacterial community structures on electrodes and in the rhizospheres were analyzed as well as to explore further the TM removal mechanism. Results show that the electric field intensities (EFI) of 100 and 200 mV cm-1 had a significantly promoting effect on TM removal. Maximum removal efficiencies for Cu, Zn, Cd, Co, Ni and Pb were 95.6, 80.1, 74.0, 67.1, 69.8 and 99.6%, respectively, in summer with a 5d-hydraulic retention time (HRT). An EFI of 100 mV cm-1 could alleviate the oxidative damage in plant cells by promoting the synthesis of reduced glutathione and an activity increase of catalase, thus increasing the phytoextraction for Cu, Zn and Cd. For biofilms, the MEF caused shifts in the bacterial community structures, and an EFI of 50 to 200 mV cm-1 significantly promoted the enrichment of Cu, Zn, Cd and Co by biofilms. Moreover, microorganisms related to TM tolerance and enrichment exhibited a high abundance with an EFI of 100 and 200 mV cm-1. It can be concluded that introducing MEF to CWs could intensify the TMs removal via the biological process and result in more efficient purification for TM-containing wastewater.
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Affiliation(s)
- Zhihao Si
- College of Environmental Science and Engineering, State Environmental Protection Engineering Center for Pollution Treatment and Control in Textile Industry, Donghua University, Shanghai, 201620, China
| | - Yuhui Wang
- College of Environmental Science and Engineering, State Environmental Protection Engineering Center for Pollution Treatment and Control in Textile Industry, Donghua University, Shanghai, 201620, China.
| | - Xinshan Song
- College of Environmental Science and Engineering, State Environmental Protection Engineering Center for Pollution Treatment and Control in Textile Industry, Donghua University, Shanghai, 201620, China
| | - Xin Cao
- College of Environmental Science and Engineering, State Environmental Protection Engineering Center for Pollution Treatment and Control in Textile Industry, Donghua University, Shanghai, 201620, China
| | - Xian Zhang
- College of Environmental Science and Engineering, State Environmental Protection Engineering Center for Pollution Treatment and Control in Textile Industry, Donghua University, Shanghai, 201620, China
| | - Wolfgang Sand
- College of Environmental Science and Engineering, State Environmental Protection Engineering Center for Pollution Treatment and Control in Textile Industry, Donghua University, Shanghai, 201620, China
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13
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Lin YF, Yousef EN, Torres E, Truong L, Zahnow JM, Donald CB, Qin Y, Angel LA. Weak Acid-Base Interactions of Histidine and Cysteine Affect the Charge States, Tertiary Structure, and Zn(II)-Binding of Heptapeptides. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2019; 30:2068-2081. [PMID: 31332742 DOI: 10.1007/s13361-019-02275-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/17/2019] [Revised: 06/10/2019] [Accepted: 06/18/2019] [Indexed: 06/10/2023]
Abstract
Zinc fingers are proteins that are characterized by the coordination of zinc ions by an amino acid sequence that commonly contains two histidines and two cysteines (2His-2Cys motif). Investigations of oligopeptides that contain the 2His-2Cys motif, e.g., acetyl-His1-Cys2-Gly3-Pro4-Tyr5-His6-Cys7, have discovered they exhibit pH-dependent Zn(II) chelation and have redox activities with Cu(I/II), forming a variety of metal complexes. To further understand how these 2His-2Cys oligopeptides bind these metal ions, we have undertaken a series of ion mobility-mass spectrometry and B3LYP/LanL2DZ computational studies of structurally related heptapeptides. Starting with the sequence above, we have modified the potential His, Cys, or C-terminus binding sites and report how these changes in primary structure affect the oligopeptides positive and negative charge states, conformational structure, collision-induced breakdown energies, and how effectively Zn(II) binds to these sequences. The results show evidence that the weak acid-base properties of Cys-His are intrinsically linked and can result in an intramolecular salt-bridged network that affects the oligopeptide properties.
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Affiliation(s)
- Yu-Fu Lin
- Department of Chemistry, Texas A&M University-Commerce, 2600 S Neal St, Commerce, TX, 75428, USA
| | - Enas N Yousef
- Department of Chemistry, Texas A&M University-Commerce, 2600 S Neal St, Commerce, TX, 75428, USA
| | - Efren Torres
- Department of Chemistry, Texas A&M University-Commerce, 2600 S Neal St, Commerce, TX, 75428, USA
| | - Linh Truong
- Department of Chemistry, Texas A&M University-Commerce, 2600 S Neal St, Commerce, TX, 75428, USA
| | - James M Zahnow
- Department of Chemistry, Texas A&M University-Commerce, 2600 S Neal St, Commerce, TX, 75428, USA
| | - Cole B Donald
- Department of Chemistry, Texas A&M University-Commerce, 2600 S Neal St, Commerce, TX, 75428, USA
| | - Ying Qin
- Department of Chemistry, Texas A&M University-Commerce, 2600 S Neal St, Commerce, TX, 75428, USA
| | - Laurence A Angel
- Department of Chemistry, Texas A&M University-Commerce, 2600 S Neal St, Commerce, TX, 75428, USA.
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14
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Malik A, Lin YF, Pratihar S, Angel LA, Hase WL. Direct Dynamics Simulations of Fragmentation of a Zn(II)-2Cys-2His Oligopeptide. Comparison with Mass Spectrometry Collision-Induced Dissociation. J Phys Chem A 2019; 123:6868-6885. [DOI: 10.1021/acs.jpca.9b05218] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Affiliation(s)
- Abdul Malik
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas 79409-1061 United States
| | - Yu-Fu Lin
- Department of Chemistry Texas A&M University—Commerce, 2600 South Neal Street, Commerce, Texas 75428, United States
| | - Subha Pratihar
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas 79409-1061 United States
| | - Laurence A. Angel
- Department of Chemistry Texas A&M University—Commerce, 2600 South Neal Street, Commerce, Texas 75428, United States
| | - William L. Hase
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas 79409-1061 United States
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15
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Puchkova LV, Broggini M, Polishchuk EV, Ilyechova EY, Polishchuk RS. Silver Ions as a Tool for Understanding Different Aspects of Copper Metabolism. Nutrients 2019; 11:E1364. [PMID: 31213024 PMCID: PMC6627586 DOI: 10.3390/nu11061364] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2019] [Revised: 06/08/2019] [Accepted: 06/12/2019] [Indexed: 12/11/2022] Open
Abstract
In humans, copper is an important micronutrient because it is a cofactor of ubiquitous and brain-specific cuproenzymes, as well as a secondary messenger. Failure of the mechanisms supporting copper balance leads to the development of neurodegenerative, oncological, and other severe disorders, whose treatment requires a detailed understanding of copper metabolism. In the body, bioavailable copper exists in two stable oxidation states, Cu(I) and Cu(II), both of which are highly toxic. The toxicity of copper ions is usually overcome by coordinating them with a wide range of ligands. These include the active cuproenzyme centers, copper-binding protein motifs to ensure the safe delivery of copper to its physiological location, and participants in the Cu(I) ↔ Cu(II) redox cycle, in which cellular copper is stored. The use of modern experimental approaches has allowed the overall picture of copper turnover in the cells and the organism to be clarified. However, many aspects of this process remain poorly understood. Some of them can be found out using abiogenic silver ions (Ag(I)), which are isoelectronic to Cu(I). This review covers the physicochemical principles of the ability of Ag(I) to substitute for copper ions in transport proteins and cuproenzyme active sites, the effectiveness of using Ag(I) to study copper routes in the cells and the body, and the limitations associated with Ag(I) remaining stable in only one oxidation state. The use of Ag(I) to restrict copper transport to tumors and the consequences of large-scale use of silver nanoparticles for human health are also discussed.
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Affiliation(s)
- Ludmila V Puchkova
- Laboratory of Trace elements metabolism, ITMO University, Kronverksky av., 49, St.-Petersburg 197101, Russia.
- Department of Molecular Genetics, Research Institute of Experimental Medicine, Acad. Pavlov str., 12, St.-Petersburg 197376, Russia.
- Department of Biophysics, Peter the Great St. Petersburg Polytechnic University, Politekhnicheskaya str., 29, St.-Petersburg 195251, Russia.
| | - Massimo Broggini
- Laboratory of Trace elements metabolism, ITMO University, Kronverksky av., 49, St.-Petersburg 197101, Russia.
- Laboratory of molecular pharmacology, Istituto di Ricerche Farmacologiche "Mario Negri" IRCCS, Via La Masa, 19, Milan 20156, Italy.
| | - Elena V Polishchuk
- Laboratory of Trace elements metabolism, ITMO University, Kronverksky av., 49, St.-Petersburg 197101, Russia.
- Telethon Institute of Genetics and Medicine, Via Campi Flegrei 34, Pozzuoli (NA) 80078, Italy.
| | - Ekaterina Y Ilyechova
- Laboratory of Trace elements metabolism, ITMO University, Kronverksky av., 49, St.-Petersburg 197101, Russia.
| | - Roman S Polishchuk
- Telethon Institute of Genetics and Medicine, Via Campi Flegrei 34, Pozzuoli (NA) 80078, Italy.
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16
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Sales TA, Prandi IG, Castro AAD, Leal DHS, Cunha EFFD, Kuca K, Ramalho TC. Recent Developments in Metal-Based Drugs and Chelating Agents for Neurodegenerative Diseases Treatments. Int J Mol Sci 2019; 20:ijms20081829. [PMID: 31013856 PMCID: PMC6514778 DOI: 10.3390/ijms20081829] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2019] [Revised: 04/07/2019] [Accepted: 04/09/2019] [Indexed: 02/07/2023] Open
Abstract
The brain has a unique biological complexity and is responsible for important functions in the human body, such as the command of cognitive and motor functions. Disruptive disorders that affect this organ, e.g. neurodegenerative diseases (NDDs), can lead to permanent damage, impairing the patients' quality of life and even causing death. In spite of their clinical diversity, these NDDs share common characteristics, such as the accumulation of specific proteins in the cells, the compromise of the metal ion homeostasis in the brain, among others. Despite considerable advances in understanding the mechanisms of these diseases and advances in the development of treatments, these disorders remain uncured. Considering the diversity of mechanisms that act in NDDs, a wide range of compounds have been developed to act by different means. Thus, promising compounds with contrasting properties, such as chelating agents and metal-based drugs have been proposed to act on different molecular targets as well as to contribute to the same goal, which is the treatment of NDDs. This review seeks to discuss the different roles and recent developments of metal-based drugs, such as metal complexes and metal chelating agents as a proposal for the treatment of NDDs.
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Affiliation(s)
- Thais A Sales
- Laboratory of Molecular Modeling, Department of Chemistry, Federal University of Lavras, Lavras/MG, 37200-000, Brazil.
| | - Ingrid G Prandi
- Laboratory of Molecular Modeling, Department of Chemistry, Federal University of Lavras, Lavras/MG, 37200-000, Brazil.
| | - Alexandre A de Castro
- Laboratory of Molecular Modeling, Department of Chemistry, Federal University of Lavras, Lavras/MG, 37200-000, Brazil.
| | - Daniel H S Leal
- Department of Health Sciences, Federal University of Espírito Santo, São Mateus/ES, 29932-540, Brazil.
| | - Elaine F F da Cunha
- Laboratory of Molecular Modeling, Department of Chemistry, Federal University of Lavras, Lavras/MG, 37200-000, Brazil.
| | - Kamil Kuca
- Department of Chemistry, Faculty of Science, University of Hradec Kralove, Hradec Kralove, 500 03, Czech Republic..
- Biomedical Research Center, University Hospital Hradec Kralove, Hradec Kralove, 500 03 Czech Republic.
| | - Teodorico C Ramalho
- Laboratory of Molecular Modeling, Department of Chemistry, Federal University of Lavras, Lavras/MG, 37200-000, Brazil.
- Department of Chemistry, Faculty of Science, University of Hradec Kralove, Hradec Kralove, 500 03, Czech Republic..
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17
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Müller JC, Lichtmannegger J, Zischka H, Sperling M, Karst U. High spatial resolution LA-ICP-MS demonstrates massive liver copper depletion in Wilson disease rats upon Methanobactin treatment. J Trace Elem Med Biol 2018; 49:119-127. [PMID: 29895360 DOI: 10.1016/j.jtemb.2018.05.009] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/12/2018] [Revised: 05/08/2018] [Accepted: 05/08/2018] [Indexed: 01/18/2023]
Abstract
Wilson disease (WD) is a rare genetic disorder of the copper metabolism leading to systemic copper accumulation, predominantly in the liver. The therapeutic approach in WD patients is the generation of a negative copper balance and the maintenance of copper homeostasis, currently by the use of copper chelators such as D-penicillamine (D-PA). However, in circumstances of delayed diagnosis, poor treatment compliance, or treatment failure, mortality is almost certain without hepatic transplantation. Moreover, even after years of D-PA treatment, high liver copper levels are present in WD patients. We have recently suggested the use of the bacterial peptide Methanobactin (MB), which has an outstanding binding affinity for copper, as potentially efficient and patient-friendly remedy against copper damage in WD. Here we substantiate these findings considerably, by demonstrating a significant removal of copper from liver samples of WD rats upon short, one week only, MB treatments. Using laser ablation-inductively coupled plasma-mass spectrometry with a spatial resolution down to 4 μm, we demonstrate that only small copper hotspots remain in MB treated animal livers. We further demonstrate in WD rat liver, seven weeks after the stopped MB treatment, a lower liver copper concentration as compared to untreated control animals. Thus, MB highly efficiently depletes liver copper overload with a sustained therapeutic effect.
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Affiliation(s)
- Jennifer-Christin Müller
- University of Münster, Institute of Inorganic and Analytical Chemistry, Corrensstraße 30, 48149 Münster, Germany
| | - Josef Lichtmannegger
- Institute of Molecular Toxicology and Pharmacology, Helmholtz Center Munich, German Research Center for Environmental Health, 85764 Neuherberg, Germany
| | - Hans Zischka
- Institute of Molecular Toxicology and Pharmacology, Helmholtz Center Munich, German Research Center for Environmental Health, 85764 Neuherberg, Germany; Institute of Toxicology and Environmental Hygiene, Technical University Munich, 80802 Munich, Germany
| | - Michael Sperling
- University of Münster, Institute of Inorganic and Analytical Chemistry, Corrensstraße 30, 48149 Münster, Germany; European Virtual Institute for Speciation Analysis (EVISA), Mendelstraße 11, 48149 Münster, Germany
| | - Uwe Karst
- University of Münster, Institute of Inorganic and Analytical Chemistry, Corrensstraße 30, 48149 Münster, Germany.
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18
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Kenney GE, Rosenzweig AC. Methanobactins: Maintaining copper homeostasis in methanotrophs and beyond. J Biol Chem 2018; 293:4606-4615. [PMID: 29348173 PMCID: PMC5880147 DOI: 10.1074/jbc.tm117.000185] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Methanobactins (Mbns) are ribosomally produced, post-translationally modified natural products that bind copper with high affinity and specificity. Originally identified in methanotrophic bacteria, which have a high need for copper, operons encoding these compounds have also been found in many non-methanotrophic bacteria. The proteins responsible for Mbn biosynthesis include several novel enzymes. Mbn transport involves export through a multidrug efflux pump and re-internalization via a TonB-dependent transporter. Release of copper from Mbn and the molecular basis for copper regulation of Mbn production remain to be elucidated. Future work is likely to result in the identification of new enzymatic chemistry, opportunities for bioengineering and drug targeting of copper metabolism, and an expanded understanding of microbial metal homeostasis.
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Affiliation(s)
- Grace E Kenney
- Departments of Molecular Biosciences, Evanston, Illinois 60208
| | - Amy C Rosenzweig
- Departments of Molecular Biosciences, Evanston, Illinois 60208; Chemistry, Northwestern University, Evanston, Illinois 60208.
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