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Das R, Karri R, Chalana A, Rai RK, Roy G. Uncovering the Role of Methylmercury on DNA Lesions at Cytotoxic Concentrations in Glutathione-Depleted Cells: Insights from Experimental and Computational Studies. Inorg Chem 2024; 63:10455-10465. [PMID: 38743433 DOI: 10.1021/acs.inorgchem.3c04579] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/16/2024]
Abstract
Organomercurials (RHg+), especially methylmercury (MeHg+) and ethylmercury (EtHg+), are considered to be more neurotoxic than the inorganic counterpart (Hg2+). They cause massive DNA damage in cells, especially in neurons, where cellular glutathione (GSH) levels are significantly low. However, the mechanism by which RHg+ exerts massive DNA damage at cytotoxic concentrations in brain cells remains obscure. In this study, we investigated the effect of RHg+ on the structural and electronic properties of nucleosides and its effects on DNA damage. The direct interaction of RHg+ with the nucleoside significantly weakens N-glycosidic bonds, decreases the C-H bond energy of sugar moieties, and increases the electrophilicity of the C8-center of purine bases. As a consequence, RHg+-conjugated DNA molecules are extremely labile and highly sensitive to any nucleophiles/radicals present in GSH-depleted cells and, thus, undergo enhanced oxidative and unusual alkylative DNA damage. We also report a functional model of organomercurial lyase, which showed excellent cytoprotective effect against RHg+-induced cytotoxicity; this reverses the activity of glutathione reductase inhibited by MeHgCl and ceases oxidative and alkylating DNA damage. This intriguing finding provides new mechanistic insight into the mode of action of organomercurials in GSH-depleted cells and their adverse effects on individuals with neurodegenerative disorders associated with oxidative stress.
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Affiliation(s)
- Ranajit Das
- Department of Chemistry, School of Natural Sciences, Shiv Nadar Institution of Eminence Deemed to be University, Dadri, UP 201314, India
| | - Ramesh Karri
- Department of Chemistry, School of Natural Sciences, Shiv Nadar Institution of Eminence Deemed to be University, Dadri, UP 201314, India
- Ruhvenile Biomedical OPC Pvt. Ltd., New Delhi 110070, Delhi, India
| | - Ashish Chalana
- Centre for Development of Biomaterials, Department of Chemistry & Biochemistry, Sharda University, Greater Noida, UP 201306, India
| | - Rakesh Kumar Rai
- Department of Chemistry, Indian Institute of Technology Tirupati, Tirupati, AP 517619, India
| | - Gouriprasanna Roy
- Department of Chemistry, Indian Institute of Technology Tirupati, Tirupati, AP 517619, India
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Barona Duque K, Gaviria D. Modelamiento in silico de la liasa organomercurial (MerB) de Pseudomonas fluorescens. REVISTA COLOMBIANA DE QUÍMICA 2022. [DOI: 10.15446/rev.colomb.quim.v51n1.98381] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
El modelamiento in silico ha sido de gran contribución en los procesos proteómicos, desarrollando estructuras de las secuencias proteicas ya existentes, que por motivos de altos costos y las diferentes tecnologías necesarias para el desarrollo de estas metodologías, se encuentran deficientes en el número de modelamientos de proteínas disponibles. Entre aquellas secuencias con carencia de estructura proteica se encuentra la proteína liasa organomercurial (MerB) de Pseudomonas fluorescens, importante en la resistencia al mercurio. En el presente artículo se analizó tanto estructural como funcionalmente la proteína MerB en Pseudomonas fluorescens, utilizando la herramienta de la química estructural “modelamiento por homología” mediante plataformas bioinformáticas, con el fin de obtener un modelo que represente la estructura 3D más precisa y que capturen las mejores variantes estructurales entre todas las posibles conformaciones de las proteínas en la familia. En este trabajo, se desarrolló un método comparativo de la secuencia estudiada con las reportadas en las bases de datos para las proteínas MerB del género Pseudomonas. Se propone un modelo tridimensional para la enzima (MerB) en P. fluorescens, mediante el modelamiento por homología, se muestra la caracterización en la estructura secundaria, terciaria, la caracterización del dominio catalítico y los motivos estructurales presentes.
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Yu Y, Li Z, Liu Y, Wang F, Liu Y, Zhao J, Li Y, Gao Y, Zhu N. Roles of plant-associated microorganisms in regulating the fate of Hg in croplands: A perspective on potential pathways in maintaining sustainable agriculture. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 834:155204. [PMID: 35421489 DOI: 10.1016/j.scitotenv.2022.155204] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2022] [Revised: 04/06/2022] [Accepted: 04/08/2022] [Indexed: 06/14/2023]
Abstract
In heavy metal-contaminated croplands, plant-associated microorganisms play important roles in the adaptation of crops to heavy metals. Plant-associated microbes can interact with Hg and stimulate plant resistance to Hg toxicity, which is crucial for impeding Hg accumulation along the food chain. The roles of rhizosphere microorganisms for the improvement of plant growth and Hg resistance have drawn great research attention. However, the interactions among plant-endophyte-Hg have been neglected although they might be important for in vivo Hg detoxification. In this study, we systematically summarized 1) the roles of plant-associated microorganisms in Hg detoxification and plant growth, 2) Hg methylation and demethylation driven by plant-associated microbes, 3) the relationships between plant-associated microbes and Hg biogeochemical cycling. The possible mechanisms underlying crop-endophyte-Hg interactions were discussed, although limited studies on this aspect are available to date. The challenges and perspectives of plant-endophytes in dampening Hg phytotoxicity and controlling Hg accumulation in croplands were proposed on the basis of the present knowledge. Taken together, this work provides evidence for further understanding the interactions between soil-plant-endophyte-Hg systems and as well as new interpretations and perspectives into regulating the fate of Hg in croplands.
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Affiliation(s)
- Yue Yu
- School of Grain Science and Technology, Jiangsu University of Science and Technology, Zhenjiang 212100, Jiangsu, China; State Environmental Protection Key Laboratory of Food Chain Pollution Control, Beijing Technology and Business University, Beijing 100048, China
| | - Zhanming Li
- School of Grain Science and Technology, Jiangsu University of Science and Technology, Zhenjiang 212100, Jiangsu, China; State Environmental Protection Key Laboratory of Food Chain Pollution Control, Beijing Technology and Business University, Beijing 100048, China; School of Environment, Hangzhou Institute for Advanced Study, University of Chinese Academy of Sciences, Hangzhou 310024, China.
| | - Yonghua Liu
- CAS Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety, & CAS-HKU Joint Laboratory of Metallomics on Health and Environment, & Beijing Metallomics Facility, & National Consortium for Excellence in Metallomics, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China; School of Chemical and Biological Engineering, Taiyuan University of Science and Technology, Taiyuan 030000, Shanxi, China
| | - Fang Wang
- State Environmental Protection Key Laboratory of Food Chain Pollution Control, Beijing Technology and Business University, Beijing 100048, China
| | - Yurong Liu
- State Key Laboratory of Agricultural Microbiology and College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China
| | - Jiating Zhao
- CAS Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety, & CAS-HKU Joint Laboratory of Metallomics on Health and Environment, & Beijing Metallomics Facility, & National Consortium for Excellence in Metallomics, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China
| | - Yufeng Li
- CAS Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety, & CAS-HKU Joint Laboratory of Metallomics on Health and Environment, & Beijing Metallomics Facility, & National Consortium for Excellence in Metallomics, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China
| | - Yuxi Gao
- CAS Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety, & CAS-HKU Joint Laboratory of Metallomics on Health and Environment, & Beijing Metallomics Facility, & National Consortium for Excellence in Metallomics, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China
| | - Nali Zhu
- School of Environment, Hangzhou Institute for Advanced Study, University of Chinese Academy of Sciences, Hangzhou 310024, China.
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Kumar Rai R, Shankar Pati R, Islam A, Roy G. Detoxification of organomercurials by thiones and selones: A short review. Inorganica Chim Acta 2022. [DOI: 10.1016/j.ica.2022.120980] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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James AK, Dolgova NV, Nehzati S, Korbas M, Cotelesage JJH, Sokaras D, Kroll T, O’Donoghue JL, Watson GE, Myers GJ, Pickering IJ, George GN. Molecular Fates of Organometallic Mercury in Human Brain. ACS Chem Neurosci 2022; 13:1756-1768. [PMID: 35543423 PMCID: PMC9977140 DOI: 10.1021/acschemneuro.2c00166] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Mercury is ubiquitous in the environment, with rising levels due to pollution and climate change being a current global concern. Many mercury compounds are notorious for their toxicity, with the potential of organometallic mercury compounds for devastating effects on the structures and functions of the central nervous system being of particular concern. Chronic exposure of human populations to low levels of methylmercury compounds occurs through consumption of fish and other seafood, although the health consequences, if any, from this exposure remain controversial. We have used high energy resolution fluorescence detected X-ray absorption spectroscopy to determine the speciation of mercury and selenium in human brain tissue. We show that the molecular fate of mercury differs dramatically between individuals who suffered acute organometallic mercury exposure (poisoning) and individuals with chronic low-level exposure from a diet rich in marine fish. For long-term low-level methylmercury exposure from fish consumption, mercury speciation in brain tissue shows methylmercury coordinated to an aliphatic thiolate, resembling the coordination environment observed in marine fish. In marked contrast, for short-term high-level exposure, we observe the presence of biologically less available mercuric selenide deposits, confirmed by X-ray fluorescence imaging, as well as mercury(II)-bis-thiolate complexes, which may be signatures of severe poisoning in humans. These differences between low-level and high-level exposures challenge the relevance of studies involving acute exposure as a proxy for low-level chronic exposure.
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Affiliation(s)
- Ashley K. James
- Toxicology Centre, 44 Campus Drive, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5B3, Canada.,Department of Geological Sciences, University of Saskatchewan, 114 Science Place, Saskatoon, Saskatchewan S7N 5E2, Canada
| | - Natalia V. Dolgova
- Department of Geological Sciences, University of Saskatchewan, 114 Science Place, Saskatoon, Saskatchewan S7N 5E2, Canada
| | - Susan Nehzati
- Department of Geological Sciences, University of Saskatchewan, 114 Science Place, Saskatoon, Saskatchewan S7N 5E2, Canada
| | - Malgorzata Korbas
- Canadian Light Source, 44 Innovation Blvd, Saskatoon, Saskatchewan S7N 2V3, Canada
| | - Julien J. H. Cotelesage
- Department of Geological Sciences, University of Saskatchewan, 114 Science Place, Saskatoon, Saskatchewan S7N 5E2, Canada
| | - Dimosthenis Sokaras
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, USA
| | - Thomas Kroll
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, USA
| | - John L. O’Donoghue
- Department of Environmental Medicine, School of Medicine and Dentistry, University of Rochester, Rochester, New York 14642, USA
| | - Gene E. Watson
- Department of Environmental Medicine, School of Medicine and Dentistry, University of Rochester, Rochester, New York 14642, USA.,Eastman Institute for Oral Health, School of Medicine and Dentistry, University of Rochester, Rochester, New York 14642, USA
| | - Gary J. Myers
- Department of Environmental Medicine, School of Medicine and Dentistry, University of Rochester, Rochester, New York 14642, USA.,Departments of Neurology and Pediatrics, School of Medicine and Dentistry, University of Rochester, Rochester, New York 14642, USA
| | - Ingrid J. Pickering
- Toxicology Centre, 44 Campus Drive, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5B3, Canada.,Department of Geological Sciences, University of Saskatchewan, 114 Science Place, Saskatoon, Saskatchewan S7N 5E2, Canada.,Department of Chemistry, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5C9, Canada.,Corresponding Authors: Ingrid J. Pickering – Department of Geological Sciences, Toxicology Centre, and Department of Chemistry, University of Saskatchewan, Saskatoon S7N 5E2, Canada; , Graham N. George – Department of Geological Sciences, Toxicology Centre, and Department of Chemistry, University of Saskatchewan, Saskatoon S7N 5E2, Canada;
| | - Graham N. George
- Toxicology Centre, 44 Campus Drive, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5B3, Canada.,Department of Geological Sciences, University of Saskatchewan, 114 Science Place, Saskatoon, Saskatchewan S7N 5E2, Canada.,Department of Chemistry, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5C9, Canada.,Corresponding Authors: Ingrid J. Pickering – Department of Geological Sciences, Toxicology Centre, and Department of Chemistry, University of Saskatchewan, Saskatoon S7N 5E2, Canada; , Graham N. George – Department of Geological Sciences, Toxicology Centre, and Department of Chemistry, University of Saskatchewan, Saskatoon S7N 5E2, Canada;
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Barkay T, Gu B. Demethylation─The Other Side of the Mercury Methylation Coin: A Critical Review. ACS ENVIRONMENTAL AU 2022; 2:77-97. [PMID: 37101582 PMCID: PMC10114901 DOI: 10.1021/acsenvironau.1c00022] [Citation(s) in RCA: 38] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The public and environmental health consequences of mercury (Hg) methylation have drawn much attention and considerable research to Hg methylation processes and their dynamics in diverse environments and under a multitude of conditions. However, the net methylmercury (MeHg) concentration that accumulates in the environment is equally determined by the rate of MeHg degradation, a complex process mediated by a variety of biotic and abiotic mechanisms, about which our knowledge is limited. Here we review the current knowledge on MeHg degradation and its potential pathways and mechanisms. We describe detoxification by resistant microorganisms that employ the Hg resistance (mer) system to reductively break the carbon-mercury (C-Hg) bond producing methane (CH4) and inorganic mercuric Hg(II), which is then reduced by the mercuric reductase to elemental Hg(0). Very recent research has begun to elucidate a mechanism for the long-recognized mer-independent oxidative demethylation, likely involving some strains of anaerobic bacteria as well as aerobic methane-oxidizing bacteria, i.e., methanotrophs. In addition, photochemical and chemical demethylation processes are described, including the roles of dissolved organic matter (DOM) and free radicals as well as dark abiotic demethylation in the natural environment about which little is currently known. We focus on mechanisms and processes of demethylation and highlight the uncertainties and known effects of environmental factors leading to MeHg degradation. Finally, we suggest future research directions to further elucidate the chemical and biochemical mechanisms of biotic and abiotic demethylation and their significance in controlling net MeHg production in natural ecosystems.
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Affiliation(s)
- Tamar Barkay
- Department of Biochemistry and Microbiology, School of Environmental and Biological Sciences, Rutgers University, New Brunswick, New Jersey 08901, United States
| | - Baohua Gu
- Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
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Chalana A, Kumar Rai R, Karri R, Kumar Jha K, Kumar B, Roy G. Interplay of the intermolecular and intramolecular interactions in stabilizing the thione-based copper(I) complexes and their significance in protecting the biomolecules against metal-mediated oxidative damage. Polyhedron 2022. [DOI: 10.1016/j.poly.2021.115647] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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Christakis CA, Barkay T, Boyd ES. Expanded Diversity and Phylogeny of mer Genes Broadens Mercury Resistance Paradigms and Reveals an Origin for MerA Among Thermophilic Archaea. Front Microbiol 2021; 12:682605. [PMID: 34248899 PMCID: PMC8261052 DOI: 10.3389/fmicb.2021.682605] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2021] [Accepted: 05/28/2021] [Indexed: 11/13/2022] Open
Abstract
Mercury (Hg) is a highly toxic element due to its high affinity for protein sulfhydryl groups, which upon binding, can destabilize protein structure and decrease enzyme activity. Prokaryotes have evolved enzymatic mechanisms to detoxify inorganic Hg and organic Hg (e.g., MeHg) through the activities of mercuric reductase (MerA) and organomercury lyase (MerB), respectively. Here, the taxonomic distribution and evolution of MerAB was examined in 84,032 archaeal and bacterial genomes, metagenome assembled genomes, and single-cell genomes. Homologs of MerA and MerB were identified in 7.8 and 2.1% percent of genomes, respectively. MerA was identified in the genomes of 10 archaeal and 28 bacterial phyla previously unknown to code for this functionality. Likewise, MerB was identified in 2 archaeal and 11 bacterial phyla previously unknown to encode this functionality. Surprisingly, homologs of MerB were identified in a number of genomes (∼50% of all MerB-encoding genomes) that did not encode MerA, suggesting alternative mechanisms to detoxify Hg(II) once it is generated in the cytoplasm. Phylogenetic reconstruction of MerA place its origin in thermophilic Thermoprotei (Crenarchaeota), consistent with high levels of Hg(II) in geothermal environments, the natural habitat of this archaeal class. MerB appears to have been recruited to the mer operon relatively recently and likely among a mesophilic ancestor of Euryarchaeota and Thaumarchaeota. This is consistent with the functional dependence of MerB on MerA and the widespread distribution of mesophilic microorganisms that methylate Hg(II) at lower temperature. Collectively, these results expand the taxonomic and ecological distribution of mer-encoded functionalities, and suggest that selection for Hg(II) and MeHg detoxification is dependent not only on the availability and type of mercury compounds in the environment but also the physiological potential of the microbes who inhabit these environments. The expanded diversity and environmental distribution of MerAB identify new targets to prioritize for future research.
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Affiliation(s)
- Christos A. Christakis
- Department of Microbiology and Immunology, Montana State University, Bozeman, MT, United States
| | - Tamar Barkay
- Department of Biochemistry and Microbiology, Rutgers, The State University of New Jersey, New Brunswick, NJ, United States
| | - Eric S. Boyd
- Department of Microbiology and Immunology, Montana State University, Bozeman, MT, United States
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