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Gautam N, Tiwari M, Kidwai M, Dutta P, Chakrabarty D. Functional characterization of rice metallothionein OsMT-I-Id: Insights into metal binding and heavy metal tolerance mechanisms. JOURNAL OF HAZARDOUS MATERIALS 2023; 458:131815. [DOI: https:/doi.org/10.1016/j.jhazmat.2023.131815] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/27/2023]
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Yan K, Ablimit M, Liu S, Liu Z, Wang Y. A novel metallothionein gene HcMT from halophyte shrub Halostachys caspica respond to cadmium and sodium stress. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2023; 201:107763. [PMID: 37301187 DOI: 10.1016/j.plaphy.2023.107763] [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: 02/17/2023] [Revised: 04/23/2023] [Accepted: 05/12/2023] [Indexed: 06/12/2023]
Abstract
Cadmium (Cd) and sodium (Na) are two of the most phytotoxic metallic elements causing environmental and agricultural problems. Metallothioneins (MTs) play an important role in the adaptation to abiotic stress. We previously isolated a novel type 2 MT gene from Halostachys caspica (H. caspica), named HcMT, which responded to metal and salt stress. To understand the regulatory mechanisms controlling HcMT expression, we cloned the HcMT promoter and characterized its tissue-specific and spatiotemporal expression patterns. β-Glucuronidase (GUS) activity analysis showed that the HcMT promoter was responsive to CdCl2, CuSO4, ZnSO4 and NaCl stress. Therefore, we further investigated the function of HcMT under abiotic stress in yeast and Arabidopsis thaliana (Arabidopsis). In CdCl2, CuSO4 or ZnSO4 stress, HcMT significantly enhanced the metal ions tolerance and accumulation in yeast through function as a metal chelator. Moreover, the HcMT protein also protected yeast cells from NaCl, PEG and hydrogen peroxide (H2O2) toxicity with less effectiveness. However, transgenic Arabidopsis carrying HcMT gene only displayed tolerance to CdCl2 and NaCl, accompanying by higher content of Cd2+ or Na+ and lower H2O2, compared to wild-type (WT) plants. Next, we demonstrated that the recombinant HcMT protein has the ability to bind Cd2+ and the potential of scavenging ROS (reactive oxygen species) in vitro. This result further confirmed that the role of HcMT to influence plants to CdCl2 and NaCl stress may bind metal ions and scavenge ROS. Overall, we described the biological functions of HcMT and developed a metal- and salt-inducible promoter system for using in genetic engineering.
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Affiliation(s)
- Kexin Yan
- Xinjiang Key Laboratory of Biological Resources and Genetic Engineering, College of Life Science and Technology, Xinjiang University, Urumqi, 830017, China.
| | - Mehriban Ablimit
- Xinjiang Key Laboratory of Biological Resources and Genetic Engineering, College of Life Science and Technology, Xinjiang University, Urumqi, 830017, China.
| | - Sai Liu
- Xinjiang Key Laboratory of Biological Resources and Genetic Engineering, College of Life Science and Technology, Xinjiang University, Urumqi, 830017, China.
| | - Zhongyuan Liu
- School of Chemical Engineering, Sichuan University of Science and Engineering, Sichuan, 643000, China.
| | - Yan Wang
- Xinjiang Key Laboratory of Biological Resources and Genetic Engineering, College of Life Science and Technology, Xinjiang University, Urumqi, 830017, China.
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Gautam N, Tiwari M, Kidwai M, Dutta P, Chakrabarty D. Functional characterization of rice metallothionein OsMT-I-Id: Insights into metal binding and heavy metal tolerance mechanisms. JOURNAL OF HAZARDOUS MATERIALS 2023; 458:131815. [PMID: 37336105 DOI: 10.1016/j.jhazmat.2023.131815] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/18/2023] [Revised: 06/07/2023] [Accepted: 06/07/2023] [Indexed: 06/21/2023]
Abstract
Metallothioneins (MTs) are cysteine-rich proteins known for their strong metal-binding capabilities, making them effective in detoxifying heavy metals (HMs). This study focuses on characterizing the functional properties of OsMT-I-Id, a type-I Metallothionein found in rice. Using a HM-responsive yeast cup1Δ (DTY4), ycf1∆ (for cadmium), and acr3∆ mutants (for trivalent arsenic), we assessed the impact of OsMT-I-Id on metal accumulation and cellular resilience. Our results demonstrated that yeast cells expressing OsMT-I-Id showed increased tolerance and accumulated higher levels of copper (Cu), arsenic (As), and cadmium (Cd), compared to control cells. This can be attributed to the protein's ability to chelate and bind HMs. Site-directed mutagenesis was employed to investigate the specific contributions of cysteine residues. The study revealed that yeast cells with a mutated C-domain displayed heightened HM sensitivity, while cells with a mutated N-domain exhibited reduced sensitivity. This underscores the critical role of C-cysteine-rich domains in metal binding and tolerance of type-I rice MTs. Furthermore, the study identified the significance of the 12th cysteine position at the N-domain and the 68th and 72nd cysteine positions at the C-domain in influencing OsMT-I-Id metal-binding capacity. This research provides novel insights into the structure-function relationship and metal binding properties of type-I plant MTs.
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Affiliation(s)
- Neelam Gautam
- Biotechnology and Molecular Biology Division, CSIR-National Botanical Research Institute, Lucknow 226001, India; Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India
| | - Madhu Tiwari
- Biotechnology and Molecular Biology Division, CSIR-National Botanical Research Institute, Lucknow 226001, India
| | - Maria Kidwai
- Biotechnology and Molecular Biology Division, CSIR-National Botanical Research Institute, Lucknow 226001, India
| | - Prasanna Dutta
- Biotechnology and Molecular Biology Division, CSIR-National Botanical Research Institute, Lucknow 226001, India; Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India
| | - Debasis Chakrabarty
- Biotechnology and Molecular Biology Division, CSIR-National Botanical Research Institute, Lucknow 226001, India; Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India.
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Abstract
The functions, purposes, and roles of metallothioneins have been the subject of speculations since the discovery of the protein over 60 years ago. This article guides through the history of investigations and resolves multiple contentions by providing new interpretations of the structure-stability-function relationship. It challenges the dogma that the biologically relevant structure of the mammalian proteins is only the one determined by X-ray diffraction and NMR spectroscopy. The terms metallothionein and thionein are ambiguous and insufficient to understand biological function. The proteins need to be seen in their biological context, which limits and defines the chemistry possible. They exist in multiple forms with different degrees of metalation and types of metal ions. The homoleptic thiolate coordination of mammalian metallothioneins is important for their molecular mechanism. It endows the proteins with redox activity and a specific pH dependence of their metal affinities. The proteins, therefore, also exist in different redox states of the sulfur donor ligands. Their coordination dynamics allows a vast conformational landscape for interactions with other proteins and ligands. Many fundamental signal transduction pathways regulate the expression of the dozen of human metallothionein genes. Recent advances in understanding the control of cellular zinc and copper homeostasis are the foundation for suggesting that mammalian metallothioneins provide a highly dynamic, regulated, and uniquely biological metal buffer to control the availability, fluctuations, and signaling transients of the most competitive Zn(II) and Cu(I) ions in cellular space and time.
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Affiliation(s)
- Artur Krężel
- Department of Chemical Biology, Faculty of Biotechnology, University of Wrocław, Wrocław 50-383, Poland
| | - Wolfgang Maret
- Departments of Biochemistry and Nutritional Sciences, School of Life Course Sciences, Faculty of Life Sciences and Medicine, King's College London, London SE1 9NH, U.K
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Salim A, Chesnov S, Freisinger E. Metallation pathway of a plant metallothionein: Cicer arietinum MT2. J Inorg Biochem 2020; 210:111157. [PMID: 32622214 DOI: 10.1016/j.jinorgbio.2020.111157] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2020] [Revised: 06/18/2020] [Accepted: 06/21/2020] [Indexed: 11/25/2022]
Abstract
The plant metallothionein 2 protein from Cicer arietinum (cicMT2) is a typical member of the plant MT subfamily p2 that is characterized by an N- and C-terminal cysteine- (Cys-)rich, metal binding sequence connected by a long cysteine-free linker region. cicMT2 coordinates up to five ZnII or CdII ions by its 14 cysteine thiolate groups forming a single metal-thiolate cluster. While MTs from other phyla are considerably well-studied, many details about plant MTs are missing. In this study the metallation pathway of cicMT2 is investigated using mass spectrometry. To evaluate the influence of the linker region as well as the interplay of the two Cys-rich stretches, the full-length cicMT2 protein as well as the individual Cys-rich domains with and without the linker region were analysed. Up to three CdII ions can be coordinated by the eight Cys residues of the N-terminal part and up to two CdII ions by the six Cys residues of the C-terminal sequence. However, no preferential binding to either of the two sequences is observed, which is in-line with the closely similar apparent binding constants of the individual domains obtained from competition reactions with the chelator 1,2-bis(2-amino-5-fluorophenoxy)ethane-N,N,N',N'-tetraacetic acid. The combination of limited proteolytic digestion, mass spectrometry, dynamic light scattering, size-exclusion chromatography, and 19F NMR spectroscopy enables us to draw conclusions about the overall protein-fold and the cluster formation process.
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Affiliation(s)
- Alma Salim
- Department of Chemistry, University of Zurich, Zurich, Switzerland
| | - Serge Chesnov
- University of Zurich/ETH Zurich, Functional Genomics Centre Zurich, Zurich, Switzerland
| | - Eva Freisinger
- Department of Chemistry, University of Zurich, Zurich, Switzerland.
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Luo JS, Xiao Y, Yao J, Wu Z, Yang Y, Ismail AM, Zhang Z. Overexpression of a Defensin-Like Gene CAL2 Enhances Cadmium Accumulation in Plants. FRONTIERS IN PLANT SCIENCE 2020; 11:217. [PMID: 32174951 PMCID: PMC7057248 DOI: 10.3389/fpls.2020.00217] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/10/2019] [Accepted: 02/12/2020] [Indexed: 05/15/2023]
Abstract
Accumulation and detoxification of cadmium in rice shoots are of great importance for adaptation to grow in cadmium contaminated soils and for limiting the transport of Cd to grains. However, the molecular mechanisms behind the processes involved in this regulation remain largely unknown. Defensin proteins play important roles in heavy metal tolerance and accumulation in plants. In rice, the cell wall-localized defensin protein (CAL1) is involved in Cd efflux and partitioning to the shoots. In the present study, we functionally characterized the CAL2 defensin protein and determined its contribution to Cd accumulation. CAL2 shared 66% similarity with CAL1, and its mRNA accumulation is mainly observed in roots and is unaffected by Cd stress, but its transcription level was lower than that of CAL1 based on the relative expression of CAL2/Actin1 observed in this study and that reported previously. A promoter-GUS assay revealed that CAL2 is expressed in root tips. Stable expression of the CAL2-mRFP fusion protein indicated that CAL2 is also localized in the cell walls. An in vitro Cd binding experiment revealed that CAL2 has Cd chelation activity. Overexpression of CAL2 increased Cd accumulation in Arabidopsis and rice shoots, but it had no effect on the accumulation of other essential elements. Heterologous expression of CAL2 enhanced Cd sensitivity in Arabidopsis, whereas overexpression of CAL2 had no effect on Cd tolerance in rice. These findings indicate that CAL2 positively regulates Cd accumulation in ectopic overexpression lines of Arabidopsis and rice. We have identified a new gene regulating Cd accumulation in rice grain, which would provide a new genetic resource for molecular breeding.
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Affiliation(s)
- Jin-Song Luo
- Southern Regional Collaborative Innovation Center for Grain and Oil Crops in China, College of Resources and Environmental Sciences, Hunan Agricultural University, Changsha, China
- Hunan Provincial Key Laboratory of Farmland Pollution Control and Agricultural Resources Use, Hunan Provincial Key Laboratory of Nutrition in Common University, National Engineering Laboratory on Soil and Fertilizer Resources Efficient Utilization, Changsha, China
| | - Yan Xiao
- Southern Regional Collaborative Innovation Center for Grain and Oil Crops in China, College of Resources and Environmental Sciences, Hunan Agricultural University, Changsha, China
- Hunan Provincial Key Laboratory of Farmland Pollution Control and Agricultural Resources Use, Hunan Provincial Key Laboratory of Nutrition in Common University, National Engineering Laboratory on Soil and Fertilizer Resources Efficient Utilization, Changsha, China
| | - Junyue Yao
- Southern Regional Collaborative Innovation Center for Grain and Oil Crops in China, College of Resources and Environmental Sciences, Hunan Agricultural University, Changsha, China
- Hunan Provincial Key Laboratory of Farmland Pollution Control and Agricultural Resources Use, Hunan Provincial Key Laboratory of Nutrition in Common University, National Engineering Laboratory on Soil and Fertilizer Resources Efficient Utilization, Changsha, China
| | - Zhimin Wu
- Southern Regional Collaborative Innovation Center for Grain and Oil Crops in China, College of Resources and Environmental Sciences, Hunan Agricultural University, Changsha, China
- Hunan Provincial Key Laboratory of Farmland Pollution Control and Agricultural Resources Use, Hunan Provincial Key Laboratory of Nutrition in Common University, National Engineering Laboratory on Soil and Fertilizer Resources Efficient Utilization, Changsha, China
| | - Yong Yang
- Southern Regional Collaborative Innovation Center for Grain and Oil Crops in China, College of Resources and Environmental Sciences, Hunan Agricultural University, Changsha, China
- Hunan Provincial Key Laboratory of Farmland Pollution Control and Agricultural Resources Use, Hunan Provincial Key Laboratory of Nutrition in Common University, National Engineering Laboratory on Soil and Fertilizer Resources Efficient Utilization, Changsha, China
| | | | - Zhenhua Zhang
- Southern Regional Collaborative Innovation Center for Grain and Oil Crops in China, College of Resources and Environmental Sciences, Hunan Agricultural University, Changsha, China
- Hunan Provincial Key Laboratory of Farmland Pollution Control and Agricultural Resources Use, Hunan Provincial Key Laboratory of Nutrition in Common University, National Engineering Laboratory on Soil and Fertilizer Resources Efficient Utilization, Changsha, China
- *Correspondence: Zhenhua Zhang,
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Luo JS, Yang Y, Gu T, Wu Z, Zhang Z. The Arabidopsis defensin gene AtPDF2.5 mediates cadmium tolerance and accumulation. PLANT, CELL & ENVIRONMENT 2019; 42:2681-2695. [PMID: 31115921 DOI: 10.1111/pce.13592] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2018] [Revised: 03/28/2019] [Accepted: 05/16/2019] [Indexed: 05/11/2023]
Abstract
Although excess cadmium (Cd) accumulation is harmful to plants, the molecular mechanisms underlying Cd detoxification and accumulation in Arabidopsis thaliana remain largely undetermined. In this study, we demonstrated that the A. thaliana PLANT DEFENSIN 2 gene AtPDF2.5 is involved in Cd tolerance and accumulation. In vitro Cd-binding assays revealed that AtPDF2.5 has Cd-chelating activity. Site-directed mutagenesis of AtPDF2.5 identified eight cysteine residues that were essential for mediating Cd tolerance and chelation. Histochemical analysis demonstrated that AtPDF2.5 was mainly expressed in root xylem vascular bundles, and that AtPDF2.5 was significantly induced by Cd. Subcellular localization analysis revealed that AtPDF2.5 was localized to the cell wall. The overexpression of AtPDF2.5 significantly enhanced Cd tolerance and accumulation in A. thaliana and its heterologous overexpression in rice increased Cd accumulation; however, the functional disruption of AtPDF2.5 decreased Cd tolerance and accumulation. Physiological analysis suggested that AtPDF2.5 promoted Cd efflux from the protoplast and its subsequent accumulation in the cell wall. These data suggest that AtPDF2.5 promotes cytoplasmic Cd efflux via chelation, thereby enhancing Cd detoxification and apoplastic accumulation.
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Affiliation(s)
- Jin-Song Luo
- Southern Regional Collaborative Innovation Center for Grain and Oil Crops in China, College of Resources and Environmental Sciences, Hunan Agricultural University, Changsha, 410128, China
- Hunan Provincial Key Laboratory of Farmland Pollution Control and Agricultural Resources Use, Hunan Provincial Key Laboratory of Nutrition in Common University, National Engineering Laboratory on Soil and Fertilizer Resources Efficient Utilization, Changsha, 410128, China
| | - Yong Yang
- Southern Regional Collaborative Innovation Center for Grain and Oil Crops in China, College of Resources and Environmental Sciences, Hunan Agricultural University, Changsha, 410128, China
- Hunan Provincial Key Laboratory of Farmland Pollution Control and Agricultural Resources Use, Hunan Provincial Key Laboratory of Nutrition in Common University, National Engineering Laboratory on Soil and Fertilizer Resources Efficient Utilization, Changsha, 410128, China
| | - Tianyu Gu
- National Key Laboratory of Plant Molecular Genetics and CAS Center for excellence in Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai, 200032, China
| | - Zhimin Wu
- Southern Regional Collaborative Innovation Center for Grain and Oil Crops in China, College of Resources and Environmental Sciences, Hunan Agricultural University, Changsha, 410128, China
- Hunan Provincial Key Laboratory of Farmland Pollution Control and Agricultural Resources Use, Hunan Provincial Key Laboratory of Nutrition in Common University, National Engineering Laboratory on Soil and Fertilizer Resources Efficient Utilization, Changsha, 410128, China
| | - Zhenhua Zhang
- Southern Regional Collaborative Innovation Center for Grain and Oil Crops in China, College of Resources and Environmental Sciences, Hunan Agricultural University, Changsha, 410128, China
- Hunan Provincial Key Laboratory of Farmland Pollution Control and Agricultural Resources Use, Hunan Provincial Key Laboratory of Nutrition in Common University, National Engineering Laboratory on Soil and Fertilizer Resources Efficient Utilization, Changsha, 410128, China
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Luo JS, Zhang Z. Proteomic changes in the xylem sap of Brassica napus under cadmium stress and functional validation. BMC PLANT BIOLOGY 2019; 19:280. [PMID: 31242871 PMCID: PMC6595625 DOI: 10.1186/s12870-019-1895-7] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2018] [Accepted: 06/19/2019] [Indexed: 05/19/2023]
Abstract
BACKGROUND The xylem sap of vascular plants primarily transports water and mineral nutrients from the roots to the shoots and also transports heavy metals such as cadmium (Cd). Proteomic changes in xylem sap is an important mechanism for detoxifying Cd by plants. However, it is unclear how proteins in xylem sap respond to Cd. Here, we investigated the effects of Cd stress on the xylem sap proteome of Brassica napus using a label-free shotgun proteomic approach to elucidate plant response mechanisms to Cd toxicity. RESULTS We identified and quantified 672 proteins; 67% were predicted to be secretory, and 11% (73 proteins) were unique to Cd-treated samples. Cd stress caused statistically significant and biologically relevant abundance changes in 28 xylem sap proteins. Among these proteins, the metabolic pathways that were most affected were related to cell wall modifications, stress/oxidoreductases, and lipid and protein metabolism. We functionally validated a plant defensin-like protein, BnPDFL, which belongs to the stress/oxidoreductase category, that was unique to the Cd-treated samples and played a positive role in Cd tolerance. Subcellular localization analysis revealed that BnPDFL is cell wall-localized. In vitro Cd-binding assays revealed that BnPDFL has Cd-chelating activity. BnPDFL heterologous overexpression significantly enhanced Cd tolerance in E. coli and Arabidopsis. Functional disruption of Arabidopsis plant defensin genes AtPDF2.3 and AtPDF2.2, which are mainly expressed in root vascular bundles, significantly decreased Cd tolerance. CONCLUSIONS Several xylem sap proteins in Brassica napus are differentially induced in response to Cd treatment, and plant defensin plays a positive role in Cd tolerance.
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Affiliation(s)
- Jin-Song Luo
- Southern Regional Collaborative Innovation Center for Grain and Oil Crops in China, College of Resources and Environmental Sciences, Hunan Agricultural University, Changsha, China
- Hunan Provincial Key Laboratory of Farmland Pollution Control and Agricultural Resources Use, National Engineering Laboratory on Soil and Fertilizer Resources Efficient Utilization, Hunan Provincial Key Laboratory of Nutrition in Common University, Changsha, 410128 China
| | - Zhenhua Zhang
- Southern Regional Collaborative Innovation Center for Grain and Oil Crops in China, College of Resources and Environmental Sciences, Hunan Agricultural University, Changsha, China
- Hunan Provincial Key Laboratory of Farmland Pollution Control and Agricultural Resources Use, National Engineering Laboratory on Soil and Fertilizer Resources Efficient Utilization, Hunan Provincial Key Laboratory of Nutrition in Common University, Changsha, 410128 China
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Scheller JS, Irvine GW, Stillman MJ. Unravelling the mechanistic details of metal binding to mammalian metallothioneins from stoichiometric, kinetic, and binding affinity data. Dalton Trans 2018; 47:3613-3637. [PMID: 29431781 DOI: 10.1039/c7dt03319b] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Metallothioneins (MTs) are small, cysteine-rich proteins, found throughout Nature. Their ability to bind a number of different metals with a range of stoichiometric ratios means that this protein family is critically important for essential metal (Zn2+ and Cu+) homeostasis, metal storage, metal donation to nascent metalloenzymes as well as heavy metal detoxification. With its 20 cysteines, metallothionein is also considered to protect cells against oxidative stress. MT has been studied by a large number of researchers over the last 6 decades using a variety of spectroscopic techniques. The lack of distinguishing chromophores for the multitude of binding sites has made the evaluation of stoichiometric properties for different metals challenging. Initially, only 113Cd-NMR spectroscopy could provide strong evidence for the proposed cluster formation of Cd-MT. The extraordinary development of electrospray ionization mass spectrometry (ESI-MS), where all coexisting species in solution are observed, revolutionized MT research. Prior to the use of ESI-MS data, a range of "magic numbers" representing metal-to-MT molar ratios were reported from optical spectroscopic studies. The availability of ESI mass spectral data led to (i) the confirmation of cluster formation, (ii) a conceptual understanding of the cooperativity involved in multiple metal binding events, (iii) the presence of domain specificity between regions of the protein and (iv) mechanistic details involving both binding affinities and rate constants. The kinetic experiments identified the presence of multiple individual binding sites, each with a unique rate constant and an analogous binding affinity. The almost linear trend in rate constants as a function of bound As3+ provided a unique insight that became a critical step in the complete understanding of the mechanistic details of the metalation of MT. To fully define the biological function of this sulfur-rich protein it is necessary to determine kinetic rate constants and binding affinities for the essential metals. Recently, Zn2+ competition experiments between both of the isolated fragments (α and β) and the full-length protein (βα-MT 1a) as well as Zn2+ competition between βα-MT 1a and carbonic anhydrase were reported. From these data, the trend in binding affinities and the values of the Kf of the 7 bimolecular reactions involved in metalation were determined. From the analysis of ESI-MS data for Cu+ binding to βα-MT 1a at different pH-values, a trend in the 20 binding affinities for the complete metalation mechanism was reported. This review details a personal view of the historical development of the determination of stoichiometry for metal binding, the structure of the binding sites, the rates of the metalation reactions and the underlying binding affinities for each metalation step. We have attempted to summarize the experimental developments that led to the publication in May 2017 of the experimental determination of the 20 binding constants for the 20 sequential bimolecular reactions for Cu+ binding to the 20 Cys of apoMT as a function of pH that show the appearance and disappearance of clusters. We report both published data and in a series of tables an assembly of stoichiometries, and equilibrium constants for Zn2+ and Cu+ for many different metallothioneins.
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Affiliation(s)
- Judith S Scheller
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada.
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Duan L, Kong JJ, Wang TQ, Sun Y. Binding of Cd(II), Pb(II), and Zn(II) to a type 1 metallothionein from maize (Zea mays). Biometals 2018; 31:539-550. [PMID: 29766364 DOI: 10.1007/s10534-018-0100-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2017] [Accepted: 04/03/2018] [Indexed: 10/16/2022]
Affiliation(s)
- Lian Duan
- School of Chemistry and Chemical Engineering, Taiyuan University of Technology, Taiyuan, 030024, China
| | - Jing-Jing Kong
- School of Chemistry and Chemical Engineering, Taiyuan University of Technology, Taiyuan, 030024, China
| | - Tong-Qing Wang
- School of Chemistry and Chemical Engineering, Taiyuan University of Technology, Taiyuan, 030024, China
| | - Yue Sun
- School of Chemistry and Chemical Engineering, Taiyuan University of Technology, Taiyuan, 030024, China.
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Singh G, Tripathi S, Shanker K, Sharma A. Cadmium-induced conformational changes in type 2 metallothionein of medicinal plant Coptis japonica: insights from molecular dynamics studies of apo, partially and fully metalated forms. J Biomol Struct Dyn 2018; 37:1520-1533. [PMID: 29624115 DOI: 10.1080/07391102.2018.1461688] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Plants play an important role in the removal of excess heavy metals from soil and water. Medicinal plants can also have non-traditional use in phytoremediation technologies. Among the heavy metals, Cadmium (Cd) is the most abundant and readily taken up by the crop plants. Plant metallothioneins (MTs) are small proteins having cysteine-rich residues and appear to play key roles in metal homoeostasis. Plant metallothionein 2 (MT 2) from Coptis japonica (Gold-thread; CjMT 2) is a typical member of this subfamily and features two cysteine-rich regions containing eight and six cysteine residues, respectively, separated by 42 amino acids long linker region. In-silico analysis of MT 2 protein sequences of C. japonica was performed. In this study, ab initio methods were utilised for the prediction of three-dimensional structure of CjMT 2. After structure validation, heavy metal-binding sites were predicted for the selected modelled structures of CjMT 2. To obtain Cdi-CjMT 2 (i = 1-7), metalated complex individual docking experiments were performed. The stability of the metalated docked structures was assessed by molecular dynamics (MD) simulation studies. Our study showed that CjMT 2 binds up to 4 Cd2+ ions in two distinct domains: a N-terminal β-domain that binds to 2 Cd2+ ions and a C-terminal α-domain that binds with 2 Cd2+ ions. Our analysis revealed that Cys residues of alpha and beta domain and some residues of spacer region of CjMT 2 protein might be important for the cadmium interaction. MD simulation studies provided insight into metal-induced conformational changes and mechanism of metalation of CjMT 2, an intrinsically disordered protein. This study provides useful insights into mechanism of cadmium-type 2 metallothionein interaction.
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Affiliation(s)
- Garima Singh
- a Biotechnology Division, CSIR-Central Institute of Medicinal and Aromatic Plants , Post Office CIMAP , Lucknow 226015 , India.,c Academy of Scientific and Innovative Research (AcSIR) , Ghaziabad 201002 , India
| | - Shubhandra Tripathi
- a Biotechnology Division, CSIR-Central Institute of Medicinal and Aromatic Plants , Post Office CIMAP , Lucknow 226015 , India
| | - Karuna Shanker
- b Chemical Science Division, CSIR-Central Institute of Medicinal and Aromatic Plants , Post Office CIMAP , Lucknow 226015 , India.,c Academy of Scientific and Innovative Research (AcSIR) , Ghaziabad 201002 , India
| | - Ashok Sharma
- a Biotechnology Division, CSIR-Central Institute of Medicinal and Aromatic Plants , Post Office CIMAP , Lucknow 226015 , India.,c Academy of Scientific and Innovative Research (AcSIR) , Ghaziabad 201002 , India
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12
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Mercury removal by engineered Escherichia coli cells expressing different rice metallothionein isoforms. ANN MICROBIOL 2018. [DOI: 10.1007/s13213-018-1326-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022] Open
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13
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Cabral ACS, Jakovleska J, Deb A, Penner-Hahn JE, Pecoraro VL, Freisinger E. Further insights into the metal ion binding abilities and the metalation pathway of a plant metallothionein from Musa acuminata. J Biol Inorg Chem 2018; 23:91-107. [PMID: 29218632 PMCID: PMC5756683 DOI: 10.1007/s00775-017-1513-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2017] [Accepted: 11/07/2017] [Indexed: 10/18/2022]
Abstract
The superfamily of metallothioneins (MTs) combines a diverse group of metalloproteins, sharing the characteristics of rather low molecular weight and high cysteine content. The latter provides MTs with the capability to coordinate thiophilic metal ions, in particular those with a d 10 electron configuration. The sub-family of plant MT3 proteins is only poorly characterized and there is a complete lack of three-dimensional structure information. Building upon our previous results on the Musa acuminata MT3 (musMT3) protein, the focus of the present work is to understand the metal cluster formation process, the role of the single histidine residue present in musMT3, and the metal ion binding affinity. We concentrate our efforts on the coordination of ZnII and CdII ions, using CoII as a spectroscopic probe for ZnII binding. The overall protein-fold is analysed with a combination of limited proteolytic digestion, mass spectrometry, and dynamic light scattering. Histidine coordination of metal ions is probed with extended X-ray absorption fine structure spectroscopy and CoII titration experiments. Initial experiments with isothermal titration calorimetry provide insights into the thermodynamics of metal ion binding.
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Affiliation(s)
- Augusto C S Cabral
- Department of Chemistry, University of Zürich, Winterthurerstrasse 190, 8057, Zurich, Switzerland
| | - Jovana Jakovleska
- Department of Chemistry, University of Zürich, Winterthurerstrasse 190, 8057, Zurich, Switzerland
| | - Aniruddha Deb
- Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, MI, 48109, USA
| | - James E Penner-Hahn
- Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, MI, 48109, USA
| | - Vincent L Pecoraro
- Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, MI, 48109, USA
| | - Eva Freisinger
- Department of Chemistry, University of Zürich, Winterthurerstrasse 190, 8057, Zurich, Switzerland.
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Peng JS, Ding G, Meng S, Yi HY, Gong JM. Enhanced metal tolerance correlates with heterotypic variation in SpMTL, a metallothionein-like protein from the hyperaccumulator Sedum plumbizincicola. PLANT, CELL & ENVIRONMENT 2017; 40:1368-1378. [PMID: 28152585 DOI: 10.1111/pce.12929] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2016] [Revised: 01/05/2017] [Accepted: 01/24/2017] [Indexed: 05/19/2023]
Abstract
Mechanistic insight into metal hyperaccumulation is largely restricted to Brassicaceae plants; therefore, it is of great importance to obtain corresponding knowledge from system outside the Brassicaceae. Here, we constructed and screened a cDNA library of the Cd/Zn hyperaccumulator Sedum plumbizincicola and identified a novel metallothionein-like protein encoding gene SpMTL. SpMTL showed functional similarity to other known MT proteins and also to its orthologues from non-hyperaccumulators. However, three additional cysteine residues were observed in SpMTL and appeared to be hyperaccumulator specific. Removal of these three residues significantly decreased its ability to tolerate Cd and the stoichiometry of Cd against SpMTL (molar ratio of Cd/SpMTL) to a level comparable to those of Cd/SaMTL and Cd/SeMTL in the corresponding non-hyperaccumulating relatives. SpMTL expressed in S. plumbizincicola roots at a much higher level than those of its orthologues in the non-hyperaccumulator roots. Interestingly, a positive correlation was observed between transcript levels of SpMTL in roots and Cd accumulation in leaves. Taking these results together, we propose that elevated transcript levels and heterotypic variation in protein sequences of SpMTL might contribute to the trait of Cd hyperaccumulation and hypertolerance in S. plumbizincicola.
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Affiliation(s)
- Jia-Shi Peng
- National Key Laboratory of Plant Molecular Genetics and National Center for Plant Gene Research (Shanghai), CAS Center for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, 200032, China
| | - Ge Ding
- National Key Laboratory of Plant Molecular Genetics and National Center for Plant Gene Research (Shanghai), CAS Center for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, 200032, China
- Crops Research Institute, Jiangxi Academy of Agricultural Sciences, Nanchang, 330200, China
| | - Shuan Meng
- National Key Laboratory of Plant Molecular Genetics and National Center for Plant Gene Research (Shanghai), CAS Center for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, 200032, China
| | - Hong-Ying Yi
- National Key Laboratory of Plant Molecular Genetics and National Center for Plant Gene Research (Shanghai), CAS Center for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, 200032, China
| | - Ji-Ming Gong
- National Key Laboratory of Plant Molecular Genetics and National Center for Plant Gene Research (Shanghai), CAS Center for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, 200032, China
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15
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Pan Y, Pan Y, Zhai J, Xiong Y, Li J, Du X, Su C, Zhang X. Cucumber Metallothionein-Like 2 (CsMTL2) Exhibits Metal-Binding Properties. Genes (Basel) 2016; 7:E106. [PMID: 27916887 PMCID: PMC5192482 DOI: 10.3390/genes7120106] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2016] [Revised: 10/24/2016] [Accepted: 11/14/2016] [Indexed: 01/25/2023] Open
Abstract
We identified a novel member of the metallothionein (MT) family, Cucumis sativus metallothionein-like 2 (CsMTL2), by screening a young cucumber fruit complementary DNA (cDNA) library. The CsMTL2 encodes a putative 77-amino acid Class II MT protein that contains two cysteine (Cys)-rich domains separated by a Cys-free spacer region. We found that CsMTL2 expression was regulated by metal stress and was specifically induced by Cd2+ treatment. We investigated the metal-binding characteristics of CsMTL2 and its possible role in the homeostasis and/or detoxification of metals by heterologous overexpression in Escherichia coli cells. Furthermore, we produced a deletion mutant form of the protein, CsMTL2m, that contained the two Cys-rich clusters but lacked the spacer region, in E. coli. We compared the metal-binding properties of CsMTL2 with those of CsMTL2m, the β domain of human metallothionein-like protein 1 (HsMTXb), and phytochelatin-like (PCL) heterologously expressed in E. coli using metal-binding assays. We found that E. coli cells expressing CsMTL2 accumulated the highest levels of Zn2+ and Cd2+ of the four transformed cell types, with levels being significantly higher than those of control cells containing empty vector. E. coli cells expressing CsMTL2 had a higher tolerance for cadmium than for zinc ions. These findings show that CsMTL2 improves metal tolerance when heterologously expressed in E. coli. Future studies should examine whether CsMTL2 improves metal tolerance in planta.
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Affiliation(s)
- Yu Pan
- Key Laboratory of Horticulture Science for Southern Mountainous Regions, Ministry of Education, College of Horticulture and Landscape Architecture, Southwest University, No. 2 Tiansheng Road, Beibei, Chongqing 400715, China.
| | - Yanglu Pan
- Key Laboratory of Horticulture Science for Southern Mountainous Regions, Ministry of Education, College of Horticulture and Landscape Architecture, Southwest University, No. 2 Tiansheng Road, Beibei, Chongqing 400715, China.
| | - Junpeng Zhai
- Key Laboratory of Horticulture Science for Southern Mountainous Regions, Ministry of Education, College of Horticulture and Landscape Architecture, Southwest University, No. 2 Tiansheng Road, Beibei, Chongqing 400715, China.
- Qijiang District Bureau of Forestry, Chongqing 401420, China.
| | - Yan Xiong
- Institute of Vegetables and Flowers, Chongqing Academy of Agricultural Sciences, Chongqing 401329, China.
| | - Jinhua Li
- Key Laboratory of Horticulture Science for Southern Mountainous Regions, Ministry of Education, College of Horticulture and Landscape Architecture, Southwest University, No. 2 Tiansheng Road, Beibei, Chongqing 400715, China.
| | - Xiaobing Du
- Key Laboratory of Horticulture Science for Southern Mountainous Regions, Ministry of Education, College of Horticulture and Landscape Architecture, Southwest University, No. 2 Tiansheng Road, Beibei, Chongqing 400715, China.
| | - Chenggang Su
- Key Laboratory of Horticulture Science for Southern Mountainous Regions, Ministry of Education, College of Horticulture and Landscape Architecture, Southwest University, No. 2 Tiansheng Road, Beibei, Chongqing 400715, China.
| | - Xingguo Zhang
- Key Laboratory of Horticulture Science for Southern Mountainous Regions, Ministry of Education, College of Horticulture and Landscape Architecture, Southwest University, No. 2 Tiansheng Road, Beibei, Chongqing 400715, China.
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16
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Cloning and characterization of metallothionein gene (HcMT) from Halostachys caspica and its expression in E. coli. Gene 2016; 585:221-7. [PMID: 27032460 DOI: 10.1016/j.gene.2016.03.039] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2016] [Revised: 03/11/2016] [Accepted: 03/21/2016] [Indexed: 02/06/2023]
Abstract
Halostachys caspica is a short shrub distributed in the semi-arid and saline-alkali area, which evolved various mechanisms for modulating salt and metal level. In the present study, a Type 2 metallothionein (HcMT) gene was cloned from the salt induced suppression subtractive hybridization (SSH) cDNA library of H.caspica. Quantitative real time PCR (qRT-PCR) analysis indicated that HcMT gene was up-regulated under the stress of Cu(2+), Zn(2+) and Cd(2+), and the tolerance of E. coli strain harboring with the recombinant HcMT (pET-32a-HcMT) to Cu(2+), Zn(2+) and Cd(2+) was enhanced compared to strain with control vector (pET-32a). Moreover, the purified TrxA-HcMT fusion protein from E. coli cells grown in the presence of 0.3mM CuSO4, 0.3mM ZnSO4, or 0.1mM CdCl2 could bind more metal ions than TrxA alone. The predicted 3D structure showed that HcMT could form a single metal-thiolate cluster, which confers the ability to bind five divalent metal ions through fourteen cysteine residues. These data indicate that HcMT may be involved in processes of metal tolerance in H. caspica and could be employed as a potential candidate for heavy metal phytoremediation.
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Pirzadeh S, Shahpiri A. Functional characterization of a type 2 metallothionein isoform (OsMTI-2b) from rice. Int J Biol Macromol 2016; 88:491-6. [DOI: 10.1016/j.ijbiomac.2016.04.021] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2015] [Revised: 04/05/2016] [Accepted: 04/07/2016] [Indexed: 11/28/2022]
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18
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Tarasava K, Chesnov S, Freisinger E. Oxidation of the N-terminal domain of the wheat metallothionein Ec -1 leads to the formation of three distinct disulfide bridges. Biopolymers 2016; 106:295-308. [PMID: 27061576 DOI: 10.1002/bip.22849] [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: 06/05/2015] [Accepted: 04/05/2016] [Indexed: 01/15/2023]
Abstract
Metallothioneins (MTs) are low molecular weight proteins, characterized by a high cysteine content and the ability to coordinate large amounts of d(10) metal ions, for example, Zn(II), Cd(II), and Cu(I), in form of metal-thiolate clusters. Depending on intracellular conditions such as redox potential or metal ion concentrations, MTs can occur in various states ranging from the fully metal-loaded holo- to the metal-free apo-form. The Cys thiolate groups in the apo-form can be either reduced or be involved in disulfide bridges. Although oxidation-mediated Zn(II) release might be a possible mechanism for the regulation of Zn(II) availability by MTs, no concise information regarding the associated pathways and the structure of oxidized apo-MT forms is available. Using the well-studied Zn2 γ-Ec -1 domain of the wheat Zn6 Ec -1 MT we attempt here to answer several question regarding the structure and biophysical properties of oxidized MT forms, such as: (1) does disulfide bond formation increase the stability against proteolysis, (2) is the overall peptide backbone fold similar for the holo- and the oxidized apo-MT form, and (3) are disulfide bridges specifically or randomly formed? Our investigations show that oxidation leads to three distinct disulfide bridges independently of the applied oxidation conditions and of the initial species used for oxidation, that is, the apo- or the holo-form. In addition, the oxidized apo-form is as stable against proteolysis as Zn2 γ-Ec -1, rendering the currently assumed degradation of oxidized MTs unlikely and suggesting a role of the oxidation process for the extension of protein lifetime in absence of sufficient amounts of metal ions. © 2016 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 106: 295-308, 2016.
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Affiliation(s)
- Katsiaryna Tarasava
- Department of Chemistry, University of Zurich, Winterthurerstrasse 190, Zurich, 8057, Switzerland
| | - Serge Chesnov
- University of Zurich/ETH Zurich, Functional Genomics Center Zurich, Winterthurerstrasse 190, Zurich, 8057, Switzerland
| | - Eva Freisinger
- Department of Chemistry, University of Zurich, Winterthurerstrasse 190, Zurich, 8057, Switzerland
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19
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Sunflower metallothionein family characterisation. Study of the Zn(II)- and Cd(II)-binding abilities of the HaMT1 and HaMT2 isoforms. J Inorg Biochem 2015; 148:35-48. [PMID: 25770010 DOI: 10.1016/j.jinorgbio.2015.02.016] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2014] [Revised: 02/21/2015] [Accepted: 02/22/2015] [Indexed: 11/21/2022]
Abstract
Plant metallothioneins (MTs) constitute a family of small Cys-rich proteins capable of coordinating metal ions, significantly differing from microbial and animal MTs. They are divided into four subfamilies depending on the Cys pattern in their sequence. In this work, the MT system of the sunflower plant (Helianthus annuus) has been defined, with ten genes coding for MTs (HaMT) belonging to the four plant MT subfamilies; three HaMT1, four HaMT2, one HaMT3 and two HaMT4 isoforms. The gene expression pattern and capacity to confer metal resistance to yeast cells have been analysed for at least one member of each subfamily. The divalent metal ion-binding abilities of HaMT1-2 and HaMT2-1 (the isoforms encoded by the most abundantly expressed HaMT1 and HaMT2 isogenes) have been characterised, as HaMT3 and HaMT4 were previously studied. Those isoforms constitute an optimum material to study the effect of Cys number variability on their coordination abilities, as they exhibit additional Cys residues regarding the canonical Cys pattern of each subfamily. Our results show that the variation in the number of Cys does not drastically modify their M(II)-binding abilities, but instead modulates the degree of heterogeneity of the corresponding recombinant syntheses. Significantly, the Zn(II)-HaMT1 complexes were highly susceptible to proteolytic cleavage. The recombinant Cd-MT preparations of both isoforms exhibit significant acid-labile sulphide content-Cd6S8 or Cd7S7 species. Overall results suggest that HaMT2-1 is probably associated with Cd(II) detoxification, in contrast to HaMT1-2, which may be more related to physiological functions, such as metal ion transport and delivery.
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20
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Blindauer CA. Advances in the molecular understanding of biological zinc transport. Chem Commun (Camb) 2015; 51:4544-63. [DOI: 10.1039/c4cc10174j] [Citation(s) in RCA: 66] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Recognition of the importance of zinc homeostasis for health has driven a surge in structural data on major zinc-transporting proteins.
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21
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Zhang M, Takano T, Liu S, Zhang X. Abiotic stress response in yeast and metal-binding ability of a type 2 metallothionein-like protein (PutMT2) from Puccinellia tenuiflora. Mol Biol Rep 2014; 41:5839-49. [PMID: 24973879 DOI: 10.1007/s11033-014-3458-1] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2013] [Accepted: 06/12/2014] [Indexed: 10/25/2022]
Abstract
Metallothioneins are low-molecular weight and cysteine-rich metal-binding proteins that play predominant cellular roles in the scavenging of reactive oxygen species and in mediating metal metabolism. To evaluate the role of a type-2 metallothionein-like gene from Puccinellia tenuiflora (PutMT2), the gene was over-expressed in yeast, and growth was assessed under a variety of abiotic stress conditions including peroxide (H2O2), salinity (NaCl and NaHCO3), and metal stress. PutMT2 overexpression in yeast improved the tolerance of cells to H2O2, NaCl, NaHCO3, Zn(2+), Fe(2+), Fe(3+), Cd(2+), Cr(6+), and Ag(+), but increased the sensitivity of cells to Mn(2+), Co(2+), Cu(2+), and Ni(2+) compared with control cells. PutMT2 was then expressed in Escherichia coli BL21as a glutathione S-transferase (GST) fusion protein (GST-PutMT2), and the metal-binding ability of GST-PutMT2 was analyzed and compared with GST alone using inductively coupled plasma atomic emission spectroscopy. Results showed that PutMT2 could bind to Cr, Cd, Co, Ag, Ba, Pb, Mn, Zn, Fe, Cu, P, Al, and Mg, but not Ni and As. There was no evidence to suggest that PutMT2 exhibited a specific or selective binding tendency to any individual metal ion. PutMT2 protein bound to Zn, Na, and Cu in vivo, perhaps with the highest affinity for Cu. Taken together, our results suggest that PutMT2 protein could play an important role in improving metal tolerance by metal binding in yeast. However, additional studies are required to confirm these results and to clarify the function of PutMT2 in transgenic plants.
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Affiliation(s)
- Min Zhang
- Key Laboratory of Saline-alkali Vegetation Ecology Restoration in Oil Field (SAVER), Ministry of Education, Alkali Soil Natural Environmental Science Centre (ASNESC), Northeast Forestry University, Harbin, 150040, China
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22
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Mudalkar S, Golla R, Sengupta D, Ghatty S, Reddy AR. Molecular cloning and characterisation of metallothionein type 2a gene from Jatropha curcas L., a promising biofuel plant. Mol Biol Rep 2013; 41:113-24. [DOI: 10.1007/s11033-013-2843-5] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2012] [Accepted: 10/26/2013] [Indexed: 11/28/2022]
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23
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Heterologous expression and metal-binding characterization of a type 1 metallothionein isoform (OsMTI-1b) from rice (Oryza sativa). Protein J 2013; 32:131-7. [PMID: 23385446 DOI: 10.1007/s10930-013-9469-2] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Metallothioneins (MTs) are ubiquitous, low molecular mass and cysteine-rich proteins that play important roles in maintaining intracellular metal homeostasis, eliminating metal toxification and protecting the cells against oxidative damages. MTs are able to bind metal ions through the thiol groups of their cysteine residues. Plants have several MT isoforms which are classified into four types based on the arrangement of cysteine residues. In the present study, a rice (Oryza sativa) gene encoding type 1 MT isoform, OsMTI-1b, was inserted in vector pET41a and overexpressed in Escherichia coli as carboxy-terminal extensions of glutathione-S-transferase (GST). The recombinant protein GST-OsMTI-1b was purified using affinity chromatography and its ability to bind with Ni(2+), Cd(2+), Zn(2+) and Cu(2+) ions was analyzed. The results demonstrated that this isoform has ability to bind Ni(2+), Cd(2+) and Zn(2+) ions in vitro, whereas it has no substantial ability to bind Cu(2+) ions. From competitive reaction with 5,5'-dithiobis(2-nitrobenzoic acid), DTNB, the affinity of metal ions for recombinant form of GST-OsMTI-1b was as follows: Ni(2+)/Cd(2+) > Zn(2+) > Cu(2+).
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24
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Wan X, Schicht O, Freisinger E. Copper(I) Coordination by Two Plant Metallothioneins. Z Anorg Allg Chem 2013. [DOI: 10.1002/zaac.201300096] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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25
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Kim YO, Jung S, Kim K, Bae HJ. Role of pCeMT, a putative metallothionein from Colocasia esculenta, in response to metal stress. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2013; 64:25-32. [PMID: 23344478 DOI: 10.1016/j.plaphy.2012.12.009] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/04/2012] [Accepted: 12/03/2012] [Indexed: 05/11/2023]
Abstract
Metallothioneins (MTs) play a major role in metal homeostasis and/or detoxification in plants. In this study, a novel gene, pCeMT, was isolated from Colocasia esculenta and characterized. Our results indicate that Escherichia coli cells expressing pCeMT exhibited enhanced Cd, Cu, and Zn tolerance and accumulation compared with control cells. Furthermore, pCeMT-overexpressing tobacco seedlings displayed better growth under Cd, Cu, and Zn stresses and accumulated more Cd and Zn compared with the wild type. Interestingly, transgenic tobacco displayed markedly decreased hydrogen peroxide (H(2)O(2)) and lipid peroxidation levels under Cd, Cu, and Zn treatments. These results suggest that pCeMT could play an important role in the protection of plant cells from oxidative stress by reactive oxygen species (ROS) scavenging and in the detoxification of free metals by metal binding, leading to improved plant metal tolerance.
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Affiliation(s)
- Yeon-Ok Kim
- Bio-energy Research Institute, Chonnam National University, Gwangju 500-757, Republic of Korea
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26
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Peroza EA, dos Santos Cabral A, Wan X, Freisinger E. Metal ion release from metallothioneins: proteolysis as an alternative to oxidation. Metallomics 2013; 5:1204-14. [DOI: 10.1039/c3mt00079f] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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27
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Huber T, Freisinger E. Sulfide ions as modulators of metal–thiolate cluster size in a plant metallothionein. Dalton Trans 2013; 42:8878-89. [DOI: 10.1039/c3dt32438a] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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28
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Leszczyszyn OI, Imam HT, Blindauer CA. Diversity and distribution of plant metallothioneins: a review of structure, properties and functions. Metallomics 2013; 5:1146-69. [DOI: 10.1039/c3mt00072a] [Citation(s) in RCA: 133] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
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29
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Wan X, Freisinger E. Incorporation of Sulfide Ions into the Cadmium(II) Thiolate Cluster of Cicer arietinum Metallothionein2. Inorg Chem 2012; 52:785-92. [DOI: 10.1021/ic301907j] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Xiaoqiong Wan
- Institute of Inorganic
Chemistry, University of Zurich, 8057 Zurich, Switzerland
- Key Laboratory of Arable Land
Conservation (Middle and Lower Reaches of Yangtse River), Ministry of Agriculture, Huazhong Agricultural University, Wuhan 430070, People's Republic of China
| | - Eva Freisinger
- Institute of Inorganic
Chemistry, University of Zurich, 8057 Zurich, Switzerland
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30
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Pagani MA, Tomas M, Carrillo J, Bofill R, Capdevila M, Atrian S, Andreo CS. The response of the different soybean metallothionein isoforms to cadmium intoxication. J Inorg Biochem 2012; 117:306-15. [PMID: 23073037 DOI: 10.1016/j.jinorgbio.2012.08.020] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2012] [Revised: 08/29/2012] [Accepted: 08/29/2012] [Indexed: 10/27/2022]
Abstract
Cadmium is a highly toxic heavy metal for both plants and animals. The presence of Cd in agricultural soils is of major concern regarding its entry into the food chain, since Cd compounds are readily taken up by plants, and accumulated in edible parts due to their high solubility. In this study, we first demonstrate the high capacity for Cd concentration of soybean grains. Consequently, we considered the study and characterization of the molecular determinants of Cd accumulation -such as metallothioneins (MT)- to be of major practical importance. We report here the first characterization of the soybean MT system, with the identification of nine genes (one of which is a truncated pseudogene), belonging to the four plant MT types. The most highly expressed of each type was chosen for further function analysis. All of them are expressed at high levels in soybean tissues: GmMT1, GmMT2 and GmMT3 in roots, shoots and seeds, and GmMT4 only in seeds. The corresponding recombinant soybean MTs, synthesized in Escherichia coli cells cultured in metal supplemented media, exhibit greater cadmium than zinc binding capacity. These results suggest a definite role of GmMTs in Cd(II) accumulation as one of the main responses of soybean to an overload of this metal.
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Affiliation(s)
- M A Pagani
- Centro de Estudios Fotosintéticos y Bioquímicos, CONICET, Suipacha 531, 2000 Rosario, Argentina.
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31
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Kim YO, Lee YG, Patel DH, Kim HM, Ahn SJ, Bae HJ. Zn tolerance of novel Colocasia esculenta metallothionein and its domains in Escherichia coli and tobacco. JOURNAL OF PLANT RESEARCH 2012; 125:793-804. [PMID: 22610130 DOI: 10.1007/s10265-012-0492-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/06/2011] [Accepted: 04/07/2012] [Indexed: 06/01/2023]
Abstract
Contrary to extensive researches on the roles of metallothioneins (MTs) in metal tolerance of animals, the roles of plant MTs in metal tolerance are largely under investigation. In this study, we evaluated the functional role of type 2 MT from Colocasia esculenta (CeMT2b) in Zn tolerance of tobacco and E. coli cells. Under Zn-stress conditions, transgenic tobacco overexpressing CeMT2b displayed much better seedling growth, a significant decrease in the levels of H(2)O(2) and an increase in Zn accumulation compared with the wild type. Overexpression of CeMT2b in E. coli greatly enhanced Zn tolerance and Zn accumulation under Zn stresses compared with control cells. CeMT2b bound 5.38 ± 0.29 atoms of Zn per protein. To identify a structural domain of CeMT2b for Zn binding, we investigated the growth of E. coli expressing each of the N-terminal, C-terminal, and central linker domains or a CNC motif deletion from the C-terminus of full-length CeMT2b. The results showed that the CNC motif is required for Zn tolerance, and the N-terminal domain is more effective in Zn tolerance than the C-terminal domain. Taken together, our results provide direct evidence for functional contributions of CeMT2b in Zn tolerance of tobacco and E. coli cells.
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Affiliation(s)
- Yeon-Ok Kim
- Bio-Energy Research Institute, Chonnam National University, 300 Youngbong-Dong, Buk-Gu, Gwangju, 500-757, Republic of Korea
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32
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Kim YO, Patel DH, Lee DS, Song Y, Bae HJ. High cadmium-binding ability of a novel Colocasia esculenta metallothionein increases cadmium tolerance in Escherichia coli and tobacco. Biosci Biotechnol Biochem 2011; 75:1912-20. [PMID: 21979068 DOI: 10.1271/bbb.110289] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Experimental evidence in vivo as to the functional roles and binding properties to cadmium (Cd) of type-2 plants metallothionein (MT) has been limited thus far. We investigated the biological role of metallothionein from Colocasia esculenta (CeMT2b) in Escherichia coli and tobacco, and developed a new model for the relationship between Cd tolerance and Cd-binding ability. Heterologous expression of CeMT2b in Escherichia coli greatly enhanced Cd tolerance and accumulated Cd content as compared to control cells. The molecular weight of CeMT2b increased with Cd, and CeMT2b bound up to 5.96±1 molar ratio (Cd/protein). Under Cd stress, transgenic tobacco plants displayed much better seedling growth and high Cd accumulation than the wild type. The presence of an extra CXC motif in CeMT2b contributed to the enhanced Cd-tolerance. The present study provides the first insight into the ability of type-2 plant MT to bind physiological Cd.
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Affiliation(s)
- Yeon-Ok Kim
- Bio-Energy Research Institute, Chonnam National University, Gwangju, Korea
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Freisinger E. Structural features specific to plant metallothioneins. J Biol Inorg Chem 2011; 16:1035-45. [PMID: 21688177 DOI: 10.1007/s00775-011-0801-z] [Citation(s) in RCA: 91] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2011] [Accepted: 06/06/2011] [Indexed: 11/26/2022]
Abstract
The metallothionein (MT) superfamily combines a large variety of small cysteine-rich proteins from nearly all phyla of life that have the ability to coordinate various transition metal ions, including Zn(II), Cd(II), and Cu(I). The members of the plant MT family are characterized by great sequence diversity, requiring further subdivision into four subfamilies. Very peculiar and not well understood is the presence of rather long cysteine-free amino acid linkers between the cysteine-rich regions. In light of the distinct differences in sequence to MTs from other families, it seems obvious to assume that these differences will also be manifested on the structural level. This was already impressively demonstrated with the elucidation of the three-dimensional structure of the wheat E(c)-1 MT, which revealed two metal cluster arrangements previously unprecedented for any MT. However, as this structure is so far the only one available for the plant MT family, other sources of information are in high demand. In this review the focus is thus set on any structural features known, deduced, or assumed for the plant MT proteins. This includes the determination of secondary structural elements by circular dichroism, IR, and Raman spectroscopy, the analysis of the influence of the long linker regions, and the evaluation of the spatial arrangement of the sequence separated cysteine-rich regions with the aid of, e.g., limited proteolytic digestion. In addition, special attention is paid to the contents of divalent metal ions as the metal ion to cysteine ratios are important for predicting and understanding possible metal-thiolate cluster structures.
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Affiliation(s)
- Eva Freisinger
- Institute of Inorganic Chemistry, University of Zurich, 8057, Zurich, Switzerland.
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Hassinen VH, Tervahauta AI, Schat H, Kärenlampi SO. Plant metallothioneins--metal chelators with ROS scavenging activity? PLANT BIOLOGY (STUTTGART, GERMANY) 2011; 13:225-32. [PMID: 21309968 DOI: 10.1111/j.1438-8677.2010.00398.x] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Metallothioneins (MTs) are ubiquitous cysteine-rich proteins present in plants, animals, fungi and cyanobacteria. In plants, MTs are suggested to be involved in metal tolerance or homeostasis, as they are able to bind metal ions through the thiol groups of their cysteine residues. Recent reports show that MTs are also involved in the scavenging of reactive oxygen species (ROS). The interplay between these roles is not entirely clear. Plants have many MT isoforms with overlapping expression patterns, and no specific role for any of them has been assigned. This review is focused on recent findings on plant MTs.
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Affiliation(s)
- V H Hassinen
- Department of Biosciences, University of Eastern Finland, Kuopio, Finland
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Blindauer CA, Leszczyszyn OI. Metallothioneins: unparalleled diversity in structures and functions for metal ion homeostasis and more. Nat Prod Rep 2010; 27:720-41. [PMID: 20442962 DOI: 10.1039/b906685n] [Citation(s) in RCA: 144] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Metallothioneins have been the subject of intense study for five decades, and have greatly inspired the development of bio-analytical methodologies including multi-dimensional and multi-nuclear NMR.With further advancements in molecular biology, protein science, and instrumental techniques, recent years have seen a renaissance of research into metallothioneins. The current report focuses on in vitro studies of so-called class II metallothioneins from a variety of phyla, highlighting the diversity of metallothioneins in terms of structure, biological functions, and molecular functions such as metal ion specificity, thermodynamic stabilities, and kinetic reactivity. We are still far from being able to predict any of these properties, and further efforts will be required to generate the knowledge that will enable a better understanding of what governs the biological and chemical properties of these unusual and intriguing small proteins.
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