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Malekzadeh R, Shahpiri A, Siapoush S. Metalation of a rice type 1 metallothionein isoform (OsMTI-1b). Protein Expr Purif 2020; 175:105719. [PMID: 32750405 DOI: 10.1016/j.pep.2020.105719] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2020] [Revised: 06/11/2020] [Accepted: 07/25/2020] [Indexed: 11/15/2022]
Abstract
The simultaneously functions of Metallothioneins (MTs) are relied on their metalation mechanisms that can be divided into non-cooperative, weakly cooperative and strongly cooperative mechanisms. In this study, we recombinantly synthesized OsMTI-1b, N- and C-terminal Cys-rich regions as glutathione-S-transferase (GST)-fusion proteins in E. coli. In comparison with control strains (The E. coli cells containing pET41a without gene), transgenic E. coli cells showed more tolerance against Cd2+ and Zn2+. The recombinant GST-proteins were purified using affinity chromatography. According to in vitro assays, the recombinant proteins showed a higher binding ability to Cd2+ and Zn2+. However, the affinity of apo-proteins to Cu2+ ions were very low. The coordination of Cd2+ ions in OsMTI-1b demonstrates a strongly cooperative mechanism with a priority for the C-terminal Cys-rich region that indicates the detoxifying of heavy metals as main role of P1 subfamily of MTs. While the metalation with Zn2+ conformed to a weakly cooperative mechanism with a specificity to N-terminal Cys-rich region. It implies the specific function of OsMTI-1b is involved in zinc homeostasis. Nevertheless, a non-cooperative metalation mechanism was perceived for Cu2+ that suggests the fully metalation does not occur and OsMTI-1b cannot play a significant role in dealing with Cu2+ ions.
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Affiliation(s)
- Rahim Malekzadeh
- Department of Medical Biotechnology, School of Advanced Technologies, Shahrekord University of Medical Sciences, Shahrekord, 88157-13471, Iran; Student Research Committee, Shahrekord University of Medical Sciences, Shahrekord, Iran.
| | - Azar Shahpiri
- Department of Biotechnology, College of Agriculture, Isfahan University of Technology, Isfahan, 84156-83111, Iran
| | - Samaneh Siapoush
- Department of Medical Biotechnology, Faculty of Advanced Medical Sciences, Tabriz University of Medical Science, Tabriz, 51664-15731, Iran
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Habjanič J, Chesnov S, Zerbe O, Freisinger E. Impact of naturally occurring serine/cysteine variations on the structure and function of Pseudomonas metallothioneins. Metallomics 2020; 12:23-33. [DOI: 10.1039/c9mt00213h] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Naturally occurring Ser/Cys variations in Pseudomonas metallothioneinss affect intra-cluster dynamics rather than binding capacity.
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Affiliation(s)
- Jelena Habjanič
- Department of Chemistry
- University of Zurich
- Zurich
- Switzerland
| | - Serge Chesnov
- University of Zurich/ETH Zurich
- Functional Genomics Centre Zurich
- Zurich
- Switzerland
| | - Oliver Zerbe
- Department of Chemistry
- University of Zurich
- Zurich
- Switzerland
| | - Eva Freisinger
- Department of Chemistry
- University of Zurich
- Zurich
- Switzerland
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Shahpiri A, Rahimi AM. Expression of Rice Metallothionein Isoforms in Escherichia coli Enhances the Accumulation of Trivalent and Hexavalent Chromium. Protein Pept Lett 2019; 26:768-775. [PMID: 31618171 DOI: 10.2174/0929866526666190503100613] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2018] [Revised: 04/07/2019] [Accepted: 04/19/2019] [Indexed: 11/22/2022]
Abstract
INTRODUCTION Metallothioneins (MTs) are members of a family of low molecular weight and cysteine-rich proteins that are involved in heavy metal homeostasis and detoxification in living organisms. Plants have multiple MT types that are generally divided into four subgroups according to the arrangement of Cys residues. METHODS In the present study the E. coli cells which heterologously express four different rice MT (OsMT) isoforms were analyzed for the accumulation of two forms of chromium, Cr3+ and Cr6+. RESULTS The results show that the transgenic bacteria were more tolerant than control cells when they were grown up in the medium comprising Cr(NO3)3.9H2O or Na2CrO4. The cells expressing OsMT1, OsMT2, OsMT3 and OsMT4 give rise to 6.5-, 2.7-, 5.5- and 2.1-fold improvements on the accumulation capacity for Cr3+ and 9-, 3-, 5- and 3- fold Cr6+ respectively compared with comparison to the control strain. Furthermore, the purified recombinant GST-OsMTs were tested for their binding ability to Cr+3 and Cr+6 in vitro. DISCUSSION The data show that the recombinant GST-OsMT1 and GST-OsMT2 were able to bind both Cr3+ and Cr6+, in vitro. However, their binding strength was low with respect to previous tested divalent ions like Cd2+.
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Affiliation(s)
- Azar Shahpiri
- Department of Biotechnology, College of Agriculture, Isfahan University of Technology, Isfahan 84156-83111, Iran
| | - Amir Mohammad Rahimi
- Department of Biotechnology, College of Agriculture, Isfahan University of Technology, Isfahan 84156-83111, Iran
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Overexpression of a Metallothionein 2A Gene from Date Palm Confers Abiotic Stress Tolerance to Yeast and Arabidopsis thaliana. Int J Mol Sci 2019; 20:ijms20122871. [PMID: 31212812 PMCID: PMC6627811 DOI: 10.3390/ijms20122871] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2019] [Revised: 06/07/2019] [Accepted: 06/11/2019] [Indexed: 11/18/2022] Open
Abstract
Although the date palm tree is an extremophile with tolerance to drought and certain levels of salinity, the damage caused by extreme salt concentrations in the soil, has created a need to explore stress-responsive traits and decode their mechanisms. Metallothioneins (MTs) are low-molecular-weight cysteine-rich proteins that are known to play a role in decreasing oxidative damage during abiotic stress conditions. Our previous study identified date palm metallothionein 2A (PdMT2A) as a salt-responsive gene, which has been functionally characterized in yeast and Arabidopsis in this study. The recombinant PdMT2A protein produced in Escherichia coli showed high reactivity against the substrate 5′-dithiobis-2-nitrobenzoic acid (DTNB), implying that the protein has the property of scavenging reactive oxygen species (ROS). Heterologous overexpression of PdMT2A in yeast (Saccharomyces cerevisiae) conferred tolerance to drought, salinity and oxidative stresses. The PdMT2A gene was also overexpressed in Arabidopsis, to assess its stress protective function in planta. Compared to the wild-type control, the transgenic plants accumulated less Na+ and maintained a high K+/Na+ ratio, which could be attributed to the regulatory role of the transgene on transporters such as HKT, as demonstrated by qPCR assay. In addition, transgenic lines exhibited higher chlorophyll content, higher superoxide dismutase (SOD) activity and improved scavenging ability for reactive oxygen species (ROS), coupled with a better survival rate during salt stress conditions. Similarly, the transgenic plants also displayed better drought and oxidative stress tolerance. Collectively, both in vitro and in planta studies revealed a role for PdMT2A in salt, drought, and oxidative stress tolerance.
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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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Ziller A, Fraissinet-Tachet L. Metallothionein diversity and distribution in the tree of life: a multifunctional protein. Metallomics 2018; 10:1549-1559. [DOI: 10.1039/c8mt00165k] [Citation(s) in RCA: 71] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Metallothioneins are diverse, but not represented yet in all phyla. Moreover, they play a central role as a [MT:T:TO] protein system.
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Affiliation(s)
- Antoine Ziller
- Microbial Ecology
- CNRS UMR 5557
- UMR INRA 1418
- Université Lyon1
- Université de Lyon
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Independent metal-thiolate cluster formation in C-terminal Cys-rich region of a rice type 1 metallothionein isoform. Int J Biol Macromol 2016; 96:436-441. [PMID: 28013008 DOI: 10.1016/j.ijbiomac.2016.12.047] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2016] [Revised: 12/14/2016] [Accepted: 12/16/2016] [Indexed: 11/23/2022]
Abstract
In this study we examined the independent self assembly of metal-binding in C-terminal Cys- rich region of a type 1 metallothionein (MT) isoform from rice (OsMTI-1b). To this end the N-terminal of OsMTI-1b (C-OsMTI-1b) was heterologously expressed in Escherichia coli as fusion protein with glutathione-S-transferase (GST). As compared with control (The E. coli cells containing pET41a without gene), transgenic E. coli cells expressing GST-C-OsMTI-1b accumulated more Ni2+, Cd2+, and Zn2+ from culture medium and showed increased tolerance against these metals. The recombinant GST-C-OsMTI-1b was purified using affinity chromatography. According to in vitro assays the protein GST-C-OsMTI-1b was able to form complexes with Ni2+, Cd2+ and Zn2+. These results demonstrate the formation of independent metal-thiolate cluster at C-terminal Cys-rich region of OsMTI-1b without participation of N-terminal Cys-rich region.
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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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Zarei M, Shahpiri A, Esmaeilnejad-Ahranjani P, Arpanaei A. Metallothionein-immobilized silica-coated magnetic particles as a novel nanobiohybrid adsorbent for highly efficient removal of cadmium from aqueous solutions. RSC Adv 2016. [DOI: 10.1039/c6ra05210j] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
In this contribution, magnetic nanocomposite particles of Fe3O4 cluster@SiO2 (MNPs) were functionalized with N-(2-aminoethyl)-3-aminopropyltrimethoxy-silane (EDS) to obtain amine-functionalized magnetic nanocomposite particles (AF-MNPs).
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Affiliation(s)
- Mohsen Zarei
- Department of Biotechnology
- College of Agriculture
- Isfahan University of Technology
- Isfahan 84156-83111
- Iran
| | - Azar Shahpiri
- Department of Biotechnology
- College of Agriculture
- Isfahan University of Technology
- Isfahan 84156-83111
- Iran
| | - Parvaneh Esmaeilnejad-Ahranjani
- Department of Industrial and Environmental Biotechnology
- National Institute of Genetic Engineering and Biotechnology
- Tehran
- Iran
| | - Ayyoob Arpanaei
- Department of Industrial and Environmental Biotechnology
- National Institute of Genetic Engineering and Biotechnology
- Tehran
- Iran
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Functional characterization of a type 3 metallolthionein isoform (OsMTI-3a) from rice. Int J Biol Macromol 2015; 73:154-9. [DOI: 10.1016/j.ijbiomac.2014.10.067] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2014] [Revised: 10/29/2014] [Accepted: 10/30/2014] [Indexed: 11/22/2022]
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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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Nezhad RM, Shahpiri A, Mirlohi A. Discrimination between two rice metallothionein isoforms belonging to type 1 and type 4 in metal-binding ability. Biotechnol Appl Biochem 2014; 60:275-82. [PMID: 23782215 DOI: 10.1002/bab.1078] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2012] [Accepted: 12/12/2012] [Indexed: 10/26/2022]
Abstract
Metallothioneins (MTs) are a superfamily of low-molecular-weight, cysteine (Cys)-rich proteins that are believed to play important roles in protection against metal toxicity and oxidative stress. Plants have several MT isoforms, which are classified into four types based on the arrangement of Cys residues. In this study, two rice (Oryza sativa) MT isoforms, OsMTI-1b and OsMTII-1a from type 1 and type 4, respectively, were heterologously expressed in Escherichia coli as carboxy-terminal extensions of glutathione-S-transferase (GST). Transformed cells expressing GST-OsMTI-1b showed increased tolerance to Ni(2+) , Cd(2+) , and Zn(2+) and accumulated more metal ions compared with cells expressing GST alone. However, heterologous expression of GST-OsMTII-1a had no significant effects on metal tolerance or ion accumulation. The UV absorption spectra and competitive reactions of in vitro Cd-incubated proteins with 5-5'-dithiobis(2-nitrobenzoic) acid revealed that GST-OsMTI-1b, but not GST-OsMTII-1a, is able to form Cd-thiolate clusters. Furthermore, heterologous expression of both GST-OsMTI-1b and GST-OsMTII-1a conferred H2 O2 tolerance to E. coli cells. Taken together, the results presented here show that two different rice MT isoforms belonging to type 1 and type 4 differ in Ni(2+) , Cd(2+) , and Zn(2+) binding abilities, but they may have overlapping function in protection of cells against oxidative stress.
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Affiliation(s)
- Rezvan Mohammadi Nezhad
- Department of Agricultural Biotechnology, College of Agriculture, Isfahan University of Technology, Isfahan, Iran
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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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Díaz S, Amaro F, Rico D, Campos V, Benítez L, Martín-González A, Hamilton EP, Orias E, Gutiérrez JC. Tetrahymena metallothioneins fall into two discrete subfamilies. PLoS One 2007; 2:e291. [PMID: 17356700 PMCID: PMC1808422 DOI: 10.1371/journal.pone.0000291] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2006] [Accepted: 02/20/2007] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND Metallothioneins are ubiquitous small, cysteine-rich, multifunctional proteins which can bind heavy metals. METHODOLOGY/PRINCIPAL FINDINGS We report the results of phylogenetic and gene expression analyses that include two new Tetrahymena thermophila metallothionein genes (MTT3 and MTT5). Sequence alignments of all known Tetrahymena metallothioneins have allowed us to rationalize the structure of these proteins. We now formally subdivide the known metallothioneins from the ciliate genus Tetrahymena into two well defined subfamilies, 7a and 7b, based on phylogenetic analysis, on the pattern of clustering of Cys residues, and on the pattern of inducibility by the heavy metals Cd and Cu. Sequence alignment also reveals a remarkably regular, conserved and hierarchical modular structure of all five subfamily 7a MTs, which include MTT3 and MTT5. The former has three modules, while the latter has only two. Induction levels of the three T. thermophila genes were determined using quantitative real time RT-PCR. Various stressors (including heavy metals) brought about dramatically different fold-inductions for each gene; MTT5 showed the highest fold-induction. Conserved DNA motifs with potential regulatory significance were identified, in an unbiased way, upstream of the start codons of subfamily 7a MTs. EST evidence for alternative splicing in the 3' UTR of the MTT5 mRNA with potential regulatory activity is reported. CONCLUSION/SIGNIFICANCE The small number and remarkably regular structure of Tetrahymena MTs, coupled with the experimental tractability of this model organism for studies of in vivo function, make it an attractive system for the experimental dissection of the roles, structure/function relationships, regulation of gene expression, and adaptive evolution of these proteins, as well as for the development of biotechnological applications for the environmental monitoring of toxic substances.
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Affiliation(s)
- Silvia Díaz
- Departamento de Microbiología-III, Facultad de Biología, Universidad Complutense (UCM), Spain
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Park H, Ahn IY, Choi HJ, Pyo SH, Lee HE. Cloning, expression and characterization of metallothionein from the Antarctic clam Laternula elliptica. Protein Expr Purif 2006; 52:82-8. [PMID: 17011209 DOI: 10.1016/j.pep.2006.08.008] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2006] [Revised: 08/11/2006] [Accepted: 08/14/2006] [Indexed: 10/24/2022]
Abstract
The genes for two apparent subtypes of metallothionein (MT) isoform were isolated from the Antarctic clam Laternula elliptica. Determination of the nucleotide sequence showed that the gene consists of 222 bp that code a 73-amino acid protein. The comparison between MT cDNA sequences of L. elliptica and other bivalves showed strong homologies on positions of cysteine residues, which are important for their metal binding abilities. The gene for the MT was inserted into a pET vector and overexpressed as a carboxyl terminal extension of glutathionein-S-transferase (GST) in Escherichia coli. After the GST fusion proteins had been purified by glutathione-Sepharose affinity chromatography column and digested with enterokinase, the MT was purified with gel filtration and analyzed for its biochemical properties. Recombinant MTs were reconstituted with Cd, Cu, and Zn, and kinetic studies of the reactions with electrophilic disulphide, DTNB, were investigated to explore their metal binding ability. It is revealed that the Cd-MT and Zn-MT react with DTNB biphasically, and that Zn-MT reacts with DTNB more rapidly, and with a significantly greater pseudo-first-order rate constant. Cu-MT reacts monophasically and releases metal slowly from MT.
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Affiliation(s)
- Hyun Park
- Korea Polar Research Institute, Korea Ocean Research and Development Institute, Sa-2-Dong 1270, Ansan 426-744, South Korea.
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Neilson JW, Artiola JF, Maier RM. Characterization of lead removal from contaminated soils by nontoxic soil-washing agents. JOURNAL OF ENVIRONMENTAL QUALITY 2003; 32:899-908. [PMID: 12809290 DOI: 10.2134/jeq2003.8990] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Few effective strategies exist for remediating and restoring metal-contaminated soils. We have evaluated the potential of two environmentally compatible, nondestructive, biological soil-washing agents for remediating aged, lead-contaminated soils. Two contaminated soils were washed with 10 mM rhamnolipid biosurfactant and 5.3% carboxymethyl-beta-cyclodextrin (CMCD). The metal removal efficiency of these agents was compared with 10 mM diethylenetriamine pentaacetic acid (DTPA) and 10 mM KNO3. Lead removal rates by both soil-washing agents exceeded the removal by KNO3, but were an order of magnitude less than removal by the synthetic chelator, DTPA. Analysis of soil extractions revealed that the Pb in the first soil (3780 mg kg(-1)) was primarily associated with the soluble, exchangeable, oxide, and residual fractions while the Pb in the second soil (23 900 mg kg(-1)) was found in the soluble, exchangeable, carbonate, and residual fractions. After 10 consecutive washes, rhamnolipid had removed 14.2 and 15.3% of the Pb from the first and second soils, respectively, and CMCD had removed 5 and 13.4% from the same two soils. The Pb removal rate by both agents either increased or was consistent throughout the 10 extractions, indicating a potential for continued removal with extended washing. Significant levels of Cu and Zn in both soils did not prevent Pb removal by either agent. Interestingly, the effectiveness of each agent varied as a function of Pb speciation in the soil. Rhamnolipid was more effective than CMCD in removing Pb bound to amorphous iron oxides, while both agents demonstrated similar potential for removing soluble, exchangeable, and carbonate-bound Pb. Neither agent demonstrated potential for the complete remediation of metal-contaminated soils.
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Affiliation(s)
- Julia W Neilson
- Department of Soil, Water, and Environmental Science, Shantz Building, Room 429, Univ. of Arizona, Tucson, AZ 85721, USA
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Miles AT, Hawksworth GM, Beattie JH, Rodilla V. Induction, regulation, degradation, and biological significance of mammalian metallothioneins. Crit Rev Biochem Mol Biol 2000; 35:35-70. [PMID: 10755665 DOI: 10.1080/10409230091169168] [Citation(s) in RCA: 300] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
MTs are small cysteine-rich metal-binding proteins found in many species and, although there are differences between them, it is of note that they have a great deal of sequence and structural homology. Mammalian MTs are 61 or 62 amino acid polypeptides containing 20 conserved cysteine residues that underpin the binding of metals. The existence of MT across species is indicative of its biological demand, while the conservation of cysteines indicates that these are undoubtedly central to the function of this protein. Four MT isoforms have been found so far, MT-1, MT-2, MT-3, and MT-4, but these also have subtypes with 17 MT genes identified in man, of which 10 are known to be functional. Different cells express different MT isoforms with varying levels of expression perhaps as a result of the different function of each isoform. Even different metals induce and bind to MTs to different extents. Over 40 years of research into MT have yielded much information on this protein, but have failed to assign to it a definitive biological role. The fact that multiple MT isoforms exist, and the great variety of substances and agents that act as inducers, further complicates the search for the biological role of MTs. This article reviews the current knowledge on the biochemistry, induction, regulation, and degradation of this protein in mammals, with a particular emphasis on human MTs. It also considers the possible biological roles of this protein, which include participation in cell proliferation and apoptosis, homeostasis of essential metals, cellular free radical scavenging, and metal detoxification.
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Affiliation(s)
- A T Miles
- Department of Medicine and Therapeutics, University of Aberdeen, Scotland, UK
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Berger B, Dallinger R, Gehrig P, Hunziker PE. Primary structure of a copper-binding metallothionein from mantle tissue of the terrestrial gastropod Helix pomatia L. Biochem J 1997; 328 ( Pt 1):219-24. [PMID: 9359856 PMCID: PMC1218909 DOI: 10.1042/bj3280219] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
A novel copper-binding metallothionein (MT) has been purified from mantle tissue of the terrestrial snail Helix pomatia using gel-permeation chromatography, ion-exchange chromatography and reverse-phase HPLC. Copper was removed from the thionein by addition of ammonium tetrathiomolybdate. The resulting apothionein (molecular mass 6247 Da) was S-methylated and digested with trypsin, endoproteinase Arg-C and endoproteinase Lys-C. Amino acid sequences of the resulting peptides were determined by collision-induced dissociation tandem MS. The protein is acetylated at its N-terminus, and consists of 64 amino acids, 18 of which are cysteine residues. A comparison with the cadmium-binding MT isolated from the midgut gland of the same species shows an identical arrangement of the cysteines, but an unexpectedly high variability in the other amino acids. The two MT isoforms differ in total length and at 26 positions of their peptide chains. We suggest that the copper-binding MT isoform from the mantle of H. pomatia is responsible for regulatory functions in favour of copper, probably in connection with the metabolism of the copper-bearing protein, haemocyanin.
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Affiliation(s)
- B Berger
- Institut für Zoologie und Limnologie, Universität Innsbruck, Austria
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