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Mehlenbacher MR, Elsiesy R, Lakha R, Villones RLE, Orman M, Vizcarra CL, Meloni G, Wilcox DE, Austin RN. Metal binding and interdomain thermodynamics of mammalian metallothionein-3: enthalpically favoured Cu + supplants entropically favoured Zn 2+ to form Cu 4 + clusters under physiological conditions. Chem Sci 2022; 13:5289-5304. [PMID: 35655557 PMCID: PMC9093145 DOI: 10.1039/d2sc00676f] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2022] [Accepted: 04/01/2022] [Indexed: 01/02/2023] Open
Abstract
Metallothioneins (MTs) are a ubiquitous class of small metal-binding proteins involved in metal homeostasis and detoxification. While known for their high affinity for d10 metal ions, there is a surprising dearth of thermodynamic data on metals binding to MTs. In this study, Zn2+ and Cu+ binding to mammalian metallothionein-3 (MT-3) were quantified at pH 7.4 by isothermal titration calorimetry (ITC). Zn2+ binding was measured by chelation titrations of Zn7MT-3, while Cu+ binding was measured by Zn2+ displacement from Zn7MT-3 with competition from glutathione (GSH). Titrations in multiple buffers enabled a detailed analysis that yielded condition-independent values for the association constant (K) and the change in enthalpy (ΔH) and entropy (ΔS) for these metal ions binding to MT-3. Zn2+ was also chelated from the individual α and β domains of MT-3 to quantify the thermodynamics of inter-domain interactions in metal binding. Comparative titrations of Zn7MT-2 with Cu+ revealed that both MT isoforms have similar Cu+ affinities and binding thermodynamics, indicating that ΔH and ΔS are determined primarily by the conserved Cys residues. Inductively coupled plasma mass spectrometry (ICP-MS) analysis and low temperature luminescence measurements of Cu-replete samples showed that both proteins form two Cu4 +-thiolate clusters when Cu+ displaces Zn2+ under physiological conditions. Comparison of the Zn2+ and Cu+ binding thermodynamics reveal that enthalpically-favoured Cu+, which forms Cu4 +-thiolate clusters, displaces the entropically-favoured Zn2+. These results provide a detailed thermodynamic analysis of d10 metal binding to these thiolate-rich proteins and quantitative support for, as well as molecular insight into, the role that MT-3 plays in the neuronal chemistry of copper.
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Affiliation(s)
| | - Rahma Elsiesy
- Department of Chemistry, Barnard College of Columbia University New York NY 10027 USA
| | - Rabina Lakha
- Department of Chemistry, Barnard College of Columbia University New York NY 10027 USA
| | - Rhiza Lyne E Villones
- Department of Chemistry and Biochemistry, University of Texas at Dallas Richardson TX 75080 USA
| | - Marina Orman
- Department of Chemistry, Barnard College of Columbia University New York NY 10027 USA
| | - Christina L Vizcarra
- Department of Chemistry, Barnard College of Columbia University New York NY 10027 USA
| | - Gabriele Meloni
- Department of Chemistry and Biochemistry, University of Texas at Dallas Richardson TX 75080 USA
| | - Dean E Wilcox
- Department of Chemistry, Dartmouth College Hanover NH 03755 USA
| | - Rachel N Austin
- Department of Chemistry, Barnard College of Columbia University New York NY 10027 USA
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2
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Dong S, Shirzadeh M, Fan L, Laganowsky A, Russell DH. Ag + Ion Binding to Human Metallothionein-2A Is Cooperative and Domain Specific. Anal Chem 2020; 92:8923-8932. [PMID: 32515580 PMCID: PMC8114364 DOI: 10.1021/acs.analchem.0c00829] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Metallothioneins (MTs) constitute a family of cysteine-rich proteins that play key biological roles for a wide range of metal ions, but unlike many other metalloproteins, the structures of apo- and partially metalated MTs are not well understood. Here, we combine nano-electrospray ionization-mass spectrometry (ESI-MS) and nano-ESI-ion mobility (IM)-MS with collision-induced unfolding (CIU), chemical labeling using N-ethylmaleimide (NEM), and both bottom-up and top-down proteomics in an effort to better understand the metal binding sites of the partially metalated forms of human MT-2A, viz., Ag4-MT. The results for Ag4-MT are then compared to similar results obtained for Cd4-MT. The results show that Ag4-MT is a cooperative product, and data from top-down and bottom-up proteomics mass spectrometry analysis combined with NEM labeling revealed that all four Ag+ ions of Ag4-MT are bound to the β-domain. The binding sites are identified as Cys13, Cys15, Cys19, Cys21, Cys24, and Cys26. While both Ag+ and Cd2+ react with MT to yield cooperative products, i.e., Ag4-MT and Cd4-MT, these products are very different; Ag+ ions of Ag4-MT are located in the β-domain, whereas Cd2+ ions of Cd4-MT are located in the α-domain. Ag6-MT has been reported to be fully metalated in the β-domain, but our data suggest the two additional Ag+ ions are more weakly bound than are the other four. Higher order Agi-MT complexes (i = 7-17) are formed in solutions that contain excess Ag+ ions, and these are assumed to be bound to the α-domain or shared between the two domains. Interestingly, the excess Ag+ ions are displaced upon addition of NEM to this solution to yield predominantly Ag4NEM14-MT. Results from CIU suggest that Agi-MT complexes are structurally more ordered and that the energy required to unfold these complexes increases as the number of coordinated Ag+ increases.
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Affiliation(s)
- Shiyu Dong
- Department of Chemistry, Texas A&M University, College Station, Texas 77843, United States
| | - Mehdi Shirzadeh
- Department of Chemistry, Texas A&M University, College Station, Texas 77843, United States
| | - Liqi Fan
- Department of Chemistry, Texas A&M University, College Station, Texas 77843, United States
| | - Arthur Laganowsky
- Department of Chemistry, Texas A&M University, College Station, Texas 77843, United States
| | - David H Russell
- Department of Chemistry, Texas A&M University, College Station, Texas 77843, United States
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3
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Šestáková I, Navrátil T, Josypčuk B. Metal Exchange Reactions in Metallothioneins Explored by Electrochemical Methods. ELECTROANAL 2019. [DOI: 10.1002/elan.201900276] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Ivana Šestáková
- J. Heyrovský Institute of Physical Chemistry of the Czech Academy of Sciences, Dolejškova 3 182 23 Prague 8 Czech Republic
| | - Tomáš Navrátil
- J. Heyrovský Institute of Physical Chemistry of the Czech Academy of Sciences, Dolejškova 3 182 23 Prague 8 Czech Republic
| | - Bohdan Josypčuk
- J. Heyrovský Institute of Physical Chemistry of the Czech Academy of Sciences, Dolejškova 3 182 23 Prague 8 Czech Republic
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4
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Dong S, Wagner ND, Russell DH. Collision-Induced Unfolding of Partially Metalated Metallothionein-2A: Tracking Unfolding Reactions of Gas-Phase Ions. Anal Chem 2018; 90:11856-11862. [PMID: 30221929 DOI: 10.1021/acs.analchem.8b01622] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Metallothioneins (MTs) constitute a group of intrinsically disordered proteins that exhibit extreme diversity in structure, biological functionality, and metal ion specificity. Structures of coordinatively saturated metalated MTs have been extensively studied, but very limited structural information for the partially metalated MTs exists. Here, the conformational preferences from partial metalation of rabbit metallothionein-2A (MT) by Cd2+, Zn2+, and Ag+ are studied using nanoelectrospray ionization ion mobility mass spectrometry. We also employ collision-induced unfolding to probe differences in the gas-phase stabilities of these partially metalated MTs. Our results show that despite their similar ion mobility profiles, Cd4-MT, Zn4-MT, Ag4-MT, and Ag6-MT differ dramatically in their gas-phase stabilities. Furthermore, the sequential addition of each Cd2+ and Zn2+ ion results in the incremental stabilization of unique unfolding intermediates.
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Affiliation(s)
- Shiyu Dong
- Department of Chemistry , Texas A&M University , College Station , Texas 77843 , United States
| | - Nicole D Wagner
- Department of Chemistry , Texas A&M University , College Station , Texas 77843 , United States
| | - David H Russell
- Department of Chemistry , Texas A&M University , College Station , Texas 77843 , United States
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5
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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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6
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Okada M, Kajimoto S, Nakabayashi T. Embedding a Metal-Binding Motif for Copper Transporter into a Lipid Bilayer by Cu(I) Binding. J Phys Chem B 2018; 122:6364-6370. [DOI: 10.1021/acs.jpcb.8b03179] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Mariko Okada
- Graduate School of Pharmaceutical Sciences, Tohoku University, Aoba-ku, Sendai 980-8578, Japan
| | - Shinji Kajimoto
- Graduate School of Pharmaceutical Sciences, Tohoku University, Aoba-ku, Sendai 980-8578, Japan
| | - Takakazu Nakabayashi
- Graduate School of Pharmaceutical Sciences, Tohoku University, Aoba-ku, Sendai 980-8578, Japan
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7
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Carpenter MC, Shami Shah A, DeSilva S, Gleaton A, Su A, Goundie B, Croteau ML, Stevenson MJ, Wilcox DE, Austin RN. Thermodynamics of Pb(ii) and Zn(ii) binding to MT-3, a neurologically important metallothionein. Metallomics 2017; 8:605-17. [PMID: 26757944 DOI: 10.1039/c5mt00209e] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Isothermal titration calorimetry (ITC) was used to quantify the thermodynamics of Pb(2+) and Zn(2+) binding to metallothionein-3 (MT-3). Pb(2+) binds to zinc-replete Zn7MT-3 displacing each zinc ion with a similar change in free energy (ΔG) and enthalpy (ΔH). EDTA chelation measurements of Zn7MT-3 and Pb7MT-3 reveal that both metal ions are extracted in a tri-phasic process, indicating that they bind to the protein in three populations with different binding thermodynamics. Metal binding is entropically favoured, with an enthalpic penalty that reflects the enthalpic cost of cysteine deprotonation accompanying thiolate ligation of the metal ions. These data indicate that Pb(2+) binding to both apo MT-3 and Zn7MT-3 is thermodynamically favourable, and implicate MT-3 in neuronal lead biochemistry.
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Affiliation(s)
- M C Carpenter
- Department of Chemistry, Dartmouth College, Hanover, NH 03755, USA.
| | - A Shami Shah
- Department of Chemistry, Bates College, Lewiston, ME 04240, USA
| | - S DeSilva
- Department of Chemistry, Bates College, Lewiston, ME 04240, USA
| | - A Gleaton
- Department of Chemistry, Bates College, Lewiston, ME 04240, USA
| | - A Su
- Department of Chemistry, Bates College, Lewiston, ME 04240, USA
| | - B Goundie
- Department of Chemistry, Bates College, Lewiston, ME 04240, USA
| | - M L Croteau
- Department of Chemistry, Dartmouth College, Hanover, NH 03755, USA.
| | - M J Stevenson
- Department of Chemistry, Dartmouth College, Hanover, NH 03755, USA.
| | - D E Wilcox
- Department of Chemistry, Dartmouth College, Hanover, NH 03755, USA.
| | - R N Austin
- Department of Chemistry, Bates College, Lewiston, ME 04240, USA and Department of Chemistry, Barnard College, Columbia University, NY, NY 10027, USA.
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8
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Okada M, Miura T, Nakabayashi T. Comparison of extracellular Cys/Trp motif between Schizosaccharomyces pombe Ctr4 and Ctr5. J Inorg Biochem 2017; 169:97-105. [PMID: 28167404 DOI: 10.1016/j.jinorgbio.2017.01.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2016] [Revised: 01/07/2017] [Accepted: 01/20/2017] [Indexed: 11/19/2022]
Abstract
The reduction and binding of copper ions to the Cys/Trp motif, which is characterized by two cysteines and two tryptophans, in the extracellular N-terminal domain of the copper transporter (Ctr) protein of fungi are investigated using the model peptides of Ctr4 and Ctr5 from Schizosaccharomyces pombe. The Cys/Trp motif of Ctr5 can reduce Cu(II) and ligate Cu(I), which is the same as that of Ctr4 previously reported. Titration of Cu(II) and Cu(I) ions indicates that both the Cys/Trp motifs of Ctr4 and Ctr5 reduce two Cu(II) and bind two Cu(I) per one peptide. However, the coordination structure of the Cu(I)-peptide complex differs between Ctr4 and Ctr5. Cu(I) is bound to the Cys/Trp motif of Ctr5 via cysteine thiolate-Cu(I) bonds and cation-π interaction with tryptophan, as reported for Ctr4, and a histidine residue in the Cys/Trp motif of Ctr5 is suggested to interact with Cu(I) via its Nτ atom. Ctr4 and Ctr5 exhibit a heterotrimeric form within cell membranes and the copper transport mechanism of the Ctr4/Ctr5 heterotrimer is discussed along with quantitative evaluation of the Cu(I)-binding constant of the Cys/Trp motif.
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Affiliation(s)
- Mariko Okada
- Graduate School of Pharmaceutical Sciences, Tohoku University, Aoba-ku, Sendai 980-8578, Japan
| | - Takashi Miura
- Department of Pharmaceutical Sciences, International University of Health and Welfare, 2600-1 Kitakanemaru, Ohtawara, Tochigi 324-8501, Japan
| | - Takakazu Nakabayashi
- Graduate School of Pharmaceutical Sciences, Tohoku University, Aoba-ku, Sendai 980-8578, Japan.
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9
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Scheller JS, Irvine GW, Wong DL, Hartwig A, Stillman MJ. Stepwise copper(i) binding to metallothionein: a mixed cooperative and non-cooperative mechanism for all 20 copper ions. Metallomics 2017; 9:447-462. [DOI: 10.1039/c7mt00041c] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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10
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Wong DL, Stillman MJ. Destructive interactions of dirhodium(ii) tetraacetate with β metallothionein rh1a. Chem Commun (Camb) 2016; 52:5698-701. [DOI: 10.1039/c5cc10319c] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The four bridging acetates of dirhodium(ii) tetraacetate are removed in a stepwise manner by human-metallothionein 1a β-fragment, a reaction captured by electrospray ionization mass spectrometry.
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Affiliation(s)
- Daisy L. Wong
- Department of Chemistry
- The University of Western Ontario
- London
- Canada
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11
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12
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Kumar V, Singh V, Gupta AN, Manar KK, Prasad LB, Drew MGB, Singh N. Influence of ligand environment on the structure and properties of silver(i) dithiocarbamate cluster-based coordination polymers and dimers. NEW J CHEM 2014. [DOI: 10.1039/c4nj00580e] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Four silver dithiocarbamate complexes have been synthesized and characterized by microanalysis.1and2are tetranuclear cluster-based coordination polymers whereas3and4are dinuclear. All complexes are strongly luminescent in solid phase.
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Affiliation(s)
- Vinod Kumar
- Department of Chemistry
- Faculty of Science
- Banaras Hindu University
- Varanasi 221005, India
| | - Vikram Singh
- Department of Chemistry
- Faculty of Science
- Banaras Hindu University
- Varanasi 221005, India
| | - Ajit N. Gupta
- Department of Chemistry
- Faculty of Science
- Banaras Hindu University
- Varanasi 221005, India
| | - Krishna K. Manar
- Department of Chemistry
- Faculty of Science
- Banaras Hindu University
- Varanasi 221005, India
| | - Lal Bahadur Prasad
- Department of Chemistry
- Faculty of Science
- Banaras Hindu University
- Varanasi 221005, India
| | | | - Nanhai Singh
- Department of Chemistry
- Faculty of Science
- Banaras Hindu University
- Varanasi 221005, India
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13
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Sutherland DEK, Stillman MJ. Challenging conventional wisdom: single domain metallothioneins. Metallomics 2014; 6:702-28. [DOI: 10.1039/c3mt00216k] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Metallation studies of human metallothioneins support the role of single metal-binding-domains as commonplace with the typical two-domain-cluster structure as exceptional.
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14
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Jin JC, Chang WG, Liu JQ, Xie CG, Wu J. A new 3D helical silver(I) cluster metal–organic framework with microporous structure and luminescent property. INORG CHEM COMMUN 2013. [DOI: 10.1016/j.inoche.2013.05.009] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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15
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Summers KL, Sutherland DEK, Stillman MJ. Single-domain metallothioneins: evidence of the onset of clustered metal binding domains in Zn-rhMT 1a. Biochemistry 2013; 52:2461-71. [PMID: 23506369 DOI: 10.1021/bi400021b] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Mammalian metallothioneins bind up to seven Zn(2+) ions in two distinct domains: an N-terminal β-domain that binds three Zn(2+) ions and a C-terminal α-domain that binds four Zn(2+) ions. Domain specificity has been invoked in the metalation mechanism with cluster formation and bridging of the 20 Cys residues taking place prior to saturation with seven Zn(2+) ions. We report a novel experiment that examines Zn(2+) metalation by exploiting the expected decrease in K(F) at the onset of clustering using electrospray ionization mass spectrometry (ESI-MS). During the titration with Zn(2+), the ESI-MS data show that several metalated species coexist until the fully saturated proteins are formed. The relative Zn binding affinities of the seven total sites in the α- and β-fragments were determined through direct competition for added Zn(2+). The K(F) values for each Zn(2+) are expected to decrease as a function of the remaining available sites and the onset of clustering. Analysis shows that Zn(2+) binds to β-rhMT with a greater affinity than α-rhMT. The incremental distribution of Zn(2+) between the competing fragments and apo-βα-rhMT (essentially three and four sites competing with seven sites) identifies the exact point at which clustering begins in the full protein. Analysis of the speciation data shows that Zn(5)-MT forms before clustering begins. This means that all 20 Cys residues of apo-βα-rhMT are bound terminally to Zn(2+) as [Zn(Cys)(4)](2-) units before clustering begins; there is no domain preference in this first metalation stage. Preferential binding of Zn(2+) to β- and α-rhMT at the point where βα-rhMT must form clusters is caused by a significant decrease in the affinity of βα-rhMT for further Zn(2+). The single-domain Zn(5)-rhMT, in which there are no exposed cysteine sulfurs, is a key component of the metalation pathway because the lower affinities of the two clustered Zn(2+) ions allow donation to apoenzymes.
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Affiliation(s)
- Kelly L Summers
- Department of Chemistry, The University of Western Ontario, London, Canada N6A 5B7
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16
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Sutherland DEK, Willans MJ, Stillman MJ. Single Domain Metallothioneins: Supermetalation of Human MT 1a. J Am Chem Soc 2012; 134:3290-9. [DOI: 10.1021/ja211767m] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Affiliation(s)
| | - Mathew J. Willans
- Department of Chemistry, University of Western Ontario, London, Ontario N6A 5B7, Canada
| | - Martin J. Stillman
- Department of Chemistry, University of Western Ontario, London, Ontario N6A 5B7, Canada
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17
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Kaluarachchi H, Siebel JF, Kaluarachchi-Duffy S, Krecisz S, Sutherland DEK, Stillman MJ, Zamble DB. Metal selectivity of the Escherichia coli nickel metallochaperone, SlyD. Biochemistry 2011; 50:10666-77. [PMID: 22047179 DOI: 10.1021/bi2014882] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
SlyD is a Ni(II)-binding protein that contributes to nickel homeostasis in Escherichia coli. The C-terminal domain of SlyD contains a rich variety of metal-binding amino acids, suggesting broader metal binding capabilities, and previous work demonstrated that the protein can coordinate several types of first-row transition metals. However, the binding of SlyD to metals other than Ni(II) has not been previously characterized. To improve our understanding of the in vitro metal-binding activity of SlyD and how it correlates with the in vivo function of this protein, the interactions between SlyD and the series of biologically relevant transition metals [Mn(II), Fe(II), Co(II), Cu(I), and Zn(II)] were examined by using a combination of optical spectroscopy and mass spectrometry. Binding of SlyD to Mn(II) or Fe(II) ions was not detected, but the protein coordinates multiple ions of Co(II), Zn(II), and Cu(I) with appreciable affinity (K(D) values in or below the nanomolar range), highlighting the promiscuous nature of this protein. The order of affinities of SlyD for the metals examined is as follows: Mn(II) and Fe(II) < Co(II) < Ni(II) ~ Zn(II) ≪ Cu(I). Although the purified protein is unable to overcome the large thermodynamic preference for Cu(I) and exclude Zn(II) chelation in the presence of Ni(II), in vivo studies reveal a Ni(II)-specific function for the protein. Furthermore, these latter experiments support a specific role for SlyD as a [NiFe]-hydrogenase enzyme maturation factor. The implications of the divergence between the metal selectivity of SlyD in vitro and the specific activity in vivo are discussed.
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Affiliation(s)
- Harini Kaluarachchi
- Department of Chemistry, University of Toronto, Toronto, Ontario, Canada M5S 3H6
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18
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Chao HY, Wu L, Li CL, Lu W, Liu L, Feng XL. Synthesis, Structures, and Photophysics of Polynuclear Silver(I) Thiolate and Silver(I) Thiocarboxylate Complexes with Dppm Ligands. Z Anorg Allg Chem 2011. [DOI: 10.1002/zaac.201100231] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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19
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Abstract
Metallothioneins (MT) are a family of small cysteine rich proteins, which since their discovery in 1957, have been implicated in a range of roles including toxic metal detoxification, protection against oxidative stress, and as a metallochaperone involved in the homeostasis of both zinc and copper. The most well studied member of the family is the mammalian metallothionein, which consists of two domains: a β-domain with 9 cysteine residues, which sequesters 3 Cd(2+) or Zn(2+) or 6 Cu(+) ions, and an α-domain with 11 cysteine residues and, which sequesters 4 Cd(2+) or Zn(2+) or 6 Cu(+) ions. Despite over half a century of research, the exact functions of MT are still unknown. Much of current research aims to elucidate the mechanism of metal binding, as well as to isolate intermediates in metal exchange reactions; reactions necessary to maintain homeostatic equilibrium. These studies further our understanding of the role(s) of this remarkable and ubiquitous protein. Recently, supermetallated forms of the protein, where supermetallation describes metallation in excess of traditional levels, have been reported. These species may potentially be the metal exchange intermediates necessary to maintain homeostatic equilibrium. This review focuses on recent advances in the understanding of the mechanistic properties of metal binding, the implications for the metal induced protein folding reactions proposed for metallothionein metallation, the value of "magic numbers", which we informally define as the commonly determined metal-to-protein stoichiometric ratios and the significance of the new supermetallated states of the protein and the possible interpretation of the structural properties of this new metallation status. Together we provide a commentary on current experimental and theoretical advances and frame our consideration in terms of the possible functions of MT.
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20
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Kaluarachchi H, Sutherland DEK, Young A, Pickering IJ, Stillman MJ, Zamble DB. The Ni(II)-Binding Properties of the Metallochaperone SlyD. J Am Chem Soc 2009; 131:18489-500. [DOI: 10.1021/ja9081765] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Harini Kaluarachchi
- Department of Chemistry, University of Toronto, Toronto, Ontario, Canada M5S 3H6, Department of Chemistry, University of Western Ontario, London, Ontario, Canada N6A 5B7, and Department of Geological Sciences, University of Saskatchewan, Saskatoon, Saskatchewan, Canada S7N 5E2
| | - Duncan E. K. Sutherland
- Department of Chemistry, University of Toronto, Toronto, Ontario, Canada M5S 3H6, Department of Chemistry, University of Western Ontario, London, Ontario, Canada N6A 5B7, and Department of Geological Sciences, University of Saskatchewan, Saskatoon, Saskatchewan, Canada S7N 5E2
| | - Alex Young
- Department of Chemistry, University of Toronto, Toronto, Ontario, Canada M5S 3H6, Department of Chemistry, University of Western Ontario, London, Ontario, Canada N6A 5B7, and Department of Geological Sciences, University of Saskatchewan, Saskatoon, Saskatchewan, Canada S7N 5E2
| | - Ingrid J. Pickering
- Department of Chemistry, University of Toronto, Toronto, Ontario, Canada M5S 3H6, Department of Chemistry, University of Western Ontario, London, Ontario, Canada N6A 5B7, and Department of Geological Sciences, University of Saskatchewan, Saskatoon, Saskatchewan, Canada S7N 5E2
| | - Martin J. Stillman
- Department of Chemistry, University of Toronto, Toronto, Ontario, Canada M5S 3H6, Department of Chemistry, University of Western Ontario, London, Ontario, Canada N6A 5B7, and Department of Geological Sciences, University of Saskatchewan, Saskatoon, Saskatchewan, Canada S7N 5E2
| | - Deborah B. Zamble
- Department of Chemistry, University of Toronto, Toronto, Ontario, Canada M5S 3H6, Department of Chemistry, University of Western Ontario, London, Ontario, Canada N6A 5B7, and Department of Geological Sciences, University of Saskatchewan, Saskatoon, Saskatchewan, Canada S7N 5E2
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Ngu TT, Easton A, Stillman MJ. Kinetic analysis of arsenic-metalation of human metallothionein: significance of the two-domain structure. J Am Chem Soc 2009; 130:17016-28. [PMID: 19053406 DOI: 10.1021/ja8060326] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Metallothionein (MT) is ubiquitous in Nature, underlying MT's importance in the cellular chemistry of metals. Mammalian MT consists of two metal-binding domains while microorganisms like cyanobacteria consist of a single metal-binding domain MT. The evolution of a two-domain protein has been speculated on for some time; however, no conclusive evidence explaining the evolutionary necessity of the two-domain structure has been reported. The results presented in this report provide the complete kinetic analysis and subsequent mechanism of the As(3+)-metalation of the two-domain beta alpha hMT and the isolated single domain fragments using time- and temperature-resolved electrospray ionization mass spectrometry. The mechanism for beta alpha hMT binding As(3+) is noncooperative and involves six sequential bimolecular reactions in which the alpha domain binds As(3+) first followed by the beta domain. At room temperature (295 K) and pH 3.5, the sequential individual rate constants, k(n) (n = 1-6) for the As(3+)-metalation of beta alpha hMT starting at k(1beta alpha) are 25, 24, 19, 14, 8.7, and 3.7 M(-1)s(-1). The six rate constants follow an almost linear trend directly dependent on the number of unoccupied sites for the incoming metal. Analysis of the temperature-dependent kinetic electrospray ionization mass spectra data allowed determination of the activation energy for the formation of As(1)-H(17)-beta alpha hMT (14 kJ mol(-1)) and As(2-6)-beta alpha hMT (22 kJ mol(-1)). On the basis of the increased rate of metalation for the two-domain protein when compared with the isolated single-domain, we propose that there is an evolutionary advantage for the two-domain MT structures in higher organism, which allows MT to bind metals faster and, therefore, be a more efficient metal scavenger.
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Affiliation(s)
- Thanh T Ngu
- Department of Chemistry, The University of Western Ontario, London, Ontario, Canada, N6A 5B7
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Jin JC, Wang YY, Zhang WH, Lermontov AS, Lermontova EK, Shi QZ. New types of di-, tetra-, hexa- and octanuclear Ag(i) complexes containing 1,3-adamantanedicarboxylic acid. Dalton Trans 2009:10181-91. [PMID: 19921052 DOI: 10.1039/b909309e] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Affiliation(s)
- Jun-Cheng Jin
- Key Laboratory of Synthetic and Natural Functional Molecule Chemistry of the Ministry of Education, Shaanxi Key Laboratory of Physico-Inorganic Chemistry, College of Chemistry and Materials Science, Northwest University, Xi'an, 710069, PR China
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Rana U, Kothinti R, Meeusen J, Tabatabai NM, Krezoski S, Petering DH. Zinc binding ligands and cellular zinc trafficking: apo-metallothionein, glutathione, TPEN, proteomic zinc, and Zn-Sp1. J Inorg Biochem 2008; 102:489-99. [PMID: 18171589 PMCID: PMC2323593 DOI: 10.1016/j.jinorgbio.2007.10.030] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2007] [Revised: 10/16/2007] [Accepted: 10/29/2007] [Indexed: 11/26/2022]
Abstract
Many cell types contain metal-ion unsaturated metallothionein (MT). Considering the Zn(2+) binding affinity of metallothionein, the existence of this species in the intracellular environment constitutes a substantial "thermodynamic sink". Indeed, the mM concentration of glutathione may be thought of in the same way. In order to understand how apo-MT and the rest of the Zn-proteome manage to co-exist, experiments examined the in vitro reactivity of Zn-proteome with apo-MT, glutathione (GSH), and a series of common Zn(2+) chelating agents including N,N,N',N'-(2-pyridylethyl)ethylenediammine (TPEN), EDTA, and [(2,2'-oxyproplylene-dinitrilo]tetraacetic acid (EGTA). Less than 10% of Zn-proteome from U87mg cells reacted with apo-MT or GSH. In contrast, each of the synthetic chelators was 2-3 times more reactive. TPEN, a cell permeant reagent, also reacted rapidly with both Zn-proteome and Zn-MT in LLC-PK(1) cells. Taking a specific zinc finger protein for further study, apo-MT, GSH, and TPEN inhibited the binding of Zn(3)-Sp1 with its cognate DNA site (GC-1) in the sodium-glucose co-transporter promoter of mouse kidney. In contrast, preformation of Zn(3)-Sp1-(GC-1) prevented reaction with apo-MT and GSH; TPEN remained active but at a higher concentration. Whereas, Zn(3)-Sp1 is active in cells containing apo-MT and GSH, exposure of LLC-PK(1) cells to TPEN for 24h largely inactivated its DNA binding activity. The results help to rationalize the steady state presence of cellular apo-MT in the midst of the many, diverse members of the Zn-proteome. They also show that TPEN is a robust intracellular chelator of proteomic Zn(2+).
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Affiliation(s)
- Ujala Rana
- Department of Chemistry and Biochemistry, University of Wisconsin-Milwaukee, Milwaukee, WI 53201, United States
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