1
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Singh AK, Pomorski A, Wu S, Peris-Díaz MD, Czepczyńska-Krężel H, Krężel A. The connection of α- and β-domains in mammalian metallothionein-2 differentiates Zn(II) binding affinities, affects folding, and determines zinc buffering properties. Metallomics 2023; 15:mfad029. [PMID: 37147085 PMCID: PMC10243857 DOI: 10.1093/mtomcs/mfad029] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2023] [Accepted: 05/03/2023] [Indexed: 05/07/2023]
Abstract
Mammalian metallothioneins (MTs) are small Cys-rich proteins involved in Zn(II) and Cu(I) homeostasis. They bind seven Zn(II) ions in two distinct β- and α-domains, forming Zn3Cys9 and Zn4Cys11 clusters, respectively. After six decades of research, their role in cellular buffering of Zn(II) ions has begun to be understood recently. This is because of different affinities of bound ions and the proteins' coexistence in variously Zn(II)-loaded Zn4-7MT species in the cell. To date, it has remained unclear how these mechanisms of action occur and how the affinities are differentiated despite the Zn(S-Cys)4 coordination environment being the same. Here, we dissect the molecular basis of these phenomena by using several MT2 mutants, hybrid protein, and isolated domains. Through a combination of spectroscopic and stability studies, thiol(ate) reactivity, and steered molecular dynamics, we demonstrate that both protein folding and thermodynamics of Zn(II) ion (un)binding significantly differ between isolated domains and the whole protein. Close proximity reduces the degrees of freedom of separated domains, making them less dynamic. It is caused by the formation of intra- and interdomain electrostatic interactions. The energetic consequence of domains connection has a critical impact on the role of MTs in the cellular environment, where they function not only as a zinc sponge but also as a zinc buffering system keeping free Zn(II) in the right concentrations. Any change of that subtle system affects the folding mechanism, zinc site stabilities, and cellular zinc buffer components.
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Affiliation(s)
- Avinash Kumar Singh
- Department of Chemical Biology, Faculty of Biotechnology, University of Wrocław, Joliot-Curie 14a, 50-383 Wrocław, Poland
| | - Adam Pomorski
- Department of Chemical Biology, Faculty of Biotechnology, University of Wrocław, Joliot-Curie 14a, 50-383 Wrocław, Poland
| | - Sylwia Wu
- Department of Chemical Biology, Faculty of Biotechnology, University of Wrocław, Joliot-Curie 14a, 50-383 Wrocław, Poland
| | - Manuel D Peris-Díaz
- Department of Chemical Biology, Faculty of Biotechnology, University of Wrocław, Joliot-Curie 14a, 50-383 Wrocław, Poland
| | - Hanna Czepczyńska-Krężel
- Department of Chemical Biology, Faculty of Biotechnology, University of Wrocław, Joliot-Curie 14a, 50-383 Wrocław, Poland
| | - Artur Krężel
- Department of Chemical Biology, Faculty of Biotechnology, University of Wrocław, Joliot-Curie 14a, 50-383 Wrocław, Poland
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2
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Mahim A, Petering DH. Zinc trafficking to apo-Zn-proteins 2. Cellular interplay of proteome, metallothionein, and glutathione. Metallomics 2022; 14:mfac081. [PMID: 36214409 PMCID: PMC9646480 DOI: 10.1093/mtomcs/mfac081] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2022] [Accepted: 10/07/2022] [Indexed: 11/12/2022]
Abstract
A recent study investigated the impact of glutathione (GSH) on the transfer of zinc (Zn) from proteome to apo-carbonic anhydrase. Here, we probed the requirement of glutathione for zinc trafficking in LLC-PK1 pig kidney epithelial cells. Depletion of GSH by at least 95% left cells viable and able to divide and synthesize Zn-proteins at the control rate over a 48-h period. Loss of GSH stimulated the accumulation of 2.5x the normal concentration of cellular Zn. According to gel filtration chromatography, differential centrifugal filtration, and spectrofluorimetry with TSQ, the extra Zn was distributed between the proteome and metallothionein (MT). To test the functionality of proteome and/or MT as sources of Zn for the constitution of Zn-proteins, GSH-deficient cells were incubated with CaEDTA to isolate them from their normal source of nutrient Zn. Control cells plus CaEDTA stopped dividing; GSH-depleted cells plus CaEDTA continued to divide at ∼40% the rate of GSH deficient cells. Evidently, proteome and/or MT served as a functional source of Zn for generating Zn-proteins. In vitro insertion of Zn bound to proteome into apo-carbonic anhydrase occurred faster at larger concentrations of Zn bound to proteome. These results support the hypothesis that enhanced transport of Zn into cells drives the conversion of apo-Zn-proteins to Zn-proteins by mass action. Similar results were also obtained with human Jurkat T lymphocyte epithelial cells. This study reveals a powerful new model for studying the chemistry of Zn trafficking, including transport processes, involvement of intermediate binding sites, and constitution of Zn-proteins.
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Affiliation(s)
- Afsana Mahim
- PPD, Biopharmaceutical Department, Middleton WI, USA
| | - David H Petering
- Department of Chemistry and Biochemistry, University of Wisconsin-Milwaukee, 3210 N. Cramer, Milwaukee, Wisconsin 53201, USA
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3
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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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4
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Mahim A, Karim M, Petering DH. Zinc trafficking 1. Probing the roles of proteome, metallothionein, and glutathione. Metallomics 2021; 13:6362609. [PMID: 34472617 DOI: 10.1093/mtomcs/mfab055] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2021] [Accepted: 08/18/2021] [Indexed: 11/13/2022]
Abstract
The cellular trafficking pathways that conduct zinc to its sites of binding in functional proteins remain largely unspecified. In this study, the hypothesis was investigated that nonspecific proteomic binding sites serve as intermediates in zinc trafficking. Proteome from pig kidney LLC-PK1 cells contains a large concentration of such sites, displaying an average conditional stability constant of 1010-11, that are dependent on sulfhydryl ligands to achieve high-affinity binding of zinc. As a result, the proteome competes effectively with induced metallothionein for Zn2+ upon exposure of cells to extracellular Zn2+ or during in vitro direct competition. The reaction of added Zn2+ bound to proteome with apo-carbonic anhydrase was examined as a potential model for intracellular zinc trafficking. The extent of this reaction was inversely dependent upon proteome concentration and under cellular conditions thought to be negligible. The rate of reaction was strictly first order in both Zn2+ and apo-carbonic anhydrase, and also considered to be insignificant in cells. Adding the low molecular weight fraction of cell supernatant to the proteome markedly enhanced the speed of this reaction, a phenomenon dependent on the presence of glutathione (GSH). In agreement, inclusion of GSH accelerated the reaction in a concentration-dependent manner. The implications of abundant high-affinity binding sites for Zn2+ within the proteome are considered in relation to their interaction with GSH in the efficient delivery of Zn2+ to functional binding sites and in the operation of fluorescent zinc sensors as a tool to observe zinc trafficking.
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Affiliation(s)
- Afsana Mahim
- Department of Chemistry and Biochemistry, University of Wisconsin-Milwaukee, Milwaukee, WI, USA
| | - Mohammad Karim
- Department of Cell and Gene Therapy, PPD, Middleton, WI, USA
| | - David H Petering
- Department of Chemistry and Biochemistry, University of Wisconsin-Milwaukee, Milwaukee, WI, USA
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5
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Marszałek I, Goch W, Bal W. Ternary Zn(II) Complexes of FluoZin-3 and the Low Molecular Weight Component of the Exchangeable Cellular Zinc Pool. Inorg Chem 2018; 57:9826-9838. [PMID: 30088924 DOI: 10.1021/acs.inorgchem.8b00489] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Knowledge of the nature of exchangeable (labile) intracellular Zn(II) is increasingly important for biomedical research. The detection and quantitative determination of Zn(II) ions is usually performed by using Zn(II)-specific fluorescent sensors, among which 2-[2-[2-[2-[bis(carboxylatomethyl)amino]-5-methoxyphenoxy]ethoxy]-4-(2,7-difluoro-3-oxido-6-oxo-4a,9a-dihydroxanthen-9-yl)anilino]acetate (FluoZin-3) has been used most widely. Selectivity of this sensor for Zn(II) over other divalent cations was demonstrated, but possible interference in its performance by other compounds has not been investigated. Many potential low molecular weight ligands for Zn(II) ions (LMWLs) are abundant in the cell. In this study we demonstrate that FluoZin-3 is susceptible to competition for Zn(II) from LMWLs and also forms strong ternary complexes with some of them. We determined the set of conditional stability constants C Ktern for ternary Zn(FluoZin-3)(LMWL) complexes using fluorescence titrations and applied it to model the response of exchangeable zinc to FluoZin-3. We found that competition and formation of ternary complexes with LMWLs together strongly affect (net reduce) the Zn(FluoZin-3) fluorescence. This effect may cause a significant underestimation of exchangeable Zn(II). We also demonstrated a strong pH dependence of this effect. Reduced glutathione (GSH) emerged as the most important Zn(II) partner among the LMWLs, characterized with Ktern = 2.8 ± 0.2 × 106 M-1. Our experiments and calculations suggest that Zn(LMWL) complexes contribute to the exchangeable cellular zinc pool.
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Affiliation(s)
- Ilona Marszałek
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences , Pawińskiego 5a , 02-106 Warsaw , Poland
| | - Wojciech Goch
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences , Pawińskiego 5a , 02-106 Warsaw , Poland.,Faculty of Pharmacy , Medical University of Warsaw , Banacha 1 , 02-091 Warsaw , Poland
| | - Wojciech Bal
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences , Pawińskiego 5a , 02-106 Warsaw , Poland
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6
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Drozd A, Wojewska D, Peris-Díaz MD, Jakimowicz P, Krężel A. Crosstalk of the structural and zinc buffering properties of mammalian metallothionein-2. Metallomics 2018; 10:595-613. [DOI: 10.1039/c7mt00332c] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Structural insights into partially Zn(ii)-depleted MT2 species and their zinc buffering properties are presented and discussed.
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Affiliation(s)
- Agnieszka Drozd
- Department of Chemical Biology
- Faculty of Biotechnology
- University of Wrocław
- 50-383 Wrocław
- Poland
| | - Dominika Wojewska
- Department of Chemical Biology
- Faculty of Biotechnology
- University of Wrocław
- 50-383 Wrocław
- Poland
| | - Manuel David Peris-Díaz
- Department of Chemical Biology
- Faculty of Biotechnology
- University of Wrocław
- 50-383 Wrocław
- Poland
| | - Piotr Jakimowicz
- Department of Protein Biotechnology
- Faculty of Biotechnology
- University of Wrocław
- 50-383 Wrocław
- Poland
| | - Artur Krężel
- Department of Chemical Biology
- Faculty of Biotechnology
- University of Wrocław
- 50-383 Wrocław
- Poland
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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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Abstract
The cellular constitution of Zn-proteins and Zn-dependent signaling depend on the capacity of Zn2+ to find specific binding sites in the face of a plethora of other high affinity ligands. The most prominent of these is metallothionein (MT). It serves as a storage site for Zn2+ under various conditions, and has chemical properties that support a dynamic role for MT in zinc trafficking. Consistent with these characteristics, changing the availability of zinc for cells and tissues causes rapid alteration of zinc bound to MT. Nevertheless, zinc trafficking occurs in metallothionein-null animals and cells, hypothetically making use of proteomic binding sites to mediate the intracellular movements of zinc. Like metallothionein, the proteome contains a large concentration of proteins that strongly coordinate zinc. In this environment, free Zn2+ may be of little significance. Instead, this review sets forth the basis for the hypothesis that components of the proteome and MT jointly provide the platform for zinc trafficking.
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Affiliation(s)
- David H Petering
- Department of Chemistry and Biochemistry, University of Wisconsin-Milwaukee, Milwaukee, WI 53217, USA.
| | - Afsana Mahim
- Department of Chemistry and Biochemistry, University of Wisconsin-Milwaukee, Milwaukee, WI 53217, USA.
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9
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The Functions of Metamorphic Metallothioneins in Zinc and Copper Metabolism. Int J Mol Sci 2017; 18:ijms18061237. [PMID: 28598392 PMCID: PMC5486060 DOI: 10.3390/ijms18061237] [Citation(s) in RCA: 149] [Impact Index Per Article: 21.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2017] [Revised: 06/02/2017] [Accepted: 06/03/2017] [Indexed: 12/15/2022] Open
Abstract
Recent discoveries in zinc biology provide a new platform for discussing the primary physiological functions of mammalian metallothioneins (MTs) and their exquisite zinc-dependent regulation. It is now understood that the control of cellular zinc homeostasis includes buffering of Zn2+ ions at picomolar concentrations, extensive subcellular re-distribution of Zn2+, the loading of exocytotic vesicles with zinc species, and the control of Zn2+ ion signalling. In parallel, characteristic features of human MTs became known: their graded affinities for Zn2+ and the redox activity of their thiolate coordination environments. Unlike the single species that structural models of mammalian MTs describe with a set of seven divalent or eight to twelve monovalent metal ions, MTs are metamorphic. In vivo, they exist as many species differing in redox state and load with different metal ions. The functions of mammalian MTs should no longer be considered elusive or enigmatic because it is now evident that the reactivity and coordination dynamics of MTs with Zn2+ and Cu+ match the biological requirements for controlling—binding and delivering—these cellular metal ions, thus completing a 60-year search for their functions. MT represents a unique biological principle for buffering the most competitive essential metal ions Zn2+ and Cu+. How this knowledge translates to the function of other families of MTs awaits further insights into the specifics of how their properties relate to zinc and copper metabolism in other organisms.
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10
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Petering DH. Reactions of the Zn Proteome with Cd2+ and Other Xenobiotics: Trafficking and Toxicity. Chem Res Toxicol 2016; 30:189-202. [DOI: 10.1021/acs.chemrestox.6b00328] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Affiliation(s)
- David H. Petering
- Department of Chemistry and
Biochemistry, University of Wisconsin−Milwaukee, Milwaukee, Wisconsin 53201, United States
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11
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Putting the pieces into place: Properties of intact zinc metallothionein 1A determined from interaction of its isolated domains with carbonic anhydrase. Biochem J 2015; 471:347-56. [DOI: 10.1042/bj20150676] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2015] [Accepted: 08/20/2015] [Indexed: 12/25/2022]
Abstract
Competitive metallation reactions between the isolated domain fragments and apo-carbonic anhydrase [CA; metal-free CA (apo-CA)] provided the binding affinities for each of the eight sites and showed that CA competed more efficiently for added zinc with the β-domain fragment. The combined effects of the number of sites, chain length and cysteine accessibility modulate the zinc-binding properties of mammalian metallothionein (MT).
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12
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Bossak K, Goch W, Piątek K, Frączyk T, Poznański J, Bonna A, Keil C, Hartwig A, Bal W. Unusual Zn(II) Affinities of Zinc Fingers of Poly(ADP-ribose) Polymerase 1 (PARP-1) Nuclear Protein. Chem Res Toxicol 2015; 28:191-201. [DOI: 10.1021/tx500320f] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Affiliation(s)
- Karolina Bossak
- Institute of Biochemistry
and Biophysics, Polish Academy of Sciences, Pawińskiego 5a, 02-106 Warsaw, Poland
| | - Wojciech Goch
- Institute of Biochemistry
and Biophysics, Polish Academy of Sciences, Pawińskiego 5a, 02-106 Warsaw, Poland
| | - Katarzyna Piątek
- Institute of Biochemistry
and Biophysics, Polish Academy of Sciences, Pawińskiego 5a, 02-106 Warsaw, Poland
| | - Tomasz Frączyk
- Institute of Biochemistry
and Biophysics, Polish Academy of Sciences, Pawińskiego 5a, 02-106 Warsaw, Poland
| | - Jarosław Poznański
- Institute of Biochemistry
and Biophysics, Polish Academy of Sciences, Pawińskiego 5a, 02-106 Warsaw, Poland
| | - Arkadiusz Bonna
- Institute of Biochemistry
and Biophysics, Polish Academy of Sciences, Pawińskiego 5a, 02-106 Warsaw, Poland
| | - Claudia Keil
- Institute of Applied Biosciences, Department of Food
Chemistry and Toxicology, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany
| | - Andrea Hartwig
- Institute of Applied Biosciences, Department of Food
Chemistry and Toxicology, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany
| | - Wojciech Bal
- Institute of Biochemistry
and Biophysics, Polish Academy of Sciences, Pawińskiego 5a, 02-106 Warsaw, Poland
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13
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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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14
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Pinter TBJ, Stillman MJ. The zinc balance: competitive zinc metalation of carbonic anhydrase and metallothionein 1A. Biochemistry 2014; 53:6276-85. [PMID: 25208334 DOI: 10.1021/bi5008673] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The small, cysteine-rich metallothionein family of proteins is currently considered to play a critical role in the provision of metals to metalloenzymes. However, there is limited information available on the mechanisms of these fundamentally important interactions. We report on the competitive zinc metalation of apocarbonic anhydrase in the presence of apometallothionein 1A using electrospray-ionization mass spectrometry. These experiments revealed the relative affinities of zinc to all species in solution. The carbonic anhydrase is shown to compete efficiently only against Zn5-7MT. The calculated equilibrium zinc binding constants of each of the 7 zinc metallothionein 1A species ranged from a high of (log(KF)) 12.5 to a low of 11.8. The 8 equilibrium constants connecting the 10 active species in competition for the zinc were modeled by fitting the KF values of the 8 competitive bimolecular reactions to the ESI-mass spectral data. These modeled K values are shown to be experimentally connected to the metalation efficiency of the carbonic anhydrase. The series of 7 metallothionein binding affinities for zinc highlight the buffering role of zinc metallothioneins that permit simultaneously zinc storage and zinc sensing. Finally, the significance of the multiple zinc binding affinities of zinc metallothionein is discussed in relation to zinc homeostasis.
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Affiliation(s)
- Tyler B J Pinter
- Department of Chemistry and ‡Department of Biology, The University of Western Ontario , London, Ontario, Canada N6A 5B7
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15
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Namdarghanbari MA, Bertling J, Krezoski S, Petering DH. Toxic metal proteomics: reaction of the mammalian zinc proteome with Cd²⁺. J Inorg Biochem 2014; 136:115-21. [PMID: 24529759 DOI: 10.1016/j.jinorgbio.2014.01.014] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2013] [Revised: 01/15/2014] [Accepted: 01/16/2014] [Indexed: 10/25/2022]
Abstract
The hypothesis was tested that Cd(2+) undergoes measureable reaction with the Zn-proteome through metal ion exchange chemistry. The Zn-proteome of pig kidney LLC-PK1 cells is relatively inert to reaction with competing ligands, including Zinquin acid, EDTA, and apo-metallothionein. Upon reaction of Cd(2+) with the Zn-proteome, Cd(2+) associates with the proteome and near stoichiometric amounts of Zn(2+) become reactive with these chelating agents. The results strongly support the hypothesis that Cd(2+) displaces Zn(2+) from native proteomic binding sites resulting in the formation of a Cd-proteome. Mobilized Zn(2+) becomes adventitiously bound to proteome and available for reaction with added metal binding ligands. Cd-proteome and Zn-metallothionein readily exchange metal ions, raising the possibility that this reaction restores functionality to Cd-proteins. In a parallel experiment, cells were exposed to Cd(2+) and pyrithione briefly to generate substantial proteome-bound Cd(2+). Upon transition to a Cd(2+) free medium, the cells generated new metallothionein protein over time that bound most of the proteomic Cd(2+) as well as additional Zn(2+).
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Affiliation(s)
| | - Joseph Bertling
- Department of Chemistry and Biochemistry, University of Wisconsin-Milwaukee, Milwaukee, WI 53201, USA
| | - Susan Krezoski
- Department of Chemistry and Biochemistry, University of Wisconsin-Milwaukee, Milwaukee, WI 53201, USA
| | - David H Petering
- Department of Chemistry and Biochemistry, University of Wisconsin-Milwaukee, Milwaukee, WI 53201, USA.
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16
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Dong Z, Le X, Zhou P, Dong C, Ma J. Sequential recognition of zinc ion and hydrogen sulfide by a new quinoline derivative with logic gate behavior. RSC Adv 2014. [DOI: 10.1039/c3ra47755j] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
A Schiff base-type fluorescent chemosensor L has been synthesized for Zn2+ detection, and the consequent product of L and Zn2+, L–2Zn, is an excellent indicator for H2S for displacement of Zn2+ from the complex L–2Zn.
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Affiliation(s)
- Zhengping Dong
- College of Chemistry and Chemical Engineering
- Gansu Provincial Engineering Laboratory for Chemical Catalysis
- Lanzhou University
- Lanzhou 730000, PR China
| | - Xuanduong Le
- College of Chemistry and Chemical Engineering
- Gansu Provincial Engineering Laboratory for Chemical Catalysis
- Lanzhou University
- Lanzhou 730000, PR China
| | - Panpan Zhou
- College of Chemistry and Chemical Engineering
- Gansu Provincial Engineering Laboratory for Chemical Catalysis
- Lanzhou University
- Lanzhou 730000, PR China
| | - Chunxu Dong
- College of Chemistry and Chemical Engineering
- Gansu Provincial Engineering Laboratory for Chemical Catalysis
- Lanzhou University
- Lanzhou 730000, PR China
| | - Jiantai Ma
- College of Chemistry and Chemical Engineering
- Gansu Provincial Engineering Laboratory for Chemical Catalysis
- Lanzhou University
- Lanzhou 730000, PR China
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17
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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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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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A synthetic cadmium metallothionein gene (PMCd1syn) of Paramecium species: expression, purification and characteristics of metallothionein protein. Mol Biol Rep 2012; 40:983-97. [DOI: 10.1007/s11033-012-2140-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2012] [Accepted: 10/03/2012] [Indexed: 10/27/2022]
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Nowakowski AB, Petering DH. Reactions of the fluorescent sensor, Zinquin, with the zinc-proteome: adduct formation and ligand substitution. Inorg Chem 2011; 50:10124-33. [PMID: 21905645 DOI: 10.1021/ic201076w] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Zinquin (ZQ) is a commonly used sensor for cellular Zn(2+) status. It has been assumed that it measures accessible Zn(2+) concentrations in the nanomolar range. Instead, this report shows a consistent pattern across seven mammalian cell and tissue types that ZQ reacts with micromolar concentrations of Zn(2+) bound as Zn-proteins. The predominant class of products were ZQ-Zn-protein adducts that were characterized in vivo and in vitro by a fluorescence emission spectrum centered at about 470 nm, by their migration over Sephadex G-75 as protein not low molecular weight species, by the exclusion of reaction with lipid vesicles, and by their large aggregate concentration. In addition, variable, minor formation of Zn(ZQ)(2) with a fluorescence band at about 490 nm was observed in vivo in each case. Because incubation of isolated Zn-proteome with ZQ also generated similar amounts of Zn(ZQ)(2), it was concluded that this species had formed through direct ligand substitution in which ZQ had successfully competed for protein-bound Zn(2+). Parallel studies with the model Zn-proteins, alcohol dehydrogenase (ADH), and alkaline phosphatase (AP) revealed a similar picture of reactivity: ZQ(ACID) (Zinquin acid, (2-methyl-8-p-toluenesulfonamido-6-quinolyloxy)acetate)) able to bind to one Zn(2+) and extract the other in Zn(2)-ADH, whereas it removed one Zn(2+) from Zn(2)-AP and did not bind to the other. Zinquin ethyl ester (ethyl(2-methyl-8-p-toluenesulfonamido-6-quinolyloxy)acetate); ZQ(EE)) bound to both proteins without sequestering Zn(2+) from either one. In contrast to a closely related sensor, 6-methoxy-8-p-toluenesulfonamido-quinoline (TSQ), neither ZQ(ACID) nor ZQ(EE) associated with Zn-carbonic anhydrase. A survey of reactivity of these sensors with partially fractionated Zn-proteome confirmed that ZQ and TSQ bind to distinct, overlapping subsets of the Zn-proteome.
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Affiliation(s)
- Andrew B Nowakowski
- Department of Chemistry and Biochemistry, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin 53201, USA
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Mammalian metallothionein in toxicology, cancer, and cancer chemotherapy. J Biol Inorg Chem 2011; 16:1087-101. [PMID: 21822976 DOI: 10.1007/s00775-011-0823-6] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2011] [Accepted: 07/20/2011] [Indexed: 12/16/2022]
Abstract
The present paper centers on mammalian metallothionein 1 and 2 in relationship to cell and tissue injury beginning with its reaction with Cd²⁺ and then considering its role in the toxicology and chemotherapy of both metals and non-metal electrophiles and oxidants. Intertwined is a consideration of MTs role in tumor cell Zn²⁺ metabolism. The paper updates and expands on our recent review by Petering et al. (Met Ions Life Sci 5:353-398, 2009).
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Meeusen JW, Tomasiewicz H, Nowakowski A, Petering DH. TSQ (6-methoxy-8-p-toluenesulfonamido-quinoline), a common fluorescent sensor for cellular zinc, images zinc proteins. Inorg Chem 2011; 50:7563-73. [PMID: 21774459 DOI: 10.1021/ic200478q] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Zn(2+) is a necessary cofactor for thousands of mammalian proteins. Research has suggested that transient fluxes of cellular Zn(2+) are also involved in processes such as apoptosis. Observations of Zn(2+) trafficking have been collected using Zn(2+) responsive fluorescent dyes. A commonly used Zn(2+) fluorophore is 6-methoxy-8-p-toluenesulfonamido-quinoline (TSQ). The chemical species responsible for TSQ's observed fluorescence in resting or activated cells have not been characterized. Parallel fluorescence microscopy and spectrofluorometry of LLC-PK(1) cells incubated with TSQ demonstrated punctate staining that concentrated around the nucleus and was characterized by an emission maximum near 470 nm. Addition of cell permeable Zn-pyrithione resulted in greatly increased, diffuse fluorescence that shifted the emission peak to 490 nm, indicative of the formation of Zn(TSQ)(2). TPEN (N,N,N'N'-tetrakis(-)[2-pyridylmethyl]-ethylenediamine), a cell permeant Zn(2+) chelator, largely quenched TSQ fluorescence returning the residual fluorescence to the 470 nm emission maximum. Gel filtration chromatography of cell supernatant from LLC-PK(1) cells treated with TSQ revealed that TSQ fluorescence (470 nm emission) eluted with the proteome fractions. Similarly, addition of TSQ to proteome prior to chromatography resulted in 470 nm fluorescence emission that was not observed in smaller molecular weight fractions. It is hypothesized that Zn-TSQ fluorescence, blue-shifted from the 490 nm emission maximum of Zn(TSQ)(2), results from ternary complex, TSQ-Zn-protein formation. As an example, Zn-carbonic anhydrase formed a ternary adduct with TSQ characterized by a fluorescence emission maximum of 470 nm and a dissociation constant of 1.55 × 10(-7) M. Quantification of TSQ-Zn-proteome fluorescence indicated that approximately 8% of cellular Zn(2+) was imaged by TSQ. These results were generalized to other cell types and model Zn-proteins.
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Affiliation(s)
- Jeffrey W Meeusen
- Department of Chemistry and Biochemistry, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin 53201, USA
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Bacterial metallothioneins: past, present, and questions for the future. J Biol Inorg Chem 2011; 16:1011-24. [DOI: 10.1007/s00775-011-0790-y] [Citation(s) in RCA: 93] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2011] [Accepted: 05/04/2011] [Indexed: 10/18/2022]
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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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