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Peris-Díaz MD, Richtera L, Zitka O, Krężel A, Adam V. A chemometric-assisted voltammetric analysis of free and Zn(II)-loaded metallothionein-3 states. Bioelectrochemistry 2020; 134:107501. [PMID: 32229323 DOI: 10.1016/j.bioelechem.2020.107501] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2020] [Revised: 03/09/2020] [Accepted: 03/09/2020] [Indexed: 12/17/2022]
Abstract
We focused on the application of mass spectrometry and electrochemical methods combined with a chemometric analysis for the characterization of partially metallothionein-3 species. The results showed decreased Cat1 and Cat2 signals for the Zn(II)-loaded MT3 species with respect to the metal-free protein, which might be explained by the arrangement of tetrahedral metal-thiolate coordination environments and the formation of metal clusters. Moreover, there was a decrease in the Cat1 and Cat2 signals, and a plateau was reached with 4-5 Zn(II) ions that corresponded to the formation of the C-terminal α-domain. Regarding the Zn7-xMT3 complexes, we observed three different electrochemical behaviours for the Zn1-2MT3, Zn3-6MT3 and Zn7MT3 species. The difference for Zn1-2MT3 might be explained by the formation of independent ZnS4 cores in this stage that differ with respect to the formation of ZnxCysy clusters with an increased Zn(II) loading. The binding of the third Zn(II) ion to MT3 resulted in high sample heterogeneity due the co-existence of Zn3-6MT3. Finally, the Zn7MT3 protein showed a third type of behaviour. The fact that there were no free Cys residues might explain this phenomenon. Thus, this research identifies the major proteins responsible for zinc buffering in the cell.
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Affiliation(s)
- Manuel David Peris-Díaz
- Department of Chemical Biology, Faculty of Biotechnology, University of Wrocław, F. Joliot-Curie 14a, 50-383 Wrocław, Poland
| | - Lukas Richtera
- Department of Chemistry and Biochemistry, Mendel University in Brno, Zemedelska 1, 613 00 Brno, Czech Republic; Central European Institute of Technology, Brno University of Technology, Purkynova 123, 612 00 Brno, Czech Republic
| | - Ondrej Zitka
- Department of Chemistry and Biochemistry, Mendel University in Brno, Zemedelska 1, 613 00 Brno, Czech Republic; Central European Institute of Technology, Brno University of Technology, Purkynova 123, 612 00 Brno, Czech Republic
| | - Artur Krężel
- Department of Chemical Biology, Faculty of Biotechnology, University of Wrocław, F. Joliot-Curie 14a, 50-383 Wrocław, Poland
| | - Vojtech Adam
- Department of Chemistry and Biochemistry, Mendel University in Brno, Zemedelska 1, 613 00 Brno, Czech Republic; Central European Institute of Technology, Brno University of Technology, Purkynova 123, 612 00 Brno, Czech Republic.
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2
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Nejdl L, Moravanska A, Smerkova K, Mravec F, Krizkova S, Pomorski A, Krężel A, Macka M, Adam V, Vaculovicova M. Short-sweep capillary electrophoresis with a selective zinc fluorescence imaging reagent FluoZin-3 for determination of free and metalothionein-2a-bound Zn2+ ions. Anal Chim Acta 2018. [DOI: 10.1016/j.aca.2018.02.008] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
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3
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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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4
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Calvo J, Jung H, Meloni G. Copper metallothioneins. IUBMB Life 2017; 69:236-245. [PMID: 28296007 DOI: 10.1002/iub.1618] [Citation(s) in RCA: 88] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2017] [Accepted: 02/16/2017] [Indexed: 11/10/2022]
Abstract
Metallothioneins (MTs) are a class of low molecular weight and cysteine-rich metal binding proteins present in all the branches of the tree of life. MTs efficiently bind with high affinity several essential and toxic divalent and monovalent transition metals by forming characteristic polynuclear metal-thiolate clusters within their structure. MTs fulfil multiple biological functions related to their metal binding properties, with essential roles in both Zn(II) and Cu(I) homeostasis as well as metal detoxification. Depending on the organism considered, the primary sequence, and the specific physiological and metabolic status, Cu(I)-bound MT isoforms have been isolated, and their chemistry and biology characterized. Besides the recognized role in the biochemistry of divalent metals, it is becoming evident that unique biological functions in selectively controlling copper levels, its reactivity as well as copper-mediated biochemical processes have evolved in some members of the MT superfamily. Selected examples are reviewed to highlight the peculiar chemical properties and biological functions of copper MTs. © 2016 IUBMB Life, 69(4):236-245, 2017.
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Affiliation(s)
- Jenifer Calvo
- Department of Chemistry and Biochemistry, University of Texas at Dallas, Richardson, TX, USA
| | - Hunmin Jung
- Department of Chemistry and Biochemistry, University of Texas at Dallas, Richardson, TX, USA
| | - Gabriele Meloni
- Department of Chemistry and Biochemistry, University of Texas at Dallas, Richardson, TX, USA
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5
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Felix-Portillo M, Martinez-Quintana JA, Peregrino-Uriarte AB, Yepiz-Plascencia G. The metallothionein gene from the white shrimp Litopenaeus vannamei: characterization and expression in response to hypoxia. MARINE ENVIRONMENTAL RESEARCH 2014; 101:91-100. [PMID: 25299575 DOI: 10.1016/j.marenvres.2014.09.005] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/04/2014] [Revised: 09/03/2014] [Accepted: 09/10/2014] [Indexed: 06/04/2023]
Abstract
Aquatic animals encounter variation in oxygen tension that leads to the accumulation of reactive oxygen species (ROS) that can harm the organisms. Under these circumstances some organisms have evolved to tolerate hypoxia. In mammals, metallothioneins (MTs) protect against hypoxia-generated ROS. Here we report the MT gene from the shrimp Litopenaeus vannamei (LvMT). LvMT is differentially expressed in hemocytes, intestine, gills, pleopods, heart, hepatopancreas and muscle, with the highest levels in hepatopancreas and heart. LvMT mRNA increases during hypoxia in hepatopancreas and gills after 3 h at 1.5 mg L(-1) dissolved oxygen (DO). This gene structure resembles the homologs from invertebrates and vertebrates possessing three exons, two introns and response elements for metal response transcription factor 1 (MTF-1), hypoxia-inducible factor 1 (HIF-1) and p53 in the promoter region. During hypoxia, HIF-1/MTF-1 might participate inducing MT to contribute towards the tolerance to ROS toxicity. MT importance in aquatic organisms may include also ROS-detoxifying processes.
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Affiliation(s)
- Monserrath Felix-Portillo
- Centro de Investigación en Alimentación y Desarrollo. A.C., P.O. Box 1735. Carretera a Ejido La Victoria Km. 0.6 Hermosillo, Sonora 83304, Mexico
| | - José A Martinez-Quintana
- Centro de Investigación en Alimentación y Desarrollo. A.C., P.O. Box 1735. Carretera a Ejido La Victoria Km. 0.6 Hermosillo, Sonora 83304, Mexico
| | - Alma B Peregrino-Uriarte
- Centro de Investigación en Alimentación y Desarrollo. A.C., P.O. Box 1735. Carretera a Ejido La Victoria Km. 0.6 Hermosillo, Sonora 83304, Mexico
| | - Gloria Yepiz-Plascencia
- Centro de Investigación en Alimentación y Desarrollo. A.C., P.O. Box 1735. Carretera a Ejido La Victoria Km. 0.6 Hermosillo, Sonora 83304, Mexico.
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6
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Huang ZX, Liu F, Zheng Q, Yu WH. Zinc Transfer Kinetics of Metallothioneins and Their Fragments with Apo-carbonic Anhydrase. CHINESE J CHEM 2010. [DOI: 10.1002/cjoc.20010190506] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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7
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Jensen KP, Rykær M. The building blocks of metallothioneins: heterometallic Zn2+ and Cd2+ clusters from first-principles calculations. Dalton Trans 2010; 39:9684-95. [DOI: 10.1039/c0dt00087f] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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8
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Baba K, Okamura TA, Yamamoto H, Yamamoto T, Ueyama N. Zinc, cadmium, and mercury 1,2-benzenedithiolates with intramolecular NH...S hydrogen bonds. Inorg Chem 2008; 47:2837-48. [PMID: 18330987 DOI: 10.1021/ic702037k] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Mononuclear Zn, Cd, and Hg 1,2-benzenedithiolates with intramolecular NH...S hydrogen bonds, [M(II){1,2-S2-3,6-(RCONH)2C6H2}2](2-) (R = CH 3, t-Bu; M = Zn, Cd, Hg), were synthesized and characterized by X-ray analysis and spectral measurements. The presence of intramolecular NH...S hydrogen bonds was established by the IR spectra. (199)Hg and (113)Cd nuclear magnetic resonance showed a stabilized four-thiolate coordinated structure and suggested the influence of the NH...S hydrogen bonds to ppi(Hg)-ppi(S) interactions. The NH stretching bands show that the NH...S hydrogen bonds in Cd and Hg complexes are stronger than those in the corresponding Zn complex. These results are supported by theoretical calculations. The experimental and theoretical results suggested that the NH...S hydrogen bond influences the efficient capture of toxic Cd and Hg ions by metallothioneins.
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Affiliation(s)
- Koji Baba
- Chemical Analysis Research Center, National Institute for Agro-Environmental Sciences, Tsukuba, Ibaraki 305-8604, Japan
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9
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Aragoni MC, Arca M, Carrea MB, Demartin F, Devillanova FA, Garau A, Hursthouse MB, Huth SL, Isaia F, Lippolis V, Ogilvie HR, Verani G. Copper(
I
) Complexes with a Cu
4
S
6
‐ and CuS
4
‐Type Core Obtained from the Reaction of Copper(0) with HN(SPPh
2
)
2
·I
2. Eur J Inorg Chem 2005. [DOI: 10.1002/ejic.200500639] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- M. Carla Aragoni
- Dipartimento di Chimica Inorganica ed Analitica, Università di Cagliari, S. S. 554 bivio per Sestu, 09042 Cagliari, Italy
| | - Massimiliano Arca
- Dipartimento di Chimica Inorganica ed Analitica, Università di Cagliari, S. S. 554 bivio per Sestu, 09042 Cagliari, Italy
| | - M. Bonaria Carrea
- Dipartimento di Chimica Inorganica ed Analitica, Università di Cagliari, S. S. 554 bivio per Sestu, 09042 Cagliari, Italy
| | - Francesco Demartin
- Dipartimento di Chimica Strutturale e Stereochimica Inorganica, Università di Milano, via G. Venezian 21, 20133 Milano, Italy
| | - Francesco A. Devillanova
- Dipartimento di Chimica Inorganica ed Analitica, Università di Cagliari, S. S. 554 bivio per Sestu, 09042 Cagliari, Italy
| | - Alessandra Garau
- Dipartimento di Chimica Inorganica ed Analitica, Università di Cagliari, S. S. 554 bivio per Sestu, 09042 Cagliari, Italy
| | - Michael B. Hursthouse
- School of Chemistry, University of Southampton, Highfield, Southampton, SO17 1BJ, UK
| | - Susanne L. Huth
- School of Chemistry, University of Southampton, Highfield, Southampton, SO17 1BJ, UK
| | - Francesco Isaia
- Dipartimento di Chimica Inorganica ed Analitica, Università di Cagliari, S. S. 554 bivio per Sestu, 09042 Cagliari, Italy
| | - Vito Lippolis
- Dipartimento di Chimica Inorganica ed Analitica, Università di Cagliari, S. S. 554 bivio per Sestu, 09042 Cagliari, Italy
| | - Helen R. Ogilvie
- School of Chemistry, University of Southampton, Highfield, Southampton, SO17 1BJ, UK
| | - Gaetano Verani
- Dipartimento di Chimica Inorganica ed Analitica, Università di Cagliari, S. S. 554 bivio per Sestu, 09042 Cagliari, Italy
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10
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Affiliation(s)
- Dennis R Winge
- University of Utah Health Sciences Center, Salt Lake City, Utah 84132, USA
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11
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Brown KR, Keller GL, Pickering IJ, Harris HH, George GN, Winge DR. Structures of the cuprous-thiolate clusters of the Mac1 and Ace1 transcriptional activators. Biochemistry 2002; 41:6469-76. [PMID: 12009910 DOI: 10.1021/bi0160664] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
X-ray absorption spectroscopy on the minimal copper-regulatory domains of the two copper-regulated transcription factors (Ace1 and Mac1) in Saccharomyces cerevisiae revealed the presence of a remarkably similar polycopper cluster in both proteins. The Cu-regulatory switch motif of Mac1 consisting of the C-terminal first Cys-rich motif, designated the C1 domain, binds four Cu(I) ions as does the Cu-regulatory domain of Ace1. The four Cu(I) ions are bound to each molecule in trigonal geometry. An extended X-ray absorption fine structure (EXAFS) arising from outer-shell Cu...Cu interactions at 2.7 and 2.9 A was apparent in each Cu(I) complex indicative of a polycopper cluster. The intensity of the 2.9 A Cu...Cu backscatter peak, apparently diminished by partial cancellation, dominates the EXAFS. The results suggest that CuAce1 and CuMac1(C1) contain somewhat distorted forms of a known [Cu(4)-S(6)] cage in which a core of Cu atoms forming an approximate tetrahedron is bound by bridging thiolates above each of the six edges. The tetracopper clusters bound by Ace1 and Mac1 differ in that the Ace1 cluster is coordinated entirely by cysteinyl thiolate, whereas the cysteine-deficient Mac1 cluster appears to consist of a Cu(4)(S-Cys)(5)(N-His) cluster with a bridging histidyl-derived nitrogen.
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Affiliation(s)
- Kenneth R Brown
- University of Utah Health Sciences Center, 50 N. Medical Drive, 4C312, Salt Lake City, Utah 84132, USA
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12
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Knudsen CB, Bjørnsdottir I, Jøns O, Hansen SH. Detection of metallothionein isoforms from three different species using on-line capillary electrophoresis-mass spectrometry. Anal Biochem 1998; 265:167-75. [PMID: 9866721 DOI: 10.1006/abio.1998.2874] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
An on-line capillary electrophoresis-mass spectrometry method (CE-MS) for the detection of metallothionein (MT) isoforms is described. The detected masses were usually within 1-1.5 mass units of the expected molecular weights. MT-containing samples from rabbit, sheep, and yeast (Saccharomyces cerevisiae) were subjected to CE-MS analysis. The analysis of rabbit liver MT revealed the masses of 10 proteins/peptides. Five of the detected masses corresponded well with the expected masses calculated from the amino acid sequence of previously described MT isoforms, one was suspected to be a deacetylated form of MT-2A, one was presumed to be a yet unknown isoform, and three masses were classified as non-MT compounds. From the analysis of a fetal sheep liver extract six proteins were detected of which three masses corresponded to previously described MT isoforms. Two purified MT subforms from S. cerivisiae (encoded by the CUP1 locus) were analyzed for their copper content and both forms were found to contain eight copper atoms per molecule.
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Affiliation(s)
- C B Knudsen
- Department of Analytical and Pharmaceutical Chemistry, Royal Danish School of Pharmacy, Copenhagen, Denmark
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13
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Faller P, Vasák M. Distinct metal-thiolate clusters in the N-terminal domain of neuronal growth inhibitory factor. Biochemistry 1997; 36:13341-8. [PMID: 9341226 DOI: 10.1021/bi9711994] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Neuronal growth inhibitory factor (GIF), a brain-specific metallothionein-like protein (metallothionein-3), impairs the survival and neurite formation of cultured neurons. The metal distribution in isolated Cu4,Zn3-GIF is not known. In the present studies, the metal-thiolate clusters formed with monovalent and divalent metal ions in the N-terminal domain of human GIF [GIF(1-32)] were investigated. The cluster formation was followed by using electronic absorption, circular dichroism (CD), and magnetic circular dichroism (MCD), and in the case of Cu(I) complexes also by luminescence spectroscopy at 77 K. With Cu(I) ions, two well-defined clusters are formed involving the nine cysteine ligands of GIF(1-32), i.e., Cu4S9- and Cu6S9-clusters. In contrast to the Cu6S9-cluster, the Cu4S9-cluster shows a remarkable stability to air oxidation. As similar properties and spectral features have also been observed with isolated Cu4-5,Zn2-3-GIF, the presence of a Cu4-cluster in this GIF form is suggested. The studies with Zn(II), Cd(II), and Co(II) ions indicated the presence of a Me3S9-cluster in GIF(1-32). However, spectral features of these metal derivatives substantially differ from those reported for the corresponding Me3S9-cluster in the beta-domain of metallothioneins, suggesting structural differences. A large conformational flexibility of the Zn3- and Cd3-GIF(1-32) structures, characterized by short T2 proton relaxations, precluded their investigation by NMR methods. The significance of Cu- and Zn-clusters for the structure of biologically active GIF(1-32) is discussed.
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Affiliation(s)
- P Faller
- Biochemisches Institut der Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland
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14
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Winge DR. Copper-regulatory domain involved in gene expression. PROGRESS IN NUCLEIC ACID RESEARCH AND MOLECULAR BIOLOGY 1997; 58:165-95. [PMID: 9308366 DOI: 10.1016/s0079-6603(08)60036-7] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Copper ion homeostasis in yeast is maintained through regulated expression of genes involved in copper ion uptake, Cu(I) sequestration, and defense against reactive oxygen intermediates. Positive and negative copper ion regulation is observed, and both effects are mediated by Cu(I)-sensing transcription factors. The mechanism of Cu(I) regulation is distinct for transcriptional activation versus transcriptional repression. Cu(I) activation of gene expression in S. cerevisiae and C. glabrata occurs through Cu-regulated DNA binding. The activation process involves Cu(I) cluster formation within the regulatory domain in Ace1 and Amt1. Cu(I) binding stabilizes a specific conformation capable of high-affinity interaction with specific DNA promoter sequences. Cu(I)-activated transcription factors are modular proteins in which the DNA-binding domain is distinct from the domain that mediates transcriptional activation. The all-or-nothing formation of the polycopper cluster permits a graded response of the cell to environmental copper. Cu(I) triggering may involve a metal exchange reaction converting Ace1 from a Zn(II)-specific conformer to a clustered Cu(I) conformer. The Cu(I) regulatory domain occurs in transcription factors from S. cerevisiae and C. glabrata. Sequence homologs are also known in Y. lipolytica and S. pombe, although no functional information is available for these candidate regulatory molecules. The presence of the Cu(I) regulatory domain in four distinct yeast strains suggests that this Cu-responsive domain may occur in other eukaryotes. Cu-mediated repression of gene expression in S. cerevisiae occurs through Cu(I) regulation of Mac1. Cu(I) binding to Mac1 appears to inhibit the transactivation domain. The Cu(I) specificity of this repression is likely to arise from formation of a polycopper thiolate cluster.
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Affiliation(s)
- D R Winge
- Department of Medicine, University of Utah Health Sciences Center, Salt Lake City 84132, USA
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15
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Bertini I, Luchinat C, Messori L, Vasak M. A two-dimensional NMR study of Co(II)7 rabbit liver metallothionein. EUROPEAN JOURNAL OF BIOCHEMISTRY 1993; 211:235-40. [PMID: 8425533 DOI: 10.1111/j.1432-1033.1993.tb19891.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The 600-MHz 1H-NMR NOESY spectra on Co(II)7-reconstituted metallothionein (Co7MT), exhibiting hyperfine signals in the range 350 ppm to -50 ppm, with nuclear relaxation times of the order of a few milliseconds, have been measured and several interproton connectivities have been detected. To our knowledge, this is the largest spectral window ever reported for a two-dimensional 1H-NMR spectrum in the case of a paramagnetic metalloprotein. No scalar connectivities could be detected. The hyperfine-shifted signals belong to the cysteine-ligand protons of the Co4S11 cluster of Co7MT. Together with results from one-dimensional NOE experiments, the two-dimensional experiments allowed us to proceed with the pairwise assignment of the isotropically shifted signals of the C beta H2 groups of the metal-coordinated cysteines. With the aid of computer-graphics inspection of the four-metal-cluster domain, based on the NMR solution structure of Cd7MT, it is possible to purpose sequence-specific assignments of a few hyperfine-shifted 1H-NMR signals. In particular, a tentative assignment is given for the six signals whose shifts exhibit an antiCurie temperature dependence. The assignment relies on the theoretical model that qualitatively rationalizes the isotropic-shift pattern and its temperature dependence. Inferences on the solution structure of the Co4S11 cluster are drawn.
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Affiliation(s)
- I Bertini
- Department of Chemistry, University of Florence, Italy
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16
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Pountney DL, Vasák M. Spectroscopic studies on metal distribution in Co(II)/Zn(II) mixed-metal clusters in rabbit liver metallothionein 2. EUROPEAN JOURNAL OF BIOCHEMISTRY 1992; 209:335-41. [PMID: 1327773 DOI: 10.1111/j.1432-1033.1992.tb17294.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Metal selectivity of metal-thiolate clusters in rabbit liver metallothionein (MT) 2 has been studied by examining the metal distribution of two similarly sized divalent metal ions, cobalt and zinc, which have different thiolate affinity. The forms of mixed-metal cluster species in (Co/Zn)7-MT generated with different ratios of both metal ions offered to the metal-free protein were investigated using EPR, ultraviolet/visible absorption and MCD spectroscopy. The results demonstrated that the distribution of these metals between the two metal-thiolate clusters is not random. Thus, the EPR absorption intensities of the bound Co(II) ions in the Zn-cluster matrix increased linearly up to a ratio of Co(II)/Zn(II) equivalents of 3:4, with the final EPR intensity of three non-interacting Co(II)-binding sites. This EPR behaviour is consistent with a binding scheme in which one Co(II) ion occupies a metal-binding site within the three-metal cluster and the remaining two Co(II) ions occupy two distinctly separate sites in the four-metal cluster. With four or more Co(II) ions in the cluster matrix, magnetic coupling between adjacent, sulphur-bridged Co(II) ions was observed. In previous studies on mixed-metal clusters in MT formed with Co(II)/Cd(II), Zn(II)/Cd(II) and Cd(II)/Fe(II), changes in the respective cluster volumes were shown to be a significant factor dictating the widely differing metal distributions in these systems. Based on the results of the current study, it is suggested that both the sizes of the two metal ions and their relative affinities towards the cysteine-thiolate ligands are important in the formation of mixed-metal clusters in MT.
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Affiliation(s)
- D L Pountney
- Biochemisches Institut, Universität Zürich, Switzerland
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