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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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Fan L, Russell DH. An ion mobility-mass spectrometry study of copper-metallothionein-2A: binding sites and stabilities of Cu-MT and mixed metal Cu-Ag and Cu-Cd complexes. Analyst 2023; 148:546-555. [PMID: 36545796 PMCID: PMC9904198 DOI: 10.1039/d2an01556k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The presence of Cu, a highly redox active metal, is known to damage DNA as well as other cellular components, but the adverse effects of cellular Cu can be mitigated by metallothioneins (MT), small cysteine rich proteins that are known to bind to a broad range of metal ions. While metal ion binding has been shown to involve the cysteine thiol groups, the specific ion binding sites are controversial as are the overall structure and stability of the Cu-MT complexes. Here, we report results obtained using nano-electrospray ionization mass spectrometry and ion mobility-mass spectrometry for several Cu-MT complexes and compare our results with those previously reported for Ag-MT complexes. The data include determination of the stoichiometries of the complex (Cui-MT, i = 1-19), and Cu+ ion binding sites for complexes where i = 4, 6, and 10 using bottom-up and top-down proteomics. The results show that Cu+ ions first bind to the β-domain to form Cu4MT then Cu6MT, followed by addition of four Cu+ ions to the α-domain to form a Cu10-MT complex. Stabilities of the Cui-MT (i = 4, 6 and 10) obtained using collision-induced unfolding (CIU) are reported and compared with previously reported CIU data for Ag-MT complexes. We also compare CIU data for mixed metal complexes (CuiAgj-MT, where i + j = 4 and 6 and CuiCdj, where i + j = 4 and 7). Lastly, higher order Cui-MT complexes, where i = 11-19, were also detected at higher concentrations of Cu+ ions, and the metalated product distributions observed are compared to previously reported results for Cu-MT-1A (Scheller et al., Metallomics, 2017, 9, 447-462).
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Affiliation(s)
- Liqi Fan
- Department of Chemistry, Texas A&M University, College Station, TX 77843, USA.
| | - David H Russell
- Department of Chemistry, Texas A&M University, College Station, TX 77843, USA.
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3
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Neuhaus D. Zinc finger structure determination by NMR: Why zinc fingers can be a handful. PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY 2022; 130-131:62-105. [PMID: 36113918 PMCID: PMC7614390 DOI: 10.1016/j.pnmrs.2022.07.001] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/25/2022] [Revised: 07/09/2022] [Accepted: 07/10/2022] [Indexed: 06/07/2023]
Abstract
Zinc fingers can be loosely defined as protein domains containing one or more tetrahedrally-co-ordinated zinc ions whose role is to stabilise the structure rather than to be involved in enzymatic chemistry; such zinc ions are often referred to as "structural zincs". Although structural zincs can occur in proteins of any size, they assume particular significance for very small protein domains, where they are often essential for maintaining a folded state. Such small structures, that sometimes have only marginal stability, can present particular difficulties in terms of sample preparation, handling and structure determination, and early on they gained a reputation for being resistant to crystallisation. As a result, NMR has played a more prominent role in structural studies of zinc finger proteins than it has for many other types of proteins. This review will present an overview of the particular issues that arise for structure determination of zinc fingers by NMR, and ways in which these may be addressed.
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Affiliation(s)
- David Neuhaus
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK.
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4
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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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5
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Peris-Díaz M, Guran R, Zitka O, Adam V, Krężel A. Metal- and Affinity-Specific Dual Labeling of Cysteine-Rich Proteins for Identification of Metal-Binding Sites. Anal Chem 2020; 92:12950-12958. [PMID: 32786475 PMCID: PMC7547867 DOI: 10.1021/acs.analchem.0c01604] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2020] [Accepted: 08/03/2020] [Indexed: 02/07/2023]
Abstract
Here, using human metallothionein (MT2) as an example, we describe an improved strategy based on differential alkylation coupled to MS, assisted by zinc probe monitoring, for identification of cysteine-rich binding sites with nanomolar and picomolar metal affinity utilizing iodoacetamide (IAM) and N-ethylmaleimide reagents. We concluded that an SN2 reaction provided by IAM is more suitable to label free Cys residues, avoiding nonspecific metal dissociation. Afterward, metal-bound Cys can be easily labeled in a nucleophilic addition reaction after separation by reverse-phase C18 at acidic pH. Finally, we evaluated the efficiency of the method by mapping metal-binding sites of Zn7-xMT species using a bottom-up MS approach with respect to metal-to-protein affinity and element(al) resolution. The methodology presented might be applied not only for MT2 but to identify metal-binding sites in other Cys-containing proteins.
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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
| | - Roman Guran
- 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
| | - 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
| | - Artur Krężel
- Department
of Chemical Biology, Faculty of Biotechnology, University of Wrocław, F. Joliot-Curie 14a, 50-383 Wrocław, Poland
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6
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Peris-Díaz MD, Guran R, Zitka O, Adam V, Krężel A. Mass Spectrometry-Based Structural Analysis of Cysteine-Rich Metal-Binding Sites in Proteins with MetaOdysseus R Software. J Proteome Res 2020; 20:776-785. [PMID: 32924499 PMCID: PMC7786378 DOI: 10.1021/acs.jproteome.0c00651] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
![]()
Identification
of metal-binding sites in proteins and understanding
metal-coupled protein folding mechanisms are aspects of high importance
for the structure-to-function relationship. Mass spectrometry (MS)
has brought a powerful adjunct perspective to structural biology,
obtaining from metal-to-protein stoichiometry to quaternary structure
information. Currently, the different experimental and/or instrumental
setups usually require the use of multiple data analysis software,
and in some cases, they lack some of the main data analysis steps
(MS processing, scoring, identification). Here, we present a comprehensive
data analysis pipeline that addresses charge-state deconvolution,
statistical scoring, and mass assignment for native MS, bottom-up,
and native top-down with emphasis on metal–protein complexes.
We have evaluated all of the approaches using assemblies of increasing
complexity, including free and chemically labeled proteins, from low-
to high-resolution MS. In all cases, the results have been compared
with common software and proved how MetaOdysseus outperformed them.
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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
| | - Roman Guran
- 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
| | - 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
| | - Artur Krężel
- Department of Chemical Biology, Faculty of Biotechnology, University of Wrocław, F. Joliot-Curie 14a, 50-383 Wrocław, Poland
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7
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Wong DL, Yuan AT, Korkola NC, Stillman MJ. Interplay between Carbonic Anhydrases and Metallothioneins: Structural Control of Metalation. Int J Mol Sci 2020; 21:E5697. [PMID: 32784815 PMCID: PMC7460868 DOI: 10.3390/ijms21165697] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2020] [Revised: 07/31/2020] [Accepted: 08/05/2020] [Indexed: 12/13/2022] Open
Abstract
Carbonic anhydrases (CAs) and metallothioneins (MTs) are both families of zinc metalloproteins central to life, however, they coordinate and interact with their Zn2+ ion cofactors in completely different ways. CAs and MTs are highly sensitive to the cellular environment and play key roles in maintaining cellular homeostasis. In addition, CAs and MTs have multiple isoforms with differentiated regulation. This review discusses current literature regarding these two families of metalloproteins in carcinogenesis, with a dialogue on the association of these two ubiquitous proteins in vitro in the context of metalation. Metalation of CA by Zn-MT and Cd-MT is described. Evidence for protein-protein interactions is introduced from changes in metalation profiles of MT from electrospray ionization mass spectrometry and the metalation rate from stopped-flow kinetics. The implications on cellular control of pH and metal donation is also discussed in the context of diseased states.
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Affiliation(s)
| | | | | | - Martin J. Stillman
- Department of Chemistry, The University of Western Ontario, 1151 Richmond St., London, ON N6A5B7, Canada; (D.L.W.); (A.T.Y.); (N.C.K.)
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8
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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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9
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Kaltashov IA, El Khoury A, Ren C, Savinov SN. Ruthenium coordination preferences in imidazole-containing systems revealed by electrospray ionization mass spectrometry and molecular modeling: Possible cues for the surprising stability of the Ru (III)/tris (hydroxymethyl)-aminomethane/imidazole complexes. JOURNAL OF MASS SPECTROMETRY : JMS 2020; 55:e4435. [PMID: 31508870 DOI: 10.1002/jms.4435] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/18/2019] [Revised: 07/19/2019] [Accepted: 09/03/2019] [Indexed: 06/10/2023]
Abstract
Ruthenium is a platinoid that exhibits a range of unique chemical properties in solution, which are exploited in a variety of applications, including luminescent probes, anticancer therapies, and artificial photosynthesis. This paper focuses on a recently demonstrated ability of this metal in its +3 oxidation state to form highly stable complexes with tris (hydroxymethyl)aminomethane (H2 NC(CH2 OH)3 , Tris-base or T) and imidazole (Im) ligands, where a single RuIII cation is coordinated by two molecules of each T and Im. High-resolution electrospray ionization mass spectrometry (ESI MS) is used to characterize RuIII complexes formed by placing a RuII complex [(NH3 )5 RuII Cl]Cl in a Tris buffer under aerobic conditions. The most abundant ionic species in ESI MS represent mononuclear complexes containing an oxidized form of the metal, ie, [Xn RuIII T2 - 2H]+ , where X could be an additional T (n = 1) or NH3 (n = 0-2). Di- and tri-metal complexes also give rise to a series of abundant ions, with the highest mass ion representing a metal complex with an empirical formula Ru3 C24 O21 N6 H66 (interpreted as cyclo(T2 RuO)3 , a cyclic oxo-bridged structure, where the coordination sphere of each metal is completed by two T ligands). The empirical formulae of the binuclear species are consistent with the structures representing acyclic fragments of cyclo(T2 RuO)3 with addition of various combinations of ammonia and dioxygen as ligands. Addition of histidine in large molar excess to this solution results in complete disassembly of poly-nuclear complexes and gives rise to a variety of ionic species in the ESI mass spectrum with a general formula [RuIII Hisk Tm (NH3 )n - 2H]+ , where k = 0 to 2, m = 0 to 3, and n = 0 to 4. Ammonia adducts are present for all observed combinations of k and m, except k = m = 2, suggesting that [His2 RuIII T2 - 2H]+ represents a complex with a fully completed coordination sphere. The observed cornucopia of RuIII complexes formed in the presence of histidine is in stark contrast to the previously reported selective reactivity of imidazole, which interacts with the metal by preserving the RuT2 core and giving rise to a single abundant ruthenium complex (represented by [Im2 RuIII T2 - 2H]+ in ESI mass spectra). Surprisingly, the behavior of a hexa-histidine peptide (HHHHHH) is similar to that of a single imidazole, rather than a single histidine amino acid: The RuT2 core is preserved, with the following ionic species observed in ESI mass spectra: [HHHHHH·(RuIII T2 )m - (3m-1)H]+ (m = 1-3). The remarkable selectivity of the imidazole interaction with the RuIII T2 core is rationalized using energetic considerations at the quantum mechanical level of theory.
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Affiliation(s)
- Igor A Kaltashov
- Department of Chemistry, University of Massachusetts-Amherst, Amherst, Massachusetts, USA
| | - Anton El Khoury
- Department of Chemistry, University of Massachusetts-Amherst, Amherst, Massachusetts, USA
| | - Chengfeng Ren
- Department of Chemistry, University of Massachusetts-Amherst, Amherst, Massachusetts, USA
| | - Sergey N Savinov
- Department of Biochemistry and Molecular Biology, University of Massachusetts-Amherst, Amherst, Massachusetts, USA
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10
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Yuan AT, Korkola NC, Wong DL, Stillman MJ. Metallothionein Cd4S11cluster formation dominates in the protection of carbonic anhydrase. Metallomics 2020; 12:767-783. [DOI: 10.1039/d0mt00023j] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Results from ESI-MS and stopped flow kinetics show that apo-MT protects from toxic metalation of apo-CA with Cd2+due to the protein–protein interactions in solution.
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Affiliation(s)
- Amelia T. Yuan
- Department of Chemistry
- University of Western Ontario
- London
- Canada
| | | | - Daisy L. Wong
- Department of Chemistry
- University of Western Ontario
- London
- Canada
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11
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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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12
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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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13
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Isolated domains of recombinant human apo-metallothionein 1A are folded at neutral pH: a denaturant and heat-induced unfolding study using ESI-MS. Biosci Rep 2018; 38:BSR20180592. [PMID: 29858425 PMCID: PMC6050192 DOI: 10.1042/bsr20180592] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2018] [Revised: 05/31/2018] [Accepted: 06/01/2018] [Indexed: 12/25/2022] Open
Abstract
Metallothioneins (MTs) are characterized by their high metal loading capacity, small molecular weight, and abundant cysteine residues. It has long been thought that metal-free, or apo-MT peptides were unstructured and only adopted as a distinct conformation upon forming the metal clusters, described as metal-induced folding. More recent studies have suggested that the presence of a globular, yet loosely defined structure actually exists that can be disrupted or unfolded. Residue modification and ion-mobility ESI (IM-ESI)-MS have been used to examine this unusual unfolding process. The structure of apo-MT plays a critical role as the starting point in the flexible metalation pathways that can accommodate numerous soft metals. ESI-MS measurements of the product species formed following the cysteine alkylation of the isolated domain fragments of recombinant human apo-MT 1A with n-ethylmaleimide (NEM) were used in the present study to monitor the denaturant- and heat-induced unfolding at physiological pH. The results indicate that these apo-MT fragments adopt distinct structures at neutral pH that react co-operatively with NEM when folded and non-cooperatively when heated or exposed to high concentrations of the denaturant guanidinium chloride (GdmCl). From these studies, we can conclude that at neutral pH, the domain fragments are folded into globular structures where some of the free cysteine residues are buried within the core and are stabilized by hydrogen bonds. Metalation therefore, must take place from the folded conformation.
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Gutowska N, Seliger P, Andrijewski G, Adamus G, Kwiecień I. Tandem mass spectroscopy as a tool for investigation of complexes of PNP-lariat ether derivative with metal ions. JOURNAL OF MASS SPECTROMETRY : JMS 2018; 53:278-285. [PMID: 29350439 DOI: 10.1002/jms.4065] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2017] [Revised: 01/02/2018] [Accepted: 01/08/2018] [Indexed: 06/07/2023]
Abstract
The novel PNP-lariat ether L with cyclotriphosphazene ring incorporated in the macrocyclic structure was synthesized and checked by the electrospray mass spectrometry (ESI-MS) method for the ability to bind different types of ions Ag+ , Ca2+ , Cd2+ , Cu2+ , and Pb2+ . Furthermore, the stability constants of the abovementioned ion complexes with the investigated ligand have been determined by direct and competitive potentiometric methods. To evaluate the stability of various complex types and to confirm the way of metal cation binding, the tandem mass spectra of the investigated ligand and its complexes were taken. As a result, we obtained quite a good relationship between the number and main types of complex species observed in ESI-MS experiments and the forms of complexes for which the stabilization constants were determined by potentiometric methods. Moreover, we also concluded that in case of big discrepancies of stability constants, ESI-MS experiments could provide information about the most stable form of the complexes, but they fail when the differences between the strength of the coordination binding are slightly different.
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Affiliation(s)
- Natalia Gutowska
- Department of Inorganic and Analytical Chemistry, Faculty of Chemistry, University of Lodz, 91-403, Lodz, Poland
| | - Piotr Seliger
- Department of Inorganic and Analytical Chemistry, Faculty of Chemistry, University of Lodz, 91-403, Lodz, Poland
| | - Grzegorz Andrijewski
- Department of Inorganic and Analytical Chemistry, Faculty of Chemistry, University of Lodz, 91-403, Lodz, Poland
| | - Grażyna Adamus
- Polish Academy of Sciences, Centre of Polymer and Carbon Materials, Marii Curie-Skłodowskiej 34, 41-800, Zabrze, Poland
| | - Iwona Kwiecień
- Polish Academy of Sciences, Centre of Polymer and Carbon Materials, Marii Curie-Skłodowskiej 34, 41-800, Zabrze, Poland
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Irvine GW, Heinlein L, Renaud JB, Sumarah MW, Stillman MJ. Formation of oxidative and non-oxidative dimers in metallothioneins: Implications for charge-state analysis for structural determination. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2017; 31:2118-2124. [PMID: 28987027 DOI: 10.1002/rcm.8006] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/18/2017] [Revised: 09/19/2017] [Accepted: 09/24/2017] [Indexed: 05/10/2023]
Abstract
RATIONALE Metallothioneins (MTs) are a class of dynamic proteins that have been investigated extensively using mass spectrometric methods due to their amenability to ionization. Here we detect the formation of oxidative and non-oxidative MT dimers using high-resolution mass spectrometry (HRMS) which has previously been overlooked with lower-resolution techniques. METHODS Recombinant human MT1a and its isolated domain fragments were analyzed by high-resolution Thermo Q-Exactive and Bruker time-of-flight (TOF) mass spectrometers. Covalent Cys modification was performed using N-ethylmalemide to probe the effect of Cys oxidation on dimer formation. RESULTS Dimerization was detected in the analysis of select charge states of Zn7 MT and apo-βMT. Specifically, high resolution (140 k) revealed the +6 dimer peaks overlapping with the +3 charge state, but not with the other charge states (+4, +5, +6). The proteins with covalently modified Cys did not show dimer formation in any of their charge states. Apo-α and apo-βαMT also did not form dimers under the conditions tested. CONCLUSIONS Dimerization of MT was detected for zinc metalated and certain apo-MT forms with HRMS, which was not seen with lower-resolution techniques. These dimers appear overlapped only with certain charge states, confounding their analysis for structural characterization of MTs. The Zn-MT dimers appeared to be non-oxidative; however, the formation of dimers in the apo-protein is likely dependent on Cys oxidation.
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Affiliation(s)
- Gordon W Irvine
- Department of Chemistry, The University of Western Ontario, London, ON, N6A 5B7, Canada
| | - Lina Heinlein
- Department of Chemistry, The University of Western Ontario, London, ON, N6A 5B7, Canada
- Department of Food Chemistry and Toxicology, University of Karlsruhe, Profach 6980, D-76128, Karlsruhe, Germany
| | - Justin B Renaud
- London Research and Development Center, Agriculture and Agri-Food Canada, London, ON, N5V 4T3, Canada
| | - Mark W Sumarah
- Department of Chemistry, The University of Western Ontario, London, ON, N6A 5B7, Canada
- London Research and Development Center, Agriculture and Agri-Food Canada, London, ON, N5V 4T3, Canada
| | - Martin J Stillman
- Department of Chemistry, The University of Western Ontario, London, ON, N6A 5B7, Canada
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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: 184] [Impact Index Per Article: 26.3] [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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Irvine GW, Santolini M, Stillman MJ. Selective cysteine modification of metal-free human metallothionein 1a and its isolated domain fragments: Solution structural properties revealed via ESI-MS. Protein Sci 2017; 26:960-971. [PMID: 28187517 DOI: 10.1002/pro.3139] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2016] [Revised: 02/06/2017] [Accepted: 02/07/2017] [Indexed: 01/11/2023]
Abstract
Human metallothionein 1a, a protein with two cysteine-rich metal-binding domains (α with 11 Cys and β with 9), was analyzed in its metal-free form by selective, covalent Cys modification coupled with ESI-MS. The modification profiles of the isolated β- and α-fragments reacted with p-benzoquinone (Bq), N-ethylmalemide (NEM) and iodoacetamide (IAM) were compared with the full length protein using ESI-mass spectral data to follow the reaction pathway. Under denaturing conditions at low pH, the reaction profile with each modifier followed pathways that resulted in stochastic, Normal distributions of species whose maxima was equal to the mol. eq. of modifier added. Our interpretation of modification at this pH is that reaction with the cysteines is unimpeded when the full protein or those of its isolated domains are denatured. At neutral pH, where the protein is expected to be folded in a more compact structure, there is a difference in the larger Bq and NEM modification, whose reaction profiles indicate a cooperative pattern. The reaction profile with IAM under native conditions follows a similar stochastic distribution as at low pH, suggesting that this modifier is small enough to access the cysteines unimpeded by the compact structure. The data emphasize the utility of residue modification coupled with electrospray ionization mass spectrometry for the study of protein structure.
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Affiliation(s)
- Gordon W Irvine
- Department of Chemistry, The University of Western Ontario, London, ON, Canada
| | - Melissa Santolini
- Department of Chemistry, The University of Western Ontario, London, ON, Canada
| | - Martin J Stillman
- Department of Chemistry, The University of Western Ontario, London, ON, Canada
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18
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Hu S, Ye B, Yi X, Cao Z, Wu D, Shen C, Wang J. Dumbbell-shaped metallothionein-templated silver nanoclusters with applications in cell imaging and Hg2+ sensing. Talanta 2016; 155:272-7. [DOI: 10.1016/j.talanta.2016.04.055] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2016] [Revised: 04/23/2016] [Accepted: 04/24/2016] [Indexed: 10/21/2022]
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19
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Irvine GW, Stillman MJ. Cadmium binding mechanisms of isolated domains of human MT isoform 1a: Non-cooperative terminal sites and cooperative cluster sites. J Inorg Biochem 2016; 158:115-121. [DOI: 10.1016/j.jinorgbio.2016.03.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2015] [Revised: 03/05/2016] [Accepted: 03/10/2016] [Indexed: 10/22/2022]
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Pawlowski JW, Kellicker N, Bobst CE, Kaltashov IA. Assessing the iron delivery efficacy of transferrin in clinical samples by native electrospray ionization mass spectrometry. Analyst 2016; 141:853-61. [PMID: 26646585 PMCID: PMC4727994 DOI: 10.1039/c5an02159f] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Serum transferrin is a key player in iron homeostasis, and its ability to deliver iron to cells via the endosomal pathway critically depends on the presence of carbonate that binds this protein synergistically with ferric ion. Oxalate is another ubiquitous anionic species that can act as a synergistic anion, and in fact its interaction with transferrin is notably stronger compared to carbonate, preventing the protein from releasing the metal in the endosomal environment. While this raises concerns that high oxalate levels in plasma may interfere with iron delivery to tissues, concentration of free oxalate in blood appears to be a poor predictor of impeded availability of iron, as previous studies showed that it cannot displace carbonate from ferro-transferrin on a physiologically relevant time scale under the conditions mimicing plasma. In this work we present a new method that allows different forms of ferro-transferrin (carbonate- vs. oxalate-bound) to be distinguished from each other by removing this protein from plasma without altering the composition of the protein/metal/synergistic anion complexes, and determining their accurate masses using native electrospray ionization mass spectrometry (ESI MS). The new method has been validated using a mixture of recombinant proteins, followed by its application to the analysis of clinical samples of human plasma, demonstrating that native ESI MS can be used in clinical analysis.
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Affiliation(s)
- Jake W Pawlowski
- University of Massachusetts-Amherst, Department of Chemistry, 240 Thatcher Drive, Life Sciences Laboratories N369, Amherst, MA 01003, USA.
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21
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Zhao H, Wang S, Nguyen SN, Elci SG, Kaltashov IA. Evaluation of Nonferrous Metals as Potential In Vivo Tracers of Transferrin-Based Therapeutics. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2016; 27:211-9. [PMID: 26392277 PMCID: PMC4724545 DOI: 10.1007/s13361-015-1267-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/11/2015] [Revised: 09/02/2015] [Accepted: 09/04/2015] [Indexed: 05/10/2023]
Abstract
Transferrin (Tf) is a promising candidate for targeted drug delivery. While development of such products is impossible without the ability to monitor biodistribution of Tf-drug conjugates in tissues and reliable measurements of their levels in blood and other biological fluids, the presence of very abundant endogenous Tf presents a significant impediment to such efforts. Several noncognate metals have been evaluated in this work as possible tracers of exogenous transferrin in complex biological matrices using inductively coupled plasma mass spectrometry (ICP MS) as a detection tool. Placing Ni(II) on a His-tag of recombinant Tf resulted in formation of a marginally stable protein-metal complex, which readily transfers the metal to ubiquitous physiological scavengers, such as serum albumin. An alternative strategy targeted iron-binding pockets of Tf, where cognate Fe(III) was replaced by metal ions known to bind this protein. Both Ga(III) and In(III) were evaluated, with the latter being vastly superior as a tracer (stronger binding to Tf unaffected by the presence of metal scavengers and the retained ability to associate with Tf receptor). Spiking serum with indium-loaded Tf followed by ICP MS detection demonstrated that protein quantities as low as 0.04 nM can be readily detected in animal blood. Combining laser ablation with ICP MS detection allows distribution of exogenous Tf to be mapped within animal tissue cross-sections with spatial resolution exceeding 100 μm. The method can be readily extended to a range of other therapeutics where metalloproteins are used as either carriers or payloads. Graphical Abstract ᅟ.
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Affiliation(s)
- Hanwei Zhao
- Department of Chemistry, University of Massachusetts-Amherst, Amherst, MA, 01003, USA
| | - Shunhai Wang
- Department of Chemistry, University of Massachusetts-Amherst, Amherst, MA, 01003, USA
| | - Son N Nguyen
- Department of Chemistry, University of Massachusetts-Amherst, Amherst, MA, 01003, USA
| | - S Gokhan Elci
- Department of Chemistry, University of Massachusetts-Amherst, Amherst, MA, 01003, USA
| | - Igor A Kaltashov
- Department of Chemistry, University of Massachusetts-Amherst, Amherst, MA, 01003, USA.
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Earthworm Lumbricus rubellus MT-2: Metal Binding and Protein Folding of a True Cadmium-MT. Int J Mol Sci 2016; 17:ijms17010065. [PMID: 26742040 PMCID: PMC4730310 DOI: 10.3390/ijms17010065] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2015] [Revised: 12/18/2015] [Accepted: 12/24/2015] [Indexed: 01/03/2023] Open
Abstract
Earthworms express, as most animals, metallothioneins (MTs)—small, cysteine-rich proteins that bind d10 metal ions (Zn(II), Cd(II), or Cu(I)) in clusters. Three MT homologues are known for Lumbricus rubellus, the common red earthworm, one of which, wMT-2, is strongly induced by exposure of worms to cadmium. This study concerns composition, metal binding affinity and metal-dependent protein folding of wMT-2 expressed recombinantly and purified in the presence of Cd(II) and Zn(II). Crucially, whilst a single Cd7wMT-2 species was isolated from wMT-2-expressing E. coli cultures supplemented with Cd(II), expressions in the presence of Zn(II) yielded mixtures. The average affinities of wMT-2 determined for either Cd(II) or Zn(II) are both within normal ranges for MTs; hence, differential behaviour cannot be explained on the basis of overall affinity. Therefore, the protein folding properties of Cd- and Zn-wMT-2 were compared by 1H NMR spectroscopy. This comparison revealed that the protein fold is better defined in the presence of cadmium than in the presence of zinc. These differences in folding and dynamics may be at the root of the differential behaviour of the cadmium- and zinc-bound protein in vitro, and may ultimately also help in distinguishing zinc and cadmium in the earthworm in vivo.
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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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Gutowska N, Pasternak B, Seliger P, Andrijewski G. Studies of the complexation behavior of tetramorpholinylo-PNP-lariat ether with Ag(i), Ca(ii), Cd(ii), Cu(ii) and Pb(ii) using Electrospray Ionization Mass Spectrometry. NEW J CHEM 2015. [DOI: 10.1039/c4nj01904k] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The identification of complexes containing PNP-lariat ether with Ag(i), Ca(ii), Cu(ii), Cd(ii) and Pb(ii) by ESI-MS technique is presented. The tandem mass spectra of these complexes were done in order to evaluate the stability of the different types of the complexes formed.
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Affiliation(s)
- Natalia Gutowska
- Department of Inorganic and Analytical Chemistry
- Faculty of Chemistry
- University of Lodz
- 91-403 Łódź
- Poland
| | - Beata Pasternak
- Laboratory of Molecular Spectroscopy
- Faculty of Chemistry
- University of Lodz
- 91-403 Łódź
- Poland
| | - Piotr Seliger
- Department of Inorganic and Analytical Chemistry
- Faculty of Chemistry
- University of Lodz
- 91-403 Łódź
- Poland
| | - Grzegorz Andrijewski
- Department of Inorganic and Analytical Chemistry
- Faculty of Chemistry
- University of Lodz
- 91-403 Łódź
- Poland
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25
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Lecina J, Palacios Ò, Atrian S, Capdevila M, Suades J. Rhenium and technetium tricarbonyl, {M(CO)3} (+) (M = Tc, Re), binding to mammalian metallothioneins: new insights into chemical and radiopharmaceutical implications. J Biol Inorg Chem 2014; 20:465-74. [PMID: 25511253 DOI: 10.1007/s00775-014-1226-2] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2014] [Accepted: 11/29/2014] [Indexed: 11/25/2022]
Abstract
This paper deals with the binding of the four mammalian metallothioneins (MTs) to the organometallic metal fragment {fac-M(CO)3}(+) (M = (99)Tc, Re), which is highly promising for the preparation of second-generation radiopharmaceuticals. The study of the transmetallation reaction between zinc and rhenium in Zn7-MT1 by means of UV-vis and CD spectroscopy demonstrated the incorporation of the {fac-Re(CO)3}(+) fragment to the MTs. This reaction should be performed at 70 °C to accelerate the reaction rate, a result that is consistent with the reported reactivity of the rhenium fragment. ESI-TOF MS demonstrated the formation of mixed-metal species as Zn6,{Re(CO)3}-MT, Zn6,{Re(CO)3}2-MT, and Zn5,{Re(CO)3}3-MT, as well as the different reactivity of the four MT isoforms. Hence, Zn-MT3 showed the highest reactivity, in agreement with its high Cu-thionein character, whereas Zn-MT2 exhibited the lowest reactivity, in line with its high Zn-thionein character. The reactivity of the Zn-loaded forms of MT1 and MT4 is intermediate between those of MT3 and MT2. The study of the binding of the {fac-(99)Tc(CO)3}(+) fragment to MTs showed a significant and very interesting different reactivity in relation to rhenium. The transmetallation reaction is much more effective with technetium than with rhenium and significant amounts of mixed Zn x ,{(99)Tc(CO)3} y -MT species were formed with the four MT isoforms whereas only MT3 rendered similar amounts of rhenium derivatives. The results obtained in this study support the possible use of technetium for labelling mammalian metallothioneins and also for possible radiopharmaceutical applications.
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Affiliation(s)
- Joan Lecina
- Departament de Química, Facultat de Ciències, Universitat Autònoma de Barcelona, 08193, Cerdanyola del Vallès, Barcelona, Spain
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Raudenska M, Gumulec J, Podlaha O, Sztalmachova M, Babula P, Eckschlager T, Adam V, Kizek R, Masarik M. Metallothionein polymorphisms in pathological processes. Metallomics 2014; 6:55-68. [PMID: 24068159 DOI: 10.1039/c3mt00132f] [Citation(s) in RCA: 83] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Metallothioneins (MTs) are a class of metal-binding proteins characterized by a high cysteine content and low molecular weight. MTs play an important role in metal metabolism and protect cells against the toxic effects of radiation, alkylating agents and oxygen free radicals. The evidence that individual genetic characteristics of MTs play an important role in physiological and pathological processes associated with antioxidant defense and detoxification inspired targeted studies of genetic polymorphisms in a clinical context. In recent years, common MT polymorphisms were identified and associated with, particularly, western lifestyle diseases such as cancer, complications of atherosclerosis, and type 2 diabetes mellitus along with related complications. This review summarizes all evidence regarding MT polymorphisms of major human MTs (MT1, MT2, MT3 and MT4), their relation to pathological processes, and outlines specific applications of MTs as a set of genetic markers for certain pathologies.
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Affiliation(s)
- Martina Raudenska
- Department of Pathological Physiology, Faculty of Medicine, Masaryk University, Kamenice 5, CZ-625 00 Brno, Czech Republic.
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Chen SH, Chen L, Russell DH. Metal-induced conformational changes of human metallothionein-2A: a combined theoretical and experimental study of metal-free and partially metalated intermediates. J Am Chem Soc 2014; 136:9499-508. [PMID: 24918957 DOI: 10.1021/ja5047878] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Electrospray ionization ion mobility mass spectrometry (ESI IM-MS) and molecular dynamics (MD) simulations reveal new insights into metal-induced conformational changes and the mechanism for metalation of human metallothionein-2A (MT), an intrinsically disordered protein. ESI of solutions containing apoMT yields multiple charge states of apoMT; following addition of Cd(2+) to the solution, ESI yields a range of CdiMT (i = 1-7) product ions (see Chen et al. Anal. Chem. 2013, 85, 7826-33). Ion mobility arrival-time distributions (ATDs) for the CdiMT (i = 0-7) ions reveal a diverse population of ion conformations. The ion mobility data clearly show that the conformational diversity for apoMT and partially metalated ions converges toward ordered, compact conformations as the number of bound Cd(2+) ions increase. MD simulations provide additional information on conformation candidates of CdiMT (i = 0-7) that supports the convergence of distinct conformational populations upon metal binding. Integrating the IM-MS and MD data provides a global view that shows stepwise conformational transition of an ensemble as a function of metal ion bound. ApoMT is comprised of a wide range of conformational states that populate between globular-like compact and coil-rich extended conformations. During the initial stepwise metal addition (number of metal ions bound i = 1-3), the metal ions bind to different sites to yield distinct conformations, whereas for i > 4, the conformational changes appear to be domain-specific, attributed to different degrees of disorder of the β domain; the β domain becomes more ordered as additional metal ions are added, promoting convergences to the dumbbell-shaped conformation.
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Affiliation(s)
- Shu-Hua Chen
- Department of Chemistry, Texas A&M University , College Station, Texas 77843, United States
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Kojima A, Konishi M, Akizawa T. Prion fragment peptides are digested with membrane type matrix metalloproteinases and acquire enzyme resistance through Cu²⁺-binding. Biomolecules 2014; 4:510-26. [PMID: 24970228 PMCID: PMC4101495 DOI: 10.3390/biom4020510] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2014] [Revised: 04/02/2014] [Accepted: 04/11/2014] [Indexed: 11/16/2022] Open
Abstract
Prions are the cause of neurodegenerative disease in humans and other mammals. The structural conversion of the prion protein (PrP) from a normal cellular protein (PrPC) to a protease-resistant isoform (PrPSc) is thought to relate to Cu2+ binding to histidine residues. In this study, we focused on the membrane-type matrix metalloproteinases (MT-MMPs) such as MT1-MMP and MT3-MMP, which are expressed in the brain as PrPC-degrading proteases. We synthesized 21 prion fragment peptides. Each purified peptide was individually incubated with recombinant MT1-MMP or MT3-MMP in the presence or absence of Cu2+ and the cleavage sites determined by LC-ESI-MS analysis. Recombinant MMP-7 and human serum (HS) were also tested as control. hPrP61-90, from the octapeptide-repeat region, was cleaved by HS but not by the MMPs tested here. On the other hand, hPrP92-168 from the central region was cleaved by MT1-MMP and MT3-MMP at various sites. These cleavages were inhibited by treatment with Cu2+. The C-terminal peptides had higher resistance than the central region. The data obtained from this study suggest that MT-MMPs expressed in the brain might possess PrPC-degrading activity.
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Affiliation(s)
- Aya Kojima
- Analytical Chemistry, Pharmaceutical Science, Setsunan University, 45-1 Nagaotoge-cho, Hirakata, Osaka 573-0101, Japan.
| | - Motomi Konishi
- Analytical Chemistry, Pharmaceutical Science, Setsunan University, 45-1 Nagaotoge-cho, Hirakata, Osaka 573-0101, Japan.
| | - Toshifumi Akizawa
- Analytical Chemistry, Pharmaceutical Science, Setsunan University, 45-1 Nagaotoge-cho, Hirakata, Osaka 573-0101, Japan.
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Sun X, Chiu JF, He QY. Application of immobilized metal affinity chromatography in proteomics. Expert Rev Proteomics 2014; 2:649-57. [PMID: 16209645 DOI: 10.1586/14789450.2.5.649] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
It has been proved that the progress of proteomics is mostly determined by the development of advanced and sensitive protein separation technologies. Immobilized metal affinity chromatography (IMAC) is a powerful protein fractionation method used to enrich metal-associated proteins and peptides. In proteomics, IMAC has been widely employed as a prefractionation method to increase the resolution in protein separation. The combination of IMAC with other protein analytical technologies has been successfully utilized to characterize metalloproteome and post-translational modifications. In the near future, newly developed IMAC integrated with other proteomic methods will greatly contribute to the revolution of expression, cell-mapping and structural proteomics.
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Affiliation(s)
- Xuesong Sun
- Department of Chemistry, University of Hong Kong, Pokfulam, Hong Kong.
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Sekar R, Kailasa SK, Chen YC, Wu HF. Electrospray ionization tandem mass spectrometric studies to probe the interaction of Cu(II) with amoxicillin. CHINESE CHEM LETT 2014. [DOI: 10.1016/j.cclet.2013.10.012] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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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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Dong J, Callahan KL, Borotto NB, Vachet RW. Identifying Zn-bound histidine residues in metalloproteins using hydrogen-deuterium exchange mass spectrometry. Anal Chem 2013; 86:766-73. [PMID: 24313328 DOI: 10.1021/ac4032719] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
In this work, we have developed a method that uses hydrogen-deuterium exchange (HDX) of C2-hydrogens of histidines coupled with mass spectrometry (MS) to identify Zn-bound histidines in metalloproteins. This method relies on differences in HDX reaction rates of Zn-bound and Zn-free His residues. Using several model peptides and proteins, we find that all Zn-bound His residues have substantially lower HDX reaction rates in the presence of the metal. The vast majority of non-Zn-binding His residues undergo no significant changes in HDX reaction rates when their reactivity is compared in the presence and absence of Zn. Using this new approach, we then determined the Zn binding site of β-2-microglobulin, a protein associated with metal-induced amyloidosis. Together, these results suggest that HDX-MS of His C2-hydrogens is a promising new method for identifying Zn-bound histidines in metalloproteins.
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Affiliation(s)
- Jia Dong
- Department of Chemistry, University of Massachusetts Amherst , LGRT, 710 North Pleasant Street, Amherst, MA 01003, United States
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Kaltashov IA, Bobst CE, Abzalimov RR. Mass spectrometry-based methods to study protein architecture and dynamics. Protein Sci 2013; 22:530-44. [PMID: 23436701 DOI: 10.1002/pro.2238] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2012] [Revised: 02/11/2013] [Accepted: 02/13/2013] [Indexed: 11/09/2022]
Abstract
Mass spectrometry is now an indispensable tool in the armamentarium of molecular biophysics, where it is used for tasks ranging from protein sequencing and mapping of post-translational modifications to studies of higher order structure, conformational dynamics, and interactions of proteins with small molecule ligands and other biopolymers. This mini-review highlights several popular mass spectrometry-based tools that are now commonly used for structural studies of proteins beyond their covalent structure with a particular emphasis on hydrogen exchange and direct electrospray ionization mass spectrometry.
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Affiliation(s)
- Igor A Kaltashov
- Department of Chemistry, University of Massachusetts-Amherst, Amherst, Massachusetts, USA.
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Chen SH, Russell WK, Russell DH. Combining chemical labeling, bottom-up and top-down ion-mobility mass spectrometry to identify metal-binding sites of partially metalated metallothionein. Anal Chem 2013; 85:3229-37. [PMID: 23421923 DOI: 10.1021/ac303522h] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Metalation and demetalation of human metallothionein-2A (MT) with Cd(2+) is investigated by using chemical labeling and "bottom-up" and "top-down" proteomics approaches. Both metalation and demetalation of MT-2A by Cd(2+) are shown to be domain specific and occur as two distinct processes. Metalation involves sequential addition of Cd(2+) to the α-domain resulting in formation of an intermediate, Cd4MT. Chemical labeling with N-ethylmaleimide (NEM) and tandem mass spectrometry experiments clearly show that the four metal ions are located in the α-domain. In the presence of excess Cd(2+), the Cd4MT intermediate reacts to add Cd(2+) to the β-domain to yield the fully metalated Cd7MT. Demetalation occurs in the reverse order, i.e., Cd(2+) is removed (by EDTA) first from the β-domain followed by Cd(2+) removal from the α-domain. Metalation of human MT-2A is shown to be metal ion specific by comparing relative metal ion binding constants for Cd(2+) and Zn(2+).
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Affiliation(s)
- Shu-Hua Chen
- Department of Chemistry, Texas A&M University, College Station, Texas 77843, United States
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35
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Blindauer CA. Lessons on the critical interplay between zinc binding and protein structure and dynamics. J Inorg Biochem 2013; 121:145-55. [PMID: 23376625 DOI: 10.1016/j.jinorgbio.2013.01.005] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2012] [Revised: 01/08/2013] [Accepted: 01/08/2013] [Indexed: 02/05/2023]
Abstract
Zinc is one of the most important micronutrients for virtually all living organisms, and hence, it is important to understand the molecular mechanisms for its homeostasis. Besides proteins involved in transmembrane transport, both extra- and intracellular zinc-binding proteins play important roles in the respective metabolic networks. Important examples for extracellular zinc transporters are mammalian serum albumins, and for intracellular zinc handling, certain metallothioneins are of relevance. The availability of protein structures including relevant metal binding sites is a fundamental prerequisite to decipher the mechanisms that govern zinc binding dynamics in these proteins, but their determination can prove to be surprisingly challenging. Due to the spectroscopic silence of Zn(2+), combinations of biophysical techniques including electrospray ionisation mass spectrometry (ESI-MS) and multinuclear NMR, isothermal titration calorimetry (ITC) and extended X-ray absorption fine structure (EXAFS) spectroscopy, coupled with site-directed mutagenesis and molecular modelling have proven to be valuable approaches to understand not only the zinc-binding properties of metallothioneins and albumins, but also the influence of other physiologically relevant competing agents. These studies have demonstrated why the bacterial metallothionein SmtA contains a site inert towards exchange with Cd(2+), why the plant metallothionein EC from wheat is partially unfolded in the presence of Cd(2+), and how fatty acids impact on the zinc-binding ability of mammalian serum albumins.
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36
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Xu M, Yang L, Wang Q. Chemical interactions of mercury species and some transition and noble metals towards metallothionein (Zn7MT-2) evaluated using SEC/ICP-MS, RP-HPLC/ESI-MS and MALDI-TOF-MS. Metallomics 2013; 5:855-60. [DOI: 10.1039/c3mt00016h] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Kondrat FDL, Kowald GR, Scarff CA, Scrivens JH, Blindauer CA. Resolution of a paradox by native mass spectrometry: facile occupation of all four metal binding sites in the dimeric zinc sensor SmtB. Chem Commun (Camb) 2013; 49:813-5. [DOI: 10.1039/c2cc38387j] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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39
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Capdevila M, Bofill R, Palacios Ò, Atrian S. State-of-the-art of metallothioneins at the beginning of the 21st century. Coord Chem Rev 2012. [DOI: 10.1016/j.ccr.2011.07.006] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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40
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Kojima A, Mabuchi Y, Konishi M, Okihara R, Nagano M, Akizawa T. Metal-binding ability of human prion protein fragment peptides analyzed by column switch HPLC. Chem Pharm Bull (Tokyo) 2011; 59:965-71. [PMID: 21804240 DOI: 10.1248/cpb.59.965] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The structural conversion of the prion protein (PrP) from the normal cellular isoform (PrP(C)) to the posttranslationally modified form (PrP(Sc)) is thought to relate to Cu²⁺ binding to histidine (H) residues. Traditionally, the binding of metals to PrP has been investigated by monitoring the conformational conversion using circular dichroism (CD). In this study, the metal-binding ability of 21 synthetic peptides representing regions of human PrP(C) was investigated by column switch high-performance liquid chromatography (CS-HPLC). The CS-HPLC system is composed of a metal chelate affinity column and an octadecylsilica (ODS) reversed-phase column that together enable the identification of metal-binding regardless of conformational conversion. Synthetic peptides were designed with respect to the position of H residues as well as the secondary structure of human PrP (hPrP). The ability of the octapeptide (PHGGGWGQ)-repeating region (OP-repeat) to bind metals was analyzed by CS-HPLC and supported by CD analysis, and indicated that CS-HPLC is a reliable and useful method for measuring peptide metal-binding. Peptides from the middle region of hPrP showed a high affinity for Cu²⁺, but binding to Zn²⁺, Ni²⁺, and Co²⁺ was dependent on peptide length. C-Terminal peptides had a lower affinity for Cu²⁺, Zn²⁺, Ni²⁺, and Co²⁺ than OP-repeat region peptides. Interestingly, hPrP193-230, which contained no H residues, also bound to Cu²⁺, Zn²⁺, Ni²⁺, and Co²⁺, indicating that this region is a novel metal-binding site in the C-terminal region of PrP(C). The CS-HPLC method described in this study is useful and convenient for assessing metal-binding affinity and characterizing metal-binding peptides or proteins.
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Affiliation(s)
- Aya Kojima
- Department of Analytical Chemistry, Pharmaceutical Science, Setsunan University, Japan
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41
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Proteomic approaches in understanding action mechanisms of metal-based anticancer drugs. Met Based Drugs 2011; 2008:716329. [PMID: 18670610 PMCID: PMC2486358 DOI: 10.1155/2008/716329] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2007] [Revised: 04/20/2008] [Accepted: 06/17/2008] [Indexed: 12/13/2022] Open
Abstract
Medicinal inorganic chemistry has been stimulating largely by the success of the anticancer drug, cisplatin. Various metal complexes are currently used as therapeutic agents (e.g., Pt, Au, and Ru) in the treatment of malignant diseases, including several types of cancers. Understanding the mechanism of action of these metal-based drugs is for the design of more effective drugs. Proteomic approaches combined with other biochemical methods can provide comprehensive understanding of responses that are involved in metal-based anticancer drugs-induced cell death, including insights into cytotoxic effects of metal-based anticancer drugs, correlation of protein alterations to drug targets, and prediction of drug resistance and toxicity. This information, when coupled with clinical data, can provide rational basses for the future design and modification of present used metal-based anticancer drugs.
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Kaltashov IA, Bobst CE, Zhang M, Leverence R, Gumerov DR. Transferrin as a model system for method development to study structure, dynamics and interactions of metalloproteins using mass spectrometry. Biochim Biophys Acta Gen Subj 2011; 1820:417-26. [PMID: 21726602 DOI: 10.1016/j.bbagen.2011.06.019] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2011] [Revised: 06/17/2011] [Accepted: 06/21/2011] [Indexed: 12/31/2022]
Abstract
BACKGROUND Transferrin (Tf) is a paradigmatic metalloprotein, which has been extensively studied in the past and still is a focal point of numerous investigation efforts owing to its unique role in iron homeostasis and enormous promise as a component of a wide range of therapies. SCOPE OF REVIEW Electrospray ionization mass spectrometry (ESI MS) is a potent analytical tool that has been used successfully to study various properties of Tf and Tf-based products, ranging from covalent structure and metal binding to conformation and interaction with their physiological partners. MAJOR CONCLUSIONS Various ESI MS-based techniques produce unique information on Tf properties and behavior that is highly complementary to information provided by other experimental techniques. GENERAL SIGNIFICANCE The experimental ESI MS-based techniques developed for Tf studies are not only useful for understanding of fundamental aspects of the iron-binding properties of this protein and optimizing Tf-based therapeutic products, but can also be applied to study a range of other metalloproteins. This article is part of a Special Issue entitled Transferrins: Molecular mechanisms of iron transport and disorders.
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Affiliation(s)
- Igor A Kaltashov
- Department of Chemistry, University of Massachusetts-Amherst, Amherst, MA, USA.
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43
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Carlton DD, Schug KA. A review on the interrogation of peptide–metal interactions using electrospray ionization-mass spectrometry. Anal Chim Acta 2011; 686:19-39. [DOI: 10.1016/j.aca.2010.11.050] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2010] [Revised: 11/24/2010] [Accepted: 11/25/2010] [Indexed: 11/27/2022]
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Mounicou S, Ouerdane L, L'Azou B, Passagne I, Ohayon-Courtès C, Szpunar J, Lobinski R. Identification of metallothionein subisoforms in HPLC using accurate mass and online sequencing by electrospray hybrid linear ion trap-orbital ion trap mass spectrometry. Anal Chem 2010; 82:6947-57. [PMID: 20669907 DOI: 10.1021/ac101245h] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A comprehensive approach to the characterization of metallothionein (MT) isoforms based on microbore HPLC with multimodal detection was developed. MTs were separated as Cd(7) complexes, detected by ICP MS and tentatively identified by molecular mass measured with 1-2 ppm accuracy using Orbital ion trap mass spectrometry. The identification was validated by accurate mass of the corresponding apo-MTs after postcolumn acidification and by their sequences acquired online by higher-energy collision dissociation MS/MS. The detection limits down to 10 fmol and 45 fmol could be obtained by ESI MS for apo- and Cd(7)-isoforms, respectively, and were lower than those obtained by ICP MS (100 fmol). The individual MT isoforms could be sequenced at levels as low as 200 fmol with the sequence coverage exceeding 90%. The approach was successfully applied to the identification of MT isoforms induced in a pig kidney cell line (LLC-PK(1)) exposed to CdS nanoparticles.
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Affiliation(s)
- Sandra Mounicou
- CNRS/UPPA, Laboratoire de Chimie Analytique Bio-Inorganique et Environnement, UMR 5254, 2, av. Pr. Angot, 64053 Pau, France
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45
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Garza S, Thomas PW, Fast W, Moini M. Metal displacement and stoichiometry of protein-metal complexes under native conditions using capillary electrophoresis/mass spectrometry. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2010; 24:2730-2734. [PMID: 20814979 DOI: 10.1002/rcm.4702] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Increases in the study of protein-metal complexes, as well as in metal displacement in protein-metal complexes under native conditions for optimum catalytic properties in drug research and catalyst design, demands a separation/detection technology that can accurately measure metal displacement and stoichiometry in protein-metal complexes. Both nuclear magnetic resonance (NMR) and X-ray diffraction techniques have been used for this purpose; however, these techniques lack sensitivity. Electrospray ionization mass spectrometry (ESI-MS) using direct infusion offers higher sensitivity than the former techniques and provides molecular distribution of various protein-metal complexes. However, since protein-metal complexes under native conditions usually are dissolved in salt solutions, their direct ESI-MS analysis requires off-line sample clean-up prior to MS analysis to avoid sample suppression during ESI. Moreover, direct infusion of the salty solution promotes non-specific salt adduct formation by the protein-metal complexes under ESI-MS, which complicates the identification and stoichiometry measurements of the protein-metal complexes. Because of the high mass of protein-metal complexes and lack of sufficient resolution by most mass spectrometers to separate non-specific from specific metal-protein complexes, accurate protein-metal stoichiometry measurements require some form of sample clean up prior to ESI-MS analysis. In this study, we demonstrate that capillary electrophoresis/electrospray ionization in conjunction with a medium-resolution (approximately 10,000) mass spectrometer is an efficient and fast method for the measurement of the stoichiometry of the protein-metal complexes under physiological conditions (pH approximately 7). The metal displacement of Co(2+) to Cd(2+), two metal ions necessary for activation in the monomeric AHL lactonase produced by B. thuringiensis, has been used as a proof of concept.
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Frimpong AK, Abzalimov RR, Uversky VN, Kaltashov IA. Characterization of intrinsically disordered proteins with electrospray ionization mass spectrometry: conformational heterogeneity of alpha-synuclein. Proteins 2010; 78:714-22. [PMID: 19847913 DOI: 10.1002/prot.22604] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Conformational heterogeneity of alpha-synuclein was studied with electrospray ionization mass spectrometry by analyzing protein ion charge state distributions, where the extent of multiple charging reflects compactness of the protein conformations in solution. Although alpha-synuclein lacks a single well-defined structure under physiological conditions, it was found to sample four distinct conformational states, ranging from a highly structured one to a random coil. The compact highly structured state of alpha-synuclein is present across the entire range of conditions tested (pH ranging from 2.5 to 10, alcohol content from 0% to 60%), but is particularly abundant in acidic solutions. The only other protein state populated in acidic solutions is a partially folded intermediate state lacking stable tertiary structure. Another, more compact intermediate state is induced by significant amounts of ethanol used as a co-solvent and appears to represent a partially folded conformation with high beta-sheet content. Protein dimerization is observed throughout the entire range of conditions tested, although only acidic solutions favor formation of highly structured dimers of alpha-synuclein. These dimers are likely to present the earliest stages in protein aggregation leading to globular oligomers and, subsequently, protofibrils.
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Affiliation(s)
- Agya K Frimpong
- Department of Chemistry, University of Massachusetts Amherst, Amherst, MA 01003, USA
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47
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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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Leszczyszyn OI, Blindauer CA. Zinc transfer from the embryo-specific metallothionein EC from wheat: a case study. Phys Chem Chem Phys 2010; 12:13408-18. [DOI: 10.1039/c0cp00680g] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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49
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Keltner Z, Meyer JA, Johnson EM, Palumbo AM, Spence DM, Reid GE. Mass spectrometric characterization and activity of zinc-activated proinsulin C-peptide and C-peptide mutants. Analyst 2009; 135:278-88. [PMID: 20098759 DOI: 10.1039/b917600d] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Numerous reports have demonstrated an active role for proinsulin C-peptide in ameliorating chronic complications associated with diabetes mellitus. It has been recently reported that some of these activities are dependent upon activation of C-peptide with certain metal ions, such as Fe(II), Cr(III) or Zn(II). In an effort to gain a greater understanding of the structure/function dependence of the peptide-metal interactions responsible for this activity, a series of experiments involving the use of electrospray ionization (ESI), matrix assisted laser desorption/ionization (MALDI) and collision-induced dissociation-tandem mass spectrometry (CID-MS/MS) of C-peptide in the presence or absence of Zn(II) have been carried out. Additionally, various C-peptide mutants with alanine substitution at individual aspartic acid or glutamic acid residues throughout the C-peptide sequence were analyzed. CID-MS/MS of wild type C-peptide in the presence of Zn(II) indicated multiple sites for metal binding, localized at acidic residues within the peptide sequence. Mutations of individual acidic residues did not significantly affect this fragmentation behavior, suggesting that no single acidic residue is critical for binding. However, ESI-MS analysis revealed an approximately 50% decrease in relative Zn(II) binding for each of the mutants compared to the wild type sequence. Furthermore, a significant decrease in activity was observed for each of the Zn(II)-activated mutant peptides compared to the wild type C-peptide, indicated by measurement of ATP released from erythrocytes, with a 75% decrease observed for the Glu27 mutant. Additional studies on the C-terminal pentapeptide of C-peptide EGSLQ, as well as a mutant C-terminal pentapeptide sequence AGSLQ, revealed that substitution of the glutamic acid residue resulted in a complete loss of activity, implicating a central role for Glu27 in Zn(II)-mediated C-peptide activity.
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Affiliation(s)
- Zachary Keltner
- Department of Chemistry, Michigan State University, East Lansing, MI 48824, USA
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50
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Ngu TT, Lee JA, Rushton MK, Stillman MJ. Arsenic metalation of seaweed Fucus vesiculosus metallothionein: the importance of the interdomain linker in metallothionein. Biochemistry 2009; 48:8806-16. [PMID: 19655782 DOI: 10.1021/bi9007462] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The presence of metallothionein in seaweed Fucus vesiculosus has been suggested as the protecting agent against toxic metals in the contaminated waters it can grow in. We report the first kinetic pathway data for A3+ binding to an algal metallothionein, F. vesiculosus metallothionein (rfMT). The time and temperature dependence of the relative concentrations of apo-rfMT and the five As-containing species have been determined following mixing of As3+ and apo-rfMT using electrospray ionization mass spectrometry (ESI MS). Kinetic analysis of the detailed time-resolved mass spectral data for As3+ metalation allows the simulation of the metalation reactions showing the consumption of apo-rfMT, the formation and consumption of As1- to As4-rfMT, and subsequent, final formation of As5-rfMT. The kinetic model proposed here provides a stepwise analysis of the metalation reaction showing time-resolved occupancy of the Cys7 and the Cys9 domain. The rate constants (M(-1) s(-1)) calculated from the fits for the 7-cysteine gamma domain are k1gamma, 19.8, and k2gamma, 1.4, and for the 9-cysteine beta domain are k1beta, 16.3, k2beta, 9.1, and k3beta, 2.2. The activation energies and Arrhenius factors for each of the reaction steps are also reported. rfMT has a long 14 residue linker, which as we show from analysis of the ESI MS data, allows each of its two domains to bind As3+ independently of each other. The analysis provides for the first time an explanation of the differing metal-binding properties of two-domain MTs with linkers of varying lengths, suggesting further comparison between plant (with long linkers) and mammalian (with short linkers) metallothioneins will shed light on the role of the interdomain linker.
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Affiliation(s)
- Thanh T Ngu
- Department of Chemistry, University of Western Ontario, London, Ontario, Canada N6A 5B7
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