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Sasanian N, Bernson D, Horvath I, Wittung-Stafshede P, Esbjörner EK. Redox-Dependent Copper Ion Modulation of Amyloid-β (1-42) Aggregation In Vitro. Biomolecules 2020; 10:E924. [PMID: 32570820 PMCID: PMC7355640 DOI: 10.3390/biom10060924] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2020] [Revised: 06/12/2020] [Accepted: 06/16/2020] [Indexed: 12/20/2022] Open
Abstract
Plaque deposits composed of amyloid-β (Aβ) fibrils are pathological hallmarks of Alzheimer's disease (AD). Although copper ion dyshomeostasis is apparent in AD brains and copper ions are found co-deposited with Aβ peptides in patients' plaques, the molecular effects of copper ion interactions and redox-state dependence on Aβ aggregation remain elusive. By combining biophysical and theoretical approaches, we here show that Cu2+ (oxidized) and Cu+ (reduced) ions have opposite effects on the assembly kinetics of recombinant Aβ(1-42) into amyloid fibrils in vitro. Cu2+ inhibits both the unseeded and seeded aggregation of Aβ(1-42) at pH 8.0. Using mathematical models to fit the kinetic data, we find that Cu2+ prevents fibril elongation. The Cu2+-mediated inhibition of Aβ aggregation shows the largest effect around pH 6.0 but is lost at pH 5.0, which corresponds to the pH in lysosomes. In contrast to Cu2+, Cu+ ion binding mildly catalyzes the Aβ(1-42) aggregation via a mechanism that accelerates primary nucleation, possibly via the formation of Cu+-bridged Aβ(1-42) dimers. Taken together, our study emphasizes redox-dependent copper ion effects on Aβ(1-42) aggregation and thereby provides further knowledge of putative copper-dependent mechanisms resulting in AD.
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Affiliation(s)
| | | | | | | | - Elin K. Esbjörner
- Department of Biology and Biological Engineering, Chalmers University of Technology, 412 96 Gothenburg, Sweden; (N.S.); (D.B.); (I.H.); (P.W.-S.)
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2
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Maghool S, Fontaine SL, Roberts BR, Kwan AH, Maher MJ. Human glutaredoxin-1 can transfer copper to isolated metal binding domains of the P 1B-type ATPase, ATP7B. Sci Rep 2020; 10:4157. [PMID: 32139726 PMCID: PMC7057996 DOI: 10.1038/s41598-020-60953-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2019] [Accepted: 01/15/2020] [Indexed: 11/25/2022] Open
Abstract
Intracellular copper (Cu) in eukaryotic organisms is regulated by homeostatic systems, which rely on the activities of soluble metallochaperones that participate in Cu exchange through highly tuned protein-protein interactions. Recently, the human enzyme glutaredoxin-1 (hGrx1) has been shown to possess Cu metallochaperone activity. The aim of this study was to ascertain whether hGrx1 can act in Cu delivery to the metal binding domains (MBDs) of the P1B-type ATPase ATP7B and to determine the thermodynamic factors that underpin this activity. hGrx1 can transfer Cu to the metallochaperone Atox1 and to the MBDs 5-6 of ATP7B (WLN5-6). This exchange is irreversible. In a mixture of the three proteins, Cu is delivered to the WLN5-6 preferentially, despite the presence of Atox1. This preferential Cu exchange appears to be driven by both the thermodynamics of the interactions between the proteins pairs and of the proteins with Cu(I). Crucially, protein-protein interactions between hGrx1, Atox1 and WLN5-6 were detected by NMR spectroscopy both in the presence and absence of Cu at a common interface. This study augments the possible activities of hGrx1 in intracellular Cu homeostasis and suggests a potential redundancy in this system, where hGrx1 has the potential to act under cellular conditions where the activity of Atox1 in Cu regulation is attenuated.
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Affiliation(s)
- Shadi Maghool
- Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, VIC, Australia
| | - Sharon La Fontaine
- School of Life and Environmental Sciences, Deakin University, Geelong, VIC, Australia.,The Florey Institute of Neuroscience, The University of Melbourne, Parkville, VIC, Australia
| | - Blaine R Roberts
- The Florey Institute of Neuroscience, The University of Melbourne, Parkville, VIC, Australia.,Department of Biochemistry, Emory University School of Medicine, Atlanta, GA, 30322, USA
| | - Ann H Kwan
- School of Life and Environmental Sciences and University of Sydney Nano Institute, Sydney, NSW, Australia.
| | - Megan J Maher
- Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, VIC, Australia. .,School of Chemistry and The Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Parkville, Australia.
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Abstract
Copper is a redox-active transition metal ion required for the function of many essential human proteins. For biosynthesis of proteins coordinating copper, the metal may bind before, during or after folding of the polypeptide. If the metal binds to unfolded or partially folded structures of the protein, such coordination may modulate the folding reaction. The molecular understanding of how copper is incorporated into proteins requires descriptions of chemical, thermodynamic, kinetic and structural parameters involved in the formation of protein-metal complexes. Because free copper ions are toxic, living systems have elaborate copper-transport systems that include particular proteins that facilitate efficient and specific delivery of copper ions to target proteins. Therefore, these pathways become an integral part of copper protein folding in vivo. This review summarizes biophysical-molecular in vitro work assessing the role of copper in folding and stability of copper-binding proteins as well as protein-protein copper exchange reactions between human copper transport proteins. We also describe some recent findings about the participation of copper ions and copper proteins in protein misfolding and aggregation reactions in vitro.
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Ariöz C, Li Y, Wittung-Stafshede P. The six metal binding domains in human copper transporter, ATP7B: molecular biophysics and disease-causing mutations. Biometals 2017; 30:823-840. [PMID: 29063292 PMCID: PMC5684295 DOI: 10.1007/s10534-017-0058-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2017] [Accepted: 10/05/2017] [Indexed: 12/16/2022]
Abstract
Wilson Disease (WD) is a hereditary genetic disorder, which coincides with a dysfunctional copper (Cu) metabolism caused by mutations in ATP7B, a membrane-bound P1B-type ATPase responsible for Cu export from hepatic cells. The N-terminal part (~ 600 residues) of the multi-domain 1400-residue ATP7B constitutes six metal binding domains (MBDs), each of which can bind a copper ion, interact with other ATP7B domains as well as with different proteins. Although the ATP7B's MBDs have been investigated in vitro and in vivo intensively, it remains unclear how these domains modulate overall structure, dynamics, stability and function of ATP7B. The presence of six MBDs is unique to mammalian ATP7B homologs, and many WD causing missense mutations are found in these domains. Here, we have summarized previously reported in vitro biophysical data on the MBDs of ATP7B and WD point mutations located in these domains. Besides the demonstration of where the research field stands today, this review showcasts the need for further biophysical investigation about the roles of MBDs in ATP7B function. Molecular mechanisms of ATP7B are important not only in the development of new WD treatment but also for other aspects of human physiology where Cu transport plays a role.
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Affiliation(s)
- Candan Ariöz
- Department of Biology and Biological Engineering, Division of Chemical Biology, Chalmers University of Technology, Kemigården 4, 412 96 Gothenburg, Sweden
| | - Yaozong Li
- Department of Chemistry, Umeå University, Kemihuset A, Linnaeus väg 10, 901 87 Umeå, Sweden
| | - Pernilla Wittung-Stafshede
- Department of Biology and Biological Engineering, Division of Chemical Biology, Chalmers University of Technology, Kemigården 4, 412 96 Gothenburg, Sweden
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Yu CH, Dolgova NV, Dmitriev OY. Dynamics of the metal binding domains and regulation of the human copper transporters ATP7B and ATP7A. IUBMB Life 2017; 69:226-235. [DOI: 10.1002/iub.1611] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2017] [Accepted: 02/03/2017] [Indexed: 01/20/2023]
Affiliation(s)
- Corey H. Yu
- Department of Biochemistry; University of Saskatchewan; Saskatoon SK Canada
| | - Natalia V. Dolgova
- Department of Biochemistry; University of Saskatchewan; Saskatoon SK Canada
| | - Oleg Y. Dmitriev
- Department of Biochemistry; University of Saskatchewan; Saskatoon SK Canada
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Matson Dzebo M, Ariöz C, Wittung-Stafshede P. Extended functional repertoire for human copper chaperones. Biomol Concepts 2016; 7:29-39. [PMID: 26745464 DOI: 10.1515/bmc-2015-0030] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2015] [Accepted: 12/08/2015] [Indexed: 12/17/2022] Open
Abstract
Copper (Cu) ions are cofactors in many essential enzymes. As free Cu ions are toxic, most organisms have highly specialized Cu transport systems involving dedicated proteins. The human cytoplasmic Cu chaperone Atox1 delivers Cu to P1B-type ATPases in the Golgi network, for incorporation into Cu-dependent enzymes following the secretory path. Atox1 homologs are found in most organisms; it is a 68-residue ferredoxin-fold protein that binds Cu in a conserved surface-exposed CXXC motif. In addition to Atox1, the human cytoplasm also contains Cu chaperones for loading of superoxide dismutase 1 (i.e. CCS) and cytochrome c oxidase in mitochondria (i.e. Cox17). Many mechanistic aspects have been resolved with respect to how Cu ions are moved between these proteins. In addition to the primary cytoplasmic Cu chaperone function, all three cytoplasmic chaperones have been reported to have other interaction partners that are involved in signaling pathways that modulate cell growth and development. These new discoveries imply that humans have evolved a highly sophisticated network of control mechanisms that connect Cu transport with cell regulatory processes. This knowledge may eventually be exploited for future drug developments towards diseases such as cancer and neurodegenerative disorders.
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Kumar R, Ariöz C, Li Y, Bosaeus N, Rocha S, Wittung-Stafshede P. Disease-causing point-mutations in metal-binding domains of Wilson disease protein decrease stability and increase structural dynamics. Biometals 2016; 30:27-35. [PMID: 27744583 PMCID: PMC5285417 DOI: 10.1007/s10534-016-9976-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2016] [Accepted: 10/10/2016] [Indexed: 11/25/2022]
Abstract
After cellular uptake, Copper (Cu) ions are transferred from the chaperone Atox1 to the Wilson disease protein (ATP7B) for incorporation into Cu-dependent enzymes in the secretory pathway. Human ATP7B is a large multi-domain membrane-spanning protein which, in contrast to homologues in other organisms, has six similar cytoplasmic metal-binding domains (MBDs). The reason for multiple MBDs is proposed to be indirect modulation of enzymatic activity and it is thus intriguing that point mutations in MBDs can promote Wilson disease. We here investigated, in vitro and in silico, the biophysical consequences of clinically-observed Wilson disease mutations, G85V in MBD1 and G591D in MBD6, incorporated in domain 4. Because G85 and G591 correspond to a conserved Gly found in all MBDs, we introduced the mutations in the well-characterized MBD4. We found the mutations to dramatically reduce the MBD4 thermal stability, shifting the midpoint temperature of unfolding by more than 20 °C. In contrast to wild type MBD4 and MBD4D, MBD4V adopted a misfolded structure with a large β-sheet content at high temperatures. Molecular dynamic simulations demonstrated that the mutations increased backbone fluctuations that extended throughout the domain. Our findings imply that reduced stability and enhanced dynamics of MBD1 or MBD6 is the origin of ATP7B dysfunction in Wilson disease patients with the G85V or G591D mutation.
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Affiliation(s)
- Ranjeet Kumar
- Department of Biology and Biological Engineering, Chalmers University of Technology, 41296, Gothenburg, Sweden
| | - Candan Ariöz
- Department of Biology and Biological Engineering, Chalmers University of Technology, 41296, Gothenburg, Sweden
| | - Yaozong Li
- Department of Chemistry, Umeå University, 90187, Umeå, Sweden
| | - Niklas Bosaeus
- Department of Biology and Biological Engineering, Chalmers University of Technology, 41296, Gothenburg, Sweden
| | - Sandra Rocha
- Department of Biology and Biological Engineering, Chalmers University of Technology, 41296, Gothenburg, Sweden
| | - Pernilla Wittung-Stafshede
- Department of Biology and Biological Engineering, Chalmers University of Technology, 41296, Gothenburg, Sweden.
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Kahra D, Kovermann M, Wittung-Stafshede P. The C-Terminus of Human Copper Importer Ctr1 Acts as a Binding Site and Transfers Copper to Atox1. Biophys J 2016; 110:95-102. [PMID: 26745413 PMCID: PMC4805863 DOI: 10.1016/j.bpj.2015.11.016] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2015] [Revised: 11/10/2015] [Accepted: 11/10/2015] [Indexed: 11/19/2022] Open
Abstract
Uptake of copper (Cu) ions into human cells is mediated by the plasma membrane protein Ctr1 and is followed by Cu transfer to cytoplasmic Cu chaperones for delivery to Cu-dependent enzymes. The C-terminal cytoplasmic tail of Ctr1 is a 13-residue peptide harboring an HCH motif that is thought to interact with Cu. We here employ biophysical experiments under anaerobic conditions in peptide models of the Ctr1 C-terminus to deduce Cu-binding residues, Cu affinity, and the ability to release Cu to the cytoplasmic Cu chaperone Atox1. Based on NMR assignments and bicinchoninic acid competition experiments, we demonstrate that Cu interacts in a 1:1 stoichiometry with the HCH motif with an affinity, KD, of ∼10(-14) M. Removing either the Cys residue or the two His residues lowers the Cu-peptide affinity, but site specificity is retained. The C-terminal peptide and Atox1 do not interact in solution in the absence of Cu. However, as directly demonstrated at the residue level via NMR spectroscopy, Atox1 readily acquires Cu from the Cu-loaded peptide. We propose that Cu binding to the Ctr1 C-terminal tail regulates Cu transport into the cytoplasm such that the metal ion is only released to high-affinity Cu chaperones.
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Affiliation(s)
- Dana Kahra
- Chemistry Department, Umeå University, Umeå, Sweden
| | - Michael Kovermann
- Chemistry Department, Umeå University, Umeå, Sweden; Chemistry Department, University of Konstanz, Konstanz, Germany.
| | - Pernilla Wittung-Stafshede
- Chemistry Department, Umeå University, Umeå, Sweden; Department of Biology and Biological Engineering, Chalmers University of Technology, Gothenburg, Sweden.
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Abstract
Copper (Cu) is an essential transition metal providing activity to key enzymes in the human body. To regulate the levels and avoid toxicity, cells have developed elaborate systems for loading these enzymes with Cu. Most Cu-dependent enzymes obtain the metal from the membrane-bound Cu pumps ATP7A/B in the Golgi network. ATP7A/B receives Cu from the cytoplasmic Cu chaperone Atox1 that acts as the cytoplasmic shuttle between the cell membrane Cu importer, Ctr1 and ATP7A/B. Biological, genetic and structural efforts have provided a tremendous amount of information for how the proteins in this pathway work. Nonetheless, basic mechanistic-biophysical questions (such as how and where ATP7A/B receives Cu, how ATP7A/B conformational changes and domain-domain interactions facilitate Cu movement through the membrane, and, finally, how target polypeptides are loaded with Cu in the Golgi) remain elusive. In this perspective, unresolved inquiries regarding ATP7A/B mechanism will be highlighted. The answers are important from a fundamental view, since mechanistic aspects may be common to other metal transport systems, and for medical purposes, since many diseases appear related to Cu transport dysregulation.
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Marković M, Ramek M, Loher C, Sabolović J. The Important Role of the Hydroxyl Group on the Conformational Adaptability in Bis(l-threoninato)copper(II) Compared to Bis(l-allo-threoninato)copper(II): Quantum Chemical Study. Inorg Chem 2016; 55:7694-708. [DOI: 10.1021/acs.inorgchem.6b01157] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Marijana Marković
- Institute for Medical Research and Occupational Health, Ksaverska cesta 2, P.O. Box 291, HR-10001 Zagreb, Croatia
- Graz University of Technology, Institute of Physical and Theoretical Chemistry, Stremayrgasse 9, A-8010 Graz, Austria
| | - Michael Ramek
- Institute for Medical Research and Occupational Health, Ksaverska cesta 2, P.O. Box 291, HR-10001 Zagreb, Croatia
- Graz University of Technology, Institute of Physical and Theoretical Chemistry, Stremayrgasse 9, A-8010 Graz, Austria
| | - Claudia Loher
- Institute for Medical Research and Occupational Health, Ksaverska cesta 2, P.O. Box 291, HR-10001 Zagreb, Croatia
- Graz University of Technology, Institute of Physical and Theoretical Chemistry, Stremayrgasse 9, A-8010 Graz, Austria
| | - Jasmina Sabolović
- Institute for Medical Research and Occupational Health, Ksaverska cesta 2, P.O. Box 291, HR-10001 Zagreb, Croatia
- Graz University of Technology, Institute of Physical and Theoretical Chemistry, Stremayrgasse 9, A-8010 Graz, Austria
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11
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Affiliation(s)
- Pernilla Wittung-Stafshede
- Department of Biology and Biological Engineering; Chalmers University of Technology; 41296 Gothenburg Sweden
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12
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Wang P, Wu J, Liu L, Zhou P, Ge Y, Liu D, Liu W, Tang Y. A peptide-based fluorescent chemosensor for measuring cadmium ions in aqueous solutions and live cells. Dalton Trans 2015; 44:18057-64. [PMID: 26411376 DOI: 10.1039/c5dt03156g] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A novel peptide fluorescent chemosensor (H2L) with a lysine backbone and both -NH2 sites conjugated with cysteine and dansyl groups has been designed and synthesized by solid phase peptide synthesis with Fmoc chemistry. This chemosensor is a promising analytical tool for detecting Cd(2+) based on the photo-induced electron transfer (PET) effect by turn-on response in 100% aqueous solutions. As designed, H2L exhibits excellent cell permeation and low biotoxicity as well as displaying relatively high selectivity and sensitivity. The chemosensor penetrated live HeLa cells and detected intracellular Cd(2+) by turn-on response. The binding stoichiometry and affinity, interference test, pH sensitivity, fluorescence quantum yield, quantum mechanical calculations, lifetimes, and cytotoxicity of the chemosensor H2L to Cd(2+) were also investigated. Moreover, H2L exhibits low biotoxicity with a limit of detection (LOD) for Cd(2+) of about 52 nM, implying that H2L can be used as a highly selective and sensitive peptide fluorescent chemosensor in biological systems.
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Affiliation(s)
- Peng Wang
- Key Laboratory of Nonferrous Metals Chemistry and Resources Utilization of Gansu Province and State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou, 730000, P. R. China.
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Ronca F, Raggi A. Structure-function relationships in mammalian histidine-proline-rich glycoprotein. Biochimie 2015; 118:207-20. [PMID: 26409900 DOI: 10.1016/j.biochi.2015.09.024] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2015] [Accepted: 09/22/2015] [Indexed: 02/01/2023]
Abstract
Histidine-proline-rich glycoprotein (HPRG), or histidine-rich glycoprotein (HRG), is a serum protein that is synthesized in the liver and is actively internalised by different cells, including skeletal muscle. The multidomain arrangement of HPRG comprises two modules at the N-terminus that are homologous to cystatin but void of cysteine proteinase inhibitor function, and a second half consisting of a histidine-proline-rich region (HPRR) located between two proline-rich regions (PRR1 and PRR2), and a C-terminus domain. HPRG has been reported to bind various ligands and to modulate angiogenesis via the histidine residues of the HPRR. However, the secondary structure prediction of the HPRR reveals that more than 98% is disordered and the structural basis of the hypothesized functions remains unclear. Comparison of the PRR1 of several mammalian species indicates the presence of a conserved binding site that might coordinate the Zn(2+) ion with an amino acid arrangement compatible with the cysteine-containing site that has been identified experimentally for rabbit HPRG. This observation provides a structural basis to the function of HPRG as an intracellular zinc chaperone which has been suggested by the involvement of the protein in the maintenance of the quaternary structure of skeletal muscle AMP deaminase (AMPD). During Anthropoidea evolution, a change of the primary structure of the PRR1 Zn(2+) binding site took place, giving rise to the sequence M-S-C-S/L-S/R-C that resembles the MxCxxC motif characteristic of metal transporters and metallochaperones.
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Affiliation(s)
- Francesca Ronca
- Laboratory of Biochemistry, Department of Pathology, University of Pisa, Via Roma 55, 56126 Pisa, Italy
| | - Antonio Raggi
- Laboratory of Biochemistry, Department of Pathology, University of Pisa, Via Roma 55, 56126 Pisa, Italy.
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Niemiec MS, Dingeldein APG, Wittung-Stafshede P. Enthalpy-entropy compensation at play in human copper ion transfer. Sci Rep 2015; 5:10518. [PMID: 26013029 PMCID: PMC4444973 DOI: 10.1038/srep10518] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2014] [Accepted: 04/16/2015] [Indexed: 11/09/2022] Open
Abstract
Copper (Cu) is an essential trace element but toxic in free form. After cell uptake, Cu is transferred, via direct protein-protein interactions, from the chaperone Atox1 to the Wilson disease protein (WD) for incorporation into Cu-dependent enzymes. Cu binds to a conserved C(1)XXC(2) motif in the chaperone as well as in each of the cytoplasmic metal-binding domains of WD. Here, we dissect mechanism and thermodynamics of Cu transfer from Atox1 to the fourth metal binding domain of WD. Using chromatography and calorimetry together with single Cys-to-Ala variants, we demonstrate that Cu-dependent protein heterocomplexes require the presence of C(1) but not C(2). Comparison of thermodynamic parameters for mutant versus wild type reactions reveals that the wild type reaction involves strong entropy-enthalpy compensation. This property is explained by a dynamic inter-conversion of Cu-Cys coordinations in the wild type ensemble and may provide functional advantage by protecting against Cu mis-ligation and bypassing enthalpic traps.
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15
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Human cytoplasmic copper chaperones Atox1 and CCS exchange copper ions in vitro. Biometals 2015; 28:577-85. [DOI: 10.1007/s10534-015-9832-1] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2014] [Accepted: 02/03/2015] [Indexed: 01/22/2023]
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