1
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Canonica F, Hennecke H, Glockshuber R. Biochemical pathway for the biosynthesis of the Cu A center in bacterial cytochrome c oxidase. FEBS Lett 2019; 593:2977-2989. [PMID: 31449676 DOI: 10.1002/1873-3468.13587] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2019] [Revised: 08/21/2019] [Accepted: 08/22/2019] [Indexed: 01/25/2023]
Abstract
The di-copper center CuA is an essential metal cofactor in cytochrome oxidase (Cox) of mitochondria and many prokaryotes, mediating one-electron transfer from cytochrome c to the site for oxygen reduction. CuA is located in subunit II (CoxB) of Cox and protrudes into the periplasm of Gram-negative bacteria or the mitochondrial intermembrane space. How the two copper ions are brought together to build CoxB·CuA is the subject of this review. It had been known that the reductase TlpA and the metallochaperones ScoI and PcuC are required for CuA formation in bacteria, but the mechanism of copper transfer has emerged only recently for the Bradyrhizobium diazoefficiens system. It consists of the following steps: (a) TlpA keeps the active site cysteine pair of CoxB in its dithiol state as a prerequisite for metal insertion; (b) ScoI·Cu2+ rapidly forms a transient complex with apo-CoxB; (c) PcuC, loaded with Cu1+ and Cu2+ , dissociates this complex to CoxB·Cu2+ , and a second PcuC·Cu1+ ·Cu2+ transfers Cu1+ to CoxB·Cu2+ , yielding mature CoxB·CuA . Variants of this pathway might exist in other bacteria or mitochondria.
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Affiliation(s)
- Fabia Canonica
- Institute of Molecular Biology and Biophysics, ETH Zurich, Switzerland
| | | | - Rudi Glockshuber
- Institute of Molecular Biology and Biophysics, ETH Zurich, Switzerland
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2
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Llases ME, Lisa MN, Morgada MN, Giannini E, Alzari PM, Vila AJ. Arabidopsis thaliana Hcc1 is a Sco-like metallochaperone for Cu A assembly in Cytochrome c Oxidase. FEBS J 2019; 287:749-762. [PMID: 31348612 DOI: 10.1111/febs.15016] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2019] [Revised: 07/03/2019] [Accepted: 07/22/2019] [Indexed: 01/13/2023]
Abstract
The assembly of the CuA site in Cytochrome c Oxidase (COX) is a critical step for aerobic respiration in COX-dependent organisms. Several gene products have been associated with the assembly of this copper site, the most conserved of them belonging to the Sco family of proteins, which have been shown to perform different roles in different organisms. Plants express two orthologs of Sco proteins: Hcc1 and Hcc2. Hcc1 is known to be essential for plant development and for COX maturation, but its precise function has not been addressed until now. Here, we report the biochemical, structural and functional characterization of Arabidopsis thaliana Hcc1 protein (here renamed Sco1). We solved the crystal structure of the Cu+1 -bound soluble domain of this protein, revealing a tri coordinated environment involving a CxxxCxn H motif. We show that AtSco1 is able to work as a copper metallochaperone, inserting two Cu+1 ions into the CuA site in a model of CoxII. We also show that AtSco1 does not act as a thiol-disulfide oxido-reductase. Overall, this information sheds new light on the biochemistry of Sco proteins, highlighting the diversity of functions among them despite their high structural similarities. DATABASE: PDB entry 6N5U (Crystal structure of Arabidopsis thaliana ScoI with copper bound).
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Affiliation(s)
- María-Eugenia Llases
- Instituto de Biología Molecular y Celular de Rosario (IBR CONICET-UNR), Rosario, Argentina
| | - María-Natalia Lisa
- Instituto de Biología Molecular y Celular de Rosario (IBR CONICET-UNR), Rosario, Argentina.,Plataforma de Biología Estructural y Metabolómica (PLABEM), Rosario, Argentina
| | - Marcos N Morgada
- Instituto de Biología Molecular y Celular de Rosario (IBR CONICET-UNR), Rosario, Argentina.,Area Biofísica, Departamento de Química Biológica, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Argentina
| | - Estefanía Giannini
- Instituto de Biología Molecular y Celular de Rosario (IBR CONICET-UNR), Rosario, Argentina
| | - Pedro M Alzari
- Unité de Microbiologie Structurale, Institut Pasteur, Université Paris Diderot, Paris, France
| | - Alejandro J Vila
- Instituto de Biología Molecular y Celular de Rosario (IBR CONICET-UNR), Rosario, Argentina.,Plataforma de Biología Estructural y Metabolómica (PLABEM), Rosario, Argentina.,Area Biofísica, Departamento de Química Biológica, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Argentina
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3
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Biochemistry of Copper Site Assembly in Heme-Copper Oxidases: A Theme with Variations. Int J Mol Sci 2019; 20:ijms20153830. [PMID: 31387303 PMCID: PMC6696091 DOI: 10.3390/ijms20153830] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2019] [Revised: 07/15/2019] [Accepted: 07/16/2019] [Indexed: 01/18/2023] Open
Abstract
Copper is an essential cofactor for aerobic respiration, since it is required as a redox cofactor in Cytochrome c Oxidase (COX). This ancient and highly conserved enzymatic complex from the family of heme-copper oxidase possesses two copper sites: CuA and CuB. Biosynthesis of the oxidase is a complex, stepwise process that requires a high number of assembly factors. In this review, we summarize the state-of-the-art in the assembly of COX, with special emphasis in the assembly of copper sites. Assembly of the CuA site is better understood, being at the same time highly variable among organisms. We also discuss the current challenges that prevent the full comprehension of the mechanisms of assembly and the pending issues in the field.
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4
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Hussain S, Andrews D, Hill BC. Exposure of Bacillus subtilis to silver inhibits activity of cytochrome c oxidase in vivo via interaction with SCO, the Cu A assembly protein. Metallomics 2019; 10:735-744. [PMID: 29676768 DOI: 10.1039/c7mt00343a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Silver has long been used as an antimicrobial agent in general and medicinal use. Here, we observe that exposure of the Gram-positive, endospore-forming bacterium Bacillus subtilis to Ag(i) effects growth in a biphasic manner. In the first phase at Ag(i) concentrations below 50 μM B. subtilis growth is not affected, but activity of the respiratory enzyme cytochrome c oxidase is disrupted completely. Between 50 to 100 μM Ag(i) B. subtilis growth is drastically diminished and completely absent above 100 μM Ag(i). Synthesis of cytochrome c oxidase, or SCO proteins, have been shown to play a role in assembly of the CuA center of cytochrome c oxidase and we suppose that the effects observed here of silver on Bacillus subtilis in culture may be explained at least in part by the interaction of Bacillus SCO (BsSCO) with Ag(i). We find that Ag(i) forms a high affinity complex with BsSCO in vitro that blocks SCO's interaction with copper indicating competition between the metals for binding BsSCO. The interaction of BsSCO with Ag(i) exhibits multiple phases and is more complex than that observed for the high-affinity, 1 : 1 copper complex with BsSCO. We propose that the initial response of B. subtilis cultures is due to high affinity binding of Ag(i) to BsSCO that blocks the functionality of BsSCO required for assembly of cytochrome c oxidase. Our results provide evidence of a specific effect of silver on Bacillus subtilis cells and implies that SCO proteins play a role in sensitivity to Ag(i).
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Affiliation(s)
- Shina Hussain
- Queen's University, Biomedical and Molecular Sciences, Kingston, Canada.
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5
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Maiti BK, Maia LB, Moro AJ, Lima JC, Cordas CM, Moura I, Moura JJG. Unusual Reduction Mechanism of Copper in Cysteine-Rich Environment. Inorg Chem 2018; 57:8078-8088. [PMID: 29956539 DOI: 10.1021/acs.inorgchem.8b00121] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Copper-cysteine interactions play an important role in Biology and herein we used the copper-substituted rubredoxin (Cu-Rd) from Desulfovibrio gigas to gain further insights into the copper-cysteine redox chemistry. EPR spectroscopy results are consistent with Cu-Rd harboring a CuII center in a sulfur-rich coordination, in a distorted tetrahedral structure ( g∥,⊥ = 2.183 and 2.032 and A∥,⊥ = 76.4 × 10-4 and 12 × 10-4 cm-1). In Cu-Rd, two oxidation states at Cu-center (CuII and CuI) are associated with Cys oxidation-reduction, alternating in the redox cycle, as pointed by electrochemical studies that suggest internal geometry rearrangements associated with the electron transfer processes. The midpoint potential of [CuI(S-Cys)2(Cys-S-S-Cys)]/[CuII(S-Cys)4] redox couple was found to be -0.15 V vs NHE showing a large separation of cathodic and anodic peaks potential (Δ Ep = 0.575 V). Interestingly, sulfur-rich CuII-Rd is highly stable under argon in dark conditions, which is thermodynamically unfavorable to Cu-thiol autoreduction. The reduction of copper and concomitant oxidation of Cys can both undergo two possible pathways: oxidative as well as photochemical. Under O2, CuII plays the role of the electron carrier from one Cys to O2 followed by internal geometry rearrangement at the Cu site, which facilitates reduction at Cu-center to yield CuI(S-Cys)2(Cys-S-S-Cys). Photoinduced (irradiated at λex = 280 nm) reduction of the CuII center is observed by UV-visible photolysis (above 300 nm all bands disappeared) and tryptophan fluorescence (∼335 nm peak enhanced) experiments. In both pathways, geometry reorganization plays an important role in copper reduction yielding an energetically compatible donor-acceptor system. This model system provides unusual stability and redox chemistry rather than the universal Cu-thiol auto redox chemistry in cysteine-rich copper complexes.
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Affiliation(s)
- Biplab K Maiti
- LAQV, REQUIMTE, Departamento de Química, Faculdade de Ciências e Tecnologia , Universidade Nova de Lisboa , 2829-516 Caparica , Portugal
| | - Luisa B Maia
- LAQV, REQUIMTE, Departamento de Química, Faculdade de Ciências e Tecnologia , Universidade Nova de Lisboa , 2829-516 Caparica , Portugal
| | - Artur J Moro
- LAQV, REQUIMTE, Departamento de Química, Faculdade de Ciências e Tecnologia , Universidade Nova de Lisboa , 2829-516 Caparica , Portugal
| | - João C Lima
- LAQV, REQUIMTE, Departamento de Química, Faculdade de Ciências e Tecnologia , Universidade Nova de Lisboa , 2829-516 Caparica , Portugal
| | - Cristina M Cordas
- LAQV, REQUIMTE, Departamento de Química, Faculdade de Ciências e Tecnologia , Universidade Nova de Lisboa , 2829-516 Caparica , Portugal
| | - Isabel Moura
- LAQV, REQUIMTE, Departamento de Química, Faculdade de Ciências e Tecnologia , Universidade Nova de Lisboa , 2829-516 Caparica , Portugal
| | - José J G Moura
- LAQV, REQUIMTE, Departamento de Química, Faculdade de Ciências e Tecnologia , Universidade Nova de Lisboa , 2829-516 Caparica , Portugal
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6
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Hussain S, Andrews D, Hill BC. Using Tryptophan Mutants To Probe the Structural and Functional Status of BsSCO, a Copper Binding, Cytochrome c Oxidase Assembly Protein from Bacillus subtilis. Biochemistry 2017; 56:6355-6367. [DOI: 10.1021/acs.biochem.7b00833] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Shina Hussain
- Department
of Biomedical and Molecular Sciences and ‡Protein Function Discovery Group, Queen’s University, Kingston, ON K7L
3N6, Canada
| | - Diann Andrews
- Department
of Biomedical and Molecular Sciences and ‡Protein Function Discovery Group, Queen’s University, Kingston, ON K7L
3N6, Canada
| | - Bruce C. Hill
- Department
of Biomedical and Molecular Sciences and ‡Protein Function Discovery Group, Queen’s University, Kingston, ON K7L
3N6, Canada
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7
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Xu S, Andrews D, Hill BC. The affinity of yeast and bacterial SCO proteins for CU(I) and CU(II). A capture and release strategy for copper transfer. Biochem Biophys Rep 2015; 4:10-19. [PMID: 29124182 PMCID: PMC5668878 DOI: 10.1016/j.bbrep.2015.08.010] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2015] [Revised: 08/11/2015] [Accepted: 08/13/2015] [Indexed: 12/20/2022] Open
Abstract
SCO (Synthesis of Cytochrome c Oxidase) proteins are present in prokaryotic and eukaryotic cells, and are often required for efficient synthesis of the respiratory enzyme cytochrome c oxidase. The Bacillus subtilis version of SCO (i.e., BsSCO) has much greater affinity for Cu(II) than it does for Cu(I) (Davidson and Hill, 2009), and this has been contrasted to mitochondrial SCO proteins that are characterized as being specific for Cu(I) (Nittis, George and Winge, 2001). This differential affinity has been proposed to reflect the different physiological environments in which these two members of the SCO protein family reside. In this study the affinity of mitochondrial SCO1 from yeast is compared directly to that of BsSCO in vitro. We find that the yeast SCO1 protein has similar preference for Cu(II) over Cu(I), as does BsSCO. We propose a mechanism for SCO function which would involve high-affinity binding to capture Cu(II), and relatively weak binding of Cu(I) to facilitate copper transfer. Yeast SCO1 prefers Cu(II) over Cu(I) by many orders of magnitude. Yeast SCO1 has similar copper-species preference as a bacterial SCO protein. High affinity binding of Cu(II) by SCO may be initial step in copper transfer. Conversion of SCO-Cu(II) to SCO-Cu(I) is required for copper transfer. A second cysteine pair in yeast SCO1 may be involved in redox sensing.
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Affiliation(s)
- Shuai Xu
- Department of Biomedical and Molecular Sciences, Queen’s University, Kingston, ON K7L3N6 Canada
| | - Diann Andrews
- Department of Biomedical and Molecular Sciences, Queen’s University, Kingston, ON K7L3N6 Canada
| | - Bruce C. Hill
- Department of Biomedical and Molecular Sciences, Queen’s University, Kingston, ON K7L3N6 Canada
- Protein Function Discovery Research Group, Queen’s University, Kingston, ON K7L3N6 Canada
- Corresponding author at: Department of Biomedical and Molecular Sciences, Queen’s University, Kingston, ON K7L3N6 Canada.Department of Biomedical and Molecular Sciences, Queen’s UniversityKingstonON K7L3N6Canada
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8
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Dash BP, Alles M, Bundschuh FA, Richter OMH, Ludwig B. Protein chaperones mediating copper insertion into the CuA site of the aa3-type cytochrome c oxidase of Paracoccus denitrificans. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2014; 1847:202-211. [PMID: 25445316 DOI: 10.1016/j.bbabio.2014.11.001] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/05/2014] [Revised: 10/31/2014] [Accepted: 11/05/2014] [Indexed: 11/27/2022]
Abstract
The biogenesis of the mitochondrial cytochrome c oxidase is a complex process involving the stepwise assembly of its multiple subunits encoded by two genetic systems. Moreover, several chaperones are required to recruit and insert the redox-active metal centers into subunits I and II, two a-type hemes and a total of three copper ions, two of which form the CuA center located in a hydrophilic domain of subunit II. The copper-binding Sco protein(s) have been implicated with the metallation of this site in various model organisms. Here we analyze the role of the two Sco homologues termed ScoA and ScoB, along with two other copper chaperones, on the biogenesis of the cytochrome c oxidase in the bacterium Paracoccus denitrificans by deleting each of the four genes individually or pairwise, followed by assessing the functionality of the assembled oxidase both in intact membranes and in the purified enzyme complex. Copper starvation leads to a drastic decrease of oxidase activity in membranes from strains involving the scoB deletion. This loss is shown to be of dual origin, (i) a severe drop in steady-state oxidase levels in membranes, and (ii) a diminished enzymatic activity of the remaining oxidase complex, traced back to a lower copper content, specifically in the CuA site of the enzyme. Neither of the other proteins addressed here, ScoA or the two PCu proteins, exhibit a direct effect on the metallation of the CuA site in P. denitrificans, but are discussed as potential interaction partners of ScoB.
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Affiliation(s)
| | - Melanie Alles
- Institute of Biochemistry, Molecular Genetics, Goethe University, D-60438 Frankfurt, Germany
| | - Freya Alena Bundschuh
- Institute of Biochemistry, Molecular Genetics, Goethe University, D-60438 Frankfurt, Germany
| | - Oliver-M H Richter
- Institute of Biochemistry, Molecular Genetics, Goethe University, D-60438 Frankfurt, Germany
| | - Bernd Ludwig
- Institute of Biochemistry, Molecular Genetics, Goethe University, D-60438 Frankfurt, Germany.
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9
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Yao X, Andrews D, Hill BC. Reactivity of ligand-swapped mutants of the SCO protein from Bacillus subtilis. Isomers of the CCH metal binding motif. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2014; 1844:2193-202. [PMID: 25192666 DOI: 10.1016/j.bbapap.2014.08.014] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/21/2014] [Revised: 08/15/2014] [Accepted: 08/20/2014] [Indexed: 11/28/2022]
Abstract
The Synthesis of Cytochrome Oxidase protein, or SCO protein, is required for the assembly of cytochrome c oxidase in many mitochondrial and bacterial respiratory chains. SCOs have been proposed to deliver copper to the CuA site of cytochrome c oxidase. We have reported that Bacillus subtilis SCO (i.e., BsSCO) binds Cu(II) with high-affinity via a two-step process mediated by three conserved residues (i.e., two cysteines and one histidine, or the CCH motif). A remarkable feature in the reaction of reduced (i.e., di-thiol) BsSCO with copper is that it does not generate any of the disulfide form of BsSCO. This molecular aversion is proposed to be a consequence of a binding mechanism in which the initial copper complex of BsSCO does not involve cysteine, but instead involves nitrogen ligands. We test this proposal here by constructing two isomers of BsSCO in which the conserved copper binding residues (i.e., the CCH-motif) are retained, but their positions are altered. In these variants the two cysteines are exchanged with histidine, and both react transiently with copper (II) with distinct kinetic profiles. The reaction generates Cu(I) and the protein is oxidized to its disulfide form. EPR analysis supports a copper binding model in which cysteine, which is at the "histidine position" in the mutant, is part of an initial encounter complex with copper. When cysteine is the initial ligating residue an oxidation reaction ensues. In contrast initial binding to native BsSCO uses nitrogen-based ligands, and thereby avoids the opportunity for thiol oxidation.
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Affiliation(s)
- Xin Yao
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, ON K7L3N6, Canada
| | - Diann Andrews
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, ON K7L3N6, Canada
| | - Bruce C Hill
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, ON K7L3N6, Canada.
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10
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Ording-Wenker ECM, van der Plas M, Siegler MA, Bonnet S, Bickelhaupt FM, Fonseca Guerra C, Bouwman E. Thermodynamics of the Cu(II) μ-thiolate and Cu(I) disulfide equilibrium: a combined experimental and theoretical study. Inorg Chem 2014; 53:8494-504. [PMID: 25090284 DOI: 10.1021/ic501060w] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The redox equilibrium between dinuclear Cu(II) μ-thiolate and Cu(I) disulfide structures has been analyzed experimentally and via DFT calculations. Two new ligands, L(2)SSL(2) and L(4)SSL(4), and their Cu(II) μ-thiolate and Cu(I) disulfide complexes were synthesized. For L(2)SSL(2), these two redox-isomeric copper species are shown to be in equilibrium, which depends on both temperature and solvent. For L(4)SSL(4) the μ-thiolate species forms as the kinetic product and further evolves into the disulfide complex under thermodynamic control, which creates the unprecedented possibility to compare both species under the same reaction conditions. The energies of the μ-thiolate and disulfide complexes for two series of related ligands have been calculated with DFT; the results rationalize the experimentally observed structures, and emphasize the important role that steric requirements play in the formation of the Cu(II) thiolate structure.
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Affiliation(s)
- Erica C M Ording-Wenker
- Leiden Institute of Chemistry, Gorlaeus Laboratories, Leiden University , P.O. Box 9502, 2300 RA Leiden, The Netherlands
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11
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Tan SH, Normi YM, Leow ATC, Salleh AB, Karjiban RA, Murad AMA, Mahadi NM, Rahman MBA. A Sco protein among the hypothetical proteins of Bacillus lehensis G1: Its 3D macromolecular structure and association with Cytochrome C Oxidase. BMC STRUCTURAL BIOLOGY 2014; 14:11. [PMID: 24641837 PMCID: PMC3994876 DOI: 10.1186/1472-6807-14-11] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/13/2013] [Accepted: 03/14/2014] [Indexed: 11/10/2022]
Abstract
BACKGROUND At least a quarter of any complete genome encodes for hypothetical proteins (HPs) which are largely non-similar to other known, well-characterized proteins. Predicting and solving their structures and functions is imperative to aid understanding of any given organism as a complete biological system. The present study highlights the primary effort to classify and cluster 1202 HPs of Bacillus lehensis G1 alkaliphile to serve as a platform to mine and select specific HP(s) to be studied further in greater detail. RESULTS All HPs of B. lehensis G1 were grouped according to their predicted functions based on the presence of functional domains in their sequences. From the metal-binding group of HPs of the cluster, an HP termed Bleg1_2507 was discovered to contain a thioredoxin (Trx) domain and highly-conserved metal-binding ligands represented by Cys69, Cys73 and His159, similar to all prokaryotic and eukaryotic Sco proteins. The built 3D structure of Bleg1_2507 showed that it shared the βαβαββ core structure of Trx-like proteins as well as three flanking β-sheets, a 310 -helix at the N-terminus and a hairpin structure unique to Sco proteins. Docking simulations provided an interesting view of Bleg1_2507 in association with its putative cytochrome c oxidase subunit II (COXII) redox partner, Bleg1_2337, where the latter can be seen to hold its partner in an embrace, facilitated by hydrophobic and ionic interactions between the proteins. Although Bleg1_2507 shares relatively low sequence identity (47%) to BsSco, interestingly, the predicted metal-binding residues of Bleg1_2507 i.e. Cys-69, Cys-73 and His-159 were located at flexible active loops similar to other Sco proteins across biological taxa. This highlights structural conservation of Sco despite their various functions in prokaryotes and eukaryotes. CONCLUSIONS We propose that HP Bleg1_2507 is a Sco protein which is able to interact with COXII, its redox partner and therefore, may possess metallochaperone and redox functions similar to other documented bacterial Sco proteins. It is hoped that this scientific effort will help to spur the search for other physiologically relevant proteins among the so-called "orphan" proteins of any given organism.
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Affiliation(s)
- Soo Huei Tan
- Center for Enzyme and Microbial Biotechnology (EMTECH), Faculty of Biotechnology and Biomolecular Sciences, Universiti Putra Malaysia, Serdang, Selangor 43400, Malaysia
| | - Yahaya M Normi
- Center for Enzyme and Microbial Biotechnology (EMTECH), Faculty of Biotechnology and Biomolecular Sciences, Universiti Putra Malaysia, Serdang, Selangor 43400, Malaysia
| | - Adam Thean Chor Leow
- Center for Enzyme and Microbial Biotechnology (EMTECH), Faculty of Biotechnology and Biomolecular Sciences, Universiti Putra Malaysia, Serdang, Selangor 43400, Malaysia
| | - Abu Bakar Salleh
- Center for Enzyme and Microbial Biotechnology (EMTECH), Faculty of Biotechnology and Biomolecular Sciences, Universiti Putra Malaysia, Serdang, Selangor 43400, Malaysia
| | - Roghayeh Abedi Karjiban
- Center for Enzyme and Microbial Biotechnology (EMTECH), Faculty of Biotechnology and Biomolecular Sciences, Universiti Putra Malaysia, Serdang, Selangor 43400, Malaysia
- Department of Chemistry, Faculty of Science, Universiti Putra Malaysia, Serdang, Selangor 43400, Malaysia
| | - Abdul Munir Abdul Murad
- School of Biosciences and Biotechnology, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 UKM, Bangi, Selangor, Malaysia
| | - Nor Muhammad Mahadi
- Malaysia Genome Institute, Ministry of Science, Technology and Innovation, Jalan Bangi, Kajang, Selangor 43000, Malaysia
| | - Mohd Basyaruddin Abdul Rahman
- Center for Enzyme and Microbial Biotechnology (EMTECH), Faculty of Biotechnology and Biomolecular Sciences, Universiti Putra Malaysia, Serdang, Selangor 43400, Malaysia
- Department of Chemistry, Faculty of Science, Universiti Putra Malaysia, Serdang, Selangor 43400, Malaysia
- Malaysia Genome Institute, Ministry of Science, Technology and Innovation, Jalan Bangi, Kajang, Selangor 43000, Malaysia
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12
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Blundell KLIM, Wilson MT, Svistunenko DA, Vijgenboom E, Worrall JAR. Morphological development and cytochrome c oxidase activity in Streptomyces lividans are dependent on the action of a copper bound Sco protein. Open Biol 2013; 3:120163. [PMID: 23345541 PMCID: PMC3603459 DOI: 10.1098/rsob.120163] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Copper has an important role in the life cycle of many streptomycetes, stimulating the developmental switch between vegetative mycelium and aerial hyphae concomitant with the production of antibiotics. In streptomycetes, a gene encoding for a putative Sco-like protein has been identified and is part of an operon that contains two other genes predicted to handle cellular copper. We report on the Sco-like protein from Streptomyces lividans (ScoSl) and present a series of experiments that firmly establish a role for ScoSl as a copper metallochaperone as opposed to a role as a thiol-disulphide reductase that has been assigned to other bacterial Sco proteins. Under low copper concentrations, a Δsco mutant in S. lividans displays two phenotypes; the development switch between vegetative mycelium and aerial hyphae stalls and cytochrome c oxidase (CcO) activity is significantly decreased. At elevated copper levels, the development and CcO activity in the Δsco mutant are restored to wild-type levels and are thus independent of ScoSl. A CcO knockout reveals that morphological development is independent of CcO activity leading us to suggest that ScoSl has at least two targets in S. lividans. We establish that one ScoSl target is the dinuclear CuA domain of CcO and it is the cupric form of ScoSl that is functionally active. The mechanism of cupric ion capture by ScoSl has been investigated, and an important role for a conserved His residue is identified.
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Affiliation(s)
- Katie L I M Blundell
- School of Biological Sciences, University of Essex, Wivenhoe Park, Colchester CO4 3SQ, UK
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13
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Blundell KLIM, Wilson MT, Vijgenboom E, Worrall JAR. The role of the Cys-X-X-X-Cys motif on the kinetics of cupric ion loading to the Streptomyces lividans Sco protein. Dalton Trans 2013; 42:10608-16. [DOI: 10.1039/c3dt50540e] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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14
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Soto IC, Fontanesi F, Liu J, Barrientos A. Biogenesis and assembly of eukaryotic cytochrome c oxidase catalytic core. BIOCHIMICA ET BIOPHYSICA ACTA 2012; 1817:883-97. [PMID: 21958598 PMCID: PMC3262112 DOI: 10.1016/j.bbabio.2011.09.005] [Citation(s) in RCA: 158] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2011] [Revised: 09/07/2011] [Accepted: 09/12/2011] [Indexed: 10/17/2022]
Abstract
Eukaryotic cytochrome c oxidase (COX) is the terminal enzyme of the mitochondrial respiratory chain. COX is a multimeric enzyme formed by subunits of dual genetic origin which assembly is intricate and highly regulated. The COX catalytic core is formed by three mitochondrial DNA encoded subunits, Cox1, Cox2 and Cox3, conserved in the bacterial enzyme. Their biogenesis requires the action of messenger-specific and subunit-specific factors which facilitate the synthesis, membrane insertion, maturation or assembly of the core subunits. The study of yeast strains and human cell lines from patients carrying mutations in structural subunits and COX assembly factors has been invaluable to identify these ancillary factors. Here we review the current state of knowledge of the biogenesis and assembly of the eukaryotic COX catalytic core and discuss the degree of conservation of the players and mechanisms operating from yeast to human. This article is part of a Special Issue entitled: Biogenesis/Assembly of Respiratory Enzyme Complexes.
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Affiliation(s)
- Ileana C. Soto
- Department of Biochemistry & Molecular Biology, University of Miami Miller School of Medicine. Miami, FL
| | - Flavia Fontanesi
- Department of Neurology. University of Miami Miller School of Medicine. Miami, FL
| | - Jingjing Liu
- Department of Biochemistry & Molecular Biology, University of Miami Miller School of Medicine. Miami, FL
| | - Antoni Barrientos
- Department of Biochemistry & Molecular Biology, University of Miami Miller School of Medicine. Miami, FL
- Department of Neurology. University of Miami Miller School of Medicine. Miami, FL
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15
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Lai M, Yam KC, Andrews D, Hill BC. Copper binding traps the folded state of the SCO protein from Bacillus subtilis. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2012; 1824:292-302. [DOI: 10.1016/j.bbapap.2011.10.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/29/2011] [Revised: 09/15/2011] [Accepted: 10/10/2011] [Indexed: 11/29/2022]
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16
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Hill BC, Andrews D. Differential affinity of BsSCO for Cu(II) and Cu(I) suggests a redox role in copper transfer to the Cu(A) center of cytochrome c oxidase. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2011; 1817:948-54. [PMID: 21945854 DOI: 10.1016/j.bbabio.2011.09.006] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2011] [Revised: 09/01/2011] [Accepted: 09/12/2011] [Indexed: 10/17/2022]
Abstract
SCO (synthesis of cytochrome c oxidase) proteins are involved in the assembly of the respiratory chain enzyme cytochrome c oxidase acting to assist in the assembly of the Cu(A) center contained within subunit II of the oxidase complex. The Cu(A) center receives electrons from the reductive substrate ferrocytochrome c, and passes them on to the cytochrome a center. Cytochrome a feeds electrons to the oxygen reaction site composed of cytochrome a(3) and Cu(B). Cu(A) consists of two copper ions positioned within bonding distance and ligated by two histidine side chains, one methionine, a backbone carbonyl and two bridging cysteine residues. The complex structure and redox capacity of Cu(A) present a potential assembly challenge. SCO proteins are members of the thioredoxin family which led to the early suggestion of a disulfide exchange function for SCO in Cu(A) assembly, whereas the copper binding capacity of the Bacillus subtilis version of SCO (i.e., BsSCO) suggests a direct role for SCO proteins in copper transfer. We have characterized redox and copper exchange properties of apo- and metalated-BsSCO. The release of copper (II) from its complex with BsSCO is best achieved by reducing it to Cu(I). We propose a mechanism involving both disulfide and copper exchange between BsSCO and the apo-Cu(A) site. This article is part of a Special Issue entitled: Biogenesis/Assembly of Respiratory Enzyme Complexes.
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Affiliation(s)
- Bruce C Hill
- Department of Biochemistry and Protein Function Discovery Group, Queen's University, Kingston, Ontario, Canada K7L 3N6.
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17
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Banci L, Bertini I, Cavallaro G, Ciofi-Baffoni S. Seeking the determinants of the elusive functions of Sco proteins. FEBS J 2011; 278:2244-62. [DOI: 10.1111/j.1742-4658.2011.08141.x] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
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18
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Bennett B, Hill BC. Avoiding premature oxidation during the binding of Cu(II) to a dithiolate site in BsSCO. A rapid freeze-quench EPR study. FEBS Lett 2011; 585:861-4. [PMID: 21333651 DOI: 10.1016/j.febslet.2011.02.014] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2011] [Revised: 02/10/2011] [Accepted: 02/11/2011] [Indexed: 10/18/2022]
Abstract
The Bacillus subtilis version of SCO1 (BsSCO) is required for assembly of Cu(A) in cytochrome c oxidase and may function in thiol-disulfide exchange and/or copper delivery. BsSCO binds Cu(II) with ligation by two cysteines, one histidine and one water. However, copper is a catalyst of cysteine oxidation and BsSCO must avoid this reaction to remain functional. Time resolved, rapid freeze-quench (RFQ) electron paramagnetic resonance of apo-BsSCO reacting with Cu(II) reveals an initial Cu(II) species with two equatorially coordinated nitrogen atoms, but no sulfur. We propose that BsSCO evolves from this initial sulfur free coordination of Cu(II) to the final dithiolate species via a change in conformation, and that the initial binding by nitrogen is a means for BsSCO to avoid premature thiol oxidation.
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Affiliation(s)
- Brian Bennett
- National Biomedical EPR Center, Department of Biophysics, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA
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19
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Banci L, Bertini I, Ciofi-Baffoni S, Kozyreva T, Mori M, Wang S. Sco proteins are involved in electron transfer processes. J Biol Inorg Chem 2010; 16:391-403. [DOI: 10.1007/s00775-010-0735-x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2010] [Accepted: 11/09/2010] [Indexed: 12/01/2022]
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20
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Siluvai GS, Nakano M, Mayfield M, Blackburn NJ. The essential role of the Cu(II) state of Sco in the maturation of the Cu(A) center of cytochrome oxidase: evidence from H135Met and H135SeM variants of the Bacillus subtilis Sco. J Biol Inorg Chem 2010; 16:285-97. [PMID: 21069401 DOI: 10.1007/s00775-010-0725-z] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2010] [Accepted: 10/19/2010] [Indexed: 01/24/2023]
Abstract
Sco is a red copper protein that plays an essential yet poorly understood role in the metalation of the Cu(A) center of cytochrome oxidase, and is stable in both the Cu(I) and Cu(II) forms. To determine which oxidation state is important for function, we constructed His135 to Met or selenomethionine (SeM) variants that were designed to stabilize the Cu(I) over the Cu(II) state. H135M was unable to complement a scoΔ strain of Bacillus subtilis, indicating that the His to Met substitution abrogated cytochrome oxidase maturation. The Cu(I) binding affinities of H135M and H135SeM were comparable to that of the WT and 100-fold tighter than that of the H135A variant. The coordination chemistry of the H135M and H135SeM variants was studied by UV/vis, EPR, and XAS spectroscopy in both the Cu(I) and the Cu(II) forms. Both oxidation states bound copper via the S atoms of C45, C49 and M135. In particular, EXAFS data collected at both the Cu and the Se edges of the H135SeM derivative provided unambiguous evidence for selenomethionine coordination. Whereas the coordination chemistry and copper binding affinity of the Cu(I) state closely resembled that of the WT protein, the Cu(II) state was unstable, undergoing autoreduction to Cu(I). H135M also reacted faster with H(2)O(2) than WT Sco. These data, when coupled with the complete elimination of function in the H135M variant, imply that the Cu(I) state cannot be the sole determinant of function; the Cu(II) state must be involved in function at some stage of the reaction cycle.
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Affiliation(s)
- Gnana S Siluvai
- Division of Environmental and Biomolecular Systems, Oregon Health and Sciences University, 20000 NW Walker Road, Beaverton, OR 97006, USA
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21
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Banci L, Bertini I, Cantini F, Ciofi-Baffoni S. Cellular copper distribution: a mechanistic systems biology approach. Cell Mol Life Sci 2010; 67:2563-89. [PMID: 20333435 PMCID: PMC11115773 DOI: 10.1007/s00018-010-0330-x] [Citation(s) in RCA: 111] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2009] [Revised: 01/27/2010] [Accepted: 02/22/2010] [Indexed: 01/01/2023]
Abstract
Copper is an essential but potentially harmful trace element required in many enzymatic processes involving redox chemistry. Cellular copper homeostasis in mammals is predominantly maintained by regulating copper transport through the copper import CTR proteins and the copper exporters ATP7A and ATP7B. Once copper is imported into the cell, several pathways involving a number of copper proteins are responsible for trafficking it specifically where it is required for cellular life, thus avoiding the release of harmful free copper ions. In this study we review recent progress made in understanding the molecular mechanisms of copper transport in cells by analyzing structural features of copper proteins, their mode of interaction, and their thermodynamic and kinetic parameters, thus contributing to systems biology of copper within the cell.
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Affiliation(s)
- Lucia Banci
- Department of Chemistry, Magnetic Resonance Center CERM, University of Florence, Via Luigi Sacconi 6, 50019 Sesto Fiorentino, Florence Italy
| | - Ivano Bertini
- Department of Chemistry, Magnetic Resonance Center CERM, University of Florence, Via Luigi Sacconi 6, 50019 Sesto Fiorentino, Florence Italy
| | - Francesca Cantini
- Department of Chemistry, Magnetic Resonance Center CERM, University of Florence, Via Luigi Sacconi 6, 50019 Sesto Fiorentino, Florence Italy
| | - Simone Ciofi-Baffoni
- Department of Chemistry, Magnetic Resonance Center CERM, University of Florence, Via Luigi Sacconi 6, 50019 Sesto Fiorentino, Florence Italy
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22
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Siluvai GS, Mayfield M, Nilges MJ, Debeer George S, Blackburn NJ. Anatomy of a red copper center: spectroscopic identification and reactivity of the copper centers of Bacillus subtilis Sco and its Cys-to-Ala variants. J Am Chem Soc 2010; 132:5215-26. [PMID: 20232870 DOI: 10.1021/ja910759v] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Sco is a mononuclear red copper protein involved in the assembly of cytochrome c oxidase. It is spectroscopically similar to red copper nitrosocyanin, but unlike the latter, which has one copper cysteine thiolate, the former has two. In addition to the two cysteine ligands (C45 and C49), the wild-type (WT) protein from Bacillus subtilis (hereafter named BSco) has a histidine (H135) and an unknown endogenous protein oxygen ligand in a distorted tetragonal array. We have compared the properties of the WT protein to variants in which each of the two coordinating Cys residues has been individually mutated to Ala, using UV/visible, Cu and S K-edge X-ray absorption, electron paramagnetic resonance, and resonance Raman spectroscopies. Unlike the Cu(II) form of native Sco, the Cu(II) complexes of the Cys variants are unstable. The copper center of C49A undergoes autoreduction to the Cu(I) form, which is shown by extended X-ray absorption fine structure to be composed of a novel two-coordinate center with one Cys and one His ligand. C45A rearranges to a new stable Cu(II) species coordinated by C49, H135 and a second His ligand recruited from a previously uncoordinated protein side chain. The different chemistry exhibited by the Cys variants can be rationalized by whether a stable Cu(I) species can be formed by autoredox chemistry. For C49A, the remaining Cys and His residues are trans, which facilitates the formation of the highly stable two-coordinate Cu(I) species, while for C45A such a configuration cannot be attained. Resonance Raman spectroscopy of the WT protein indicates a net weak Cu-S bond strength at approximately 2.24 A corresponding to the two thiolate-copper bonds, whereas the single variant C45A shows a moderately strong Cu-S bond at approximately 2.16 A. S K-edge data give a total covalency of 28% for both Cu-S bonds in the WT protein. These data suggest an average covalency per Cu-S bond lower than that observed for nitrosocyanin and close to that expected for type-2 Cu(II)-thiolate systems. The data are discussed relative to the unique Cu-S characteristics of cupredoxins, from which it is concluded that Sco does not contain highly covalent Cu-S bonds of the type expected for long-range electron-transfer reactivity.
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Affiliation(s)
- Gnana S Siluvai
- Department of Science & Engineering, Oregon Health & Science University, Beaverton, Oregon 97006, USA
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23
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Bühler D, Rossmann R, Landolt S, Balsiger S, Fischer HM, Hennecke H. Disparate pathways for the biogenesis of cytochrome oxidases in Bradyrhizobium japonicum. J Biol Chem 2010; 285:15704-13. [PMID: 20335176 DOI: 10.1074/jbc.m109.085217] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
This work addresses the biogenesis of heme-copper terminal oxidases in Bradyrhizobium japonicum, the nitrogen-fixing root nodule symbiont of soybean. B. japonicum has four quinol oxidases and four cytochrome oxidases. The latter include the aa(3)- and cbb(3)-type oxidases. Although both have a Cu(B) center in subunit I, the subunit II proteins differ in having either a Cu(A) center (in aa(3)) or a covalently bound heme c (in cbb(3)). Two biogenesis factors were genetically studied here, the periplasmically exposed CoxG and ScoI proteins, which are the respective homologs of the mitochondrial copper-trafficking chaperones Cox11 and Sco1 for the formation of the Cu(B) center in subunit I and the Cu(A) center in subunit II of cytochrome aa(3). We could demonstrate copper binding to ScoI in vitro, a process for which the thiols of cysteine residues 74 and 78 in the ScoI polypeptide were shown to be essential. Knock-out mutations in the B. japonicum coxG and scoI genes led to loss of cytochrome aa(3) assembly and activity in the cytoplasmic membrane, whereas the cbb(3)-type cytochrome oxidase apparently remained unaffected. This suggests that subunit I of the cbb(3)-type oxidase obtains its copper cofactor via a different pathway than cytochrome aa(3). In contrast to the coxG mutation, the scoI mutation caused a decreased symbiotic nitrogen fixation activity. We hypothesize that a periplasmic B. japonicum protein other than any of the identified Cu(A) proteins depends on ScoI and is required for an effective symbiosis.
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Affiliation(s)
- Doris Bühler
- Institute of Microbiology, Swiss Federal Institute of Technology, Wolfgang-Pauli-Strasse 10, CH-8093 Zürich, Switzerland
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24
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Siluvai GS, Nakano MM, Mayfield M, Nilges MJ, Blackburn NJ. H135A controls the redox activity of the Sco copper center. Kinetic and spectroscopic studies of the His135Ala variant of Bacillus subtilis Sco. Biochemistry 2010; 48:12133-44. [PMID: 19921776 DOI: 10.1021/bi901480g] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Sco-like proteins contain copper bound by two cysteines and a histidine residue. Although their function is still incompletely understood, there is a clear involvement with the assembly of cytochrome oxidases that contain the Cu(A) center in subunit 2, possibly mediating the transfer of copper into the Cu(A) binuclear site. We are investigating the reaction chemistry of BSco, the homologue from Bacillus subtilis. Our studies have revealed that BSco behaves more like a redox protein than a metallochaperone. The essential H135 residue that coordinates copper plays a role in stabilizing the Cu(II) rather than the Cu(I) form. When H135 is mutated to alanine, the oxidation rate of both hydrogen peroxide and one-electron outer-sphere reductants increases by 3 orders of magnitude, suggestive of a redox switch mechanism between the His-on and His-off conformational states of the protein. Imidazole binds to the H135A protein, restoring the N superhyperfine coupling in the EPR, but is unable to rescue the redox properties of wild-type Sco. These findings reveal a unique role for H135 in Sco function. We propose a hypothesis that electron transfer from Sco to the maturing oxidase may be essential for proper maturation and/or protection from oxidative damage during the assembly process. The findings also suggest that interaction of Sco with its protein partner(s) may perturb the Cu(II)-H135 interaction and thus induce a sensitive redox activity to the protein.
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Affiliation(s)
- Gnana S Siluvai
- Department of Science and Engineering, Oregon Health and Science University, Beaverton, Oregon 97006, USA
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25
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Davidson DE, Hill BC. Stability of oxidized, reduced and copper bound forms of Bacillus subtilis Sco. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2008; 1794:275-81. [PMID: 19027886 DOI: 10.1016/j.bbapap.2008.10.005] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2008] [Revised: 10/21/2008] [Accepted: 10/24/2008] [Indexed: 11/30/2022]
Abstract
Sco is an accessory protein required for assembly of the Cu(A) center of cytochrome c oxidase. Functions proposed for Sco include as a copper chaperone and as a thiol-disulfide exchange protein. Differential scanning calorimetry (DSC) is used here to assess the interaction between the Bacillis subtilis version of Sco (BsSco) and Cu(II). When BsSco binds Cu(II) its melting temperature increases by 23 degrees C, which corresponds to an equilibrium dissociation constant of 3.50 pM. In contrast BsSco exhibits a much weaker affinity for Cu(I) (K(D)=10 microM). BsSco-Cu(II) is stable over days indicating an extremely slow dissociation for BsSco-Cu(II). However, at high ionic strength in the presence of excess copper, BsSco-Cu(II) returns to its oxidized, disulfide-bonded state and loses its copper binding capacity with a half time of 100 s. DSC of BsSco at high ionic strength indicates an increase in stability of metal free, reduced BsSco combined with a small destabilization of BsSco-Cu(II). It is proposed that BsSco undergoes an ionic strength induced conformational change that promotes electron transfer from the thiol groups on BsSco to Cu(II) to effect copper release. Such a redox transformation could be an important aspect of the copper transfer role proposed for BsSco in Cu(A) assembly.
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Affiliation(s)
- David E Davidson
- Department of Biochemistry, Queen's University, Kingston, Ontario K7L 3N6, Canada
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26
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Abriata LA, Banci L, Bertini I, Ciofi-Baffoni S, Gkazonis P, Spyroulias GA, Vila AJ, Wang S. Mechanism of Cu(A) assembly. Nat Chem Biol 2008; 4:599-601. [PMID: 18758441 PMCID: PMC2596924 DOI: 10.1038/nchembio.110] [Citation(s) in RCA: 105] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2008] [Accepted: 08/08/2008] [Indexed: 11/10/2022]
Abstract
Copper is essential for proper functioning of cytochrome c oxidases, and therefore for cellular respiration in eukaryotes and many bacteria. Here we show that a new periplasmic protein (PCu(A)C) selectively inserts Cu(I) ions into subunit II of Thermus thermophilus ba(3) oxidase to generate a native Cu(A) site. The purported metallochaperone Sco1 is unable to deliver copper ions; instead, it works as a thiol-disulfide reductase to maintain the correct oxidation state of the Cu(A) cysteine ligands.
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Affiliation(s)
- Luciano A Abriata
- Instituto de Biología Molecular y Celular de Rosario, Consejo Nacional de Investigaciones Científicas y Técnicas, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Suipacha 531, (S2002LRK) Rosario, Argentina
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27
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Horn D, Barrientos A. Mitochondrial copper metabolism and delivery to cytochrome c oxidase. IUBMB Life 2008; 60:421-9. [PMID: 18459161 DOI: 10.1002/iub.50] [Citation(s) in RCA: 173] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Metals are essential elements of all living organisms. Among them, copper is required for a multiplicity of functions including mitochondrial oxidative phosphorylation and protection against oxidative stress. Here we will focus on describing the pathways involved in the delivery of copper to cytochrome c oxidase (COX), a mitochondrial metalloenzyme acting as the terminal enzyme of the mitochondrial respiratory chain. The catalytic core of COX is formed by three mitochondrially-encoded subunits and contains three copper atoms. Two copper atoms bound to subunit 2 constitute the Cu(A) site, the primary acceptor of electrons from ferrocytochrome c. The third copper, Cu(B), is associated with the high-spin heme a(3) group of subunit 1. Recent studies, mostly performed in the yeast Saccharomyces cerevisiae, have provided new clues about 1) the source of the copper used for COX metallation; 2) the roles of Sco1p and Cox11p, the proteins involved in the direct delivery of copper to the Cu(A) and Cu(B) sites, respectively; 3) the action mechanism of Cox17p, a copper chaperone that provides copper to Sco1p and Cox11p; 4) the existence of at least four Cox17p homologues carrying a similar twin CX(9)C domain suggestive of metal binding, Cox19p, Cox23p, Pet191p and Cmc1p, that could be part of the same pathway; and 5) the presence of a disulfide relay system in the intermembrane space of mitochondria that mediates import of proteins with conserved cysteines motifs such as the CX(9)C characteristic of Cox17p and its homologues. The different pathways are reviewed and discussed in the context of both mitochondrial COX assembly and copper homeostasis.
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Affiliation(s)
- Darryl Horn
- Department of Biochemistry & Molecular Biology, The John T. MacDonald Foundation Center for Medical Genetics,University of Miami Miller School of Medicine, Miami, FL 33136, USA
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28
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Barrientos A, Gouget K, Horn D, Soto IC, Fontanesi F. Suppression mechanisms of COX assembly defects in yeast and human: insights into the COX assembly process. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2008; 1793:97-107. [PMID: 18522805 DOI: 10.1016/j.bbamcr.2008.05.003] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2008] [Revised: 04/29/2008] [Accepted: 05/05/2008] [Indexed: 12/11/2022]
Abstract
Eukaryotic cytochrome c oxidase (COX) is the terminal enzyme of the mitochondrial respiratory chain. COX is a multimeric enzyme formed by subunits of dual genetic origin whose assembly is intricate and highly regulated. In addition to the structural subunits, a large number of accessory factors are required to build the holoenzyme. The function of these factors is required in all stages of the assembly process. They are relevant to human health because devastating human disorders have been associated with mutations in nuclear genes encoding conserved COX assembly factors. The study of yeast strains and human cell lines from patients carrying mutations in structural subunits and COX assembly factors has been invaluable to attain the current state of knowledge, even if still fragmentary, of the COX assembly process. After the identification of the genes involved, the isolation and characterization of genetic and metabolic suppressors of COX assembly defects, reviewed here, have become a profitable strategy to gain insight into their functions and the pathways in which they operate. Additionally, they have the potential to provide useful information for devising therapeutic approaches to combat human disorders associated with COX deficiency.
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Affiliation(s)
- Antoni Barrientos
- Department of Neurology, University of Miami Miller School of Medicine, Miami, FL 33136, USA.
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29
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Badrick AC, Hamilton AJ, Bernhardt PV, Jones CE, Kappler U, Jennings MP, McEwan AG. PrrC, a Sco homologue fromRhodobacter sphaeroides, possesses thiol-disulfide oxidoreductase activity. FEBS Lett 2007; 581:4663-7. [PMID: 17850796 DOI: 10.1016/j.febslet.2007.08.058] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2007] [Accepted: 08/23/2007] [Indexed: 11/17/2022]
Abstract
PrrC is a Sco homologue in Rhodobacter sphaeroides that is associated with PrrBA, a two-component signal transduction system that induces photosynthesis gene expression in response to a decrease in oxygen tension. Although Sco proteins have been shown to bind copper the observation that they are structurally-related to thioredoxins suggested that they might possess thiol-disulfide oxidoreductase activity. Our results show that PrrC reduces Cu(2+) to Cu(+) and possesses disulfide reductase activity. These results indicate that some bacterial Sco proteins may have biochemical properties that are distinct from those of mitochondrial Sco proteins.
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Affiliation(s)
- Alison C Badrick
- Centre for Metals in Biology, School of Molecular and Microbial Sciences, The University of Queensland, Brisbane, Queensland 4072, Australia
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30
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Khalimonchuk O, Bird A, Winge DR. Evidence for a pro-oxidant intermediate in the assembly of cytochrome oxidase. J Biol Chem 2007; 282:17442-9. [PMID: 17430883 DOI: 10.1074/jbc.m702379200] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The hydrogen peroxide sensitivity of cells lacking two proteins, Sco1 and Cox11, important in the assembly of cytochrome c oxidase (CcO), is shown to arise from the transient accumulation of a pro-oxidant heme A-Cox1 stalled intermediate. The peroxide sensitivity of these cells is abrogated by a reduction in either Cox1 expression or heme A formation but exacerbated by either enhanced Cox1 expression or heme A production arising from overexpression of COX15. Sco1 and Cox11 are implicated in the formation of the Cu(A) and Cu(B) sites of CcO, respectively. The respective wild-type genes suppress the peroxide sensitivities of sco1Delta and cox11Delta cells, but no cross-complementation is seen with noncognate genes. Copper-binding mutant alleles of Sco1 and Cox11 that are nonfunctional in promoting the assembly of CcO are functional in suppressing the peroxide sensitivity of their respective null mutants. Likewise, human Sco1 that is nonfunctional in yeast CcO assembly is able to suppress the peroxide sensitivity of yeast sco1Delta cells. Thus, a disconnect exists between the respiratory capacity of cells and hydrogen peroxide sensitivity. Hydrogen peroxide sensitivity of sco1Delta and cox11Delta cells is abrogated by overexpression of a novel mitochondrial ATPase Afg1 that promotes the degradation of CcO mitochondrially encoded subunits. Studies on the hydrogen peroxide sensitivity in CcO assembly mutants reveal new aspects of the CcO assembly process.
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Affiliation(s)
- Oleh Khalimonchuk
- University of Utah Health Sciences Center, Department of Medicine, Salt Lake City, Utah 84132, USA
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31
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Zee JM, Glerum DM. Defects in cytochrome oxidase assembly in humans: lessons from yeast. Biochem Cell Biol 2007; 84:859-69. [PMID: 17215873 DOI: 10.1139/o06-201] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The biogenesis of the inner mitochondrial membrane enzyme cytochrome c oxidase (COX) is a complex process that requires the actions of ancillary proteins, collectively called assembly factors. Studies with the yeast Saccharomyces cerevisiae have provided considerable insight into the COX assembly pathway and have proven to be a fruitful model for understanding the molecular bases for inherited COX deficiencies in humans. In this review, we focus on critical steps in the COX assembly pathway. These processes are conserved from yeast to humans and are known to be involved in the etiology of human COX deficiencies. The contributions from our studies in yeast suggest that this organism remains an excellent model system for delineating the molecular mechanisms underlying COX assembly defects in humans. Current progress suggests that a complete picture of COX assembly will be achieved in the near future.
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Affiliation(s)
- Jennifer M Zee
- Department of Medical Genetics, University of Alberta, Edmonton, AB T6G 0M2, Canada
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Banci L, Bertini I, Ciofi-Baffoni S, Leontari I, Martinelli M, Palumaa P, Sillard R, Wang S. Human Sco1 functional studies and pathological implications of the P174L mutant. Proc Natl Acad Sci U S A 2006; 104:15-20. [PMID: 17182746 PMCID: PMC1765425 DOI: 10.1073/pnas.0606189103] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The pathogenic mutant (P174L) of human Sco1 produces respiratory chain deficiency associated with cytochrome c oxidase (CcO) assembly defects. The solution structure of the mutant in its Cu(I) form shows that Leu-174 prevents the formation of a well packed hydrophobic region around the metal-binding site and causes a reduction of the affinity of copper(I) for the protein. K(D) values for Cu(I)WT-HSco1 and Cu(I)P174L-HSco1 are approximately 10(-17) and approximately 10(-13), respectively. The reduction potentials of the two apo proteins are similar, but slower reduction/oxidation rates are found for the mutant with respect to the WT. The mitochondrial metallochaperone in the partially oxidized Cu(1)(I)Cox17(2S-S) form, at variance with the fully reduced Cu(4)(I)Cox17, interacts transiently with both WT-HSco1 and the mutant, forming the Cox17/Cu(I)/HSco1 complex, but copper is efficiently transferred only in the case of WT protein. Cu(1)(I)Cox17(2S-S) indeed has an affinity for copper(I) (K(D) approximately 10(-15)) higher than that of the P174L-HSco1 mutant but lower than that of WT-HSco1. We propose that HSco1 mutation, altering the structure around the metal-binding site, affects both copper(I) binding and redox properties of the protein, thus impairing the efficiency of copper transfer to CcO. The pathogenic mutation therefore could (i) lessen the Sco1 affinity for copper(I) and hence copper supply for CcO or (ii) decrease the efficiency of reduction of CcO thiols involved in copper binding, or both effects could be produced by the mutation.
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Affiliation(s)
- Lucia Banci
- *Magnetic Resonance Center (CERM) and Department of Chemistry, University of Florence, Via Luigi Sacconi 6, 50019 Sesto Fiorentino, Florence, Italy
- FiorGen Foundation, Via Luigi Sacconi 6, 50019 Sesto Fiorentino, Florence, Italy
| | - Ivano Bertini
- *Magnetic Resonance Center (CERM) and Department of Chemistry, University of Florence, Via Luigi Sacconi 6, 50019 Sesto Fiorentino, Florence, Italy
- To whom correspondence should be addressed. E-mail:
| | - Simone Ciofi-Baffoni
- *Magnetic Resonance Center (CERM) and Department of Chemistry, University of Florence, Via Luigi Sacconi 6, 50019 Sesto Fiorentino, Florence, Italy
| | - Iliana Leontari
- *Magnetic Resonance Center (CERM) and Department of Chemistry, University of Florence, Via Luigi Sacconi 6, 50019 Sesto Fiorentino, Florence, Italy
| | - Manuele Martinelli
- *Magnetic Resonance Center (CERM) and Department of Chemistry, University of Florence, Via Luigi Sacconi 6, 50019 Sesto Fiorentino, Florence, Italy
| | - Peep Palumaa
- Department of Gene Technology, Tallinn University of Technology, Akadeemia tee 15, 12618 Tallinn, Estonia
| | - Rannar Sillard
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, SE-171 77 Stockholm, Sweden; and
- Department of Gene Technology, Tallinn University of Technology, Akadeemia tee 15, 12618 Tallinn, Estonia
| | - Shenlin Wang
- *Magnetic Resonance Center (CERM) and Department of Chemistry, University of Florence, Via Luigi Sacconi 6, 50019 Sesto Fiorentino, Florence, Italy
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Fontanesi F, Soto IC, Horn D, Barrientos A. Assembly of mitochondrial cytochrome c-oxidase, a complicated and highly regulated cellular process. Am J Physiol Cell Physiol 2006; 291:C1129-47. [PMID: 16760263 DOI: 10.1152/ajpcell.00233.2006] [Citation(s) in RCA: 189] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Cytochrome c-oxidase (COX), the terminal enzyme of the mitochondrial respiratory chain, plays a key role in the regulation of aerobic production of energy. Biogenesis of eukaryotic COX involves the coordinated action of two genomes. Three mitochondrial DNA-encoded subunits form the catalytic core of the enzyme, which contains metal prosthetic groups. Another 10 subunits encoded in the nuclear DNA act as a protective shield surrounding the core. COX biogenesis requires the assistance of >20 additional nuclear-encoded factors acting at all levels of the process. Expression of the mitochondrial-encoded subunits, expression and import of the nuclear-encoded subunits, insertion of the structural subunits into the mitochondrial inner membrane, addition of prosthetic groups, assembly of the holoenzyme, further maturation to form a dimer, and additional assembly into supercomplexes are all tightly regulated processes in a nuclear-mitochondrial-coordinated fashion. Such regulation ensures the building of a highly efficient machine able to catalyze the safe transfer of electrons from cytochrome c to molecular oxygen and ultimately facilitate the aerobic production of ATP. In this review, we will focus on describing and analyzing the present knowledge about the different regulatory checkpoints in COX assembly and the dynamic relationships between the different factors involved in the process. We have used information mostly obtained from the suitable yeast model, but also from bacterial and animal systems, by means of large-scale genetic, molecular biology, and physiological approaches and by integrating information concerning individual elements into a cellular system network.
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Affiliation(s)
- Flavia Fontanesi
- Departments of Neurology, The John T. Macdonald Foundation Center for Medical Genetics, University of Miami Miller School of Medicine, Miami, Florida 33136, USA
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Banci L, Bertini I, Calderone V, Ciofi-Baffoni S, Mangani S, Martinelli M, Palumaa P, Wang S. A hint for the function of human Sco1 from different structures. Proc Natl Acad Sci U S A 2006; 103:8595-600. [PMID: 16735468 PMCID: PMC1482625 DOI: 10.1073/pnas.0601375103] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2006] [Indexed: 11/18/2022] Open
Abstract
The solution structures of apo, Cu(I), and Ni(II) human Sco1 have been determined. The protein passes from an open and conformationally mobile state to a closed and rigid conformation upon metal binding as shown by electrospray ionization MS and NMR data. The metal ligands of Cu(I) are two Cys residues of the CPXXCP motif and a His residue. The latter is suitably located to coordinate the metal anchored by the two Cys residues. The coordination sphere of Ni(II) in solution is completed by another ligand, possibly Asp. Crystals of the Ni(II) derivative were also obtained with the Ni(II) ion bound to the same His residue and to the two oxidized Cys residues of the CPXXCP motif. We propose that the various structures solved here represent the various states of the protein in its functional cycle and that the metal can be bound to the oxidized protein at a certain stage. Although it now seems reasonable that Sco1, which is characterized by a thioredoxin fold, has evolved to bind a metal atom via the di-Cys motif to act as a copper chaperone, the oxidized form of the nickel-bound protein suggests that it may also maintain the thioredoxin function.
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Affiliation(s)
- Lucia Banci
- *Magnetic Resonance Center and Department of Chemistry, University of Florence, Via Luigi Sacconi 6, 50019 Florence, Italy
| | - Ivano Bertini
- *Magnetic Resonance Center and Department of Chemistry, University of Florence, Via Luigi Sacconi 6, 50019 Florence, Italy
| | - Vito Calderone
- *Magnetic Resonance Center and Department of Chemistry, University of Florence, Via Luigi Sacconi 6, 50019 Florence, Italy
| | - Simone Ciofi-Baffoni
- *Magnetic Resonance Center and Department of Chemistry, University of Florence, Via Luigi Sacconi 6, 50019 Florence, Italy
| | - Stefano Mangani
- *Magnetic Resonance Center and Department of Chemistry, University of Florence, Via Luigi Sacconi 6, 50019 Florence, Italy
- Department of Chemistry, Università degli Studi di Siena, Via Aldo Moro 1, 53100 Siena, Italy; and
| | - Manuele Martinelli
- *Magnetic Resonance Center and Department of Chemistry, University of Florence, Via Luigi Sacconi 6, 50019 Florence, Italy
| | - Peep Palumaa
- Department of Gene Technology, Tallinn University of Technology, Akadeemia tee 15, 12618 Tallinn, Estonia
| | - Shenlin Wang
- *Magnetic Resonance Center and Department of Chemistry, University of Florence, Via Luigi Sacconi 6, 50019 Florence, Italy
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Arnesano F, Banci L, Bertini I, Capozzi F, Ciofi-Baffoni S, Ciurli S, Luchinat C, Mangani S, Rosato A, Turano P, Viezzoli MS. An Italian contribution to structural genomics: Understanding metalloproteins. Coord Chem Rev 2006. [DOI: 10.1016/j.ccr.2006.01.008] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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Abajian C, Rosenzweig AC. Crystal structure of yeast Sco1. J Biol Inorg Chem 2006; 11:459-66. [PMID: 16570183 DOI: 10.1007/s00775-006-0096-7] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2006] [Accepted: 02/25/2006] [Indexed: 10/24/2022]
Abstract
The Sco family of proteins are involved in the assembly of the dinuclear CuA site in cytochrome c oxidase (COX), the terminal enzyme in aerobic respiration. These proteins, which are found in both eukaryotes and prokaryotes, are characterized by a conserved CXXXC sequence motif that binds copper ions and that has also been proposed to perform a thiol:disulfide oxidoreductase function. The crystal structures of Saccharomyces cerevisiae apo Sco1 (apo-ySco1) and Sco1 in the presence of copper ions (Cu-ySco1) were determined to 1.8- and 2.3-A resolutions, respectively. Yeast Sco1 exhibits a thioredoxin-like fold, similar to that observed for human Sco1 and a homolog from Bacillus subtilis. The Cu-ySco1 structure, obtained by soaking apo-ySco1 crystals in copper ions, reveals an unexpected copper-binding site involving Cys181 and Cys216, cysteine residues present in ySco1 but not in other homologs. The conserved CXXXC cysteines, Cys148 and Cys152, can undergo redox chemistry in the crystal. An essential histidine residue, His239, is located on a highly flexible loop, denoted the Sco loop, and can adopt positions proximal to both pairs of cysteines. Interactions between ySco1 and its partner proteins yeast Cox17 and yeast COX2 are likely to occur via complementary electrostatic surfaces. This high-resolution model of a eukaryotic Sco protein provides new insight into Sco copper binding and function.
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Affiliation(s)
- Carnie Abajian
- Department of Biochemistry, Molecular Biology, and Cell Biology, Northwestern University, Evanston, IL 60208, USA
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Swem DL, Swem LR, Setterdahl A, Bauer CE. Involvement of SenC in assembly of cytochrome c oxidase in Rhodobacter capsulatus. J Bacteriol 2005; 187:8081-7. [PMID: 16291681 PMCID: PMC1291261 DOI: 10.1128/jb.187.23.8081-8087.2005] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
SenC, a Sco1 homolog found in the purple photosynthetic bacteria, has been implicated in affecting photosynthesis and respiratory gene expression, as well as assembly of cytochrome c oxidase. In this study, we show that SenC from Rhodobacter capsulatus is involved in the assembly of a fully functional cbb(3)-type cytochrome c oxidase, as revealed by decreased cytochrome c oxidase activity in a senC mutant. We also show that a putative copper-binding site in SenC is required for activity and that a SenC deletion phenotype can be rescued by the addition of exogenous copper to the growth medium. In addition, we demonstrate that a SenC mutation has an indirect effect on gene expression caused by a reduction in cytochrome c oxidase activity. A model is proposed whereby a reduction in cytochrome c oxidase activity impedes the flow of electrons through the respiratory pathway, thereby affecting the oxidation/reduction state of the ubiquinone pool, leading to alterations of photosystem and respiratory gene expression.
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Affiliation(s)
- Danielle L Swem
- Department of Biology, Indiana University, Bloomington, 47405, USA
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Horng YC, Leary SC, Cobine PA, Young FBJ, George GN, Shoubridge EA, Winge DR. Human Sco1 and Sco2 function as copper-binding proteins. J Biol Chem 2005; 280:34113-22. [PMID: 16091356 DOI: 10.1074/jbc.m506801200] [Citation(s) in RCA: 133] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The function of human Sco1 and Sco2 is shown to be dependent on copper ion binding. Expression of soluble domains of human Sco1 and Sco2 either in bacteria or the yeast cytoplasm resulted in the recovery of copper-containing proteins. The metallation of human Sco1, but not Sco2, when expressed in the yeast cytoplasm is dependent on the co-expression of human Cox17. Two conserved cysteines and a histidyl residue, known to be important for both copper binding and in vivo function in yeast Sco1, are also critical for in vivo function of human Sco1 and Sco2. Human and yeast Sco proteins can bind either a single Cu(I) or Cu(II) ion. The Cu(II) site yields S-Cu(II) charge transfer transitions that are not bleached by weak reductants or chelators. The Cu(I) site exhibits trigonal geometry, whereas the Cu(II) site resembles a type II Cu(II) site with a higher coordination number. To identify additional potential ligands for the Cu(II) site, a series of mutant proteins with substitutions in conserved residues in the vicinity of the Cu(I) site were examined. Mutation of several conserved carboxylates did not alter either in vivo function or the presence of the Cu(II) chromophore. In contrast, replacement of Asp238 in human or yeast Sco1 abrogated the Cu(II) visible transitions and in yeast Sco1 attenuated Cu(II), but not Cu(I), binding. Both the mutant yeast and human proteins were nonfunctional, suggesting the importance of this aspartate for normal function. Taken together, these data suggest that both Cu(I) and Cu(II) binding are critical for normal Sco function.
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Affiliation(s)
- Yih-Chern Horng
- Department of Medicine, University of Utah Health Sciences Center, Salt Lake City, Utah 84132, USA
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