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Miralles-Robledillo JM, Martínez-Espinosa RM, Pire C. Transcriptomic profiling of haloarchaeal denitrification through RNA-Seq analysis. Appl Environ Microbiol 2024; 90:e0057124. [PMID: 38814058 PMCID: PMC11218638 DOI: 10.1128/aem.00571-24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2024] [Accepted: 04/26/2024] [Indexed: 05/31/2024] Open
Abstract
Denitrification, a crucial biochemical pathway prevalent among haloarchaea in hypersaline ecosystems, has garnered considerable attention in recent years due to its ecological implications. Nevertheless, the underlying molecular mechanisms and genetic regulation governing this respiration/detoxification process in haloarchaea remain largely unexplored. In this study, RNA-sequencing was used to compare the transcriptomes of the haloarchaeon Haloferax mediterranei under oxic and denitrifying conditions, shedding light on the intricate metabolic alterations occurring within the cell, such as the accurate control of the metal homeostasis. Furthermore, the investigation identifies several genes encoding transcriptional regulators and potential accessory proteins with putative roles in denitrification. Among these are bacterioopsin-like transcriptional activators, proteins harboring a domain of unknown function (DUF2249), and cyanoglobin. In addition, the study delves into the genetic regulation of denitrification, finding a regulatory motif within promoter regions that activates numerous denitrification-related genes. This research serves as a starting point for future molecular biology studies in haloarchaea, offering a promising avenue to unravel the intricate mechanisms governing haloarchaeal denitrification, a pathway of paramount ecological importance.IMPORTANCEDenitrification, a fundamental process within the nitrogen cycle, has been subject to extensive investigation due to its close association with anthropogenic activities, and its contribution to the global warming issue, mainly through the release of N2O emissions. Although our comprehension of denitrification and its implications is generally well established, most studies have been conducted in non-extreme environments with mesophilic microorganisms. Consequently, there is a significant knowledge gap concerning extremophilic denitrifiers, particularly those inhabiting hypersaline environments. The significance of this research was to delve into the process of haloarchaeal denitrification, utilizing the complete denitrifier haloarchaeon Haloferax mediterranei as a model organism. This research led to the analysis of the metabolic state of this microorganism under denitrifying conditions and the identification of regulatory signals and genes encoding proteins potentially involved in this pathway, serving as a valuable resource for future molecular studies.
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Affiliation(s)
- Jose María Miralles-Robledillo
- Biochemistry, Molecular Biology, Edaphology and Agricultural Chemistry Department, Faculty of Sciences, Universitat d'Alacant, Alicante, Spain
| | - Rosa María Martínez-Espinosa
- Biochemistry, Molecular Biology, Edaphology and Agricultural Chemistry Department, Faculty of Sciences, Universitat d'Alacant, Alicante, Spain
- Multidisciplinary Institute for Environmental Studies “Ramón Margalef”, University of Alicante, Alicante, Spain
| | - Carmen Pire
- Biochemistry, Molecular Biology, Edaphology and Agricultural Chemistry Department, Faculty of Sciences, Universitat d'Alacant, Alicante, Spain
- Multidisciplinary Institute for Environmental Studies “Ramón Margalef”, University of Alicante, Alicante, Spain
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2
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Caron-Godon CA, Collington E, Wolf JL, Coletta G, Glerum DM. More than Just Bread and Wine: Using Yeast to Understand Inherited Cytochrome Oxidase Deficiencies in Humans. Int J Mol Sci 2024; 25:3814. [PMID: 38612624 PMCID: PMC11011759 DOI: 10.3390/ijms25073814] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2024] [Revised: 03/26/2024] [Accepted: 03/28/2024] [Indexed: 04/14/2024] Open
Abstract
Inherited defects in cytochrome c oxidase (COX) are associated with a substantial subset of diseases adversely affecting the structure and function of the mitochondrial respiratory chain. This multi-subunit enzyme consists of 14 subunits and numerous cofactors, and it requires the function of some 30 proteins to assemble. COX assembly was first shown to be the primary defect in the majority of COX deficiencies 36 years ago. Over the last three decades, most COX assembly genes have been identified in the yeast Saccharomyces cerevisiae, and studies in yeast have proven instrumental in testing the impact of mutations identified in patients with a specific COX deficiency. The advent of accessible genome-wide sequencing capabilities has led to more patient mutations being identified, with the subsequent identification of several new COX assembly factors. However, the lack of genotype-phenotype correlations and the large number of genes involved in generating a functional COX mean that functional studies must be undertaken to assign a genetic variant as being causal. In this review, we provide a brief overview of the use of yeast as a model system and briefly compare the COX assembly process in yeast and humans. We focus primarily on the studies in yeast that have allowed us to both identify new COX assembly factors and to demonstrate the pathogenicity of a subset of the mutations that have been identified in patients with inherited defects in COX. We conclude with an overview of the areas in which studies in yeast are likely to continue to contribute to progress in understanding disease arising from inherited COX deficiencies.
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Affiliation(s)
- Chenelle A. Caron-Godon
- Department of Biology, University of Waterloo, Waterloo, ON N2L 3G1, Canada; (C.A.C.-G.); (E.C.); (J.L.W.); (G.C.)
| | - Emma Collington
- Department of Biology, University of Waterloo, Waterloo, ON N2L 3G1, Canada; (C.A.C.-G.); (E.C.); (J.L.W.); (G.C.)
| | - Jessica L. Wolf
- Department of Biology, University of Waterloo, Waterloo, ON N2L 3G1, Canada; (C.A.C.-G.); (E.C.); (J.L.W.); (G.C.)
| | - Genna Coletta
- Department of Biology, University of Waterloo, Waterloo, ON N2L 3G1, Canada; (C.A.C.-G.); (E.C.); (J.L.W.); (G.C.)
| | - D. Moira Glerum
- Department of Biology, University of Waterloo, Waterloo, ON N2L 3G1, Canada; (C.A.C.-G.); (E.C.); (J.L.W.); (G.C.)
- Waterloo Institute for Nanotechnology, University of Waterloo, Waterloo, ON N2L 3G1, Canada
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ATP7A-Regulated Enzyme Metalation and Trafficking in the Menkes Disease Puzzle. Biomedicines 2021; 9:biomedicines9040391. [PMID: 33917579 PMCID: PMC8067471 DOI: 10.3390/biomedicines9040391] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2021] [Revised: 04/01/2021] [Accepted: 04/02/2021] [Indexed: 12/12/2022] Open
Abstract
Copper is vital for numerous cellular functions affecting all tissues and organ systems in the body. The copper pump, ATP7A is critical for whole-body, cellular, and subcellular copper homeostasis, and dysfunction due to genetic defects results in Menkes disease. ATP7A dysfunction leads to copper deficiency in nervous tissue, liver, and blood but accumulation in other tissues. Site-specific cellular deficiencies of copper lead to loss of function of copper-dependent enzymes in all tissues, and the range of Menkes disease pathologies observed can now be explained in full by lack of specific copper enzymes. New pathways involving copper activated lysosomal and steroid sulfatases link patient symptoms usually related to other inborn errors of metabolism to Menkes disease. Additionally, new roles for lysyl oxidase in activation of molecules necessary for the innate immune system, and novel adapter molecules that play roles in ERGIC trafficking of brain receptors and other proteins, are emerging. We here summarize the current knowledge of the roles of copper enzyme function in Menkes disease, with a focus on ATP7A-mediated enzyme metalation in the secretory pathway. By establishing mechanistic relationships between copper-dependent cellular processes and Menkes disease symptoms in patients will not only increase understanding of copper biology but will also allow for the identification of an expanding range of copper-dependent enzymes and pathways. This will raise awareness of rare patient symptoms, and thus aid in early diagnosis of Menkes disease patients.
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Cytochrome c oxidase deficiency. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2020; 1862:148335. [PMID: 33171185 DOI: 10.1016/j.bbabio.2020.148335] [Citation(s) in RCA: 57] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 09/10/2020] [Revised: 10/31/2020] [Accepted: 11/03/2020] [Indexed: 12/23/2022]
Abstract
Cytochrome c oxidase (COX) deficiency is characterized by a high degree of genetic and phenotypic heterogeneity, partly reflecting the extreme structural complexity, multiple post-translational modification, variable, tissue-specific composition, and the high number of and intricate connections among the assembly factors of this enzyme. In fact, decreased COX specific activity can manifest with different degrees of severity, affect the whole organism or specific tissues, and develop a wide spectrum of disease natural history, including disease onsets ranging from birth to late adulthood. More than 30 genes have been linked to COX deficiency, but the list is still incomplete and in fact constantly updated. We here discuss the current knowledge about COX in health and disease, focusing on genetic aetiology and link to clinical manifestations. In addition, information concerning either fundamental biological features of the enzymes or biochemical signatures of its defects have been provided by experimental in vivo models, including yeast, fly, mouse and fish, which expanded our knowledge on the functional features and the phenotypical consequences of different forms of COX deficiency.
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Ekim Kocabey A, Rödel G, Gey U. The antioxidant function of Sco proteins depends on a critical surface-exposed residue. Biochim Biophys Acta Gen Subj 2020; 1865:129781. [PMID: 33171213 DOI: 10.1016/j.bbagen.2020.129781] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2020] [Revised: 10/08/2020] [Accepted: 11/02/2020] [Indexed: 11/16/2022]
Abstract
BACKGROUND Besides their role in copper metabolism, Sco proteins from different organisms have been shown to play a defensive role against oxidative stress. In the present study, we set out to identify crucial amino acid residues for the antioxidant activity. METHODS Native and mutated Sco proteins from human, Arabidopsis thaliana and the yeast Kluyveromyces lactis were expressed in the model organism Saccharomyces cerevisiae. The oxidative stress resistance of the respective transformants was determined by growth and lipid peroxidation assays. RESULTS A functionally important site, located 15 amino acids downstream of the well-conserved copper binding CxxxC motif, was identified. Mutational analysis revealed that a positive charge at this position has a detrimental effect on the antioxidant capacity. Bioinformatic analysis predicts that this site is surface-exposed, and according to Co-IP data it is required for binding of proteins that are connected to known antioxidant pathways. CONCLUSION This study shows that the antioxidant capacity of eukaryotic Sco proteins is conserved and depends on the presence of functional site(s) rather than the extent of overall sequence homology. GENERAL SIGNIFICANCE These findings provide an insight into the conserved functional sites of eukaryotic Sco proteins that are crucial for combating oxidative stress. This capacity is probably not due to an enzymatic activity but rather is indirectly mediated by interaction with other proteins.
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Affiliation(s)
| | - Gerhard Rödel
- Institute of Genetics, Technische Universität Dresden, 01062 Dresden, Germany
| | - Uta Gey
- Institute of Genetics, Technische Universität Dresden, 01062 Dresden, Germany.
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6
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Andrei A, Öztürk Y, Khalfaoui-Hassani B, Rauch J, Marckmann D, Trasnea PI, Daldal F, Koch HG. Cu Homeostasis in Bacteria: The Ins and Outs. MEMBRANES 2020; 10:E242. [PMID: 32962054 PMCID: PMC7558416 DOI: 10.3390/membranes10090242] [Citation(s) in RCA: 47] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/22/2020] [Revised: 09/11/2020] [Accepted: 09/15/2020] [Indexed: 12/16/2022]
Abstract
Copper (Cu) is an essential trace element for all living organisms and used as cofactor in key enzymes of important biological processes, such as aerobic respiration or superoxide dismutation. However, due to its toxicity, cells have developed elaborate mechanisms for Cu homeostasis, which balance Cu supply for cuproprotein biogenesis with the need to remove excess Cu. This review summarizes our current knowledge on bacterial Cu homeostasis with a focus on Gram-negative bacteria and describes the multiple strategies that bacteria use for uptake, storage and export of Cu. We furthermore describe general mechanistic principles that aid the bacterial response to toxic Cu concentrations and illustrate dedicated Cu relay systems that facilitate Cu delivery for cuproenzyme biogenesis. Progress in understanding how bacteria avoid Cu poisoning while maintaining a certain Cu quota for cell proliferation is of particular importance for microbial pathogens because Cu is utilized by the host immune system for attenuating pathogen survival in host cells.
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Affiliation(s)
- Andreea Andrei
- Institut für Biochemie und Molekularbiologie, ZBMZ, Medizinische Fakultät, Albert-Ludwigs Universität Freiburg; Stefan Meier Str. 17, 79104 Freiburg, Germany; (A.A.); (Y.O.); (J.R.); (D.M.)
- Fakultät für Biologie, Albert-Ludwigs Universität Freiburg; Schänzlestrasse 1, 79104 Freiburg, Germany
| | - Yavuz Öztürk
- Institut für Biochemie und Molekularbiologie, ZBMZ, Medizinische Fakultät, Albert-Ludwigs Universität Freiburg; Stefan Meier Str. 17, 79104 Freiburg, Germany; (A.A.); (Y.O.); (J.R.); (D.M.)
| | | | - Juna Rauch
- Institut für Biochemie und Molekularbiologie, ZBMZ, Medizinische Fakultät, Albert-Ludwigs Universität Freiburg; Stefan Meier Str. 17, 79104 Freiburg, Germany; (A.A.); (Y.O.); (J.R.); (D.M.)
| | - Dorian Marckmann
- Institut für Biochemie und Molekularbiologie, ZBMZ, Medizinische Fakultät, Albert-Ludwigs Universität Freiburg; Stefan Meier Str. 17, 79104 Freiburg, Germany; (A.A.); (Y.O.); (J.R.); (D.M.)
| | | | - Fevzi Daldal
- Department of Biology, University of Pennsylvania, Philadelphia, PA 19104, USA;
| | - Hans-Georg Koch
- Institut für Biochemie und Molekularbiologie, ZBMZ, Medizinische Fakultät, Albert-Ludwigs Universität Freiburg; Stefan Meier Str. 17, 79104 Freiburg, Germany; (A.A.); (Y.O.); (J.R.); (D.M.)
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Esposti MD. On the evolution of cytochrome oxidases consuming oxygen. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2020; 1861:148304. [PMID: 32890468 DOI: 10.1016/j.bbabio.2020.148304] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2020] [Revised: 08/21/2020] [Accepted: 08/31/2020] [Indexed: 02/07/2023]
Abstract
This review examines the current state of the art on the evolution of the families of Heme Copper Oxygen reductases (HCO) that oxidize cytochrome c and reduce oxygen to water, chiefly cytochrome oxidase, COX. COX is present in many bacterial and most eukaryotic lineages, but its origin has remained elusive. After examining previous proposals for COX evolution, the review summarizes recent insights suggesting that COX enzymes might have evolved in soil dwelling, probably iron-oxidizing bacteria which lived on emerged land over two billion years ago. These bacteria were the likely ancestors of extant acidophilic iron-oxidizers such as Acidithiobacillus spp., which belong to basal lineages of the phylum Proteobacteria. Proteobacteria may thus be considered the originators of COX, which was then laterally transferred to other prokaryotes. The taxonomy of bacteria is presented in relation to the current distribution of COX and C family oxidases, from which COX may have evolved.
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Affiliation(s)
- Mauro Degli Esposti
- Center for Genomic Sciences UNAM, Ave. Universidad 701, Cuernavaca, CP 62130, Morelos, Mexico.
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8
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Mansilla N, Welchen E, Gonzalez DH. Arabidopsis SCO Proteins Oppositely Influence Cytochrome c Oxidase Levels and Gene Expression during Salinity Stress. PLANT & CELL PHYSIOLOGY 2019; 60:2769-2784. [PMID: 31418792 DOI: 10.1093/pcp/pcz166] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/07/2018] [Accepted: 08/12/2019] [Indexed: 06/10/2023]
Abstract
SCO (synthesis of cytochrome c oxidase) proteins are involved in the insertion of copper during the assembly of cytochrome c oxidase (COX), the final enzyme of the mitochondrial respiratory chain. Two SCO proteins, namely, homolog of copper chaperone 1 and 2 (HCC1 and HCC2) are present in seed plants, but HCC2 lacks the residues involved in copper binding, leading to uncertainties about its function. In this study, we performed a transcriptomic and phenotypic analysis of Arabidopsis thaliana plants with reduced expression of HCC1 or HCC2. We observed that a deficiency in HCC1 causes a decrease in the expression of several stress-responsive genes, both under basal growth conditions and after applying a short-term high salinity treatment. In addition, HCC1 deficient plants show a faster decrease in chlorophyll content, photosystem II quantum efficiency and COX levels after salinity stress, as well as a faster increase in alternative oxidase capacity. Notably, HCC2 deficiency causes opposite changes in most of these parameters. Bimolecular fluorescence complementation analysis indicated that both proteins are able to interact. We postulate that HCC1 is a limiting factor for COX assembly during high salinity conditions and that HCC2 probably acts as a negative modulator of HCC1 activity through protein-protein interactions. In addition, a direct or indirect role of HCC1 and HCC2 in the gene expression response to stress is proposed.
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Affiliation(s)
- Natanael Mansilla
- Instituto de Agrobiotecnolog�a del Litoral (CONICET-UNL), C�tedra de Biolog�a Celular y Molecular, Facultad de Bioqu�mica y Ciencias Biol�gicas, Universidad Nacional del Litoral, Santa Fe 3000, Argentina
| | - Elina Welchen
- Instituto de Agrobiotecnolog�a del Litoral (CONICET-UNL), C�tedra de Biolog�a Celular y Molecular, Facultad de Bioqu�mica y Ciencias Biol�gicas, Universidad Nacional del Litoral, Santa Fe 3000, Argentina
| | - Daniel H Gonzalez
- Instituto de Agrobiotecnolog�a del Litoral (CONICET-UNL), C�tedra de Biolog�a Celular y Molecular, Facultad de Bioqu�mica y Ciencias Biol�gicas, Universidad Nacional del Litoral, Santa Fe 3000, Argentina
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9
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Bacterial nitrous oxide respiration: electron transport chains and copper transfer reactions. Adv Microb Physiol 2019; 75:137-175. [PMID: 31655736 DOI: 10.1016/bs.ampbs.2019.07.001] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Biologically catalyzed nitrous oxide (N2O, laughing gas) reduction to dinitrogen gas (N2) is a desirable process in the light of ever-increasing atmospheric concentrations of this important greenhouse gas and ozone depleting substance. A diverse range of bacterial species produce the copper cluster-containing enzyme N2O reductase (NosZ), which is the only known enzyme that converts N2O to N2. Based on phylogenetic analyses, NosZ enzymes have been classified into clade I or clade II and it has turned out that this differentiation is also applicable to nos gene clusters (NGCs) and some physiological traits of the corresponding microbial cells. The NosZ enzyme is the terminal reductase of anaerobic N2O respiration, in which electrons derived from a donor substrate are transferred to NosZ by means of an electron transport chain (ETC) that conserves energy through proton motive force generation. This chapter presents models of the ETCs involved in clade I and clade II N2O respiration as well as of the respective NosZ maturation and maintenance processes. Despite differences in NGCs and growth yields of N2O-respiring microorganisms, the deduced bioenergetic framework in clade I and clade II N2O respiration is assumed to be equivalent. In both cases proton motive quinol oxidation by N2O is thought to be catalyzed by the Q cycle mechanism of a membrane-bound Rieske/cytochrome bc complex. However, clade I and clade II organisms are expected to differ significantly in terms of auxiliary electron transport processes as well as NosZ active site maintenance and repair.
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10
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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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11
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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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12
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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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13
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Canonica F, Klose D, Ledermann R, Sauer MM, Abicht HK, Quade N, Gossert AD, Chesnov S, Fischer HM, Jeschke G, Hennecke H, Glockshuber R. Structural basis and mechanism for metallochaperone-assisted assembly of the Cu A center in cytochrome oxidase. SCIENCE ADVANCES 2019; 5:eaaw8478. [PMID: 31392273 PMCID: PMC6669012 DOI: 10.1126/sciadv.aaw8478] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/30/2019] [Accepted: 06/26/2019] [Indexed: 06/10/2023]
Abstract
The mechanisms underlying the biogenesis of the structurally unique, binuclear Cu1.5+•Cu1.5+ redox center (CuA) on subunit II (CoxB) of cytochrome oxidases have been a long-standing mystery. Here, we reconstituted the CoxB•CuA center in vitro from apo-CoxB and the holo-forms of the copper transfer chaperones ScoI and PcuC. A previously unknown, highly stable ScoI•Cu2+•CoxB complex was shown to be rapidly formed as the first intermediate in the pathway. Moreover, our structural data revealed that PcuC has two copper-binding sites, one each for Cu1+ and Cu2+, and that only PcuC•Cu1+•Cu2+ can release CoxB•Cu2+ from the ScoI•Cu2+•CoxB complex. The CoxB•CuA center was then formed quantitatively by transfer of Cu1+ from a second equivalent of PcuC•Cu1+•Cu2+ to CoxB•Cu2+. This metalation pathway is consistent with all available in vivo data and identifies the sources of the Cu ions required for CuA center formation and the order of their delivery to CoxB.
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Affiliation(s)
- Fabia Canonica
- Institute of Molecular Biology and Biophysics, ETH Zurich, Zurich, Switzerland
| | - Daniel Klose
- Laboratory of Physical Chemistry, ETH Zurich, Zurich, Switzerland
| | | | - Maximilian M. Sauer
- Institute of Molecular Biology and Biophysics, ETH Zurich, Zurich, Switzerland
| | - Helge K. Abicht
- Institute of Molecular Biology and Biophysics, ETH Zurich, Zurich, Switzerland
| | - Nick Quade
- Institute of Molecular Biology and Biophysics, ETH Zurich, Zurich, Switzerland
| | - Alvar D. Gossert
- Institute of Molecular Biology and Biophysics, ETH Zurich, Zurich, Switzerland
| | - Serge Chesnov
- Functional Genomics Center Zurich, University of Zurich/ETH Zurich, Zurich, Switzerland
| | | | - Gunnar Jeschke
- Laboratory of Physical Chemistry, ETH Zurich, Zurich, Switzerland
| | - Hauke Hennecke
- Institute of Microbiology, ETH Zurich, Zurich, Switzerland
| | - Rudi Glockshuber
- Institute of Molecular Biology and Biophysics, ETH Zurich, Zurich, Switzerland
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Terashima M, Ohashi K, Takasuka TE, Kojima H, Fukui M. Antarctic heterotrophic bacterium Hymenobacter nivis P3 T displays light-enhanced growth and expresses putative photoactive proteins. ENVIRONMENTAL MICROBIOLOGY REPORTS 2019; 11:227-235. [PMID: 30298689 DOI: 10.1111/1758-2229.12702] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/10/2018] [Accepted: 10/02/2018] [Indexed: 06/08/2023]
Abstract
Hymenobacter nivis P3T is a heterotrophic bacterium isolated from Antarctic red snow generated by algal blooms. Despite being non-photosynthetic, H. nivis was dominantly found in the red snow environment that is exposed to high light and UV irradiation, suggesting that this species can flourish under such harsh conditions. In order to further understand the adaptive strategies on the snow surface environment of Antarctica, the genome of H. nivis P3T was sequenced and analyzed, which identified genes putatively encoding for light-reactive proteins such as proteorhodopsin, phytochrome, photolyase and several copies of cryptochromes. Culture-based experiments revealed that H. nivis P3T growth was significantly enhanced under light conditions, while dark conditions had increased extracellular polymeric substances. Furthermore, the expression of several putative light-reactive proteins was determined by proteomic analysis. These results indicate that H. nivis P3T is able to potentially utilize light, which may explain its dominance on the red snow surface environment of Antarctica. ORIGINALITY-SIGNIFICANCE STATEMENT: The role of proteorhodopsin in heterotrophic bacteria is not well-characterized, as only a handful of proteorhodopsin-harbouring isolates were shown to have a light-enhanced phenotype through culture-based experiments to date. This is the first study that demonstrates light-stimulated growth and protein expression evidence of photoactive proteins for a non-marine psychrophile and for a member of the genus Hymenobacter. It is also the first study that provides comprehensive proteome information for this genus. This study presents significant results in understanding the adaptive mechanism of a heterotrophic non-photosynthetic bacterium thriving on the snow surface environment of Antarctica as well as demonstrating the role of light-utilization in promoting growth, possibly through proteorhodopsin.
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Affiliation(s)
- Mia Terashima
- Institute of Low Temperature Science, Hokkaido University, Kita-ku, Sapporo, 060-0819, Japan
| | - Keisuke Ohashi
- Research Faculty of Agriculture, Hokkaido University, Kita-ku, Sapporo, 060-8589, Japan
| | - Taichi E Takasuka
- Research Faculty of Agriculture, Hokkaido University, Kita-ku, Sapporo, 060-8589, Japan
| | - Hisaya Kojima
- Institute of Low Temperature Science, Hokkaido University, Kita-ku, Sapporo, 060-0819, Japan
| | - Manabu Fukui
- Institute of Low Temperature Science, Hokkaido University, Kita-ku, Sapporo, 060-0819, Japan
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15
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Ekim Kocabey A, Kost L, Gehlhar M, Rödel G, Gey U. Mitochondrial Sco proteins are involved in oxidative stress defense. Redox Biol 2018; 21:101079. [PMID: 30593977 PMCID: PMC6307045 DOI: 10.1016/j.redox.2018.101079] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2018] [Revised: 12/10/2018] [Accepted: 12/11/2018] [Indexed: 12/31/2022] Open
Abstract
Members of the evolutionary conserved Sco protein family have been intensively studied regarding their role in the assembly of the mitochondrial cytochrome c oxidase. However, experimental and structural data, specifically the presence of a thioredoxin-like fold, suggest that Sco proteins may also play a role in redox homeostasis. In our study, we addressed this putative function of Sco proteins using Saccharomyces cerevisiae as a model system. Like many eukaryotes, this yeast possesses two SCO homologs (SCO1 and SCO2). Mutants bearing a deletion of either of the two genes are not affected in their growth under oxidative stress. However, the concomitant deletion of the SOD1 gene encoding the superoxide dismutase 1 resulted in a distinct phenotype: double deletion strains lacking SCO1 or SCO2 and SOD1 are highly sensitive to oxidative stress and show dramatically increased ROS levels. The respiratory competent double deletion strain Δsco2Δsod1 paved the way to investigate the putative antioxidant function of SCO homologs apart from their role in respiration by complementation analysis. Sco homologs from Drosophila, Arabidopsis, human and two other yeast species were integrated into the genome of the double deletion mutant and the transformants were analyzed for their growth under oxidative stress. Interestingly, all homologs except for Kluyveromyces lactis K07152 and Arabidopsis thaliana HCC1 were able to complement the phenotype, indicating their role in oxidative stress defense. We further applied this complementation-based system to investigate whether pathogenic point mutations affect the putative antioxidant role of hSco2. Surprisingly, all of the mutant alleles failed to restore the ROS-sensitivity of the Δsco2Δsod1 strain. In conclusion, our data not only provide clear evidence for the function of Sco proteins in oxidative stress defense but also offer a valuable tool to investigate this role for other homologous proteins. Concomitant deletion of SCO and SOD1 leads to a high ROS sensitivity. SCO homologs from higher organisms can rescue the oxidative stress sensitive phenotype of the double deletion mutant. Pathogenic human Sco2 mutations affect the antioxidant function of the protein. The role of the Sco proteins in oxidative stress defense is discussed.
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Affiliation(s)
| | - Luise Kost
- Institute of Genetics, Technische Universität Dresden, 01062 Dresden, Germany
| | - Maria Gehlhar
- Institute of Genetics, Technische Universität Dresden, 01062 Dresden, Germany
| | - Gerhard Rödel
- Institute of Genetics, Technische Universität Dresden, 01062 Dresden, Germany
| | - Uta Gey
- Institute of Genetics, Technische Universität Dresden, 01062 Dresden, Germany.
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16
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Lopez LC, Mukhitov N, Handley LD, Hamme CS, Hofman CR, Euers L, McKinney JR, Piers AD, Wadler E, Hunsicker-Wang LM. Characterization and effect of metal ions on the formation of the Thermus thermophilus Sco mixed disulfide intermediate. Protein Sci 2018; 27:1942-1954. [PMID: 30168216 DOI: 10.1002/pro.3502] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2018] [Revised: 08/22/2018] [Accepted: 08/23/2018] [Indexed: 11/09/2022]
Abstract
The Sco protein from Thermus thermophilus has previously been shown to perform a disulfide bond reduction in the CuA protein from T. thermophilus, which is a soluble protein engineered from subunit II of cytochrome ba 3 oxidase that lacks the transmembrane helix. The native cysteines on TtSco and TtCuA were mutated to serine residues to probe the reactivities of the individual cysteines. Conjugation of TNB to the remaining cysteine in TtCuA and subsequent release upon incubation with the complementary TtSco protein demonstrated the formation of the mixed disulfide intermediate. The cysteine of TtSco that attacks the disulfide bond in the target TtCuA protein was determined to be TtSco Cysteine 49. This cysteine is likely more reactive than Cysteine 53 due to a higher degree of solvent exposure. Removal of the metal binding histidine, His 139, does not change MDI formation. However, altering the arginine adjacent to the reactive cysteine in Sco (Arginine 48) does alter the formation of the MDI. Binding of Cu2+ or Cu+ to TtSco prior to reaction with TtCuA was found to preclude formation of the mixed disulfide intermediate. These results shed light on a mechanism of disulfide bond reduction by the TtSco protein and may point to a possible role of metal binding in regulating the activity. IMPORTANCE: The function of Sco is at the center of many studies. The disulfide bond reduction in CuA by Sco is investigated herein and the effect of metal ions on the ability to reduce and form a mixed disulfide intermediate are also probed.
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Affiliation(s)
- Liezelle C Lopez
- Department of Chemistry, Trinity University, One Trinity Place, San Antonio, Texas, 78212-7200.,Baylor School of Medicine, One Baylor Plaza, Houston, Texas, 77030
| | - Nikita Mukhitov
- Department of Chemistry, Trinity University, One Trinity Place, San Antonio, Texas, 78212-7200.,Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, 02139
| | - Lindsey D Handley
- Department of Chemistry, Trinity University, One Trinity Place, San Antonio, Texas, 78212-7200.,ThoughtSTEM, San Diego, California, 92108
| | - Cristina S Hamme
- Department of Chemistry, Trinity University, One Trinity Place, San Antonio, Texas, 78212-7200.,Lone Star Family Health Center, Conroe, Texas, 77034
| | - Cristina R Hofman
- Department of Chemistry, Trinity University, One Trinity Place, San Antonio, Texas, 78212-7200
| | - Lindsay Euers
- Department of Chemistry, Trinity University, One Trinity Place, San Antonio, Texas, 78212-7200.,Houston Methodist Hospital, Houston, Texas, 77303
| | - Jennifer R McKinney
- Department of Chemistry, Trinity University, One Trinity Place, San Antonio, Texas, 78212-7200.,Department of Maternal Fetal Medicine, Baylor College of Medicine, One Baylor Plaza, Houston, Texas, 77004
| | - Amani D Piers
- Department of Chemistry, Trinity University, One Trinity Place, San Antonio, Texas, 78212-7200.,Department of Psychology, Drexel University, Philadelphia, Pennsylvania, 19104
| | - Ellen Wadler
- Department of Chemistry, Trinity University, One Trinity Place, San Antonio, Texas, 78212-7200.,University of Texas Health Science Center Houston School of Public Health, Houston, Texas, 77030
| | - Laura M Hunsicker-Wang
- Department of Chemistry, Trinity University, One Trinity Place, San Antonio, Texas, 78212-7200
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17
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18
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Jiang F, Siegler MA, Sun X, Jiang L, Fonseca Guerra C, Bouwman E. Redox Interconversion between Cobalt(III) Thiolate and Cobalt(II) Disulfide Compounds. Inorg Chem 2018; 57:8796-8805. [PMID: 30024150 PMCID: PMC6150680 DOI: 10.1021/acs.inorgchem.8b00549] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
![]()
The redox interconversion
between Co(III) thiolate and Co(II) disulfide
compounds has been investigated experimentally and computationally.
Reactions of cobalt(II) salts with disulfide ligand L1SSL1 (L1SSL1 = di-2-(bis(2-pyridylmethyl)amino)-ethyl
disulfide) result in the formation of either the high-spin cobalt(II)
disulfide compound [CoII2(L1SSL1)Cl4] or a low-spin, octahedral cobalt(III) thiolate
compound, such as [CoIII(L1S)(MeCN)2](BF4)2. Addition of thiocyanate anions to
a solution containing the latter compound yielded crystals of [CoIII(L1S)(NCS)2]. The addition of chloride
ions to a solution of [CoIII(L1S)(MeCN)2](BF4)2 in acetonitrile results in conversion
of the cobalt(III) thiolate compound to the cobalt(II) disulfide compound
[CoII2(L1SSL1)Cl4], as monitored with UV–vis spectroscopy; subsequent addition
of AgBF4 regenerates the Co(III) compound. Computational
studies show that exchange by a chloride anion of the coordinated
acetonitrile molecule or thiocyanate anion in compounds [CoIII(L1S)(MeCN)2]2+ and [CoIII(L1S)(NCS)2] induces a change in the character
of the highest occupied molecular orbitals, showing a decrease of
the contribution of the p orbital on sulfur and an increase of the
d orbital on cobalt. As a comparison, the synthesis of iron compounds
was undertaken. X-ray crystallography revealed that structure of the
dinuclear iron(II) disulfide compound [FeII2(L1SSL1)Cl4] is different from that
of cobalt(II) compound [CoII2(L1SSL1)Cl4]. In contrast to cobalt, reaction of ligand
L1SSL1 with [Fe(MeCN)6](BF4)2 did not yield the expected Fe(III) thiolate compound.
This work is an unprecedented example of redox interconversion between
a high-spin Co(II) disulfide compound and a low-spin Co(III) thiolate
compound triggered by the nature of the anion. Low-spin
CoIII−thiolate compounds and
high-spin CoII and FeII disulfide compound have
been synthesized from reactions of a disulfide ligand with CoII and FeII salts. The redox interconversion between
the cobalt compounds has been investigated. It is shown that addition
of chloride ions to a solution of the CoIII−thiolate
compound results in the formation of the CoII-disulfide
compound, whereas removal of chloride anions from the CoII disulfide compound regenerates the CoIII−thiolate
complex.
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Affiliation(s)
- Feng Jiang
- Leiden Institute of Chemistry, Gorlaeus Laboratories , Leiden University , P.O. Box 9502, 2300 RA Leiden , The Netherlands
| | - Maxime A Siegler
- Department of Chemistry , Johns Hopkins University , 3400 North Charles Street , Baltimore , Maryland 21218 , United States
| | - Xiaobo Sun
- Department of Theoretical Chemistry, Amsterdam Center for Multiscale Modeling (ACMM) , Vrije Universiteit Amsterdam , De Boelelaan 1083 , 1081 HV Amsterdam , The Netherlands
| | - Lin Jiang
- Leiden Institute of Chemistry, Gorlaeus Laboratories , Leiden University , P.O. Box 9502, 2300 RA Leiden , The Netherlands
| | - Célia Fonseca Guerra
- Leiden Institute of Chemistry, Gorlaeus Laboratories , Leiden University , P.O. Box 9502, 2300 RA Leiden , The Netherlands.,Department of Theoretical Chemistry, Amsterdam Center for Multiscale Modeling (ACMM) , Vrije Universiteit Amsterdam , De Boelelaan 1083 , 1081 HV Amsterdam , The Netherlands
| | - Elisabeth Bouwman
- Leiden Institute of Chemistry, Gorlaeus Laboratories , Leiden University , P.O. Box 9502, 2300 RA Leiden , The Netherlands
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19
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Chakraborty S, Polen MJ, Chacón KN, Wilson TD, Yu Y, Reed J, Nilges MJ, Blackburn NJ, Lu Y. Binuclear Cu(A) Formation in Biosynthetic Models of Cu(A) in Azurin Proceeds via a Novel Cu(Cys)2His Mononuclear Copper Intermediate. Biochemistry 2016; 54:6071-81. [PMID: 26352296 DOI: 10.1021/acs.biochem.5b00659] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Cu(A) is a binuclear electron transfer (ET) center found in cytochrome c oxidases (CcOs), nitrous oxide reductases (N₂ORs), and nitric oxide reductase (NOR). In these proteins, the Cu(A) centers facilitate efficient ET (kET > 10⁴s⁻¹) under low thermodynamic driving forces (10-90 mV). While the structure and functional properties of Cu(A) are well understood, a detailed mechanism of the incorporation of copper into the protein and the identity of the intermediates formed during the Cu(A) maturation process are still lacking. Previous studies of the Cu(A) assembly mechanism in vitro using a biosynthetic model Cu(A) center in azurin (Cu(A)Az) identified a novel intermediate X (Ix) during reconstitution of the binuclear site. However, because of the instability of Ix and the coexistence of other Cu centers, such as Cu(A)' and type 1 copper centers, the identity of this intermediate could not be established. Here, we report the mechanism of Cu(A) assembly using variants of Glu114XCuAAz (X = Gly, Ala, Leu, or Gln), the backbone carbonyl of which acts as a ligand to the Cu(A) site, with a major focus on characterization of the novel intermediate Ix. We show that Cu(A) assembly in these variants proceeds through several types of Cu centers, such as mononuclear red type 2 Cu, the novel intermediate Ix, and blue type 1 Cu. Our results show that the backbone flexibility of the Glu114 residue is an important factor in determining the rates of T2Cu → Ix formation, suggesting that Cu(A) formation is facilitated by swinging of the ligand loop, which internalizes the T2Cu capture complex to the protein interior. The kinetic data further suggest that the nature of the Glu114 side chain influences the time scales on which these intermediates are formed, the wavelengths of the absorption peaks, and how cleanly one intermediate is converted to another. Through careful understanding of these mechanisms and optimization of the conditions, we have obtained Ix in ∼80-85% population in these variants, which allowed us to employ ultraviolet-visible, electron paramagnetic resonance, and extended X-ray absorption fine structure spectroscopic techniques to identify the Ix as a mononuclear Cu(Cys)(2)(His) complex. Because some of the intermediates have been proposed to be involved in the assembly of native Cu(A), these results shed light on the structural features of the important intermediates and mechanism of Cu(A) formation.
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Affiliation(s)
- Saumen Chakraborty
- Department of Chemistry, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States
| | - Michael J Polen
- Department of Chemistry, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States
| | - Kelly N Chacón
- Institute of Environmental Health, Oregon Health & Sciences University , Portland, Oregon 97239, United States
| | - Tiffany D Wilson
- Department of Chemistry, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States
| | - Yang Yu
- Department of Chemistry, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States
| | - Julian Reed
- Department of Chemistry, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States
| | - Mark J Nilges
- Department of Chemistry, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States
| | - Ninian J Blackburn
- Institute of Environmental Health, Oregon Health & Sciences University , Portland, Oregon 97239, United States
| | - Yi Lu
- Department of Chemistry, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States
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20
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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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21
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Cooperation between COA6 and SCO2 in COX2 maturation during cytochrome c oxidase assembly links two mitochondrial cardiomyopathies. Cell Metab 2015; 21:823-33. [PMID: 25959673 DOI: 10.1016/j.cmet.2015.04.012] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/17/2014] [Revised: 03/03/2015] [Accepted: 04/04/2015] [Indexed: 11/20/2022]
Abstract
Three mitochondria-encoded subunits form the catalytic core of cytochrome c oxidase, the terminal enzyme of the respiratory chain. COX1 and COX2 contain heme and copper redox centers, which are integrated during assembly of the enzyme. Defects in this process lead to an enzyme deficiency and manifest as mitochondrial disorders in humans. Here we demonstrate that COA6 is specifically required for COX2 biogenesis. Absence of COA6 leads to fast turnover of newly synthesized COX2 and a concomitant reduction in cytochrome c oxidase levels. COA6 interacts transiently with the copper-containing catalytic domain of newly synthesized COX2. Interestingly, similar to the copper metallochaperone SCO2, loss of COA6 causes cardiomyopathy in humans. We show that COA6 and SCO2 interact and that corresponding pathogenic mutations in each protein affect complex formation. Our analyses define COA6 as a constituent of the mitochondrial copper relay system, linking defects in COX2 metallation to cardiac cytochrome c oxidase deficiency.
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22
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Hirooka K. Transcriptional response machineries of Bacillus subtilis conducive to plant growth promotion. Biosci Biotechnol Biochem 2015; 78:1471-84. [PMID: 25209494 DOI: 10.1080/09168451.2014.943689] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Bacillus subtilis collectively inhabits the rhizosphere, where it contributes to the promotion of plant growth, although it does not have a direct symbiotic relationship to plants as observed in the case of rhizobia between leguminous plants. As rhizobia sense the flavonoids released from their host roots through the NodD transcriptional factor, which triggers transcription of the nod genes involved in the symbiotic processes, we supposed that B. subtilis utilizes certain flavonoids as signaling molecules to perceive and adapt to the rhizospheric environment that it is in. Our approaches to identify the flavonoid-responsive transcriptional regulatory system from B. subtilis resulted in the findings that three transcriptional factors (LmrA/QdoR, YetL, and Fur) are responsive to flavonoids, with the modes of action being different from each other. We also revealed a unique regulatory system by two transcriptional factors, YcnK and CsoR, for copper homeostasis in B. subtilis. In this review, we summarize the molecular mechanisms of these regulatory systems with the relevant information and discuss their physiological significances in the mutually beneficial interaction between B. subtilis and plants, considering the possibility of their application for plant cultivation.
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Affiliation(s)
- Kazutake Hirooka
- a Department of Biotechnology, Faculty of Life Science and Biotechnology , Fukuyama University , Fukuyama , Hiroshima , Japan
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23
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Abicht HK, Schärer MA, Quade N, Ledermann R, Mohorko E, Capitani G, Hennecke H, Glockshuber R. How periplasmic thioredoxin TlpA reduces bacterial copper chaperone ScoI and cytochrome oxidase subunit II (CoxB) prior to metallation. J Biol Chem 2014; 289:32431-44. [PMID: 25274631 DOI: 10.1074/jbc.m114.607127] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Two critical cysteine residues in the copper-A site (Cu(A)) on subunit II (CoxB) of bacterial cytochrome c oxidase lie on the periplasmic side of the cytoplasmic membrane. As the periplasm is an oxidizing environment as compared with the reducing cytoplasm, the prediction was that a disulfide bond formed between these cysteines must be eliminated by reduction prior to copper insertion. We show here that a periplasmic thioredoxin (TlpA) acts as a specific reductant not only for the Cu(2+) transfer chaperone ScoI but also for CoxB. The dual role of TlpA was documented best with high-resolution crystal structures of the kinetically trapped TlpA-ScoI and TlpA-CoxB mixed disulfide intermediates. They uncovered surprisingly disparate contact sites on TlpA for each of the two protein substrates. The equilibrium of CoxB reduction by TlpA revealed a thermodynamically favorable reaction, with a less negative redox potential of CoxB (E'0 = -231 mV) as compared with that of TlpA (E'0 = -256 mV). The reduction of CoxB by TlpA via disulfide exchange proved to be very fast, with a rate constant of 8.4 × 10(4) M(-1) s(-1) that is similar to that found previously for ScoI reduction. Hence, TlpA is a physiologically relevant reductase for both ScoI and CoxB. Although the requirement of ScoI for assembly of the Cu(A)-CoxB complex may be bypassed in vivo by high environmental Cu(2+) concentrations, TlpA is essential in this process because only reduced CoxB can bind copper ions.
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Affiliation(s)
- Helge K Abicht
- From the Institute of Molecular Biology and Biophysics and Institute of Microbiology, ETH Zürich, CH-8093 Zürich and
| | - Martin A Schärer
- From the Institute of Molecular Biology and Biophysics and the Laboratory of Biomolecular Research, Paul Scherrer Institute, CH-5232 Villigen-PSI, Switzerland
| | - Nick Quade
- From the Institute of Molecular Biology and Biophysics and
| | | | | | - Guido Capitani
- the Laboratory of Biomolecular Research, Paul Scherrer Institute, CH-5232 Villigen-PSI, Switzerland
| | - Hauke Hennecke
- Institute of Microbiology, ETH Zürich, CH-8093 Zürich and
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24
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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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25
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Structural and mechanistic insights into an extracytoplasmic copper trafficking pathway in Streptomyces lividans. Biochem J 2014; 459:525-38. [PMID: 24548299 DOI: 10.1042/bj20140017] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
In Streptomyces lividans an extracytoplasmic copper-binding Sco protein plays a role in two unlinked processes: (i) initiating a morphological development switch and (ii) facilitating the co-factoring of the CuA domain of CcO (cytochrome c oxidase). How Sco obtains copper once secreted to the extracytoplasmic environment is unknown. In the present paper we report on a protein possessing an HX₆MX₂₁HXM motif that binds a single cuprous ion with subfemtomolar affinity. High-resolution X-ray structures of this extracytoplasmic copper chaperone-like protein (ECuC) in the apo- and Cu(I)-bound states reveal that the latter possesses a surface-accessible cuprous-ion-binding site located in a dish-shaped region of β-sheet structure. A cuprous ion is transferred under a favourable thermodynamic gradient from ECuC to Sco with no back transfer occurring. The ionization properties of the cysteine residues in the Cys⁸⁶xxxCys⁹⁰ copper-binding motif of Sco, together with their positional locations identified from an X-ray structure of Sco, suggests a role for Cys⁸⁶ in initiating an inter-complex ligand-exchange reaction with Cu(I)-ECuC. Generation of the genetic knockouts, Δsco, Δecuc and Δsco/ecuc, and subsequent in vivo assays lend support to the existence of a branched extracytoplasmic copper-trafficking pathway in S. lividans. One branch requires both Sco and to a certain extent ECuC to cofactor the CuA domain, whereas the other uses only Sco to deliver copper to a cuproenzyme to initiate morphological development.
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Liu J, Chakraborty S, Hosseinzadeh P, Yu Y, Tian S, Petrik I, Bhagi A, Lu Y. Metalloproteins containing cytochrome, iron-sulfur, or copper redox centers. Chem Rev 2014; 114:4366-469. [PMID: 24758379 PMCID: PMC4002152 DOI: 10.1021/cr400479b] [Citation(s) in RCA: 559] [Impact Index Per Article: 55.9] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2013] [Indexed: 02/07/2023]
Affiliation(s)
- Jing Liu
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Saumen Chakraborty
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Parisa Hosseinzadeh
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Yang Yu
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Shiliang Tian
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Igor Petrik
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Ambika Bhagi
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Yi Lu
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
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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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Garcia L, Welchen E, Gonzalez DH. Mitochondria and copper homeostasis in plants. Mitochondrion 2014; 19 Pt B:269-74. [PMID: 24582977 DOI: 10.1016/j.mito.2014.02.011] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2013] [Revised: 02/18/2014] [Accepted: 02/19/2014] [Indexed: 11/17/2022]
Abstract
Copper (Cu) and other transition metals are essential for living organisms but also toxic when present in excess. To cope with this apparent paradox, organisms have developed sophisticated mechanisms to acquire, transport and store these metals. Particularly, plant mitochondria require Cu for the assembly and function of cytochrome c oxidase (COX), the terminal enzyme of the respiratory chain. COX assembly is a complex process that requires the action of multiple factors, many of them involved in the delivery and insertion of Cu into the enzyme. In this review, we summarize what is known about the processes involved in Cu delivery to mitochondria and how these processes impact in Cu homeostasis at the cellular level. We also discuss evidence indicating that metallochaperones involved in COX assembly play additional roles in signaling pathways related to changes in Cu and redox homeostasis and the response of plants to stress. We propose that cysteine-rich proteins present in the mitochondrial intermembrane space are excellent candidates as sensors of these changes and transducers of signals originated in the organelle to the rest of the cell.
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Affiliation(s)
- Lucila Garcia
- Instituto de Agrobiotecnología del Litoral (CONICET-UNL), Cátedra de Biología Celular y Molecular, Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, CC 242 Paraje El Pozo, 3000 Santa Fe, Argentina
| | - Elina Welchen
- Instituto de Agrobiotecnología del Litoral (CONICET-UNL), Cátedra de Biología Celular y Molecular, Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, CC 242 Paraje El Pozo, 3000 Santa Fe, Argentina
| | - Daniel H Gonzalez
- Instituto de Agrobiotecnología del Litoral (CONICET-UNL), Cátedra de Biología Celular y Molecular, Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, CC 242 Paraje El Pozo, 3000 Santa Fe, Argentina.
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Steinebrunner I, Gey U, Andres M, Garcia L, Gonzalez DH. Divergent functions of the Arabidopsis mitochondrial SCO proteins: HCC1 is essential for COX activity while HCC2 is involved in the UV-B stress response. FRONTIERS IN PLANT SCIENCE 2014; 5:87. [PMID: 24723925 PMCID: PMC3971200 DOI: 10.3389/fpls.2014.00087] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2013] [Accepted: 02/24/2014] [Indexed: 05/07/2023]
Abstract
The two related putative cytochrome c oxidase (COX) assembly factors HCC1 and HCC2 from Arabidopsis thaliana are Homologs of the yeast Copper Chaperones Sco1p and Sco2p. The hcc1 null mutation was previously shown to be embryo lethal while the disruption of the HCC2 gene function had no obvious effect on plant development, but increased the expression of stress-responsive genes. Both HCC1 and HCC2 contain a thioredoxin domain, but only HCC1 carries a Cu-binding motif also found in Sco1p and Sco2p. In order to investigate the physiological implications suggested by this difference, various hcc1 and hcc2 mutants were generated and analyzed. The lethality of the hcc1 knockout mutation was rescued by complementation with the HCC1 gene under the control of the embryo-specific promoter ABSCISIC ACID INSENSITIVE 3. However, the complemented seedlings did not grow into mature plants, underscoring the general importance of HCC1 for plant growth. The HCC2 homolog was shown to localize to mitochondria like HCC1, yet the function of HCC2 is evidently different, because two hcc2 knockout lines developed normally and exhibited only mild growth suppression compared with the wild type (WT). However, hcc2 knockouts were more sensitive to UV-B treatment than the WT. Complementation of the hcc2 knockout with HCC2 rescued the UV-B-sensitive phenotype. In agreement with this, exposure of wild-type plants to UV-B led to an increase of HCC2 transcripts. In order to corroborate a function of HCC1 and HCC2 in COX biogenesis, COX activity of hcc1 and hcc2 mutants was compared. While the loss of HCC2 function had no significant effect on COX activity, the disruption of one HCC1 gene copy was enough to suppress respiration by more than half compared with the WT. Therefore, we conclude that HCC1 is essential for COX function, most likely by delivering Cu to the catalytic center. HCC2, on the other hand, seems to be involved directly or indirectly in UV-B-stress responses.
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Affiliation(s)
- Iris Steinebrunner
- Department of Biology, Technische Universität DresdenDresden, Germany
- *Correspondence: Iris Steinebrunner, Department of Biology, Technische Universität Dresden, Helmholtzstr. 10, 01062 Dresden, Germany e-mail:
| | - Uta Gey
- Department of Biology, Technische Universität DresdenDresden, Germany
| | - Manuela Andres
- Department of Biology, Technische Universität DresdenDresden, Germany
| | - Lucila Garcia
- Instituto de Agrobiotecnología del Litoral (CONICET-UNL), Universidad Nacional del LitoralSanta Fe, Argentina
| | - Daniel H. Gonzalez
- Instituto de Agrobiotecnología del Litoral (CONICET-UNL), Universidad Nacional del LitoralSanta Fe, Argentina
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30
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Thomas AM, Lin BL, Wasinger EC, Stack TDP. Ligand noninnocence of thiolate/disulfide in dinuclear copper complexes: solvent-dependent redox isomerization and proton-coupled electron transfer. J Am Chem Soc 2013; 135:18912-9. [PMID: 24279864 DOI: 10.1021/ja409603m] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Copper thiolate/disulfide interconversions are related to the functions of several important proteins such as human Sco1, Cu-Zn superoxide dismutase (SOD1), and mammalian zinc-bonded metallothionein. The synthesis and characterization of well-defined synthetic analogues for such interconversions are challenging yet provide important insights into the mechanisms of such redox processes. Solvent-dependent redox isomerization and proton-coupled electron transfer mimicking these interconversions are observed in two structurally related dimeric μ,η(2):η(2)-thiolato Cu(II)Cu(II) complexes by various methods, including X-ray diffraction, XAS, NMR, and UV-vis. Spectroscopic evidence shows that a solvent-dependent equilibrium exists between the dimeric μ-thiolato Cu(II)Cu(II) state and its redox isomeric μ-disulfido Cu(I)Cu(I) form. Complete formation of μ-disulfido Cu(I)Cu(I) complexes, however, only occurs after the addition of 2 equiv of protons, which promote electron transfer from thiolate to Cu(II) and formation of disulfide and Cu(I) via protonation of the coordinating ligand. Proton removal reverses this reaction. The reported unusual reductive protonation/oxidative deprotonation of the metal centers may serve as a new chemical precedent for how related proteins manage Cu ions in living organisms.
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Affiliation(s)
- Andrew M Thomas
- Department of Chemistry, Stanford University , Stanford, California 94305, United States
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31
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Wrzesinski J, Błaszczyk L, Wrońska M, Kasprowicz A, Stokowa-Sołtys K, Nagaj J, Szafraniec M, Kulinski T, Jeżowska-Bojczuk M, Ciesiołka J. Mapping the interactions of selected antibiotics and their Cu2+complexes with the antigenomic delta ribozyme. FEBS J 2013; 280:2652-64. [DOI: 10.1111/febs.12257] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2013] [Revised: 03/15/2013] [Accepted: 03/18/2013] [Indexed: 11/30/2022]
Affiliation(s)
- Jan Wrzesinski
- Institute of Bioorganic Chemistry; Polish Academy of Sciences; Poznań; Poland
| | - Leszek Błaszczyk
- Institute of Bioorganic Chemistry; Polish Academy of Sciences; Poznań; Poland
| | | | | | | | | | - Milena Szafraniec
- Institute of Bioorganic Chemistry; Polish Academy of Sciences; Poznań; Poland
| | - Tadeusz Kulinski
- Institute of Bioorganic Chemistry; Polish Academy of Sciences; Poznań; Poland
| | | | - Jerzy Ciesiołka
- Institute of Bioorganic Chemistry; Polish Academy of Sciences; Poznań; Poland
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32
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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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33
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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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Abstract
As a trace element copper has an important role in cellular function like many other transition metals. Its ability to undergo redox changes [Cu(I) ↔ Cu(II)] makes copper an ideal cofactor in enzymes catalyzing electron transfers. However, this redox change makes copper dangerous for a cell since it is able to be involved in Fenton-like reactions creating reactive oxygen species (ROS). Cu(I) also is a strong soft metal and can attack and destroy iron-sulfur clusters thereby releasing iron which can in turn cause oxidative stress. Therefore, copper homeostasis has to be highly balanced to ensure proper cellular function while avoiding cell damage.Throughout evolution bacteria and archaea have developed a highly regulated balance in copper metabolism. While for many prokaryotes copper uptake seems to be unspecific, others have developed highly sophisticated uptake mechanisms to ensure the availability of sufficient amounts of copper. Within the cytoplasm copper is sequestered by various proteins and molecules, including specific copper chaperones, to prevent cellular damage. Copper-containing proteins are usually located in the cytoplasmic membrane with the catalytic domain facing the periplasm, in the periplasm of Gram-negative bacteria, or they are secreted, limiting the necessity of copper to accumulate in the cytoplasm. To prevent cellular damage due to excess copper, bacteria and archaea have developed various copper detoxification strategies. In this chapter we attempt to give an overview of the mechanisms employed by bacteria and archaea to handle copper and the importance of the metal for cellular function as well as in the global nutrient cycle.
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Affiliation(s)
- Christopher Rensing
- Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, DK-1870, Frederiksberg C, Denmark
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35
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Wilson TD, Yu Y, Lu Y. Understanding copper-thiolate containing electron transfer centers by incorporation of unnatural amino acids and the CuA center into the type 1 copper protein azurin. Coord Chem Rev 2013. [DOI: 10.1016/j.ccr.2012.06.015] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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36
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Darby AC, Armstrong SD, Bah GS, Kaur G, Hughes MA, Kay SM, Koldkjær P, Rainbow L, Radford AD, Blaxter ML, Tanya VN, Trees AJ, Cordaux R, Wastling JM, Makepeace BL. Analysis of gene expression from the Wolbachia genome of a filarial nematode supports both metabolic and defensive roles within the symbiosis. Genome Res 2012; 22:2467-77. [PMID: 22919073 PMCID: PMC3514676 DOI: 10.1101/gr.138420.112] [Citation(s) in RCA: 146] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2012] [Accepted: 07/27/2012] [Indexed: 02/06/2023]
Abstract
The α-proteobacterium Wolbachia is probably the most prevalent, vertically transmitted symbiont on Earth. In contrast with its wide distribution in arthropods, Wolbachia is restricted to one family of animal-parasitic nematodes, the Onchocercidae. This includes filarial pathogens such as Onchocerca volvulus, the cause of human onchocerciasis, or river blindness. The symbiosis between filariae and Wolbachia is obligate, although the basis of this dependency is not fully understood. Previous studies suggested that Wolbachia may provision metabolites (e.g., haem, riboflavin, and nucleotides) and/or contribute to immune defense. Importantly, Wolbachia is restricted to somatic tissues in adult male worms, whereas females also harbor bacteria in the germline. We sought to characterize the nature of the symbiosis between Wolbachia and O. ochengi, a bovine parasite representing the closest relative of O. volvulus. First, we sequenced the complete genome of Wolbachia strain wOo, which revealed an inability to synthesize riboflavin de novo. Using RNA-seq, we also generated endobacterial transcriptomes from male soma and female germline. In the soma, transcripts for membrane transport and respiration were up-regulated, while the gonad exhibited enrichment for DNA replication and translation. The most abundant Wolbachia proteins, as determined by geLC-MS, included ligands for mammalian Toll-like receptors. Enzymes involved in nucleotide synthesis were dominant among metabolism-related proteins, whereas the haem biosynthetic pathway was poorly represented. We conclude that Wolbachia may have a mitochondrion-like function in the soma, generating ATP for its host. Moreover, the abundance of immunogenic proteins in wOo suggests a role in diverting the immune system toward an ineffective antibacterial response.
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Affiliation(s)
- Alistair C. Darby
- Institute of Integrative Biology and the Centre for Genomic Research, Biosciences Building, University of Liverpool, Liverpool, Merseyside L69 7ZB, United Kingdom
| | - Stuart D. Armstrong
- Institute of Infection & Global Health, Liverpool Science Park IC2, University of Liverpool, Liverpool, Merseyside L3 5RF, United Kingdom
| | - Germanus S. Bah
- Institute of Infection & Global Health, Liverpool Science Park IC2, University of Liverpool, Liverpool, Merseyside L3 5RF, United Kingdom
- Institut de Recherche Agricole pour le Développement, Regional Centre of Wakwa, Ngaoundéré, BP65 Adamawa Region, Cameroon
| | - Gaganjot Kaur
- Institute of Evolutionary Biology and the GenePool Genomics Facility, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3JT, United Kingdom
| | - Margaret A. Hughes
- Institute of Integrative Biology and the Centre for Genomic Research, Biosciences Building, University of Liverpool, Liverpool, Merseyside L69 7ZB, United Kingdom
| | - Suzanne M. Kay
- Institute of Integrative Biology and the Centre for Genomic Research, Biosciences Building, University of Liverpool, Liverpool, Merseyside L69 7ZB, United Kingdom
| | - Pia Koldkjær
- Institute of Integrative Biology and the Centre for Genomic Research, Biosciences Building, University of Liverpool, Liverpool, Merseyside L69 7ZB, United Kingdom
| | - Lucille Rainbow
- Institute of Integrative Biology and the Centre for Genomic Research, Biosciences Building, University of Liverpool, Liverpool, Merseyside L69 7ZB, United Kingdom
| | - Alan D. Radford
- Institute of Infection & Global Health, Liverpool Science Park IC2, University of Liverpool, Liverpool, Merseyside L3 5RF, United Kingdom
| | - Mark L. Blaxter
- Institute of Evolutionary Biology and the GenePool Genomics Facility, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3JT, United Kingdom
| | - Vincent N. Tanya
- Institut de Recherche Agricole pour le Développement, Regional Centre of Wakwa, Ngaoundéré, BP65 Adamawa Region, Cameroon
| | - Alexander J. Trees
- Institute of Infection & Global Health, Liverpool Science Park IC2, University of Liverpool, Liverpool, Merseyside L3 5RF, United Kingdom
| | - Richard Cordaux
- Laboratoire Ecologie et Biologie des Interactions (UMR CNRS 7267), Equipe Ecologie Evolution Symbiose, Université de Poitiers, 86022 Poitiers CEDEX, France
| | - Jonathan M. Wastling
- Institute of Infection & Global Health, Liverpool Science Park IC2, University of Liverpool, Liverpool, Merseyside L3 5RF, United Kingdom
| | - Benjamin L. Makepeace
- Institute of Infection & Global Health, Liverpool Science Park IC2, University of Liverpool, Liverpool, Merseyside L3 5RF, United Kingdom
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Mohorko E, Abicht HK, Bühler D, Glockshuber R, Hennecke H, Fischer HM. Thioredoxin-like protein TlpA from Bradyrhizobium japonicum
is a reductant for the copper metallochaperone ScoI. FEBS Lett 2012; 586:4094-9. [DOI: 10.1016/j.febslet.2012.10.026] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2012] [Revised: 10/12/2012] [Accepted: 10/12/2012] [Indexed: 12/17/2022]
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Direct and indirect regulation of the ycnKJI operon involved in copper uptake through two transcriptional repressors, YcnK and CsoR, in Bacillus subtilis. J Bacteriol 2012; 194:5675-87. [PMID: 22904286 DOI: 10.1128/jb.00919-12] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Northern blot and primer extension analyses revealed that the ycnKJI operon and the ycnL gene of Bacillus subtilis are transcribed from adjacent promoters that are divergently oriented. The ycnK and ycnJ genes encode a DeoR-type transcriptional regulator and a membrane protein involved in copper uptake, respectively. DNA binding experiments showed that the YcnK protein specifically binds to the ycnK-ycnL intergenic region, including a 16-bp direct repeat that is essential for the high binding affinity of YcnK, and that a copper-specific chelator significantly inhibits YcnK's DNA binding. lacZ reporter analysis showed that the ycnK promoter is induced by copper limitation or ycnK disruption. These results are consistent with YcnK functioning as a copper-responsive repressor that derepresses ycnKJI expression under copper limitation. On the other hand, the ycnL promoter was hardly induced by copper limitation, but ycnK disruption resulted in a slight induction of the ycnL promoter, suggesting that YcnK also represses ycnL weakly. Moreover, while the CsoR protein did not bind to the ycnK-ycnL intergenic region, lacZ reporter analysis demonstrated that csoR disruption induces the ycnK promoter only in the presence of intact ycnK and copZA genes. Since the copZA operon is involved in copper export and repressed by CsoR, it appears that the constitutive copZA expression brought by csoR disruption causes intracellular copper depletion, which releases the repression of the ycnKJI operon by YcnK.
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Lohmeyer E, Schröder S, Pawlik G, Trasnea PI, Peters A, Daldal F, Koch HG. The ScoI homologue SenC is a copper binding protein that interacts directly with the cbb₃-type cytochrome oxidase in Rhodobacter capsulatus. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2012; 1817:2005-15. [PMID: 22771512 DOI: 10.1016/j.bbabio.2012.06.621] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/23/2012] [Revised: 06/27/2012] [Accepted: 06/28/2012] [Indexed: 11/28/2022]
Abstract
Sco proteins are widespread assembly factors for the Cu(A) centre of aa₃-type cytochrome oxidases in eukaryotic and prokaryotic organisms. However, Sco homologues are also found in bacteria like Rhodobacter capsulatus which lack aa₃-type cytochrome oxidases and instead use a cbb₃-type cytochrome oxidase (cbb₃ Cox) without a Cu(A) centre as a terminal oxidase. In the current study, we have analyzed the role of Sco (SenC) during cbb₃ Cox assembly in R. capsulatus. In agreement with earlier works, we found a strong cbb₃ Cox defect in the absence of SenC that impairs the steady-state stability of the CcoN, CcoO and CcoP core subunits, without the accumulation of detectable assembly intermediates. In vivo cross-linking results demonstrate that SenC is in close proximity to the CcoP and CcoH subunits of cbb₃ Cox, suggesting that SenC interacts directly with cbb₃ Cox during its assembly. SenC binds copper and the cbb₃ Cox assembly defect in the absence of SenC can be rescued by the addition of least 0.5μM Cu. Neither copper nor SenC influenced the transcription of the ccoNOQP operon encoding for cbb₃ Cox. Transcription of senC itself was also not influenced by Cu unless the putative Cu-export ATPase CcoI was absent. As CcoI is specifically required for the cbb₃ Cox assembly, these data provide a direct link between Cu delivery to cbb₃ Cox and SenC function.
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Affiliation(s)
- Eva Lohmeyer
- Institut für Biochemie und Molekularbiologie, ZBMZ, Stefan-Meier-Strasse 17, Albert-Ludwigs-Universität Freiburg, 79104 Freiburg, Germany.
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Völlmecke C, Drees SL, Reimann J, Albers SV, Lübben M. The ATPases CopA and CopB both contribute to copper resistance of the thermoacidophilic archaeon Sulfolobus solfataricus. MICROBIOLOGY-SGM 2012; 158:1622-1633. [PMID: 22361944 DOI: 10.1099/mic.0.055905-0] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
Certain heavy metal ions such as copper and zinc serve as essential cofactors of many enzymes, but are toxic at high concentrations. Thus, intracellular levels have to be subtly balanced. P-type ATPases of the P(IB)-subclass play a major role in metal homeostasis. The thermoacidophile Sulfolobus solfataricus possesses two P(IB)-ATPases named CopA and CopB. Both enzymes are present in cells grown in copper-depleted medium and are accumulated upon an increase in the external copper concentration. We studied the physiological roles of both ATPases by disrupting genes copA and copB. Neither of them affected the sensitivity of S. solfataricus to reactive oxygen species, nor were they a strict prerequisite to the biosynthesis of the copper protein cytochrome oxidase. Deletion mutant analysis demonstrated that CopA is an effective copper pump at low and high copper concentrations. CopB appeared to be a low-affinity copper export ATPase, which was only relevant if the media copper concentration was exceedingly high. CopA and CopB thus act as resistance factors to copper ions at overlapping concentrations. Moreover, growth tests on solid media indicated that both ATPases are involved in resistance to silver.
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Affiliation(s)
- Christian Völlmecke
- Lehrstuhl für Biophysik, Ruhr-Universität Bochum, Universitätsstr. 150, D-44780 Bochum, Germany
| | - Steffen L Drees
- Lehrstuhl für Biophysik, Ruhr-Universität Bochum, Universitätsstr. 150, D-44780 Bochum, Germany
| | - Julia Reimann
- Molecular Biology of Archaea, MPI für Terrestrische Mikrobiologie, Marburg, Karl-von-Frisch-Straße 10, D-35043 Marburg, Germany
| | - Sonja-Verena Albers
- Molecular Biology of Archaea, MPI für Terrestrische Mikrobiologie, Marburg, Karl-von-Frisch-Straße 10, D-35043 Marburg, Germany
| | - Mathias Lübben
- Lehrstuhl für Biophysik, Ruhr-Universität Bochum, Universitätsstr. 150, D-44780 Bochum, Germany
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Thompson AK, Gray J, Liu A, Hosler JP. The roles of Rhodobacter sphaeroides copper chaperones PCu(A)C and Sco (PrrC) in the assembly of the copper centers of the aa(3)-type and the cbb(3)-type cytochrome c oxidases. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2012; 1817:955-64. [PMID: 22248670 DOI: 10.1016/j.bbabio.2012.01.003] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2011] [Revised: 12/30/2011] [Accepted: 01/02/2012] [Indexed: 11/28/2022]
Abstract
The α proteobacter Rhodobacter sphaeroides accumulates two cytochrome c oxidases (CcO) in its cytoplasmic membrane during aerobic growth: a mitochondrial-like aa(3)-type CcO containing a di-copper Cu(A) center and mono-copper Cu(B), plus a cbb(3)-type CcO that contains Cu(B) but lacks Cu(A). Three copper chaperones are located in the periplasm of R. sphaeroides, PCu(A)C, PrrC (Sco) and Cox11. Cox11 is required to assemble Cu(B) of the aa(3)-type but not the cbb(3)-type CcO. PrrC is homologous to mitochondrial Sco1; Sco proteins are implicated in Cu(A) assembly in mitochondria and bacteria, and with Cu(B) assembly of the cbb(3)-type CcO. PCu(A)C is present in many bacteria, but not mitochondria. PCu(A)C of Thermus thermophilus metallates a Cu(A) center in vitro, but its in vivo function has not been explored. Here, the extent of copper center assembly in the aa(3)- and cbb(3)-type CcOs of R. sphaeroides has been examined in strains lacking PCu(A)C, PrrC, or both. The absence of either chaperone strongly lowers the accumulation of both CcOs in the cells grown in low concentrations of Cu(2+). The absence of PrrC has a greater effect than the absence of PCu(A)C and PCu(A)C appears to function upstream of PrrC. Analysis of purified aa(3)-type CcO shows that PrrC has a greater effect on the assembly of its Cu(A) than does PCu(A)C, and both chaperones have a lesser but significant effect on the assembly of its Cu(B) even though Cox11 is present. Scenarios for the cellular roles of PCu(A)C and PrrC are considered. The results are most consistent with a role for PrrC in the capture and delivery of copper to Cu(A) of the aa(3)-type CcO and to Cu(B) of the cbb(3)-type CcO, while the predominant role of PCu(A)C may be to capture and deliver copper to PrrC and Cox11. This article is part of a Special Issue entitled: Biogenesis/Assembly of Respiratory Enzyme Complexes.
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Affiliation(s)
- Audie K Thompson
- Department of Biochemistry, The University of Mississippi Medical Center, Jackson, MS 39216, USA.
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Cytochrome c signalosome in mitochondria. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2011; 40:1301-15. [DOI: 10.1007/s00249-011-0774-4] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2011] [Revised: 10/12/2011] [Accepted: 10/21/2011] [Indexed: 10/15/2022]
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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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