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Enemark JH. Mechanistic complexities of sulfite oxidase: An enzyme with multiple domains, subunits, and cofactors. J Inorg Biochem 2023; 247:112312. [PMID: 37441922 DOI: 10.1016/j.jinorgbio.2023.112312] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2023] [Revised: 05/13/2023] [Accepted: 07/01/2023] [Indexed: 07/15/2023]
Abstract
Sulfite oxidase (SO) deficiency, an inherited disease that causes severe neonatal neurological problems and early death, arises from defects in the biosynthesis of the molybdenum cofactor (Moco) (general sulfite oxidase deficiency) or from inborn errors in the SUOX gene for SO (isolated sulfite oxidase deficiency, ISOD). The X-ray structure of the highly homologous homonuclear dimeric chicken sulfite oxidase (cSO) provides a template for locating ISOD mutation sites in human sulfite oxidase (hSO). Catalysis occurs within an individual subunit of hSO, but mutations that disrupt the hSO dimer are pathological. The catalytic cycle of SO involves five metal oxidation states (MoVI, MoV, MoIV, FeIII, FeII), two intramolecular electron transfer (IET) steps, and couples a two-electron oxygen atom transfer reaction at the Mo center with two one-electron transfers from the integral b-type heme to exogenous cytochrome c, the physiological oxidant. Several ISOD examples are analyzed using steady-state, stopped-flow, and laser flash photolysis kinetics and physical measurements of recombinant variants of hSO and native cSO. In the structure of cSO, Mo…Fe = 32 Å, much too long for efficient IET through the protein. Interdomain motion that brings the Mo and heme centers closer together to facilitate IET is supported indirectly by decreasing the length of the interdomain tether, by changes in the charges of surface residues of the Mo and heme domains, as well as by preliminary molecular dynamics calculations. However, direct dynamic measurements of interdomain motion are in their infancy.
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Affiliation(s)
- John H Enemark
- Department of Chemistry and Biochemistry, The University of Arizona, 1306 East University Blvd, Tucson, AZ 85721-0041, United States of America.
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2
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Maia LB. Bringing Nitric Oxide to the Molybdenum World-A Personal Perspective. Molecules 2023; 28:5819. [PMID: 37570788 PMCID: PMC10420851 DOI: 10.3390/molecules28155819] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2023] [Revised: 07/29/2023] [Accepted: 07/30/2023] [Indexed: 08/13/2023] Open
Abstract
Molybdenum-containing enzymes of the xanthine oxidase (XO) family are well known to catalyse oxygen atom transfer reactions, with the great majority of the characterised enzymes catalysing the insertion of an oxygen atom into the substrate. Although some family members are known to catalyse the "reverse" reaction, the capability to abstract an oxygen atom from the substrate molecule is not generally recognised for these enzymes. Hence, it was with surprise and scepticism that the "molybdenum community" noticed the reports on the mammalian XO capability to catalyse the oxygen atom abstraction of nitrite to form nitric oxide (NO). The lack of precedent for a molybdenum- (or tungsten) containing nitrite reductase on the nitrogen biogeochemical cycle contributed also to the scepticism. It took several kinetic, spectroscopic and mechanistic studies on enzymes of the XO family and also of sulfite oxidase and DMSO reductase families to finally have wide recognition of the molybdoenzymes' ability to form NO from nitrite. Herein, integrated in a collection of "personal views" edited by Professor Ralf Mendel, is an overview of my personal journey on the XO and aldehyde oxidase-catalysed nitrite reduction to NO. The main research findings and the path followed to establish XO and AO as competent nitrite reductases are reviewed. The evidence suggesting that these enzymes are probable players of the mammalian NO metabolism is also discussed.
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Affiliation(s)
- Luisa B Maia
- LAQV, REQUIMTE, Department of Chemistry, NOVA School of Science and Technology (FCT NOVA), 2829-516 Caparica, Portugal
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3
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Molecular mechanism of intramolecular electron transfer in dimeric sulfite oxidase. J Biol Chem 2022; 298:101668. [PMID: 35120924 PMCID: PMC8908248 DOI: 10.1016/j.jbc.2022.101668] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2021] [Revised: 01/26/2022] [Accepted: 01/28/2022] [Indexed: 12/02/2022] Open
Abstract
Sulfite oxidase (SOX) is a homodimeric molybdoheme enzyme that oxidizes sulfite to sulfate at the molybdenum center. Following substrate oxidation, molybdenum is reduced and subsequently regenerated by two sequential electron transfers (ETs) via heme to cytochrome c. SOX harbors both metals in spatially separated domains within each subunit, suggesting that domain movement is necessary to allow intramolecular ET. To address whether one subunit in a SOX dimer is sufficient for catalysis, we produced heterodimeric SOX variants with abolished sulfite oxidation by replacing the molybdenum-coordinating and essential cysteine in the active site. To further elucidate whether electrons can bifurcate between subunits, we truncated one or both subunits by deleting the heme domain. We generated three SOX heterodimers: (i) SOX/Mo with two active molybdenum centers but one deleted heme domain, (ii) SOX/Mo_C264S with one unmodified and one inactive subunit, and (iii) SOX_C264S/Mo harboring a functional molybdenum center on one subunit and a heme domain on the other subunit. Steady-state kinetics showed 50% SOX activity for the SOX/Mo and SOX/Mo_C264S heterodimers, whereas SOX_C264S/Mo activity was reduced by two orders of magnitude. Rapid reaction kinetics monitoring revealed comparable ET rates in SOX/Mo, SOX/Mo_C264S, and SOX/SOX, whereas in SOX_C264S/Mo, ET was strongly compromised. We also combined a functional SOX Mo domain with an inactive full-length SOX R217W variant and demonstrated interdimer ET that resembled SOX_C264S/Mo activity. Collectively, our results indicate that one functional subunit in SOX is sufficient for catalysis and that electrons derived from either Mo(IV) or Mo(V) follow this path.
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Landry AP, Ballou DP, Banerjee R. Hydrogen Sulfide Oxidation by Sulfide Quinone Oxidoreductase. Chembiochem 2021; 22:949-960. [PMID: 33080111 PMCID: PMC7969369 DOI: 10.1002/cbic.202000661] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2020] [Revised: 10/19/2020] [Indexed: 02/05/2023]
Abstract
Hydrogen sulfide (H2 S) is an environmental toxin and a heritage of ancient microbial metabolism that has stimulated new interest following its discovery as a neuromodulator. While many physiological responses have been attributed to low H2 S levels, higher levels inhibit complex IV in the electron transport chain. To prevent respiratory poisoning, a dedicated set of enzymes that make up the mitochondrial sulfide oxidation pathway exists to clear H2 S. The committed step in this pathway is catalyzed by sulfide quinone oxidoreductase (SQOR), which couples sulfide oxidation to coenzyme Q10 reduction in the electron transport chain. The SQOR reaction prevents H2 S accumulation and generates highly reactive persulfide species as products; these can be further oxidized or can modify cysteine residues in proteins by persulfidation. Here, we review the kinetic and structural characteristics of human SQOR, and how its unconventional redox cofactor configuration and substrate promiscuity lead to sulfide clearance and potentially expand the signaling potential of H2 S. This dual role of SQOR makes it a promising target for H2 S-based therapeutics.
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Affiliation(s)
- Aaron P. Landry
- Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, Michigan 48109, United States
| | - David P. Ballou
- Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, Michigan 48109, United States
| | - Ruma Banerjee
- Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, Michigan 48109, United States
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Yan J, Frøkjær EE, Engelbrekt C, Leimkühler S, Ulstrup J, Wollenberger U, Xiao X, Zhang J. Voltammetry and Single‐Molecule In Situ Scanning Tunnelling Microscopy of the Redox Metalloenzyme Human Sulfite Oxidase. ChemElectroChem 2021. [DOI: 10.1002/celc.202001258] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Jiawei Yan
- Department of Chemistry Technical University of Denmark Building 207, Kemitorvet 2800 Kgs. Lyngby Denmark
- State key Laboratory of Physical Chemistry of Solid Surfaces and College of Chemistry and Chemical Engineering Xiamen University Xiamen 361005 Fujian P.R. China
| | - Emil Egede Frøkjær
- Department of Chemistry Technical University of Denmark Building 207, Kemitorvet 2800 Kgs. Lyngby Denmark
| | - Christian Engelbrekt
- Department of Chemistry Technical University of Denmark Building 207, Kemitorvet 2800 Kgs. Lyngby Denmark
| | - Silke Leimkühler
- Department of Molecular Enzymology University of Potsdam 14476 PotsdamPotsdam-Golm Germany
| | - Jens Ulstrup
- Department of Chemistry Technical University of Denmark Building 207, Kemitorvet 2800 Kgs. Lyngby Denmark
| | - Ulla Wollenberger
- Department of Molecular Enzymology University of Potsdam 14476 PotsdamPotsdam-Golm Germany
| | - Xinxin Xiao
- Department of Chemistry Technical University of Denmark Building 207, Kemitorvet 2800 Kgs. Lyngby Denmark
| | - Jingdong Zhang
- Department of Chemistry Technical University of Denmark Building 207, Kemitorvet 2800 Kgs. Lyngby Denmark
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6
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Kirk ML, Kc K. Molybdenum and Tungsten Cofactors and the Reactions They Catalyze. Met Ions Life Sci 2020; 20:/books/9783110589757/9783110589757-015/9783110589757-015.xml. [PMID: 32851830 PMCID: PMC8176780 DOI: 10.1515/9783110589757-015] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2023]
Abstract
The last 20 years have seen a dramatic increase in our mechanistic understanding of the reactions catalyzed by pyranopterin Mo and W enzymes. These enzymes possess a unique cofactor (Moco) that contains a novel ligand in bioinorganic chemistry, the pyranopterin ene-1,2-dithiolate. A synopsis of Moco biosynthesis and structure is presented, along with our current understanding of the role Moco plays in enzymatic catalysis. Oxygen atom transfer (OAT) reactivity is discussed in terms of breaking strong metal-oxo bonds and the mechanism of OAT catalyzed by enzymes of the sulfite oxidase (SO) family that possess dioxo Mo(VI) active sites. OAT reactivity is also discussed in members of the dimethyl sulfoxide (DMSO) reductase family, which possess des-oxo Mo(IV) sites. Finally, we reveal what is known about hydride transfer reactivity in xanthine oxidase (XO) family enzymes and the formate dehydrogenases. The formal hydride transfer reactivity catalyzed by xanthine oxidase family enzymes is complex and cleaves substrate C-H bonds using a mechanism that is distinct from monooxygenases. The chapter primarily highlights developments in the field that have occurred since ~2000, which have contributed to our collective structural and mechanistic understanding of the three canonical pyranopterin Mo enzymes families: XO, SO, and DMSO reductase.
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8
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Bender D, Kaczmarek AT, Santamaria-Araujo JA, Stueve B, Waltz S, Bartsch D, Kurian L, Cirak S, Schwarz G. Impaired mitochondrial maturation of sulfite oxidase in a patient with severe sulfite oxidase deficiency. Hum Mol Genet 2019; 28:2885-2899. [DOI: 10.1093/hmg/ddz109] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2019] [Revised: 04/09/2019] [Accepted: 05/07/2019] [Indexed: 01/24/2023] Open
Abstract
AbstractSulfite oxidase (SO) is encoded by the nuclear SUOX gene and catalyzes the final step in cysteine catabolism thereby oxidizing sulfite to sulfate. Oxidation of sulfite is dependent on two cofactors within SO, a heme and the molybdenum cofactor (Moco), the latter forming the catalytic site of sulfite oxidation. SO localizes to the intermembrane space of mitochondria where both—pre-SO processing and cofactor insertion—are essential steps during SO maturation. Isolated SO deficiency (iSOD) is a rare inborn error of metabolism caused by mutations in the SUOX gene that lead to non-functional SO. ISOD is characterized by rapidly progressive neurodegeneration and death in early infancy. We diagnosed an iSOD patient with homozygous mutation of SUOX at c.1084G>A replacing Gly362 to serine. To understand the mechanism of disease, we expressed patient-derived G362S SO in Escherichia coli and surprisingly found full catalytic activity, while in patient fibroblasts no SO activity was detected, suggesting differences between bacterial and human expression. Moco reconstitution of apo-G362S SO was found to be approximately 90-fold reduced in comparison to apo-WT SO in vitro. In line, levels of SO-bound Moco in cells overexpressing G362S SO were significantly reduced compared to cells expressing WT SO providing evidence for compromised maturation of G362S SO in cellulo. Addition of molybdate to culture medium partially rescued impaired Moco binding of G362S SO and restored SO activity in patient fibroblasts. Thus, this study demonstrates the importance of the orchestrated maturation of SO and provides a first case of Moco-responsive iSOD.
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Affiliation(s)
- Daniel Bender
- Department of Chemistry, Institute for Biochemistry, University of Cologne, 50674 Cologne, Germany
- Center for Molecular Medicine Cologne, University of Cologne, 50931 Cologne Germany
| | - Alexander Tobias Kaczmarek
- Department of Chemistry, Institute for Biochemistry, University of Cologne, 50674 Cologne, Germany
- Center for Molecular Medicine Cologne, University of Cologne, 50931 Cologne Germany
| | | | - Burkard Stueve
- Abteilung für Kinderneurologie, Epileptologie und Sozialpädiatrie, Kliniken Köln, Kinderkrankenhaus, 51058 Cologne, Germany
| | - Stephan Waltz
- Abteilung für Kinderneurologie, Epileptologie und Sozialpädiatrie, Kliniken Köln, Kinderkrankenhaus, 51058 Cologne, Germany
| | - Deniz Bartsch
- Center for Molecular Medicine Cologne, University of Cologne, 50931 Cologne Germany
| | - Leo Kurian
- Center for Molecular Medicine Cologne, University of Cologne, 50931 Cologne Germany
| | - Sebahattin Cirak
- Center for Molecular Medicine Cologne, University of Cologne, 50931 Cologne Germany
- Klinik für Kinderheilkunde und Jugendmedizin, Uniklinikum Köln, 50937 Cologne, Germany
| | - Guenter Schwarz
- Department of Chemistry, Institute for Biochemistry, University of Cologne, 50674 Cologne, Germany
- Center for Molecular Medicine Cologne, University of Cologne, 50931 Cologne Germany
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9
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Kalimuthu P, Belaidi AA, Schwarz G, Bernhardt PV. Chitosan-Promoted Direct Electrochemistry of Human Sulfite Oxidase. J Phys Chem B 2017; 121:9149-9159. [DOI: 10.1021/acs.jpcb.7b06712] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Palraj Kalimuthu
- School
of Chemistry and Molecular Biosciences, University of Queensland, Brisbane, 4072, Australia
| | - Abdel A. Belaidi
- Department
of Chemistry and Center for Molecular Medicine, Institute of Biochemistry, Cologne University, Zülicher Strasse 47, 50674 Köln, Germany
- The Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Victoria 3052, Australia
| | - Guenter Schwarz
- Department
of Chemistry and Center for Molecular Medicine, Institute of Biochemistry, Cologne University, Zülicher Strasse 47, 50674 Köln, Germany
| | - Paul V. Bernhardt
- School
of Chemistry and Molecular Biosciences, University of Queensland, Brisbane, 4072, Australia
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10
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Zeng T, Leimkühler S, Wollenberger U, Fourmond V. Transient Catalytic Voltammetry of Sulfite Oxidase Reveals Rate Limiting Conformational Changes. J Am Chem Soc 2017; 139:11559-11567. [DOI: 10.1021/jacs.7b05480] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Ting Zeng
- Institute of Biochemistry
and Biology, University of Potsdam, Karl-Liebknecht-Str.24-25, 14476 Potsdam-Golm, Germany
| | - Silke Leimkühler
- Institute of Biochemistry
and Biology, University of Potsdam, Karl-Liebknecht-Str.24-25, 14476 Potsdam-Golm, Germany
| | - Ulla Wollenberger
- Institute of Biochemistry
and Biology, University of Potsdam, Karl-Liebknecht-Str.24-25, 14476 Potsdam-Golm, Germany
| | - Vincent Fourmond
- Aix-Marseille Université, CNRS, BIP UMR 7281, 31 chemin J. Aiguier, F-13402 Marseille cedex 20, France
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11
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Landry AP, Ballou DP, Banerjee R. H 2S oxidation by nanodisc-embedded human sulfide quinone oxidoreductase. J Biol Chem 2017; 292:11641-11649. [PMID: 28512131 DOI: 10.1074/jbc.m117.788547] [Citation(s) in RCA: 51] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2017] [Revised: 05/05/2017] [Indexed: 01/09/2023] Open
Abstract
Buildup of hydrogen sulfide (H2S), which functions as a signaling molecule but is toxic at high concentrations, is averted by its efficient oxidation by the mitochondrial sulfide oxidation pathway. The first step in this pathway is catalyzed by a flavoprotein, sulfide quinone oxidoreductase (SQR), which converts H2S to a persulfide and transfers electrons to coenzyme Q via a flavin cofactor. All previous studies on human SQR have used detergent-solubilized protein. Here, we embedded human SQR in nanodiscs (ndSQR) and studied highly homogenous preparations by steady-state and rapid-kinetics techniques. ndSQR exhibited higher catalytic rates in its membranous environment than in its solubilized state. Stopped-flow spectroscopic data revealed that transfer of the sulfane sulfur from an SQR-bound cysteine persulfide intermediate to a small-molecule acceptor is the rate-limiting step. The physiological acceptor of sulfane sulfur from SQR has been the subject of controversy; we report that the kinetic analysis of ndSQR is consistent with glutathione rather than sulfite being the predominant acceptor at physiologically relevant concentrations of the respective metabolites. The identity of the acceptor has an important bearing on how the sulfide oxidation pathway is organized. Our data are more consistent with the reaction sequence for sulfide oxidation being: H2S → glutathione persulfide → sulfite → sulfate, than with a more convoluted route that would result if sulfite were the primary acceptor of sulfane sulfur. In summary, nanodisc-incorporated human SQR exhibits enhanced catalytic performance, and pre-steady-state kinetics characterization of the complete SQR catalytic cycle indicates that GSH serves as the physiologically relevant sulfur acceptor.
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Affiliation(s)
- Aaron P Landry
- Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, Michigan 48109
| | - David P Ballou
- Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, Michigan 48109
| | - Ruma Banerjee
- Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, Michigan 48109.
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12
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Kalimuthu P, Belaidi AA, Schwarz G, Bernhardt PV. Mediated Catalytic Voltammetry of Holo and Heme‐Free Human Sulfite Oxidases. ChemElectroChem 2017. [DOI: 10.1002/celc.201600685] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Palraj Kalimuthu
- School of Chemistry and Molecular Biosciences University of Queensland Brisbane 4072 Australia
| | - Abdel A. Belaidi
- The Florey Institute of Neuroscience and Mental Health University of Melbourne Victoria 3052 Australia
- Institute of Biochemistry Department of Chemistry and Center for Molecular Medicine Cologne University Zülicher Str. 47 50674 Köln Germany
| | - Guenter Schwarz
- Institute of Biochemistry Department of Chemistry and Center for Molecular Medicine Cologne University Zülicher Str. 47 50674 Köln Germany
| | - Paul V. Bernhardt
- School of Chemistry and Molecular Biosciences University of Queensland Brisbane 4072 Australia
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13
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Maia LB, Moura I, Moura JJ. EPR Spectroscopy on Mononuclear Molybdenum-Containing Enzymes. FUTURE DIRECTIONS IN METALLOPROTEIN AND METALLOENZYME RESEARCH 2017. [DOI: 10.1007/978-3-319-59100-1_4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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15
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Libiad M, Sriraman A, Banerjee R. Polymorphic Variants of Human Rhodanese Exhibit Differences in Thermal Stability and Sulfur Transfer Kinetics. J Biol Chem 2015; 290:23579-88. [PMID: 26269602 DOI: 10.1074/jbc.m115.675694] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2015] [Indexed: 11/06/2022] Open
Abstract
Rhodanese is a component of the mitochondrial H2S oxidation pathway. Rhodanese catalyzes the transfer of sulfane sulfur from glutathione persulfide (GSSH) to sulfite generating thiosulfate and from thiosulfate to cyanide generating thiocyanate. Two polymorphic variations have been identified in the rhodanese coding sequence in the French Caucasian population. The first, 306A→C, has an allelic frequency of 1% and results in an E102D substitution in the encoded protein. The second polymorphism, 853C→G, has an allelic frequency of 5% and leads to a P285A substitution. In this study, we have examined differences in the stability between wild-type rhodanese and the E102D and P285A variants and in the kinetics of the sulfur transfer reactions. The Asp-102 and Ala-285 variants are more stable than wild-type rhodanese and exhibit kcat/Km,CN values that are 17- and 1.6-fold higher, respectively. All three rhodanese forms preferentially catalyze sulfur transfer from GSSH to sulfite, generating thiosulfate and glutathione. The kcat/Km,sulfite values for the variants in the sulfur transfer reaction from GSSH to sulfite were 1.6- (Asp-102) and 4-fold (Ala-285) lower than for wild-type rhodanese, whereas the kcat/Km,GSSH values were similar for all three enzymes. Thiosulfate-dependent H2S production in murine liver lysate is low, consistent with a role for rhodanese in sulfide oxidation. Our studies show that polymorphic variations that are distant from the active site differentially modulate the sulfurtransferase activity of human rhodanese to cyanide versus sulfite and might be important in differences in susceptibility to diseases where rhodanese dysfunction has been implicated, e.g. inflammatory bowel diseases.
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Affiliation(s)
- Marouane Libiad
- From the Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, Michigan 48109-0600
| | - Anusha Sriraman
- From the Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, Michigan 48109-0600
| | - Ruma Banerjee
- From the Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, Michigan 48109-0600
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16
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Wang J, Krizowski S, Fischer-Schrader K, Niks D, Tejero J, Sparacino-Watkins C, Wang L, Ragireddy V, Frizzell S, Kelley EE, Zhang Y, Basu P, Hille R, Schwarz G, Gladwin MT. Sulfite Oxidase Catalyzes Single-Electron Transfer at Molybdenum Domain to Reduce Nitrite to Nitric Oxide. Antioxid Redox Signal 2015; 23:283-94. [PMID: 25314640 PMCID: PMC4523048 DOI: 10.1089/ars.2013.5397] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
AIMS Recent studies suggest that the molybdenum enzymes xanthine oxidase, aldehyde oxidase, and mARC exhibit nitrite reductase activity at low oxygen pressures. However, inhibition studies of xanthine oxidase in humans have failed to block nitrite-dependent changes in blood flow, leading to continued exploration for other candidate nitrite reductases. Another physiologically important molybdenum enzyme—sulfite oxidase (SO)—has not been extensively studied. RESULTS Using gas-phase nitric oxide (NO) detection and physiological concentrations of nitrite, SO functions as nitrite reductase in the presence of a one-electron donor, exhibiting redox coupling of substrate oxidation and nitrite reduction to form NO. With sulfite, the physiological substrate, SO only facilitates one turnover of nitrite reduction. Studies with recombinant heme and molybdenum domains of SO indicate that nitrite reduction occurs at the molybdenum center via coupled oxidation of Mo(IV) to Mo(V). Reaction rates of nitrite to NO decreased in the presence of a functional heme domain, mediated by steric and redox effects of this domain. Using knockdown of all molybdopterin enzymes and SO in fibroblasts isolated from patients with genetic deficiencies of molybdenum cofactor and SO, respectively, SO was found to significantly contribute to hypoxic nitrite signaling as demonstrated by activation of the canonical NO-sGC-cGMP pathway. INNOVATION Nitrite binds to and is reduced at the molybdenum site of mammalian SO, which may be allosterically regulated by heme and molybdenum domain interactions, and contributes to the mammalian nitrate-nitrite-NO signaling pathway in human fibroblasts. CONCLUSION SO is a putative mammalian nitrite reductase, catalyzing nitrite reduction at the Mo(IV) center.
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Affiliation(s)
- Jun Wang
- 1 Pittsburgh Heart, Lung, Blood and Vascular Medicine Institute, University of Pittsburgh , Pittsburgh, Pennsylvania.,2 Pulmonary, Allergy and Critical Care Medicine, Department of Medicine, University of Pittsburgh , Pittsburgh, Pennsylvania
| | - Sabina Krizowski
- 3 Department of Biochemistry, Center for Molecular Medicine, Institute of Biochemistry, Cologne University , Cologne, Germany
| | - Katrin Fischer-Schrader
- 3 Department of Biochemistry, Center for Molecular Medicine, Institute of Biochemistry, Cologne University , Cologne, Germany
| | - Dimitri Niks
- 4 Department of Biochemistry, University of California at Riverside , Riverside, California
| | - Jesús Tejero
- 1 Pittsburgh Heart, Lung, Blood and Vascular Medicine Institute, University of Pittsburgh , Pittsburgh, Pennsylvania.,2 Pulmonary, Allergy and Critical Care Medicine, Department of Medicine, University of Pittsburgh , Pittsburgh, Pennsylvania
| | - Courtney Sparacino-Watkins
- 1 Pittsburgh Heart, Lung, Blood and Vascular Medicine Institute, University of Pittsburgh , Pittsburgh, Pennsylvania.,2 Pulmonary, Allergy and Critical Care Medicine, Department of Medicine, University of Pittsburgh , Pittsburgh, Pennsylvania
| | - Ling Wang
- 1 Pittsburgh Heart, Lung, Blood and Vascular Medicine Institute, University of Pittsburgh , Pittsburgh, Pennsylvania.,2 Pulmonary, Allergy and Critical Care Medicine, Department of Medicine, University of Pittsburgh , Pittsburgh, Pennsylvania
| | - Venkata Ragireddy
- 1 Pittsburgh Heart, Lung, Blood and Vascular Medicine Institute, University of Pittsburgh , Pittsburgh, Pennsylvania.,2 Pulmonary, Allergy and Critical Care Medicine, Department of Medicine, University of Pittsburgh , Pittsburgh, Pennsylvania
| | - Sheila Frizzell
- 1 Pittsburgh Heart, Lung, Blood and Vascular Medicine Institute, University of Pittsburgh , Pittsburgh, Pennsylvania.,2 Pulmonary, Allergy and Critical Care Medicine, Department of Medicine, University of Pittsburgh , Pittsburgh, Pennsylvania
| | - Eric E Kelley
- 1 Pittsburgh Heart, Lung, Blood and Vascular Medicine Institute, University of Pittsburgh , Pittsburgh, Pennsylvania.,5 Department of Anesthesiology, University of Pittsburgh , Pittsburgh, Pennsylvania
| | - Yingze Zhang
- 2 Pulmonary, Allergy and Critical Care Medicine, Department of Medicine, University of Pittsburgh , Pittsburgh, Pennsylvania
| | - Partha Basu
- 6 Department of Chemistry and Biochemistry, Duquesne University , Pittsburgh, Pennsylvania
| | - Russ Hille
- 4 Department of Biochemistry, University of California at Riverside , Riverside, California
| | - Guenter Schwarz
- 3 Department of Biochemistry, Center for Molecular Medicine, Institute of Biochemistry, Cologne University , Cologne, Germany
| | - Mark T Gladwin
- 1 Pittsburgh Heart, Lung, Blood and Vascular Medicine Institute, University of Pittsburgh , Pittsburgh, Pennsylvania.,2 Pulmonary, Allergy and Critical Care Medicine, Department of Medicine, University of Pittsburgh , Pittsburgh, Pennsylvania
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Davis AC, Johnson-Winters K, Arnold AR, Tollin G, Enemark JH. Kinetic results for mutations of conserved residues H304 and R309 of human sulfite oxidase point to mechanistic complexities. Metallomics 2015; 6:1664-70. [PMID: 24968320 DOI: 10.1039/c4mt00099d] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Several point mutations in the gene of human sulfite oxidase (hSO) result in isolated sulfite oxidase deficiency, an inherited metabolic disorder. Three conserved residues (H304, R309, K322) are hydrogen bonded to the phosphate group of the molybdenum cofactor, and the R309H and K322R mutations are responsible for isolated sulfite oxidase deficiency. The kinetic effects of the K322R mutation have been previously reported (Rajapakshe et al., Chem. Biodiversity, 2012, 9, 1621-1634); here we investigate several mutants of H304 and R309 by steady-state kinetics, laser flash photolysis studies of intramolecular electron transfer (IET), and spectroelectrochemistry. An unexpected result is that all of the mutants show decreased rates of IET but increased steady-state rates of catalysis. However, in all cases the rate of IET is greater than the overall turnover rate, showing that IET is not the rate determining step for any of the mutations.
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Affiliation(s)
- Amanda C Davis
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721-0041, USA
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Nitrite reduction by molybdoenzymes: a new class of nitric oxide-forming nitrite reductases. J Biol Inorg Chem 2015; 20:403-33. [DOI: 10.1007/s00775-014-1234-2] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2014] [Accepted: 12/14/2014] [Indexed: 02/07/2023]
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19
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Kappler U, Enemark JH. Sulfite-oxidizing enzymes. J Biol Inorg Chem 2014; 20:253-64. [DOI: 10.1007/s00775-014-1197-3] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2014] [Accepted: 09/15/2014] [Indexed: 11/24/2022]
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20
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Melideo SL, Jackson MR, Jorns MS. Biosynthesis of a central intermediate in hydrogen sulfide metabolism by a novel human sulfurtransferase and its yeast ortholog. Biochemistry 2014; 53:4739-53. [PMID: 24981631 PMCID: PMC4108183 DOI: 10.1021/bi500650h] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Human sulfide:quinone oxidoreductase (SQOR) catalyzes the conversion of H2S to thiosulfate, the first step in mammalian H2S metabolism. SQOR's inability to produce the glutathione persulfide (GSS(-)) substrate for sulfur dioxygenase (SDO) suggested that a thiosulfate:glutathione sulfurtransferase (TST) was required to provide the missing link between the SQOR and SDO reactions. Although TST could be purified from yeast, attempts to isolate the mammalian enzyme were not successful. We used bioinformatic approaches to identify genes likely to encode human TST (TSTD1) and its yeast ortholog (RDL1). Recombinant TSTD1 and RDL1 catalyze a predicted thiosulfate-dependent conversion of glutathione to GSS(-). Both enzymes contain a rhodanese homology domain and a single catalytically essential cysteine, which is converted to cysteine persulfide upon reaction with thiosulfate. GSS(-) is a potent inhibitor of TSTD1 and RDL1, as judged by initial rate accelerations and ≥25-fold lower Km values for glutathione observed in the presence of SDO. The combined action of GSS(-) and SDO is likely to regulate the biosynthesis of the reactive metabolite. SDO drives to completion p-toluenethiosulfonate:glutathione sulfurtransferase reactions catalyzed by TSTD1 and RDL1. The thermodynamic coupling of the irreversible SDO and reversible TST reactions provides a model for the physiologically relevant reaction with thiosulfate as the sulfane donor. The discovery of bacterial Rosetta Stone proteins that comprise fusions of SDO and TSTD1 provides phylogenetic evidence of the association of these enzymes. The presence of adjacent bacterial genes encoding SDO-TSTD1 fusion proteins and human-like SQORs suggests these prokaryotes and mammals exhibit strikingly similar pathways for H2S metabolism.
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Affiliation(s)
- Scott L Melideo
- Department of Biochemistry and Molecular Biology, Drexel University College of Medicine , Philadelphia, Pennsylvania 19102, United States
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Affiliation(s)
- Russ Hille
- Department of Biochemistry, University of California, Riverside, Riverside, California 92521, United States
| | - James Hall
- Department of Biochemistry, University of California, Riverside, Riverside, California 92521, United States
| | - Partha Basu
- Department of Chemistry and Biochemistry, Duquesne University, Pittsburgh, Pennsylvania 15282, United States
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Johnson-Winters K, Davis AC, Arnold AR, Berry RE, Tollin G, Enemark JH. Probing the role of a conserved salt bridge in the intramolecular electron transfer kinetics of human sulfite oxidase. J Biol Inorg Chem 2013; 18:645-53. [DOI: 10.1007/s00775-013-1010-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2012] [Accepted: 05/14/2013] [Indexed: 10/26/2022]
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Cantu-Medellin N, Kelley EE. Xanthine oxidoreductase-catalyzed reduction of nitrite to nitric oxide: insights regarding where, when and how. Nitric Oxide 2013; 34:19-26. [PMID: 23454592 DOI: 10.1016/j.niox.2013.02.081] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2012] [Revised: 02/13/2013] [Accepted: 02/19/2013] [Indexed: 01/13/2023]
Abstract
Numerous inflammatory disorders are associated with elevated levels of xanthine oxidoreductase (XOR) and allied enhancement of reactive species formation contributory to systemic pathology. Despite a long standing association between increased XOR activity and negative clinical outcomes, recent reports describe a paradigm shift where XOR mediates beneficial actions by catalyzing the reduction of NO2(-) to NO. While provocative, these observations contradict reports of improved outcomes in similar models upon XOR inhibition as well as reports revealing strict anoxia as a requisite for XOR-mediated NO formation. To garner a more clear understanding of conditions necessary for in vivo XOR-catalyzed NO production, this review critically analyzes the impact of O2 tension, pH, substrate concentrations, glycoaminoglycan docking and inhibition strategies on the nitrite reductase activity of XOR and reveals a hypoxic milieu where this process may be operative. As such, information herein serves to link recent reports in which XOR activity has been identified as mediating the beneficial outcomes resulting from nitrite supplementation to a microenvironmental setting where XOR can serve as substantial source of NO.
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Affiliation(s)
- Nadiezhda Cantu-Medellin
- University of Pittsburgh, Department of Anesthesiology and Vascular Medicine Institute, United States
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24
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Davis AC, Cornelison MJ, Meyers KT, Rajapakshe A, Berry RE, Tollin G, Enemark JH. Effects of mutating aromatic surface residues of the heme domain of human sulfite oxidase on its heme midpoint potential, intramolecular electron transfer, and steady-state kinetics. Dalton Trans 2013; 42:3043-9. [DOI: 10.1039/c2dt31508d] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Rajapakshe A, Tollin G, Enemark JH. Kinetic and thermodynamic effects of mutations of human sulfite oxidase. Chem Biodivers 2012; 9:1621-34. [PMID: 22976958 PMCID: PMC3517162 DOI: 10.1002/cbdv.201200010] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Asha Rajapakshe
- Department of Chemistry and Biochemistry, The University of Arizona, 1306 E. University Blvd., Tucson, Arizona 85721-0041 U.S.A
| | - Gordon Tollin
- Department of Chemistry and Biochemistry, The University of Arizona, 1306 E. University Blvd., Tucson, Arizona 85721-0041 U.S.A
| | - John H. Enemark
- Department of Chemistry and Biochemistry, The University of Arizona, 1306 E. University Blvd., Tucson, Arizona 85721-0041 U.S.A
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Jackson MR, Melideo SL, Jorns MS. Human sulfide:quinone oxidoreductase catalyzes the first step in hydrogen sulfide metabolism and produces a sulfane sulfur metabolite. Biochemistry 2012; 51:6804-15. [PMID: 22852582 DOI: 10.1021/bi300778t] [Citation(s) in RCA: 193] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Sulfide:quinone oxidoreductase (SQOR) is a membrane-bound enzyme that catalyzes the first step in the mitochondrial metabolism of H(2)S. Human SQOR is successfully expressed at low temperature in Escherichia coli by using an optimized synthetic gene and cold-adapted chaperonins. Recombinant SQOR contains noncovalently bound FAD and catalyzes the two-electron oxidation of H(2)S to S(0) (sulfane sulfur) using CoQ(1) as an electron acceptor. The prosthetic group is reduced upon anaerobic addition of H(2)S in a reaction that proceeds via a long-wavelength-absorbing intermediate (λ(max) = 673 nm). Cyanide, sulfite, or sulfide can act as the sulfane sulfur acceptor in reactions that (i) exhibit pH optima at 8.5, 7.5, or 7.0, respectively, and (ii) produce thiocyanate, thiosulfate, or a putative sulfur analogue of hydrogen peroxide (H(2)S(2)), respectively. Importantly, thiosulfate is a known intermediate in the oxidation of H(2)S by intact animals and the major product formed in glutathione-depleted cells or mitochondria. Oxidation of H(2)S by SQOR with sulfite as the sulfane sulfur acceptor is rapid and highly efficient at physiological pH (k(cat)/K(m,H(2)S) = 2.9 × 10(7) M(-1) s(-1)). A similar efficiency is observed with cyanide, a clearly artificial acceptor, at pH 8.5, whereas a 100-fold lower value is seen with sulfide as the acceptor at pH 7.0. The latter reaction is unlikely to occur in healthy individuals but may become significant under certain pathological conditions. We propose that sulfite is the physiological acceptor of the sulfane sulfur and that the SQOR reaction is the predominant source of the thiosulfate produced during H(2)S oxidation by mammalian tissues.
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Affiliation(s)
- Michael R Jackson
- Department of Biochemistry and Molecular Biology, Drexel University College of Medicine, Philadelphia, PA 19102, USA
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Utesch T, Sezer M, Weidinger IM, Mroginski MA. Adsorption of sulfite oxidase on self-assembled monolayers from molecular dynamics simulations. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2012; 28:5761-5769. [PMID: 22385217 DOI: 10.1021/la205055g] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Sulfite oxidase (SO) is an enzyme catalyzing the terminal step of the metabolism of sulfur-containing amino acids that is essential for almost all living organisms. The catalytic activity of SO in vertebrates strongly depends on the efficiency of the intramolecular electron transfer (IET) between the catalytic Moco domain and the cytochrome b5 (cyt b5) domain. The IET process is assumed to be mediated by large domain motions of the cyt b5 domains within the enzyme. Thus, the interaction of SO with charged surfaces may affect the mobility of the cyt b5 domain required for IET and consequently hinder SO activation. In this study, we present a molecular dynamics approach to investigating the ionic strength dependence of the initial surface adsorption of SO in two different conformations-the crystallographic structure and the model structure for an activated SO-onto mixed amino- and hydroxyl-terminated SAMs. The results show for both conformations at low ionic strengths a strong adsorption of the cyt b5 units onto the SAM, which inhibits the domain motion event required for IET. Under higher ion concentrations, however, the interaction with the surface is weakened by the negatively charged ions acting as a buffer and competing in adsorption with the cathodic cyt b5 domains. This competition prevents the immobilization of the cytochrome b5 units onto the surface, allowing the intramolecular domain motions favoring IET. Our predictions support the interpretation of recent experimental spectroelectrochemical studies on SO.
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Affiliation(s)
- Tillmann Utesch
- Technische Universität Berlin, Institut für Chemie, Berlin, Germany
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Astashkin AV, Rajapakshe A, Cornelison MJ, Johnson-Winters K, Enemark JH. Determination of the distance between the Mo(V) and Fe(III) heme centers of wild type human sulfite oxidase by pulsed EPR spectroscopy. J Phys Chem B 2012; 116:1942-50. [PMID: 22229742 DOI: 10.1021/jp210578f] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Intramolecular electron transfer (IET) between the molybdenum and heme centers of vertebrate sulfite oxidase (SO) is proposed to be a key step in the catalytic cycle of the enzyme. However, the X-ray crystallographic distance between these centers, R(MoFe) = 32.3 Å, appears to be too long for the rapid IET rates observed in liquid solution. The Mo and heme domains are linked by a flexible tether, and it has been proposed that dynamic interdomain motion brings the two metal centers closer together and thereby facilitates rapid IET. To date, there have been no direct distance measurements for SO in solution that would support or contradict this model. In this work, pulsed electron-electron double resonance (ELDOR) and relaxation induced dipolar modulation enhancement (RIDME) techniques were used to obtain information about R(MoFe) in the Mo(V)Fe(III) state of wild type recombinant human SO in frozen glassy solution. Surprisingly, the data obtained suggest a fixed structure with R(MoFe) = 32 Å, similar to that determined by X-ray crystallography for chicken SO, although the orientation of the R(MoFe) radius-vector with respect to the heme center was found to be somewhat different. The implications of these findings for the flexible tether model are discussed.
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Affiliation(s)
- Andrei V Astashkin
- Department of Chemistry & Biochemistry, University of Arizona, Tucson, Arizona 85721, USA.
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Kyndt JA, Fitch JC, Berry RE, Stewart MC, Whitley K, Meyer TE, Walker FA, Cusanovich MA. Tyrosine triad at the interface between the Rieske iron-sulfur protein, cytochrome c1 and cytochrome c2 in the bc1 complex of Rhodobacter capsulatus. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2012; 1817:811-8. [PMID: 22306765 DOI: 10.1016/j.bbabio.2012.01.013] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2011] [Revised: 01/20/2012] [Accepted: 01/20/2012] [Indexed: 11/25/2022]
Abstract
A triad of tyrosine residues (Y152-154) in the cytochrome c(1) subunit (C1) of the Rhodobacter capsulatus cytochrome bc(1) complex (BC1) is ideally positioned to interact with cytochrome c(2) (C2). Mutational analysis of these three tyrosines showed that, of the three, Y154 is the most important, since its mutation to alanine resulted in significantly reduced levels, destabilization, and inactivation of BC1. A second-site revertant of this mutant that regained photosynthetic capacity was found to have acquired two further mutations-A181T and A200V. The Y152Q mutation did not change the spectral or electrochemical properties of C1, and showed wild-type enzymatic C2 reduction rates, indicating that this mutation did not introduce major structural changes in C1 nor affect overall activity. Mutations Y153Q and Y153A, on the other hand, clearly affect the redox properties of C1 (e.g. by lowering the midpoint potential as much as 117 mV in Y153Q) and the activity by 90% and 50%, respectively. A more conservative Y153F mutant on the other hand, behaves similarly to wild-type. This underscores the importance of an aromatic residue at position Y153, presumably to maintain close packing with P184, which modeling indicates is likely to stabilize the sixth heme ligand conformation.
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Affiliation(s)
- John A Kyndt
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721, USA.
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Intramolecular electron transfer in sulfite-oxidizing enzymes: probing the role of aromatic amino acids. J Biol Inorg Chem 2011; 17:345-52. [DOI: 10.1007/s00775-011-0856-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2011] [Accepted: 10/13/2011] [Indexed: 10/15/2022]
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Haque MM, Kenney C, Tejero J, Stuehr DJ. A kinetic model linking protein conformational motions, interflavin electron transfer and electron flux through a dual-flavin enzyme-simulating the reductase activity of the endothelial and neuronal nitric oxide synthase flavoprotein domains. FEBS J 2011; 278:4055-69. [PMID: 21848659 DOI: 10.1111/j.1742-4658.2011.08310.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
NADPH-dependent dual-flavin enzymes provide electrons in many redox reactions, although the mechanism responsible for regulating their electron flux remains unclear. We recently proposed a four-state kinetic model that links the electron flux through a dual-flavin enzyme to its rates of interflavin electron transfer and FMN domain conformational motion [Stuehr DJ et al. (2009) FEBS J276, 3959-3974]. In the present study, we ran computer simulations of the kinetic model to determine whether it could fit the experimentally-determined, pre-steady-state and steady-state traces of electron flux through the neuronal and endothelial NO synthase flavoproteins (reductase domains of neuronal nitric oxide synthase and endothelial nitric oxide synthase, respectively) to cytochrome c. We found that the kinetic model accurately fitted the experimental data. The simulations gave estimates for the ensemble rates of interflavin electron transfer and FMN domain conformational motion in the reductase domains of neuronal nitric oxide synthase and endothelial nitric oxide synthase, provided the minimum rate boundary values, and predicted the concentrations of the four enzyme species that cycle during catalysis. The findings of the present study suggest that the rates of interflavin electron transfer and FMN domain conformational motion are counterbalanced such that both processes may limit electron flux through the enzymes. Such counterbalancing would allow a robust electron flux at the same time as keeping the rates of interflavin electron transfer and FMN domain conformational motion set at relatively slow levels.
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Affiliation(s)
- Mohammad M Haque
- Department of Pathobiology, Lerner Research Institute, Cleveland Clinic, OH 44195, USA
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Lee BH, Kim JM, Heo SH, Mun JH, Kim J, Kim JH, Jin HY, Kim GH, Choi JH, Yoo HW. Proteomic analysis of the hepatic tissue of Long-Evans Cinnamon (LEC) rats according to the natural course of Wilson disease. Proteomics 2011; 11:3698-705. [PMID: 21751376 DOI: 10.1002/pmic.201100122] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2011] [Revised: 05/27/2011] [Accepted: 06/27/2011] [Indexed: 12/17/2022]
Abstract
Copper-induced toxicity is important in the pathogenic process of Wilson's disease (WD). Using Long-Evans Cinnamon (LEC) rats, an animal model of WD, the study was undertaken to identify proteins involved in the process of WD and to investigate their functional roles in copper-induced hepatotoxicity. In early stages, expression levels of mitochondrial matrix proteins including agmatinase, isovaleryl coenzyme A dehydrogenase, and cytochrome b5 were downregulated. As mitochondrial injuries progressed, along with subsequent apoptotic processes, expressions of malate dehydrogenase 1, annexin A5, transferrin, S-adenosylhomocysteine hydrolase, and sulfite oxidase 1 were differentially regulated. Notably, the expression of malate dehydrogenase 1 was downregulated while the annexin A5 was overexpressed in an age-dependent manner, indicating that these proteins may be involved in the WD process. In addition, pronounced under-expression of S-adenosylhomocysteine hydrolase in elderly LEC rats, also involved in monoamine neurotransmitter metabolism, indicates that this protein might be related to the development of neurological manifestations in WD. The results of our study help to understand the pathogenic process of WD in hepatic tissues, identifying the important proteins associated with the disease process of WD, and to investigate the molecular pathogenic process underlying the development of neurological manifestations in WD.
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Affiliation(s)
- Beom H Lee
- Department of Pediatrics, Asan Medical Center Children's Hospital, University of Ulsan College of Medicine, Seoul, Korea
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Abstract
Recent progress in our understanding of the structural and catalytic properties of molybdenum-containing enzymes in eukaryotes is reviewed, along with aspects of the biosynthesis of the cofactor and its insertion into apoprotein.
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Affiliation(s)
- Russ Hille
- Department of Biochemistry, University of California, Riverside, CA 92521
| | - Takeshi Nishino
- Department of Biochemistry and Molecular Biology, Nippon Medical School, 1-1-5 Sendagi, Bunkyo-ku, Tokyo, Japan and Department of Biochemistry, University of California, Riverside, CA 92521
| | - Florian Bittner
- Department of Plant Biology, Technical University of Braunschweig, 38023 Braunschweig, Germany
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Lederer F. Another look at the interaction between mitochondrial cytochrome c and flavocytochrome b (2). EUROPEAN BIOPHYSICS JOURNAL: EBJ 2011; 40:1283-99. [PMID: 21503671 DOI: 10.1007/s00249-011-0697-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/12/2011] [Revised: 02/28/2011] [Accepted: 03/16/2011] [Indexed: 11/29/2022]
Abstract
Yeast flavocytochrome b (2) tranfers reducing equivalents from lactate to oxygen via cytochrome c and cytochrome c oxidase. The enzyme catalytic cycle includes FMN reduction by lactate and reoxidation by intramolecular electron transfer to heme b (2). Each subunit of the soluble tetrameric enzyme consists of an N terminal b (5)-like heme-binding domain and a C terminal flavodehydrogenase. In the crystal structure, FMN and heme are face to face, and appear to be in a suitable orientation and at a suitable distance for exchanging electrons. But in one subunit out of two, the heme domain is disordered and invisible. This raises a central question: is this mobility required for interaction with the physiological acceptor cytochrome c, which only receives electrons from the heme and not from the FMN? The present review summarizes the results of the variety of methods used over the years that shed light on the interactions between the flavin and heme domains and between the enzyme and cytochrome c. The conclusion is that one should consider the interaction between the flavin and heme domains as a transient one, and that the cytochrome c and the flavin domain docking areas on the heme b (2) domain must overlap at least in part. The heme domain mobility is an essential component of the flavocytochrome b (2) functioning. In this respect, the enzyme bears similarity to a variety of redox enzyme systems, in particular those in which a cytochrome b (5)-like domain is fused to proteins carrying other redox functions.
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Affiliation(s)
- Florence Lederer
- Laboratoire de Chimie Physique, Université Paris-Sud, Orsay Cedex, France.
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Kappler U. Bacterial sulfite-oxidizing enzymes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2011; 1807:1-10. [DOI: 10.1016/j.bbabio.2010.09.004] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2010] [Revised: 09/05/2010] [Accepted: 09/14/2010] [Indexed: 11/25/2022]
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36
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Johnson-Winters K, Nordstrom AR, Davis AC, Tollin G, Enemark JH. Effects of large-scale amino acid substitution in the polypeptide tether connecting the heme and molybdenum domains on catalysis in human sulfite oxidase. Metallomics 2010; 2:766-70. [PMID: 21072368 DOI: 10.1039/c0mt00021c] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Sulfite oxidase (SO) is a molybdenum-cofactor-dependent enzyme that catalyzes the oxidation of sulfite to sulfate, the final step in the catabolism of the sulfur-containing amino acids, cysteine and methionine. The catalytic mechanism of vertebrate SO involves intramolecular electron transfer (IET) from molybdenum to the integral b-type heme of SO and then to exogenous cytochrome c. However, the crystal structure of chicken sulfite oxidase (CSO) has shown that there is a 32 Å distance between the Fe and Mo atoms of the respective heme and molybdenum domains, which are connected by a flexible polypeptide tether. This distance is too long to be consistent with the measured IET rates. Previous studies have shown that IET is viscosity dependent (Feng et al., Biochemistry, 2002, 41, 5816) and also dependent upon the flexibility and length of the tether (Johnson-Winters et al., Biochemistry, 2010, 49, 1290). Since IET in CSO is more rapid than in human sulfite oxidase (HSO) (Feng et al., Biochemistry, 2003, 42, 12235) the tether sequence of HSO has been mutated into that of CSO, and the resultant chimeric HSO enzyme investigated by laser flash photolysis and steady-state kinetics in order to study the specificity of the tether sequence of SO on the kinetic properties. Surprisingly, the IET kinetics of the chimeric HSO protein with the CSO tether sequence are slower than wildtype HSO. This observation raises the possibility that the composition of the non-conserved tether sequence of animal SOs may be optimized for individual species.
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Affiliation(s)
- Kayunta Johnson-Winters
- Department of Chemistry and Biochemistry, The University of Arizona, 1306 E. University Blvd., Tucson, AZ 85721, USA
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Johnson-Winters K, Tollin G, Enemark JH. Elucidating the catalytic mechanism of sulfite oxidizing enzymes using structural, spectroscopic, and kinetic analyses. Biochemistry 2010; 49:7242-54. [PMID: 20666399 DOI: 10.1021/bi1008485] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Sulfite oxidizing enzymes (SOEs) are molybdenum cofactor-dependent enzymes that are found in plants, animals, and bacteria. Sulfite oxidase (SO) is found in animals and plants, while sulfite dehydrogenase (SDH) is found in bacteria. In animals, SO catalyzes the oxidation of toxic sulfite to sulfate as the final step in the catabolism of the sulfur-containing amino acids, methionine and cysteine. In humans, sulfite oxidase deficiency is an inherited recessive disorder that produces severe neonatal neurological problems that lead to early death. Plant SO (PSO) also plays an important role in sulfite detoxification and in addition serves as an intermediate enzyme in the assimilatory reduction of sulfate. In vertebrates, the proposed catalytic mechanism of SO involves two intramolecular one-electron transfer (IET) steps from the molybdenum cofactor to the iron of the integral b-type heme. A similar mechanism is proposed for SDH, involving its molybdenum cofactor and c-type heme. However, PSO, which lacks an integral heme cofactor, uses molecular oxygen as its electron acceptor. Here we review recent results for SOEs from kinetic measurements, computational studies, electron paramagnetic resonance (EPR) spectroscopy, electrochemical measurements, and site-directed mutagenesis on active site residues of SOEs and of the flexible polypepetide tether that connects the heme and molybdenum domains of human SO. Rapid kinetic studies of PSO are also discussed.
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Affiliation(s)
- Kayunta Johnson-Winters
- Department of Chemistry and Biochemistry, The University of Arizona, Tucson, Arizona 85721, USA
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38
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Structural evidence for the functional importance of the heme domain mobility in flavocytochrome b2. J Mol Biol 2010; 400:518-30. [PMID: 20546754 DOI: 10.1016/j.jmb.2010.05.035] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2010] [Revised: 05/12/2010] [Accepted: 05/14/2010] [Indexed: 11/24/2022]
Abstract
Yeast flavocytochrome b(2) (Fcb2) is an L-lactate:cytochrome c oxidoreductase in the mitochondrial intermembrane space participating in cellular respiration. Each enzyme subunit consists of a cytochrome b(5)-like heme domain and a flavodehydrogenase (FDH) domain. In the Fcb2 crystal structure, the heme domain is mobile relative to the tetrameric FDH core in one out of two subunits. The monoclonal antibody B2B4, elicited against the holoenzyme, recognizes only the native heme domain in the holoenzyme. When bound, it suppresses the intramolecular electron transfer from flavin to heme b(2), hence cytochrome c reduction. We report here the crystal structure of the heme domain in complex with the Fab at 2.7 A resolution. The Fab epitope on the heme domain includes the two exposed propionate groups of the heme, which are hidden in the interface between the domains in the complete subunit. The structure discloses an unexpected plasticity of Fcb2 in the neighborhood of the heme cavity, in which the heme has rotated. The epitope overlaps with the docking area of the FDH domain onto the heme domain, indicating that the antibody displaces the heme domain in a movement of large amplitude. We suggest that the binding sites on the heme domain of cytochrome c and of the FDH domain also overlap and therefore that cytochrome c binding also requires the heme domain to move away from the FDH domain, so as to allow electron transfer between the two hemes. Based on this hypothesis, we propose a possible model of the Fcb2.cytochrome c complex. Interestingly, this model shares similarity with that of the cytochrome b(5) x cytochrome c complex, in which cytochrome c binds to the surface around the exposed heme edge of cytochrome b(5). The present results therefore support the idea that the heme domain mobility is an inherent component of the Fcb2 functioning.
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