1
|
Kirk ML, Lepluart J, Yang J. Resonance Raman spectroscopy of pyranopterin molybdenum enzymes. J Inorg Biochem 2022; 235:111907. [PMID: 35932756 PMCID: PMC10575615 DOI: 10.1016/j.jinorgbio.2022.111907] [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: 01/30/2022] [Revised: 05/16/2022] [Accepted: 06/16/2022] [Indexed: 10/17/2022]
Abstract
Resonance Raman spectroscopy (rR) is a powerful spectroscopic probe that is widely used for studying the geometric and electronic structure of metalloproteins. In this focused review, we detail how resonance Raman spectroscopy has contributed to a greater understanding of electronic structure, geometric structure, and the reaction mechanisms of pyranopterin molybdenum enzymes. The review focuses on the enzymes sulfite oxidase (SO), dimethyl sulfoxide reductase (DMSOR), xanthine oxidase (XO), and carbon monoxide dehydrogenase. Specifically, we highlight how Mo-Ooxo, Mo-Ssulfido, Mo-Sdithiolene, and dithiolene CC vibrational modes, isotope and heavy atom perturbations, resonance enhancement, and associated Raman studies of small molecule analogs have provided detailed insight into the nature of these metalloenzyme active sites.
Collapse
Affiliation(s)
- Martin L Kirk
- Department of Chemistry and Chemical Biology, The University of New Mexico, MSC03 2060, 1 University of New Mexico, Albuquerque, NM 87131-0001, United States.
| | - Jesse Lepluart
- Department of Chemistry and Chemical Biology, The University of New Mexico, MSC03 2060, 1 University of New Mexico, Albuquerque, NM 87131-0001, United States
| | - Jing Yang
- Department of Chemistry and Chemical Biology, The University of New Mexico, MSC03 2060, 1 University of New Mexico, Albuquerque, NM 87131-0001, United States
| |
Collapse
|
2
|
Kirk ML, Hille R. Spectroscopic Studies of Mononuclear Molybdenum Enzyme Centers. Molecules 2022; 27:molecules27154802. [PMID: 35956757 PMCID: PMC9370002 DOI: 10.3390/molecules27154802] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2022] [Revised: 06/26/2022] [Accepted: 06/29/2022] [Indexed: 02/06/2023] Open
Abstract
A concise review is provided of the contributions that various spectroscopic methods have made to our understanding of the physical and electronic structures of mononuclear molybdenum enzymes. Contributions to our understanding of the structure and function of each of the major families of these enzymes is considered, providing a perspective on how spectroscopy has impacted the field.
Collapse
Affiliation(s)
- Martin L. Kirk
- Department of Chemistry and Chemical Biology, The University of New Mexico, MSC03 2060, 1 University of New Mexico, Albuquerque, NM 87131-0001, USA
- Correspondence: (M.L.K.); (R.H.)
| | - Russ Hille
- Department of Biochemistry, Boyce Hall 1463, University of California, Riverside, CA 82521, USA
- Correspondence: (M.L.K.); (R.H.)
| |
Collapse
|
3
|
Hille R, Niks D. Application of EPR and related methods to molybdenum-containing enzymes. Methods Enzymol 2022; 666:373-412. [PMID: 35465925 DOI: 10.1016/bs.mie.2022.02.006] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
A description is provided of the contributions made to our understanding of molybdenum-containing enzymes through the application of electron paramagnetic resonance spectroscopy and related methods, by way of illustrating how these can be applied to better understand enzyme structure and function. An emphasis is placed on the use of EPR to identify both the coordination environment of the molybdenum coordination sphere as well as the structures of paramagnetic intermediates observed transiently in the course of reaction that have led to the elucidation of reaction mechanism.
Collapse
Affiliation(s)
- Russ Hille
- Department of Biochemistry, University of California, Riverside, CA, United States.
| | - Dimitri Niks
- Department of Biochemistry, University of California, Riverside, CA, United States
| |
Collapse
|
4
|
González PJ, Rivas MG, Ferroni FM, Rizzi AC, Brondino CD. Electron transfer pathways and spin–spin interactions in Mo- and Cu-containing oxidoreductases. Coord Chem Rev 2021. [DOI: 10.1016/j.ccr.2021.214202] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
|
5
|
Tan Y, Wang Y, Wang Y, Xu D, Huang Y, Wang D, Wang G, Rensing C, Zheng S. Novel mechanisms of selenate and selenite reduction in the obligate aerobic bacterium Comamonas testosteroni S44. JOURNAL OF HAZARDOUS MATERIALS 2018; 359:129-138. [PMID: 30014908 DOI: 10.1016/j.jhazmat.2018.07.014] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/2018] [Revised: 07/02/2018] [Accepted: 07/03/2018] [Indexed: 06/08/2023]
Abstract
Selenium oxyanion reduction is an effective detoxification or/and assimilation processes in organisms, but little is known the mechanisms in aerobic bacteria. Aerobic Comamonas testosteroni S44 reduces Se(VI)/Se(IV) to less-toxic elemental selenium nanoparticles (SeNPs). For Se(VI) reduction, sulfate and Se(VI) reduction displayed a competitive relationship. When essential sulfate reducing genes were respectively disrupted, Se(VI) was not reduced to red-colored SeNPs. Consequently, Se(VI) reduction was catalyzed by enzymes of the sulfate reducing pathway. For Se(IV) reduction, one of the potential periplasm molybdenum oxidoreductase named SerT was screened and further used to analyze Se(IV) reduction. Compared to the wild type and the complemented mutant strain, the ability of Se(IV) reduction was reduced 75% in the deletion mutant ΔserT. Moreover, the Se(IV) reduction rate was significantly enhanced when the gene serT was overexpressed in Escherichia coli W3110. In addition, Se(IV) was reduced to SeNPs by the purified SerT with the presence of NADPH as the electron donor in vitro, showing a Vmax of 61 nmol/min·mg and a Km of 180 μmol/L. A model of Se(VI)/Se(IV) reduction was generated in aerobic C. testosteroni S44. This work provides new insights into the molecular mechanisms of Se(VI)/Se(IV) reduction activities in aerobic bacteria.
Collapse
Affiliation(s)
- Yuanqing Tan
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, 430070, PR China
| | - Yuantao Wang
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, 430070, PR China
| | - Yu Wang
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, 430070, PR China
| | - Ding Xu
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, 430070, PR China
| | - Yeting Huang
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, 430070, PR China
| | - Dan Wang
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, 430070, PR China
| | - Gejiao Wang
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, 430070, PR China
| | - Christopher Rensing
- Institute of Environmental Microbiology, College of Resources and Environment, Fujian Agriculture & Forestry University, Fuzhou, Fujian 350002, PR China
| | - Shixue Zheng
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, 430070, PR China.
| |
Collapse
|
6
|
Abstract
Sulfite oxidase is a mononuclear molybdenum enzyme that oxidises sulfite to sulfate in many organisms, including man. Three different reaction mechanisms have been suggested, based on experimental and computational studies. Here, we study all three with combined quantum mechanical (QM) and molecular mechanical (QM/MM) methods, including calculations with large basis sets, very large QM regions (803 atoms) and QM/MM free-energy perturbations. Our results show that the enzyme is set up to follow a mechanism in which the sulfur atom of the sulfite substrate reacts directly with the equatorial oxo ligand of the Mo ion, forming a Mo-bound sulfate product, which dissociates in the second step. The first step is rate limiting, with a barrier of 39–49 kJ/mol. The low barrier is obtained by an intricate hydrogen-bond network around the substrate, which is preserved during the reaction. This network favours the deprotonated substrate and disfavours the other two reaction mechanisms. We have studied the reaction with both an oxidised and a reduced form of the molybdopterin ligand and quantum-refinement calculations indicate that it is in the normal reduced tetrahydro form in this protein.
Collapse
|
7
|
Hsiao JC, McGrath AP, Kielmann L, Kalimuthu P, Darain F, Bernhardt PV, Harmer J, Lee M, Meyers K, Maher MJ, Kappler U. The central active site arginine in sulfite oxidizing enzymes alters kinetic properties by controlling electron transfer and redox interactions. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2017; 1859:19-27. [PMID: 28986298 DOI: 10.1016/j.bbabio.2017.10.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/12/2017] [Revised: 09/29/2017] [Accepted: 10/02/2017] [Indexed: 10/18/2022]
Abstract
A central conserved arginine, first identified as a clinical mutation leading to sulfite oxidase deficiency, is essential for catalytic competency of sulfite oxidizing molybdoenzymes, but the molecular basis for its effects on turnover and substrate affinity have not been fully elucidated. We have used a bacterial sulfite dehydrogenase, SorT, which lacks an internal heme group, but transfers electrons to an external, electron accepting cytochrome, SorU, to investigate the molecular functions of this arginine residue (Arg78). Assay of the SorT Mo centre catalytic competency in the absence of SorU showed that substitutions in the central arginine (R78Q, R78K and R78M mutations) only moderately altered SorT catalytic properties, except for R78M which caused significant reduction in SorT activity. The substitutions also altered the Mo-centre redox potentials (MoVI/V potential lowered by ca. 60-80mV). However, all Arg78 mutations significantly impaired the ability of SorT to transfer electrons to SorU, where activities were reduced 17 to 46-fold compared to SorTWT, precluding determination of kinetic parameters. This was accompanied by the observation of conformational changes in both the introduced Gln and Lys residues in the crystal structure of the enzymes. Taking into account data collected by others on related SOE mutations we propose that the formation and maintenance of an electron transfer complex between the Mo centre and electron accepting heme groups is the main function of the central arginine, and that the reduced turnover and increases in KMsulfite are caused by the inefficient operation of the oxidative half reaction of the catalytic cycle in enzymes carrying these mutations.
Collapse
Affiliation(s)
- Ju-Chun Hsiao
- Centre for Metals in Biology, School of Chemistry and Molecular Biosciences, University of Queensland, St Lucia, QLD 4072, Australia
| | - Aaron P McGrath
- Structural Biology Program, Centenary Institute, Locked Bag 6, NSW 2042, Australia
| | - Linda Kielmann
- Centre for Metals in Biology, School of Chemistry and Molecular Biosciences, University of Queensland, St Lucia, QLD 4072, Australia
| | - Palraj Kalimuthu
- Centre for Metals in Biology, School of Chemistry and Molecular Biosciences, University of Queensland, St Lucia, QLD 4072, Australia
| | - Farzana Darain
- Centre for Metals in Biology, School of Chemistry and Molecular Biosciences, University of Queensland, St Lucia, QLD 4072, Australia
| | - Paul V Bernhardt
- Centre for Metals in Biology, School of Chemistry and Molecular Biosciences, University of Queensland, St Lucia, QLD 4072, Australia
| | - Jeffrey Harmer
- Centre for Advanced Imaging, The University of Queensland, St. Lucia, QLD 4072, Australia
| | - Mihwa Lee
- Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria 3086, Australia
| | - Kimberley Meyers
- Centre for Metals in Biology, School of Chemistry and Molecular Biosciences, University of Queensland, St Lucia, QLD 4072, Australia
| | - Megan J Maher
- Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria 3086, Australia.
| | - Ulrike Kappler
- Centre for Metals in Biology, School of Chemistry and Molecular Biosciences, University of Queensland, St Lucia, QLD 4072, Australia.
| |
Collapse
|
8
|
Kilmartin JR, Bernhardt PV, Dhouib R, Hanson GR, Riley MJ, Kappler U. Effects of mutations in active site heme ligands on the spectroscopic and catalytic properties of SoxAX cytochromes. J Inorg Biochem 2016; 162:309-318. [PMID: 27112898 DOI: 10.1016/j.jinorgbio.2016.04.015] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2015] [Revised: 04/04/2016] [Accepted: 04/12/2016] [Indexed: 10/21/2022]
Abstract
By attaching a sulfur substrate to a conserved cysteine of the SoxYZ carrier protein SoxAX cytochromes initiate the reaction cycle of the Sox (sulfur oxidation) multienzyme complex, which is the major pathway for microbial reoxidation of sulfur compounds in the environment. Despite their important role in this process, the reaction mechanism of the SoxAX cytochromes has not been fully elucidated. Here we report the effects of several active site mutations on the spectroscopic and enzymatic properties of the type II SoxAX protein from Starkeya novella, which in addition to two heme groups also contains a Cu redox centre. All substituted proteins contained these redox centres except for His231Ala which was unable to bind Cu(II). Substitution of the SoxA active site heme cysteine ligand with histidine resulted in increased microheterogeneity around the SoxA heme as determined by CW-EPR, while a SnSoxAXC236A substituted protein revealed a completely new, nitrogenous SoxA heme ligand. The same novel ligand was present in SnSoxAXH231A CW-EPR spectra, the first time that a ligand switch of the SoxA heme involving a nearby amino acid has been demonstrated. Kinetically, SnSoxAXC236A and SnSoxAXC236H showed reduced turnover, and in assays containing SoxYZ these mutants retained only ~25% of the wildtype activity. Together, these data indicate that the Cu redox centre can mediate a low level of activity, and that a possible ligand switch can occur during catalysis. It also appears that the SoxA heme cysteine ligand (and possibly the low redox potential) is important for an efficient reaction with SnSoxYZ/thiosulfate.
Collapse
Affiliation(s)
- James R Kilmartin
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Qld 4072, Australia
| | - Paul V Bernhardt
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Qld 4072, Australia
| | - Rabeb Dhouib
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Qld 4072, Australia
| | - Graeme R Hanson
- Centre for Advanced Imaging, The University of Queensland, Brisbane, Qld 4072, Australia
| | - Mark J Riley
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Qld 4072, Australia
| | - Ulrike Kappler
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Qld 4072, Australia.
| |
Collapse
|
9
|
McGrath AP, Laming EL, Casas Garcia GP, Kvansakul M, Guss JM, Trewhella J, Calmes B, Bernhardt PV, Hanson GR, Kappler U, Maher MJ. Structural basis of interprotein electron transfer in bacterial sulfite oxidation. eLife 2015; 4:e09066. [PMID: 26687009 PMCID: PMC4760952 DOI: 10.7554/elife.09066] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2015] [Accepted: 11/12/2015] [Indexed: 11/13/2022] Open
Abstract
Interprotein electron transfer underpins the essential processes of life and relies on the formation of specific, yet transient protein-protein interactions. In biological systems, the detoxification of sulfite is catalyzed by the sulfite-oxidizing enzymes (SOEs), which interact with an electron acceptor for catalytic turnover. Here, we report the structural and functional analyses of the SOE SorT from Sinorhizobium meliloti and its cognate electron acceptor SorU. Kinetic and thermodynamic analyses of the SorT/SorU interaction show the complex is dynamic in solution, and that the proteins interact with Kd = 13.5 ± 0.8 μM. The crystal structures of the oxidized SorT and SorU, both in isolation and in complex, reveal the interface to be remarkably electrostatic, with an unusually large number of direct hydrogen bonding interactions. The assembly of the complex is accompanied by an adjustment in the structure of SorU, and conformational sampling provides a mechanism for dissociation of the SorT/SorU assembly.
Collapse
Affiliation(s)
- Aaron P McGrath
- Structural Biology Program, Centenary Institute, Sydney, Australia
| | - Elise L Laming
- School of Molecular Bioscience, University of Sydney, Sydney, Australia
| | - G Patricia Casas Garcia
- Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Australia
| | - Marc Kvansakul
- Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Australia
| | - J Mitchell Guss
- School of Molecular Bioscience, University of Sydney, Sydney, Australia
| | - Jill Trewhella
- School of Molecular Bioscience, University of Sydney, Sydney, Australia
| | - Benoit Calmes
- Centre for Metals in Biology, The University of Queensland, Brisbane, Australia
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Australia
| | - Paul V Bernhardt
- Centre for Metals in Biology, The University of Queensland, Brisbane, Australia
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Australia
| | - Graeme R Hanson
- Centre for Metals in Biology, The University of Queensland, Brisbane, Australia
- Centre for Advanced Imaging, University of Queensland, Brisbane, Australia
| | - Ulrike Kappler
- Centre for Metals in Biology, The University of Queensland, Brisbane, Australia
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Australia
| | - Megan J Maher
- Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Australia
| |
Collapse
|
10
|
Alvarez S, Menjón B, Falceto A, Casanova D, Alemany P. Stereochemistry of Complexes with Double and Triple Metal–Ligand Bonds: A Continuous Shape Measures Analysis. Inorg Chem 2014; 53:12151-63. [DOI: 10.1021/ic5021077] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Affiliation(s)
| | - Babil Menjón
- Instituto de Síntesis
Química y Catálisis Homogénea, CSIC−Universidad de Zaragoza, Pedro Cerbuna 12, E-50009 Zaragoza, Spain
| | | | - David Casanova
- Kimika Fakultatea, Euskal Herriko Unibertsitatea (UPV/EHU), P.K: 1072, 20080 Donostia, Spain
- Donostia International Physics Center (DIPC), 20018 Donostia, Spain
- IKERBASQUE, Basque Foundation for Science, 48013 Bilbao, Spain
| | | |
Collapse
|
11
|
Rothery RA, Weiner JH. Shifting the metallocentric molybdoenzyme paradigm: the importance of pyranopterin coordination. J Biol Inorg Chem 2014; 20:349-72. [PMID: 25267303 DOI: 10.1007/s00775-014-1194-6] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2014] [Accepted: 09/15/2014] [Indexed: 01/10/2023]
Abstract
In this review, we test the hypothesis that pyranopterin coordination plays a critical role in defining substrate reactivities in the four families of mononuclear molybdenum and tungsten enzymes (Mo/W-enzymes). Enzyme families containing a single pyranopterin dithiolene chelate have been demonstrated to have reactivity towards two (sulfite oxidase, SUOX-fold) and five (xanthine dehydrogenase, XDH-fold) types of substrate, whereas the major family of enzymes containing a bis-pyranopterin dithiolene chelate (dimethylsulfoxide reductase, DMSOR-fold) is reactive towards eight types of substrate. A second bis-pyranopterin enzyme (aldehyde oxidoreductase, AOR-fold) family catalyzes a single type of reaction. The diversity of reactions catalyzed by each family correlates with active site variability, and also with the number of pyranopterins and their coordination by the protein. In the case of the AOR-fold enzymes, inflexibility of pyranopterin coordination correlates with their limited substrate specificity (oxidation of aldehydes). In examples of the SUOX-fold and DMSOR-fold enzymes, we observe three types of histidine-containing charge-transfer relays that can: (1) connect the piperazine ring of the pyranopterin to the substrate-binding site (SUOX-fold enzymes); (2) provide inter-pyranopterin communication (DMSOR-fold enzymes); and (3) connect a pyran ring oxygen to deeply buried water molecules (the DMSOR-fold NarGHI-type nitrate reductases). Finally, sequence data mining reveals a number of bacterial species whose predicted proteomes contain large numbers (up to 64) of Mo/W-enzymes, with the DMSOR-fold enzymes being dominant. These analyses also reveal an inverse correlation between Mo/W-enzyme content and pathogenicity.
Collapse
Affiliation(s)
- Richard A Rothery
- Department of Biochemistry, University of Alberta, Edmonton, AB, T6G 2H7, Canada
| | | |
Collapse
|
12
|
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]
|
13
|
A quantum-mechanical study of the reaction mechanism of sulfite oxidase. J Biol Inorg Chem 2014; 19:1165-79. [PMID: 24957901 DOI: 10.1007/s00775-014-1172-z] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2013] [Accepted: 06/05/2014] [Indexed: 10/25/2022]
Abstract
The oxidation of sulfite to sulfate by two different models of the active site of sulfite oxidase has been studied. Both protonated and deprotonated substrates were tested. Geometries were optimized with density functional theory (TPSS/def2-SV(P)) and energies were calculated either with hybrid functionals and large basis sets (B3LYP/def2-TZVPD) including corrections for dispersion, solvation, and entropy, or with coupled-cluster theory (LCCSD(T0)) extrapolated toward a complete basis set. Three suggested reaction mechanisms have been compared and the results show that the lowest barriers are obtained for a mechanism where the substrate attacks a Mo-bound oxo ligand, directly forming a Mo-bound sulfate complex, which then dissociates into the products. Such a mechanism is more favorable than mechanisms involving a Mo-sulfite complex with the substrate coordinating either by the S or O atom. The activation energy is dominated by the Coulomb repulsion between the Mo complex and the substrate, which both have a negative charge of -1 or -2.
Collapse
|
14
|
Kappler U, Nouwens AS. Metabolic adaptation and trophic strategies of soil bacteria-C1- metabolism and sulfur chemolithotrophy in Starkeya novella. Front Microbiol 2013; 4:304. [PMID: 24146664 PMCID: PMC3797975 DOI: 10.3389/fmicb.2013.00304] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2013] [Accepted: 09/23/2013] [Indexed: 11/22/2022] Open
Abstract
The highly diverse and metabolically versatile microbial communities found in soil environments are major contributors to the global carbon, nitrogen, and sulfur cycles. We have used a combination of genome -based pathway analysis with proteomics and gene expression studies to investigate metabolic adaptation in a representative of these bacteria, Starkeya novella, which was originally isolated from agricultural soil. This bacterium was the first facultative sulfur chemolithoautotroph that was isolated and it is also able to grow with methanol and on over 39 substrates as a heterotroph. However, using glucose, fructose, methanol, thiosulfate as well as combinations of the carbon compounds with thiosulfate as growth substrates we have demonstrated here that contrary to the previous classification, S. novella is not a facultative sulfur chemolitho- and methylotroph, as the enzyme systems required for these two growth modes are always expressed at high levels. This is typical for key metabolic pathways. In addition enzymes for various pathways of carbon dioxide fixation were always expressed at high levels, even during heterotrophic growth on glucose or fructose, which suggests a role for these pathways beyond the generation of reduced carbon units for cell growth, possibly in redox balancing of metabolism. Our results then indicate that S. novella, a representative of the Xanthobacteraceae family of methylotrophic soil and freshwater dwelling bacteria, employs a mixotrophic growth strategy under all conditions tested here. As a result the contribution of this bacterium to either carbon sequestration or the release of climate active substances could vary very quickly, which has direct implications for the modeling of such processes if mixotrophy proves to be the main growth strategy for large populations of soil bacteria.
Collapse
Affiliation(s)
- Ulrike Kappler
- School of Chemistry and Molecular Biosciences, The University of Queensland, St LuciaQLD, Australia
| | | |
Collapse
|
15
|
Kappler U, Nouwens AS. The molybdoproteome of Starkeya novella – insights into the diversity and functions of molybdenum containing proteins in response to changing growth conditions. Metallomics 2013; 5:325-34. [DOI: 10.1039/c2mt20230a] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
|
16
|
Kappler U, Davenport K, Beatson S, Lucas S, Lapidus A, Copeland A, Berry KW, Glavina Del Rio T, Hammon N, Dalin E, Tice H, Pitluck S, Richardson P, Bruce D, Goodwin LA, Han C, Tapia R, Detter JC, Chang YJ, Jeffries CD, Land M, Hauser L, Kyrpides NC, Göker M, Ivanova N, Klenk HP, Woyke T. Complete genome sequence of the facultatively chemolithoautotrophic and methylotrophic alpha Proteobacterium Starkeya novella type strain (ATCC 8093(T)). Stand Genomic Sci 2012; 7:44-58. [PMID: 23450099 PMCID: PMC3570799 DOI: 10.4056/sigs.3006378] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Starkeya novella (Starkey 1934) Kelly et al. 2000 is a member of the family Xanthobacteraceae in the order 'Rhizobiales', which is thus far poorly characterized at the genome level. Cultures from this species are most interesting due to their facultatively chemolithoautotrophic lifestyle, which allows them to both consume carbon dioxide and to produce it. This feature makes S. novella an interesting model organism for studying the genomic basis of regulatory networks required for the switch between consumption and production of carbon dioxide, a key component of the global carbon cycle. In addition, S. novella is of interest for its ability to grow on various inorganic sulfur compounds and several C1-compounds such as methanol. Besides Azorhizobium caulinodans, S. novella is only the second species in the family Xanthobacteraceae with a completely sequenced genome of a type strain. The current taxonomic classification of this group is in significant conflict with the 16S rRNA data. The genomic data indicate that the physiological capabilities of the organism might have been underestimated. The 4,765,023 bp long chromosome with its 4,511 protein-coding and 52 RNA genes was sequenced as part of the DOE Joint Genome Institute Community Sequencing Program (CSP) 2008.
Collapse
Affiliation(s)
| | - Karen Davenport
- Los Alamos National Laboratory, Bioscience Division, Los Alamos, New Mexico, USA
| | | | - Susan Lucas
- DOE Joint Genome Institute, Walnut Creek, California, USA
| | - Alla Lapidus
- DOE Joint Genome Institute, Walnut Creek, California, USA
| | - Alex Copeland
- DOE Joint Genome Institute, Walnut Creek, California, USA
| | | | | | - Nancy Hammon
- DOE Joint Genome Institute, Walnut Creek, California, USA
| | - Eileen Dalin
- DOE Joint Genome Institute, Walnut Creek, California, USA
| | - Hope Tice
- DOE Joint Genome Institute, Walnut Creek, California, USA
| | - Sam Pitluck
- DOE Joint Genome Institute, Walnut Creek, California, USA
| | | | - David Bruce
- Los Alamos National Laboratory, Bioscience Division, Los Alamos, New Mexico, USA
- DOE Joint Genome Institute, Walnut Creek, California, USA
| | - Lynne A. Goodwin
- Los Alamos National Laboratory, Bioscience Division, Los Alamos, New Mexico, USA
- DOE Joint Genome Institute, Walnut Creek, California, USA
| | - Cliff Han
- Los Alamos National Laboratory, Bioscience Division, Los Alamos, New Mexico, USA
- DOE Joint Genome Institute, Walnut Creek, California, USA
| | - Roxanne Tapia
- Los Alamos National Laboratory, Bioscience Division, Los Alamos, New Mexico, USA
- DOE Joint Genome Institute, Walnut Creek, California, USA
| | - John C. Detter
- Los Alamos National Laboratory, Bioscience Division, Los Alamos, New Mexico, USA
- DOE Joint Genome Institute, Walnut Creek, California, USA
| | - Yun-juan Chang
- DOE Joint Genome Institute, Walnut Creek, California, USA
- Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA
| | - Cynthia D. Jeffries
- DOE Joint Genome Institute, Walnut Creek, California, USA
- Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA
| | - Miriam Land
- DOE Joint Genome Institute, Walnut Creek, California, USA
- Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA
| | - Loren Hauser
- DOE Joint Genome Institute, Walnut Creek, California, USA
- Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA
| | | | - Markus Göker
- Leibniz Institute DSMZ – German Collection of Microorganisms and Cell Cultures, Braunschweig, Germany
| | | | - Hans-Peter Klenk
- Leibniz Institute DSMZ – German Collection of Microorganisms and Cell Cultures, Braunschweig, Germany
| | - Tanja Woyke
- DOE Joint Genome Institute, Walnut Creek, California, USA
| |
Collapse
|
17
|
Kappler U, Davenport K, Beatson S, Lucas S, Lapidus A, Copeland A, Berry KW, Glavina Del Rio T, Hammon N, Dalin E, Tice H, Pitluck S, Richardson P, Bruce D, Goodwin LA, Han C, Tapia R, Detter JC, Chang YJ, Jeffries CD, Land M, Hauser L, Kyrpides NC, Göker M, Ivanova N, Klenk HP, Woyke T. Complete genome sequence of the facultatively chemolithoautotrophic and methylotrophic alpha Proteobacterium Starkeya novella type strain (ATCC 8093T). Stand Genomic Sci 2012. [DOI: 10.4056/sogs.3006378] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Affiliation(s)
| | - Karen Davenport
- 2Los Alamos National Laboratory, Bioscience Division, Los Alamos, New Mexico, USA
| | | | - Susan Lucas
- 3DOE Joint Genome Institute, Walnut Creek, California, USA
| | - Alla Lapidus
- 3DOE Joint Genome Institute, Walnut Creek, California, USA
| | - Alex Copeland
- 3DOE Joint Genome Institute, Walnut Creek, California, USA
| | | | | | - Nancy Hammon
- 3DOE Joint Genome Institute, Walnut Creek, California, USA
| | - Eileen Dalin
- 3DOE Joint Genome Institute, Walnut Creek, California, USA
| | - Hope Tice
- 3DOE Joint Genome Institute, Walnut Creek, California, USA
| | - Sam Pitluck
- 3DOE Joint Genome Institute, Walnut Creek, California, USA
| | | | - David Bruce
- 3DOE Joint Genome Institute, Walnut Creek, California, USA
| | | | - Cliff Han
- 3DOE Joint Genome Institute, Walnut Creek, California, USA
| | - Roxanne Tapia
- 3DOE Joint Genome Institute, Walnut Creek, California, USA
| | - John C. Detter
- 3DOE Joint Genome Institute, Walnut Creek, California, USA
| | - Yun-juan Chang
- 4Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA
| | | | - Miriam Land
- 4Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA
| | - Loren Hauser
- 4Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA
| | | | - Markus Göker
- 5Leibniz Institute DSMZ – German Collection of Microorganisms and Cell Cultures, Braunschweig, Germany
| | | | - Hans-Peter Klenk
- 5Leibniz Institute DSMZ – German Collection of Microorganisms and Cell Cultures, Braunschweig, Germany
| | - Tanja Woyke
- 3DOE Joint Genome Institute, Walnut Creek, California, USA
| |
Collapse
|
18
|
Kilmartin JR, Maher MJ, Krusong K, Noble CJ, Hanson GR, Bernhardt PV, Riley MJ, Kappler U. Insights into structure and function of the active site of SoxAX cytochromes. J Biol Chem 2011; 286:24872-81. [PMID: 21592966 PMCID: PMC3137062 DOI: 10.1074/jbc.m110.212183] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2010] [Revised: 04/20/2011] [Indexed: 11/06/2022] Open
Abstract
SoxAX cytochromes catalyze the formation of heterodisulfide bonds between inorganic sulfur compounds and a carrier protein, SoxYZ. They contain unusual His/Cys-ligated heme groups with complex spectroscopic signatures. The heme-ligating cysteine has been implicated in SoxAX catalysis, but neither the SoxAX spectroscopic properties nor its catalysis are fully understood at present. We have solved the first crystal structure for a group 2 SoxAX protein (SnSoxAX), where an N-terminal extension of SoxX forms a novel structure that supports dimer formation. Crystal structures of SoxAX with a heme ligand substitution (C236M) uncovered an inherent flexibility of this SoxA heme site, with both bonding distances and relative ligand orientation differing between asymmetric units and the new residue, Met(236), representing an unusual rotamer of methionine. The flexibility of the SnSoxAX(C236M) SoxA heme environment is probably the cause of the four distinct, new EPR signals, including a high spin ferric heme form, that were observed for the enzyme. Despite the removal of the catalytically active cysteine heme ligand and drastic changes in the redox potential of the SoxA heme (WT, -479 mV; C236M, +85 mV), the substituted enzyme was catalytically active in glutathione-based assays although with reduced turnover numbers (WT, 3.7 s(-1); C236M, 2.0 s(-1)). SnSoxAX(C236M) was also active in assays using SoxYZ and thiosulfate as the sulfur substrate, suggesting that Cys(236) aids catalysis but is not crucial for it. The SoxYZ-based SoxAX assay is the first assay for an isolated component of the Sox multienzyme system.
Collapse
Affiliation(s)
- James R. Kilmartin
- From the Centre for Metals in Biology, School of Chemistry and Molecular Biosciences, and
| | - Megan J. Maher
- the Structural Biology Program, Centenary Institute, Locked Bag 6, Sydney, New South Wales 2042, Australia
- the School of Molecular Bioscience, University of Sydney, New South Wales 2006, Australia, and
| | - Kuakarun Krusong
- the Department of Biochemistry, Chulalongkorn University, Bangkok 10330, Thailand
| | - Christopher J. Noble
- the Centre for Advanced Imaging, University of Queensland, St. Lucia, Queensland 4072, Australia
| | - Graeme R. Hanson
- the Centre for Advanced Imaging, University of Queensland, St. Lucia, Queensland 4072, Australia
| | - Paul V. Bernhardt
- From the Centre for Metals in Biology, School of Chemistry and Molecular Biosciences, and
| | - Mark J. Riley
- From the Centre for Metals in Biology, School of Chemistry and Molecular Biosciences, and
| | - Ulrike Kappler
- From the Centre for Metals in Biology, School of Chemistry and Molecular Biosciences, and
| |
Collapse
|
19
|
|
20
|
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]
|
21
|
Bernhardt PV. Exploiting the versatility and selectivity of Mo enzymes with electrochemistry. Chem Commun (Camb) 2011; 47:1663-73. [DOI: 10.1039/c0cc03681a] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
22
|
Rapson TD, Kappler U, Hanson GR, Bernhardt PV. Short circuiting a sulfite oxidising enzyme with direct electrochemistry: Active site substitutions and their effect on catalysis and electron transfer. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2011; 1807:108-18. [DOI: 10.1016/j.bbabio.2010.09.005] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2010] [Revised: 09/06/2010] [Accepted: 09/15/2010] [Indexed: 10/19/2022]
|
23
|
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.
Collapse
Affiliation(s)
- Kayunta Johnson-Winters
- Department of Chemistry and Biochemistry, The University of Arizona, Tucson, Arizona 85721, USA
| | | | | |
Collapse
|
24
|
Yang J, Rothery R, Sempombe J, Weiner JH, Kirk ML. Spectroscopic characterization of YedY: the role of sulfur coordination in a Mo(V) sulfite oxidase family enzyme form. J Am Chem Soc 2010; 131:15612-4. [PMID: 19860477 DOI: 10.1021/ja903087k] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Electronic paramagnetic resonance (EPR), electronic absorption, and magnetic circular dichroism spectroscopies have been performed on YedY, a SUOX fold protein with a Mo domain that is remarkably similar to that found in chicken sulfite oxidase, Arabidopsis thaliana plant sulfite oxidase, and the bacterial sulfite dehydrogenase from Starkeya novella. Low-energy dithiolene --> Mo and cysteine thiolate --> Mo charge-transfer bands have been assigned for the first time in a Mo(V) form of a SUOX fold protein, and the spectroscopic data have been used to interpret the results of bonding calculations. The analysis shows that second coordination sphere effects modulate dithiolene and cysteine sulfur covalency contributions to the Mo bonding scheme. In particular, a more acute O(oxo)-Mo-S(Cys)-C dihedral angle results in increased cysteine thiolate S --> Mo charge transfer and a large g(1) in the EPR spectrum. The spectrosocopic results, coupled with the available structural data, indicate that these second coordination sphere effects may play key roles in modulating the active-site redox potential, facilitating hole superexchange pathways for electron transfer regeneration, and affecting the type of reactions catalyzed by sulfite oxidase family enzymes.
Collapse
Affiliation(s)
- Jing Yang
- Department of Chemistry and Chemical Biology, The University of New Mexico, Albuquerque, New Mexico 87131, USA
| | | | | | | | | |
Collapse
|
25
|
Rapson TD, Astashkin AV, Johnson-Winters K, Bernhardt PV, Kappler U, Raitsimring AM, Enemark JH. Pulsed EPR investigations of the Mo(V) centers of the R55Q and R55M variants of sulfite dehydrogenase from Starkeya novella. J Biol Inorg Chem 2010; 15:505-14. [PMID: 20084533 DOI: 10.1007/s00775-009-0619-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2009] [Accepted: 12/13/2009] [Indexed: 10/20/2022]
Abstract
Continuous-wave and pulsed electron paramagnetic resonance (EPR) spectroscopy have been used to characterize two variants of bacterial sulfite dehydrogenase (SDH) from Starkeya novella in which the conserved active-site arginine residue (R55) is replaced by a neutral amino acid residue. Substitution by the hydrophobic methionine residue (SDH(R55M)) has essentially no effect on the pH dependence of the EPR properties of the Mo(V) center, even though the X-ray structure of this variant shows that the methionine residue is rotated away from the Mo center and a sulfate anion is present in the active-site pocket (Bailey et al. in J Biol Chem 284:2053-2063, 2009). For SDH(R55M) only the high-pH form is observed, and samples prepared in H(2)(17)O-enriched buffer show essentially the same (17)O hyperfine interaction and nuclear quadrupole interaction parameters as SDH(WT) enzyme. However, the pH dependence of the EPR spectra of SDH(R55Q), in which the positively charged arginine is replaced by the neutral hydrophilic glutamine, differs significantly from that of SDH(WT). For SDH(R55Q) the blocked form with bound sulfate is generated at low pH, as verified by (33)S couplings observed upon reduction with (33)S-labeled sulfite. This observation of bound sulfate for SDH(R55Q) supports our previous hypothesis that sulfite-oxidizing enzymes can exhibit multiple pathways for electron transfer and product release (Emesh et al. in Biochemistry 48:2156-2163, 2009). At pH > or = 8 the high-pH form dominates for SDH(R55Q).
Collapse
Affiliation(s)
- Trevor D Rapson
- Centre for Metals in Biology, School of Chemistry and Molecular Biosciences, The University of Queensland, St. Lucia, QLD, 4072, Australia
| | | | | | | | | | | | | |
Collapse
|
26
|
HIGH-RESOLUTION EPR SPECTROSCOPY OF MO ENZYMES. SULFITE OXIDASES: STRUCTURAL AND FUNCTIONAL IMPLICATIONS. BIOLOGICAL MAGNETIC RESONANCE 2010; 29:121-168. [PMID: 21283528 PMCID: PMC3030814 DOI: 10.1007/978-1-4419-1139-1_6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/11/2023]
Abstract
Sulfite oxidases (SOs) are physiologically vital Mo-containing enzymes that occur in animals, plants, and bacteria and which catalyze the oxidation of sulfite to sulfate, the terminal reaction in the oxidative degradation of sulfur-containing compounds. X-ray structure determinations of SOs from several species show nearly identical coordination structures of the molybdenum active center, and a common catalytic mechanism has been proposed that involves the generation of a transient paramagnetic Mo(V) state through a series of coupled electron-proton transfer steps. This chapter describes the use of pulsed electron-nuclear double resonance (ENDOR) and electron spin echo envelope modulation (ESEEM) spectroscopic techniques to obtain information about the structure of this Mo(V) species from the hyperfine interactions (hfi) and nuclear quadrupole interactions (nqi) of nearby magnetic nuclei. Variable frequency instrumentation is essential to optimize the experimental conditions for measuring the couplings of different types of nuclei (e.g., (1)H, (2)H, (31)P, and (17)O). The theoretical background necessary for understanding the ESEEM and ENDOR spectra of the Mo(V) centers of SOs is outlined, and examples of the use of advanced pulsed EPR methods (RP-ESEEM, HYSCORE, integrated four-pulse ESEEM) for structure determination are presented. The analysis of variable-frequency pulsed EPR data from SOs is aided by parallel studies of model compounds that contain key functional groups or that are isotopically labeled and thus provide benchmark data for enzymes. Enormous progress has been made on the use of high-resolution variable-frequency pulsed EPR methods to investigate the structures and mechanisms of SOs during the past ~15 years, and the future is bright for the continued development and application of this technology to SOs, other molybdenum enzymes, and other problems in metallobiochemistry.
Collapse
|
27
|
Emesh S, Rapson TD, Rajapakshe A, Kappler U, Bernhardt PV, Tollin G, Enemark JH. Intramolecular electron transfer in sulfite-oxidizing enzymes: elucidating the role of a conserved active site arginine. Biochemistry 2009; 48:2156-63. [PMID: 19226119 DOI: 10.1021/bi801553q] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
All reported sulfite-oxidizing enzymes have a conserved arginine in their active site which hydrogen bonds to the equatorial oxygen ligand on the Mo atom. Previous studies on the pathogenic R160Q mutant of human sulfite oxidase (HSO) have shown that Mo-heme intramolecular electron transfer (IET) is dramatically slowed when positive charge is lost at this position. To improve our understanding of the function that this conserved positively charged residue plays in IET, we have studied the equivalent uncharged substitutions R55Q and R55M as well as the positively charged substitution R55K in bacterial sulfite dehydrogenase (SDH). The heme and molybdenum cofactor (Moco) subunits are tightly associated in SDH, which makes it an ideal system for improving our understanding of residue function in IET without the added complexity of the interdomain movement that occurs in HSO. Unexpectedly, the uncharged SDH variants (R55Q and R55M) exhibited increased IET rate constants relative to that of the wild type (3-4-fold) when studied by laser flash photolysis. The gain in function observed in SDH(R55Q) and SDH(R55M) suggests that the reduction in the level of IET seen in HSO(R160Q) is not due to a required role of this residue in the IET pathway itself, but to the fact that it plays an important role in heme orientation during the interdomain movement necessary for IET in HSO (as seen in viscosity experiments). The pH profiles of SDH(WT), SDH(R55M), and SDH(R55Q) show that the arginine substitution also alters the behavior of the Mo-heme IET equilibrium (K(eq)) and rate constants (k(et)) of both variants with respect to the SDH(WT) enzyme. SDH(WT) has a k(et) that is independent of pH and a K(eq) that increases as pH decreases; on the other hand, both SDH(R55M) and SDH(R55Q) have a k(et) that increases as pH decreases, and SDH(R55M) has a K(eq) that is pH-independent. IET in the SDH(R55Q) variant is inhibited by sulfate in laser flash photolysis experiments, a behavior that differs from that of SDH(WT), but which also occurs in HSO. IET in SDH(R55K) is slower than in SDH(WT). A new analysis of the possible mechanistic pathways for sulfite-oxidizing enzymes is presented and related to available kinetic and EPR results for these enzymes.
Collapse
Affiliation(s)
- Safia Emesh
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721, USA
| | | | | | | | | | | | | |
Collapse
|
28
|
Sulfite oxidation in Sinorhizobium meliloti. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2009; 1787:1516-25. [DOI: 10.1016/j.bbabio.2009.07.005] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/26/2009] [Revised: 07/16/2009] [Accepted: 07/16/2009] [Indexed: 11/21/2022]
|
29
|
Astashkin AV, Klein EL, Ganyushin D, Johnson-Winters K, Neese F, Kappler U, Enemark JH. Exchangeable oxygens in the vicinity of the molybdenum center of the high-pH form of sulfite oxidase and sulfite dehydrogenase. Phys Chem Chem Phys 2009; 11:6733-42. [PMID: 19639147 PMCID: PMC2789977 DOI: 10.1039/b907029j] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The electron spin echo envelope modulation (ESEEM) investigation of the high-pH (hpH) form of sulfite oxidase (SO) and sulfite dehydrogenase (SDH) prepared in buffer enriched with H(2)(17)O reveals the presence of three types of exchangeable oxygen atoms at the molybdenum center. Two of these oxygen atoms belong to the equatorial OH ligand and the axial oxo ligand, and are characterized by (17)O hyperfine interaction (hfi) constants of about 37 MHz and 6 MHz, respectively. The third oxygen has an isotropic hfi constant of 3-4 MHz and likely belongs to a hydroxyl moiety hydrogen-bonded to the equatorial OH ligand. This exchangeable oxygen atom is not observed in the ESEEM spectra of the Y236F mutant of SDH, where the active site tyrosine has been replaced by phenylalanine.
Collapse
Affiliation(s)
- Andrei V. Astashkin
- Department of Chemistry, University of Arizona, Tucson, AZ 85721, USA; Fax: +1 (1)520 6218407; Tel: +1 (1)520 6219968
| | - Eric L. Klein
- Department of Chemistry, University of Arizona, Tucson, AZ 85721, USA; Fax: +1 (1)520 6218407; Tel: +1 (1)520 6219968
| | - Dmitry Ganyushin
- Institut für Physikalische und Theoretische Chemie, Universität Bonn, Wegelerstrasse 12, 53115 Bonn, Germany; Fax: +49 (0)228 739064; Tel: +49 28 732351
| | - Kayunta Johnson-Winters
- Department of Chemistry, University of Arizona, Tucson, AZ 85721, USA; Fax: +1 (1)520 6218407; Tel: +1 (1)520 6219968
| | - Frank Neese
- Institut für Physikalische und Theoretische Chemie, Universität Bonn, Wegelerstrasse 12, 53115 Bonn, Germany; Fax: +49 (0)228 739064; Tel: +49 28 732351
| | - Ulrike Kappler
- Centre for Metals in Biology, University of Queensland, St. Lucia, Queensland 4072, Australia; Fax: +61 (07)3365 4620; Tel: +61 (07)3365 2978
| | - John H. Enemark
- Department of Chemistry, University of Arizona, Tucson, AZ 85721, USA; Fax: +1 (1)520 6218407; Tel: +1 (1)520 6219968
| |
Collapse
|
30
|
Klein EL, Astashkin AV, Ganyushin D, Riplinger C, Johnson-Winters K, Neese F, Enemark JH. Direct detection and characterization of chloride in the active site of the low-pH form of sulfite oxidase using electron spin echo envelope modulation spectroscopy, isotopic labeling, and density functional theory calculations. Inorg Chem 2009; 48:4743-52. [PMID: 19402624 DOI: 10.1021/ic801787s] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Electron spin echo envelope modulation (ESEEM) investigations were carried out on samples of the low-pH (lpH) form of vertebrate sulfite oxidase (SO) prepared with (35)Cl- and (37)Cl-enriched buffers, as well as with buffer containing the natural abundance of Cl isotopes. The isotope-related changes observed in the ESEEM spectra provide direct and unequivocal evidence that Cl(-) is located in close proximity to the Mo(V) center of lpH SO. The measured isotropic hyperfine interaction constant of about 4 MHz ((35)Cl) suggests that the Cl(-) ion is either weakly coordinated to Mo(V) at its otherwise vacant axial position, trans to the oxo ligand, or is hydrogen-bonded to the equatorial exchangeable OH ligand. Scalar relativistic all-electron density functional theory (DFT) calculations of the hyperfine and nuclear quadrupole interaction parameters, along with steric and energetic arguments, strongly support the possibility that Cl(-) is hydrogen-bonded to the equatorial OH ligand rather than being directly coordinated to the Mo(V).
Collapse
Affiliation(s)
- Eric L Klein
- Department of Chemistry and Biochemistry, University of Arizona, 1306 E. University Boulevard, Tucson, Arizona 85721, USA
| | | | | | | | | | | | | |
Collapse
|
31
|
Bailey S, Rapson T, Johnson-Winters K, Astashkin AV, Enemark JH, Kappler U. Molecular basis for enzymatic sulfite oxidation: how three conserved active site residues shape enzyme activity. J Biol Chem 2009; 284:2053-63. [PMID: 19004819 PMCID: PMC2629113 DOI: 10.1074/jbc.m807718200] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2008] [Revised: 11/12/2008] [Indexed: 11/06/2022] Open
Abstract
Sulfite dehydrogenases (SDHs) catalyze the oxidation and detoxification of sulfite to sulfate, a reaction critical to all forms of life. Sulfite-oxidizing enzymes contain three conserved active site amino acids (Arg-55, His-57, and Tyr-236) that are crucial for catalytic competency. Here we have studied the kinetic and structural effects of two novel and one previously reported substitution (R55M, H57A, Y236F) in these residues on SDH catalysis. Both Arg-55 and His-57 were found to have key roles in substrate binding. An R55M substitution increased Km(sulfite)(app) by 2-3 orders of magnitude, whereas His-57 was required for maintaining a high substrate affinity at low pH when the imidazole ring is fully protonated. This effect may be mediated by interactions of His-57 with Arg-55 that stabilize the position of the Arg-55 side chain or, alternatively, may reflect changes in the protonation state of sulfite. Unlike what is seen for SDHWT and SDHY236F, the catalytic turnover rates of SDH R55M and SDHH57A are relatively insensitive to pH (approximately 60 and 200 s(-1), respectively). On the structural level, striking kinetic effects appeared to correlate with disorder (in SDHH57A and SDHY236F) or absence of Arg-55 (SDHR55M), suggesting that Arg-55 and the hydrogen bonding interactions it engages in are crucial for substrate binding and catalysis. The structure of SDHR55M has sulfate bound at the active site, a fact that coincides with a significant increase in the inhibitory effect of sulfate in SDHR55M. Thus, Arg-55 also appears to be involved in enabling discrimination between the substrate and product in SDH.
Collapse
Affiliation(s)
- Susan Bailey
- Molecular Biophysics Group, Science and Technology Facilities Council Daresbury Laboratory, Warrington WA4 4AD, United Kingdom
| | | | | | | | | | | |
Collapse
|
32
|
Direct catalytic electrochemistry of sulfite dehydrogenase: Mechanistic insights and contrasts with related Mo enzymes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2008; 1777:1319-25. [DOI: 10.1016/j.bbabio.2008.06.005] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/16/2008] [Revised: 06/06/2008] [Accepted: 06/06/2008] [Indexed: 11/21/2022]
|
33
|
Evolutionary persistence of the molybdopyranopterin-containing sulfite oxidase protein fold. Microbiol Mol Biol Rev 2008; 72:228-48, table of contents. [PMID: 18535145 DOI: 10.1128/mmbr.00041-07] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
SUMMARY The importance of molybdoenzymes is exemplified both by the debilitating and fatal human diseases caused by their deficiency and by their persistence throughout evolution. Here, we show that the protein fold of the molybdopyranopterin-containing domain of sulfite oxidase (the SUOX fold) can be found in all three domains of life. Analyses of sequence data and protein structure comparisons (secondary structure matching) show that the SUOX fold is found in enzymes that have quite distinct macromolecular architectures comprising one or more domains and sometimes subsidiary subunits. These are summarized as follows: (i) animal SUOXs that contain an N-terminal cytochrome b(5) domain and an SUOX fold fused to a C-terminal dimerization domain; (ii) plant SUOX that contains an SUOX fold fused to a C-terminal dimerization domain; (iii) the YedY protein from Escherichia coli, which comprises only the SUOX fold; (iv) the sulfite dehydrogenase from Starkeya novella that contains the SUOX fold, a dimerization domain, and an additional c-type cytochrome subunit; and (v) the plant-type nitrate reductases, exemplified by that of Pichia angusta, that contain an N-terminal SUOX fold, a dimerization domain, a cytochrome b(5) domain, and a C-terminal NADH binding flavin adenine dinucleotide-containing domain. We used the primary sequences of the proteins containing an SUOX fold to mine 559 sequences of related proteins. A phylogeny of a nonredundant subset of these sequences was generated, and the resultant clades were categorized by sequence motif analyses in the context of the available protein structures. Based on the motif analyses, cladistics, and domain conservations, we are able to postulate a plausible pathway of SUOX fold enzyme evolution.
Collapse
|
34
|
Léger C, Bertrand P. Direct Electrochemistry of Redox Enzymes as a Tool for Mechanistic Studies. Chem Rev 2008; 108:2379-438. [DOI: 10.1021/cr0680742] [Citation(s) in RCA: 594] [Impact Index Per Article: 37.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
|
35
|
Raitsimring AM, Astashkin AV, Feng C, Wilson HL, Rajagopalan KV, Enemark JH. Studies of the Mo(V) Center of the Y343F Mutant of Human Sulfite Oxidase by Variable Frequency Pulsed EPR Spectroscopy. Inorganica Chim Acta 2008; 361:941-946. [PMID: 18496596 PMCID: PMC2390843 DOI: 10.1016/j.ica.2007.05.023] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
The Mo(V) forms of the Tyr343Phe (Y343F) mutant of human sulfite oxidase (SO) have been investigated by continuous wave (CW) and variable frequency pulsed EPR spectroscopies as a function of pH. The CW EPR spectrum recorded at low pH (∼6.9) has g-values similar to those known for the low-pH form of the native vertebrate SO (original lpH form); however, unlike the spectrum of original lpH SO, it does not show any hyperfine splittings from a nearby exchangeable proton. The detailed electron spin echo (ESE) envelope modulation (ESEEM) and pulsed electron-nuclear double resonance (ENDOR) experiments also did not reveal any nearby protons that could belong to an exchangeable ligand at the molybdenum center. These results suggest that under low-pH conditions the active site of Y343F SO is in the "blocked" form, with the Mo(V) center coordinated by sulfate. With increasing pH the EPR signal from the "blocked" form decreases, while a signal similar to that of the original lpH form appears and becomes the dominant signal at pH>9. In addition, both the CW EPR and ESE-detected field sweep spectra reveal a considerable contribution from a signal similar to that usually detected for the high-pH form of native vertebrate SO (original hpH form). The nearby exchangeable protons in both of the component forms observed at high pH were studied by the ESEEM spectroscopy. These results indicate that the Y343F mutation increases the apparent pK(a) of the transition from the lpH to hpH forms by ∼2 pH units.
Collapse
Affiliation(s)
| | | | - Changjian Feng
- Department of Chemistry, University of Arizona, Tucson, AZ 85721, USA
| | - Heather L. Wilson
- Department of Biochemistry, Duke University Medical Center, Durham, North Carolina 27710
| | - K. V. Rajagopalan
- Department of Biochemistry, Duke University Medical Center, Durham, North Carolina 27710
| | - John H. Enemark
- Department of Chemistry, University of Arizona, Tucson, AZ 85721, USA
| |
Collapse
|
36
|
Doonan CJ, Wilson HL, Rajagopalan KV, Garrett RM, Bennett B, Prince RC, George GN. Modified active site coordination in a clinical mutant of sulfite oxidase. J Am Chem Soc 2007; 129:9421-8. [PMID: 17608478 DOI: 10.1021/ja071402a] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The molybdenum site of the Arginine 160 --> Glutamine clinical mutant of the physiologically vital enzyme sulfite oxidase has been investigated by a combination of X-ray absorption spectroscopy and density functional theory calculations. We conclude that the mutant enzyme has a six-coordinate pseudo-octahedral active site with coordination of Glutamine Oepsilon to molybdenum. This contrasts with the wild-type enzyme which is five-coordinate with approximately square-based pyramidal geometry. This difference in the structure of the molybdenum site explains many of the properties of the mutant enzyme which have previously been reported.
Collapse
Affiliation(s)
- Christian J Doonan
- Department of Geological Sciences, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | | | | | | | | | | | | |
Collapse
|
37
|
Feng C, Tollin G, Enemark JH. Sulfite oxidizing enzymes. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2007; 1774:527-39. [PMID: 17459792 PMCID: PMC1993547 DOI: 10.1016/j.bbapap.2007.03.006] [Citation(s) in RCA: 143] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/14/2007] [Revised: 03/02/2007] [Indexed: 11/19/2022]
Abstract
Sulfite oxidizing enzymes are essential mononuclear molybdenum (Mo) proteins involved in sulfur metabolism of animals, plants and bacteria. There are three such enzymes presently known: (1) sulfite oxidase (SO) in animals, (2) SO in plants, and (3) sulfite dehydrogenase (SDH) in bacteria. X-ray crystal structures of enzymes from all three sources (chicken SO, Arabidopsis thaliana SO, and Starkeya novella SDH) show nearly identical square pyramidal coordination around the Mo atom, even though the overall structures of the proteins and the presence of additional cofactors vary. This structural information provides a molecular basis for studying the role of specific amino acids in catalysis. Animal SO catalyzes the final step in the degradation of sulfur-containing amino acids and is critical in detoxifying excess sulfite. Human SO deficiency is a fatal genetic disorder that leads to early death, and impaired SO activity is implicated in sulfite neurotoxicity. Animal SO and bacterial SDH contain both Mo and heme domains, whereas plant SO only has the Mo domain. Intraprotein electron transfer (IET) between the Mo and Fe centers in animal SO and bacterial SDH is a key step in the catalysis, which can be studied by laser flash photolysis in the presence of deazariboflavin. IET studies on animal SO and bacterial SDH clearly demonstrate the similarities and differences between these two types of sulfite oxidizing enzymes. Conformational change is involved in the IET of animal SO, in which electrostatic interactions may play a major role in guiding the docking of the heme domain to the Mo domain prior to electron transfer. In contrast, IET measurements for SDH demonstrate that IET occurs directly through the protein medium, which is distinctly different from that in animal SO. Point mutations in human SO can result in significantly impaired IET or no IET, thus rationalizing their fatal effects. The recent developments in our understanding of sulfite oxidizing enzyme mechanisms that are driven by a combination of molecular biology, rapid kinetics, pulsed electron paramagnetic resonance (EPR), and computational techniques are the subject of this review.
Collapse
Affiliation(s)
- Changjian Feng
- College of Pharmacy, University of New Mexico, Albuquerque, NM 87131
| | - Gordon Tollin
- Department of Biochemistry and Molecular Biophysics, University of Arizona, Tucson, Arizona 85721, USA
| | - John H. Enemark
- Department of Chemistry, University of Arizona, Tucson, Arizona 85721, USA
| |
Collapse
|