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Structural and mechanistic analysis of the arsenate respiratory reductase provides insight into environmental arsenic transformations. Proc Natl Acad Sci U S A 2018; 115:E8614-E8623. [PMID: 30104376 DOI: 10.1073/pnas.1807984115] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Arsenate respiration by bacteria was discovered over two decades ago and is catalyzed by diverse organisms using the well-conserved Arr enzyme complex. Until now, the mechanisms underpinning this metabolism have been relatively opaque. Here, we report the structure of an Arr complex (solved by X-ray crystallography to 1.6-Å resolution), which was enabled by an improved Arr expression method in the genetically tractable arsenate respirer Shewanella sp. ANA-3. We also obtained structures bound with the substrate arsenate (1.8 Å), the product arsenite (1.8 Å), and the natural inhibitor phosphate (1.7 Å). The structures reveal a conserved active-site motif that distinguishes Arr [(R/K)GRY] from the closely related arsenite respiratory oxidase (Arx) complex (XGRGWG). Arr activity assays using methyl viologen as the electron donor and arsenate as the electron acceptor display two-site ping-pong kinetics. A Mo(V) species was detected with EPR spectroscopy, which is typical for proteins with a pyranopterin guanine dinucleotide cofactor. Arr is an extraordinarily fast enzyme that approaches the diffusion limit (Km = 44.6 ± 1.6 μM, kcat = 9,810 ± 220 seconds-1), and phosphate is a competitive inhibitor of arsenate reduction (Ki = 325 ± 12 μM). These observations, combined with knowledge of typical sedimentary arsenate and phosphate concentrations and known rates of arsenate desorption from minerals in the presence of phosphate, suggest that (i) arsenate desorption limits microbiologically induced arsenate reductive mobilization and (ii) phosphate enhances arsenic mobility by stimulating arsenate desorption rather than by inhibiting it at the enzymatic level.
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Gómez MC, Neuman NI, Dalosto SD, González PJ, Moura JJG, Rizzi AC, Brondino CD. Isotropic exchange interaction between Mo and the proximal FeS center in the xanthine oxidase family member aldehyde oxidoreductase from Desulfovibrio gigas on native and polyalcohol inhibited samples: an EPR and QM/MM study. J Biol Inorg Chem 2014; 20:233-42. [PMID: 25344343 DOI: 10.1007/s00775-014-1204-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2014] [Accepted: 10/07/2014] [Indexed: 11/25/2022]
Abstract
Aldehyde oxidoreductase from Desulfovibrio gigas (DgAOR) is a homodimeric molybdenum-containing protein that catalyzes the hydroxylation of aldehydes to carboxylic acids and contains a Mo-pyranopterin active site and two FeS centers called FeS 1 and FeS 2. The electron transfer reaction inside DgAOR is proposed to be performed through a chemical pathway linking Mo and the two FeS clusters involving the pyranopterin ligand. EPR studies performed on reduced as-prepared DgAOR showed that this pathway is able to transmit very weak exchange interactions between Mo(V) and reduced FeS 1. Similar EPR studies but performed on DgAOR samples inhibited with glycerol and ethylene glycol showed that the value of the exchange coupling constant J increases ~2 times upon alcohol inhibition. Structural studies in these DgAOR samples have demonstrated that the Mo-FeS 1 bridging pathway does not show significant differences, confirming that the changes in J observed upon inhibition cannot be ascribed to structural changes associated neither with pyranopterin and FeS 1 nor with changes in the electronic structure of FeS 1, as its EPR properties remain unchanged. Theoretical calculations indicate that the changes in J detected by EPR are related to changes in the electronic structure of Mo(V) determined by the replacement of the OHx labile ligand for an alcohol molecule. Since the relationship between electron transfer rate and isotropic exchange interaction, the present results suggest that the intraenzyme electron transfer process mediated by the pyranopterin moiety is governed by a Mo ligand-based regulatory mechanism.
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Affiliation(s)
- María C Gómez
- Departamento de Física, Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, Ciudad Universitaria, Paraje El Pozo, S3000ZAA, Santa Fe, Argentina
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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.
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Affiliation(s)
- Richard A Rothery
- Department of Biochemistry, University of Alberta, Edmonton, AB, T6G 2H7, Canada
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Cao H, Hall J, Hille R. X-ray crystal structure of arsenite-inhibited xanthine oxidase: μ-sulfido,μ-oxo double bridge between molybdenum and arsenic in the active site. J Am Chem Soc 2011; 133:12414-7. [PMID: 21761899 PMCID: PMC3163118 DOI: 10.1021/ja2050265] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Xanthine oxidoreductase is a molybdenum-containing enzyme that catalyzes the hydroxylation reaction of sp(2)-hybridized carbon centers of a variety of substrates, including purines, aldehydes, and other heterocyclic compounds. The complex of arsenite-inhibited xanthine oxidase has been characterized previously by UV-vis, electron paramagnetic resonance, and X-ray absorption spectroscopy (XAS), and the catalytically essential sulfido ligand of the square-pyrimidal molybdenum center has been suggested to be involved in arsenite binding through either a μ-sulfido,μ-oxo double bridge or a single μ-sulfido bridge. However, this is contrary to the crystallographically observed single μ-oxo bridge between molybdenum and arsenic in the desulfo form of aldehyde oxidoreductase from Desulfovibrio gigas (an enzyme closely related to xanthine oxidase), whose molybdenum center has an oxo ligand replacing the catalytically essential sulfur, as seen in the functional form of xanthine oxidase. Here we use X-ray crystallography to characterize the molybdenum center of arsenite-inhibited xanthine oxidase and solve the structures of the oxidized and reduced inhibition complexes at 1.82 and 2.11 Å resolution, respectively. We observe μ-sulfido,μ-oxo double bridges between molybdenum and arsenic in the active sites of both complexes. Arsenic is four-coordinate with a distorted trigonal-pyramidal geometry in the oxidized complex and three-coordinate with a distorted trigonal-planar geometry in the reduced complex. The doubly bridged binding mode is in agreement with previous XAS data indicating that the catalytically essential sulfur is also essential for the high affinity of reduced xanthine oxidoreductase for arsenite.
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Affiliation(s)
- Hongnan Cao
- University of California, Riverside, Department of Biochemistry, 1463 Boyce Hall, CA 92521
| | - James Hall
- University of California, Riverside, Department of Biochemistry, 1463 Boyce Hall, CA 92521
| | - Russ Hille
- University of California, Riverside, Department of Biochemistry, 1463 Boyce Hall, CA 92521
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González PJ, Barrera GI, Rizzi AC, Moura JJG, Passeggi MCG, Brondino CD. EPR studies of the Mo-enzyme aldehyde oxidoreductase from Desulfovibrio gigas: an application of the Bloch-Wangsness-Redfield theory to a system containing weakly-coupled paramagnetic redox centers with different relaxation rates. J Inorg Biochem 2009; 103:1342-6. [PMID: 19628281 DOI: 10.1016/j.jinorgbio.2009.06.006] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2009] [Revised: 06/19/2009] [Accepted: 06/22/2009] [Indexed: 11/15/2022]
Abstract
Electron transfer proteins and redox enzymes containing paramagnetic redox centers with different relaxation rates are widespread in nature. Despite both the long distances and chemical paths connecting these centers, they can present weak magnetic couplings produced by spin-spin interactions such as dipolar and isotropic exchange. We present here a theoretical model based on the Bloch-Wangsness-Redfield theory to analyze the dependence with temperature of EPR spectra of interacting pairs of spin 1/2 centers having different relaxation rates, as is the case of the molybdenum-containing enzyme aldehyde oxidoreductase from Desulfovibrio gigas. We analyze the changes of the EPR spectra of the slow relaxing center (Mo(V)) induced by the faster relaxing center (FeS center). At high temperatures, when the relaxation time T(1) of the fast relaxing center is very short, the magnetic coupling between centers is averaged to zero. Conversely, at low temperatures when T(1) is longer, no modulation of the coupling between metal centers can be detected.
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Affiliation(s)
- Pablo J González
- REQUIMTE, Departamento de Quimica, Centro de Quimica Fina e Biotecnologia, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal
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13
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Santos-Silva T, Ferroni F, Thapper A, Marangon J, González PJ, Rizzi AC, Moura I, Moura JJG, Romão MJ, Brondino CD. Kinetic, Structural, and EPR Studies Reveal That Aldehyde Oxidoreductase from Desulfovibrio gigas Does Not Need a Sulfido Ligand for Catalysis and Give Evidence for a Direct Mo−C Interaction in a Biological System. J Am Chem Soc 2009; 131:7990-8. [PMID: 19459677 DOI: 10.1021/ja809448r] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Teresa Santos-Silva
- REQUIMTE, Departamento de Química, Centro de Química Fina e Biotecnologia, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal, and Departamento de Física, Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, 3000ZAA Santa Fe, Argentina
| | - Felix Ferroni
- REQUIMTE, Departamento de Química, Centro de Química Fina e Biotecnologia, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal, and Departamento de Física, Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, 3000ZAA Santa Fe, Argentina
| | - Anders Thapper
- REQUIMTE, Departamento de Química, Centro de Química Fina e Biotecnologia, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal, and Departamento de Física, Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, 3000ZAA Santa Fe, Argentina
| | - Jacopo Marangon
- REQUIMTE, Departamento de Química, Centro de Química Fina e Biotecnologia, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal, and Departamento de Física, Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, 3000ZAA Santa Fe, Argentina
| | - Pablo J. González
- REQUIMTE, Departamento de Química, Centro de Química Fina e Biotecnologia, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal, and Departamento de Física, Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, 3000ZAA Santa Fe, Argentina
| | - Alberto C. Rizzi
- REQUIMTE, Departamento de Química, Centro de Química Fina e Biotecnologia, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal, and Departamento de Física, Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, 3000ZAA Santa Fe, Argentina
| | - Isabel Moura
- REQUIMTE, Departamento de Química, Centro de Química Fina e Biotecnologia, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal, and Departamento de Física, Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, 3000ZAA Santa Fe, Argentina
| | - José J. G. Moura
- REQUIMTE, Departamento de Química, Centro de Química Fina e Biotecnologia, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal, and Departamento de Física, Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, 3000ZAA Santa Fe, Argentina
| | - Maria J. Romão
- REQUIMTE, Departamento de Química, Centro de Química Fina e Biotecnologia, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal, and Departamento de Física, Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, 3000ZAA Santa Fe, Argentina
| | - Carlos D. Brondino
- REQUIMTE, Departamento de Química, Centro de Química Fina e Biotecnologia, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal, and Departamento de Física, Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, 3000ZAA Santa Fe, Argentina
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Joosten RP, Womack T, Vriend G, Bricogne G. Re-refinement from deposited X-ray data can deliver improved models for most PDB entries. ACTA CRYSTALLOGRAPHICA. SECTION D, BIOLOGICAL CRYSTALLOGRAPHY 2009; 65:176-85. [PMID: 19171973 PMCID: PMC2631631 DOI: 10.1107/s0907444908037591] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/08/2008] [Accepted: 11/12/2008] [Indexed: 11/17/2022]
Abstract
The deposition of X-ray data along with the customary structural models defining PDB entries makes it possible to apply large-scale re-refinement protocols to these entries, thus giving users the benefit of improvements in X-ray methods that have occurred since the structure was deposited. Automated gradient refinement is an effective method to achieve this goal, but real-space intervention is most often required in order to adequately address problems detected by structure-validation software. In order to improve the existing protocol, automated re-refinement was combined with structure validation and difference-density peak analysis to produce a catalogue of problems in PDB entries that are amenable to automatic correction. It is shown that re-refinement can be effective in producing improvements, which are often associated with the systematic use of the TLS parameterization of B factors, even for relatively new and high-resolution PDB entries, while the accompanying manual or semi-manual map analysis and fitting steps show good prospects for eventual automation. It is proposed that the potential for simultaneous improvements in methods and in re-refinement results be further encouraged by broadening the scope of depositions to include refinement metadata and ultimately primary rather than reduced X-ray data.
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Affiliation(s)
- Robbie P. Joosten
- CMBI, NCMLS, Radboud University Nijmegen Medical Centre, PO Box 9101, 6500 HB Nijmegen, The Netherlands
| | - Thomas Womack
- Global Phasing, Sheraton House, Castle Park, Cambridge CB3 0AX, England
| | - Gert Vriend
- CMBI, NCMLS, Radboud University Nijmegen Medical Centre, PO Box 9101, 6500 HB Nijmegen, The Netherlands
| | - Gérard Bricogne
- Global Phasing, Sheraton House, Castle Park, Cambridge CB3 0AX, England
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