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Doyle L, Magherusan A, Xu S, Murphy K, Farquhar ER, Molton F, Duboc C, Que L, McDonald AR. Class Ib Ribonucleotide Reductases: Activation of a Peroxido-Mn IIMn III to Generate a Reactive Oxo-Mn IIIMn IV Oxidant. Inorg Chem 2024; 63:2194-2203. [PMID: 38231137 PMCID: PMC10828993 DOI: 10.1021/acs.inorgchem.3c04163] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2023] [Revised: 12/18/2023] [Accepted: 12/22/2023] [Indexed: 01/18/2024]
Abstract
In the postulated catalytic cycle of class Ib Mn2 ribonucleotide reductases (RNRs), a MnII2 core is suggested to react with superoxide (O2·-) to generate peroxido-MnIIMnIII and oxo-MnIIIMnIV entities prior to proton-coupled electron transfer (PCET) oxidation of tyrosine. There is limited experimental support for this mechanism. We demonstrate that [MnII2(BPMP)(OAc)2](ClO4) (1, HBPMP = 2,6-bis[(bis(2 pyridylmethyl)amino)methyl]-4-methylphenol) was converted to peroxido-MnIIMnIII (2) in the presence of superoxide anion that converted to (μ-O)(μ-OH)MnIIIMnIV (3) via the addition of an H+-donor (p-TsOH) or (μ-O)2MnIIIMnIV (4) upon warming to room temperature. The physical properties of 3 and 4 were probed using UV-vis, EPR, X-ray absorption, and IR spectroscopies and mass spectrometry. Compounds 3 and 4 were capable of phenol oxidation to yield a phenoxyl radical via a concerted PCET oxidation, supporting the proposed mechanism of tyrosyl radical cofactor generation in RNRs. The synthetic models demonstrate that the postulated O2/Mn2/tyrosine activation mechanism in class Ib Mn2 RNRs is plausible and provides spectral insights into intermediates currently elusive in the native enzyme.
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Affiliation(s)
- Lorna Doyle
- School
of Chemistry, Trinity College Dublin, The
University of Dublin, College Green, Dublin 2, Ireland
| | - Adriana Magherusan
- School
of Chemistry, Trinity College Dublin, The
University of Dublin, College Green, Dublin 2, Ireland
| | - Shuangning Xu
- Department
of Chemistry and Centre for Metals in Biocatalysis, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455, United States
| | - Kayleigh Murphy
- School
of Chemistry, Trinity College Dublin, The
University of Dublin, College Green, Dublin 2, Ireland
| | - Erik R. Farquhar
- Case
Western Reserve University Center for Synchrotron Biosciences, National
Synchrotron Light Source II, Brookhaven
National Laboratory Upton, New
York 11973, United States
| | - Florian Molton
- CNRS
UMR 5250, DCM, Univ. Grenoble Alpes, Grenoble F-38000, France
| | - Carole Duboc
- CNRS
UMR 5250, DCM, Univ. Grenoble Alpes, Grenoble F-38000, France
| | - Lawrence Que
- Department
of Chemistry and Centre for Metals in Biocatalysis, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455, United States
| | - Aidan R. McDonald
- School
of Chemistry, Trinity College Dublin, The
University of Dublin, College Green, Dublin 2, Ireland
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2
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Petrie S, Stranger R, Pace RJ. Explaining the Different Geometries of the Water Oxidising Complex in the Nominal S 3 State Crystal Structures of Photosystem II at 2.25 Å and 2.35 Å. Chemphyschem 2018; 19:3296-3309. [PMID: 30290080 DOI: 10.1002/cphc.201800686] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2018] [Indexed: 11/10/2022]
Abstract
Recently two atomic resolution crystal structures of Photosystem II, in the double flashed, nominal S3 intermediate state of its Mn4 Ca water oxidising complex (WOC), have been presented (Young et al., Nature 2016, 540, 453; Suga et al., Nature 2017, 543, 131). These structures are at 2.25 Å and 2.35 Å resolution, respectively. Although highly similar in most respects, the structures differ in a key region within the WOC catalytic site. In the 2.25 Å structure, one oxy species (O5) is observed within the WOC cavity, weakly associated with the Mn centres, similar to that seen earlier in the 1.95 Å XRD structure of the S1 intermediate (Suga et al., Nature, 2015, 517, 99). In the 2.35 Å structure, two such species are seen (O5, O6), with the Mn centres and O5 positioned as in the 2.25 Å structure and an O5-O6 separation of ∼1.5 Å, consistent with peroxo formation. This suggests O5 and O6 are substrate water derived species in this double flashed form. Recently we have presented (Petrie, et al., Chem. Phys. Chem., 2017) a large scale (220 atom) quantum chemical model of the Young et al. 2.25 Å structure, which quantitatively explains all significant features within the WOC region of that structure, particularly the positions of the metal centres and O5 group. Critical to this was our assumption of a 'low' Mn oxidation paradigm (mean S1 Mn oxidation level of +3.0, Petrie et al., Angew. Chem. Int. Ed., 2015), rather than a 'high' oxidation model (mean S1 oxidation level of +3.5), widely assumed in the literature. Here we show that our same oxidation state model predicts two classes of energetically close S3 structural forms, analogous to the S1 state, one with the metal centres and O5 positioned as in the 2.25 Å structure, and the other with the metals similarly placed, but with O5 located in the O6 position of the 2.35 Å structure. We show that the Suga et al. 2.35 Å structure is likely a superposition of two such forms, one from each class, which is consistent with reported atomic occupancies for that structure and the relative total energies we calculate for the two structural forms.
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Affiliation(s)
- Simon Petrie
- Research School of Chemistry, College of Physical and Mathematical Sciences, The Australian National University, Acton ACT, Australia, 2601
| | - Robert Stranger
- Research School of Chemistry, College of Physical and Mathematical Sciences, The Australian National University, Acton ACT, Australia, 2601
| | - Ron J Pace
- Research School of Chemistry, College of Physical and Mathematical Sciences, The Australian National University, Acton ACT, Australia, 2601
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3
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Ro SY, Ross MO, Deng YW, Batelu S, Lawton TJ, Hurley JD, Stemmler TL, Hoffman BM, Rosenzweig AC. From micelles to bicelles: Effect of the membrane on particulate methane monooxygenase activity. J Biol Chem 2018; 293:10457-10465. [PMID: 29739854 DOI: 10.1074/jbc.ra118.003348] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2018] [Revised: 05/06/2018] [Indexed: 11/06/2022] Open
Abstract
Particulate methane monooxygenase (pMMO) is a copper-dependent integral membrane metalloenzyme that converts methane to methanol in methanotrophic bacteria. Studies of isolated pMMO have been hindered by loss of enzymatic activity upon its removal from the native membrane. To characterize pMMO in a membrane-like environment, we reconstituted pMMOs from Methylococcus (Mcc.) capsulatus (Bath) and Methylomicrobium (Mm.) alcaliphilum 20Z into bicelles. Reconstitution into bicelles recovers methane oxidation activity lost upon detergent solubilization and purification without substantial alterations to copper content or copper electronic structure, as observed by electron paramagnetic resonance (EPR) spectroscopy. These findings suggest that loss of pMMO activity upon isolation is due to removal from the membranes rather than caused by loss of the catalytic copper ions. A 2.7 Å resolution crystal structure of pMMO from Mm. alcaliphilum 20Z reveals a mononuclear copper center in the PmoB subunit and indicates that the transmembrane PmoC subunit may be conformationally flexible. Finally, results from extended X-ray absorption fine structure (EXAFS) analysis of pMMO from Mm. alcaliphilum 20Z were consistent with the observed monocopper center in the PmoB subunit. These results underscore the importance of studying membrane proteins in a membrane-like environment and provide valuable insight into pMMO function.
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Affiliation(s)
- Soo Y Ro
- From the Departments of Molecular Biosciences and Chemistry, Northwestern University, Evanston, Illinois 60208 and
| | - Matthew O Ross
- From the Departments of Molecular Biosciences and Chemistry, Northwestern University, Evanston, Illinois 60208 and
| | - Yue Wen Deng
- From the Departments of Molecular Biosciences and Chemistry, Northwestern University, Evanston, Illinois 60208 and
| | - Sharon Batelu
- the Department of Pharmaceutical Sciences, Wayne State University, Detroit, Michigan 48201
| | - Thomas J Lawton
- From the Departments of Molecular Biosciences and Chemistry, Northwestern University, Evanston, Illinois 60208 and
| | - Joseph D Hurley
- From the Departments of Molecular Biosciences and Chemistry, Northwestern University, Evanston, Illinois 60208 and
| | - Timothy L Stemmler
- the Department of Pharmaceutical Sciences, Wayne State University, Detroit, Michigan 48201
| | - Brian M Hoffman
- From the Departments of Molecular Biosciences and Chemistry, Northwestern University, Evanston, Illinois 60208 and
| | - Amy C Rosenzweig
- From the Departments of Molecular Biosciences and Chemistry, Northwestern University, Evanston, Illinois 60208 and
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4
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Blahut M, Dzul S, Wang S, Kandegedara A, Grossoehme NE, Stemmler T, Outten FW. Conserved cysteine residues are necessary for nickel-induced allosteric regulation of the metalloregulatory protein YqjI (NfeR) in E. coli. J Inorg Biochem 2018; 184:123-133. [PMID: 29723740 DOI: 10.1016/j.jinorgbio.2018.04.016] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2017] [Revised: 04/19/2018] [Accepted: 04/22/2018] [Indexed: 11/28/2022]
Abstract
Transition metal homeostasis is necessary to sustain life. First row transition metals act as cofactors within the cell, performing vital functions ranging from DNA repair to respiration. However, intracellular metal concentrations exceeding physiological requirements may be toxic. In E. coli, the YqjH flavoprotein is thought to play a role in iron homeostasis. YqjH is transcriptionally regulated by the ferric uptake regulator and a newly discovered regulator encoded by yqjI. The apo-form of YqjI is a transcriptional repressor of both the yqjH and yqjI genes. YqjI repressor function is disrupted upon binding of nickel. The YqjI N-terminus is homologous to nickel-binding proteins, implicating this region as a nickel-binding domain. Based on function, yqjI and yqjH should be renamed Ni-responsive Fe-uptake regulator (nfeR) and Ni-responsive Fe-uptake flavoprotein (nfeF), respectively. X-ray Absorption Spectroscopy was employed to characterize the nickel binding site(s) within YqjI. Putative nickel binding ligands were targeted by site-directed mutagenesis and resulting variants were analyzed in vivo for repressor function. Isothermal titration calorimetry and competitive binding assays were used to further quantify nickel interactions with wild-type YqjI and its mutant derivatives. Results indicate plasticity in the nickel binding domain of YqjI. Residues C42 and C43 were found to be required for in vivo response of YqjI to nickel stress, though these residues are not required for in vitro nickel binding. We propose that YqjI may contain a vicinal disulfide bond between C42 and C43 that is important for nickel-responsive allosteric interactions between YqjI domains.
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Affiliation(s)
- Matthew Blahut
- University of South Carolina, Department of Chemistry and Biochemistry, Columbia, SC 29208, USA
| | - Stephen Dzul
- Wayne State University, Department of Pharmaceutical Sciences, Detroit, MI 48201, USA
| | - Suning Wang
- University of South Carolina, Department of Chemistry and Biochemistry, Columbia, SC 29208, USA
| | - Ashoka Kandegedara
- Wayne State University, Department of Pharmaceutical Sciences, Detroit, MI 48201, USA
| | - Nicholas E Grossoehme
- Winthrop University, Department of Chemistry, Physics, and Geology, Rock Hill, SC 29733, USA
| | - Timothy Stemmler
- Wayne State University, Department of Pharmaceutical Sciences, Detroit, MI 48201, USA
| | - F Wayne Outten
- University of South Carolina, Department of Chemistry and Biochemistry, Columbia, SC 29208, USA.
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5
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Mn(acac) 2 and Mn(acac) 3 complexes, a theoretical modeling of their L 2,3 -edges X-ray absorption spectra. Polyhedron 2017. [DOI: 10.1016/j.poly.2017.07.007] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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6
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Bafaro EM, Antala S, Nguyen TV, Dzul SP, Doyon B, Stemmler TL, Dempski RE. The large intracellular loop of hZIP4 is an intrinsically disordered zinc binding domain. Metallomics 2015; 7:1319-30. [PMID: 25882556 PMCID: PMC4558264 DOI: 10.1039/c5mt00066a] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
The human (h) ZIP4 transporter is a plasma membrane protein which functions to increase the cytosolic concentration of zinc. hZIP4 transports zinc into intestinal cells and therefore has a central role in the absorption of dietary zinc. hZIP4 has eight transmembrane domains and encodes a large intracellular loop between transmembrane domains III and IV, M3M4. Previously, it has been postulated that this domain regulates hZIP4 levels in the plasma membrane in a zinc-dependent manner. The objective of this research was to examine the zinc binding properties of the large intracellular loop of hZIP4. Therefore, we have recombinantly expressed and purified M3M4 and showed that this domain binds two zinc ions. Using a combination of site-directed mutagenesis, metal binding affinity assays, and X-ray absorption spectroscopy, we demonstrated that the two Zn(2+) ions bind sequentially, with the first Zn(2+) binding to a CysHis3 site with a nanomolar binding affinity, and the second Zn(2+) binding to a His4 site with a weaker affinity. Circular dichroism spectroscopy revealed that the M3M4 domain is intrinsically disordered, with only a small structural change induced upon Zn(2+) coordination. Our data supports a model in which the intracellular M3M4 domain senses high cytosolic Zn(2+) concentrations and regulates the plasma membrane levels of the hZIP4 transporter in response to Zn(2+) binding.
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Affiliation(s)
- Elizabeth M Bafaro
- Department of Chemistry and Biochemistry, Worcester Polytechnic Institute, 100 Institute Road, Worcester, MA 01609, USA.
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7
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Crystal structures and magnetic properties of manganese(III) complexes with tridentate Schiff base ligands. J INCL PHENOM MACRO 2015. [DOI: 10.1007/s10847-015-0492-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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8
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Tierney DL, Schenk G. X-ray absorption spectroscopy of dinuclear metallohydrolases. Biophys J 2015; 107:1263-72. [PMID: 25229134 DOI: 10.1016/j.bpj.2014.07.066] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2014] [Revised: 06/14/2014] [Accepted: 07/24/2014] [Indexed: 12/26/2022] Open
Abstract
In this mini-review, we briefly discuss the physical origin of x-ray absorption spectroscopy (XAS) before illustrating its application using dinuclear metallohydrolases as exemplary systems. The systems we have selected for illustrative purposes present a challenging problem for XAS, one that is ideal to demonstrate the potential of this methodology for structure/function studies of metalloenzymes in general. When the metal ion is redox active, XAS provides a sensitive measure of oxidation-state-dependent differences. When the metal ion is zinc, XAS is the only spectroscopic method that will provide easily accessible structural information in solution. In the case of heterodimetallic sites, XAS has the unique ability to interrogate each metal site independently in the same sample. One of the strongest advantages of XAS is its ability to examine metal ion site structures with crystallographic precision, without the need for a crystal. This is key for studying flexible metal ion sites, such as those described in the selected examples, because it allows one to monitor structural changes that occur during substrate turnover.
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Affiliation(s)
- David L Tierney
- Department of Chemistry and Biochemistry, Miami University, Oxford, Ohio.
| | - Gerhard Schenk
- School of Chemistry and Molecular Biosciences, The University of Queensland, St. Lucia, Queensland, Australia
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9
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Sirajuddin S, Barupala D, Helling S, Marcus K, Stemmler TL, Rosenzweig AC. Effects of zinc on particulate methane monooxygenase activity and structure. J Biol Chem 2014; 289:21782-94. [PMID: 24942740 PMCID: PMC4118136 DOI: 10.1074/jbc.m114.581363] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2014] [Revised: 06/11/2014] [Indexed: 11/06/2022] Open
Abstract
Particulate methane monooxygenase (pMMO) is a membrane-bound metalloenzyme that oxidizes methane to methanol in methanotrophic bacteria. Zinc is a known inhibitor of pMMO, but the details of zinc binding and the mechanism of inhibition are not understood. Metal binding and activity assays on membrane-bound pMMO from Methylococcus capsulatus (Bath) reveal that zinc inhibits pMMO at two sites that are distinct from the copper active site. The 2.6 Å resolution crystal structure of Methylocystis species strain Rockwell pMMO reveals two previously undetected bound lipids, and metal soaking experiments identify likely locations for the two zinc inhibition sites. The first is the crystallographic zinc site in the pmoC subunit, and zinc binding here leads to the ordering of 10 previously unobserved residues. A second zinc site is present on the cytoplasmic side of the pmoC subunit. Parallels between these results and zinc inhibition studies of several respiratory complexes suggest that zinc might inhibit proton transfer in pMMO.
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Affiliation(s)
- Sarah Sirajuddin
- From the Departments of Molecular Biosciences and of Chemistry, Northwestern University, Evanston, Illinois 60208
| | - Dulmini Barupala
- the Department of Pharmaceutical Sciences, Wayne State University, Detroit, Michigan 48201, and
| | - Stefan Helling
- the Medical Proteome Center, Department of Functional Proteomics, Ruhr-Universität Bochum, 44801 Bochum, Germany
| | - Katrin Marcus
- the Medical Proteome Center, Department of Functional Proteomics, Ruhr-Universität Bochum, 44801 Bochum, Germany
| | - Timothy L Stemmler
- the Department of Pharmaceutical Sciences, Wayne State University, Detroit, Michigan 48201, and
| | - Amy C Rosenzweig
- From the Departments of Molecular Biosciences and of Chemistry, Northwestern University, Evanston, Illinois 60208,
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10
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Abstract
Metalloproteins are enormously important in biology. While a variety of techniques exist for studying metals in biology, X-ray absorption spectroscopy is particularly useful in that it can determine the local electronic and physical structure around the metal center, and is one of the few avenues for studying "spectroscopically silent" metal ions like Zn(II) and Cu(I) that have completely filled valence bands. While X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) are useful for studying metalloprotein structure, they suffer the limitation that the detected signal is an average of all the various metal centers in the sample, which limits its usefulness for studying metal centers in situ or in cell lysates. It would be desirable to be able to separate the various proteins in a mixture prior to performing X-ray absorption studies, so that the derived signal is from one species only. Here we describe a method for performing X-ray absorption spectroscopy on protein bands following electrophoretic separation and western blotting.
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Affiliation(s)
- Jesse Ward
- X-Ray Science Division, Advanced Photon Source, Argonne National Laboratory, 9700 S. Cass Avenue, Argonne, IL, 60439, USA
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11
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Zielazinski EL, González-Guerrero M, Subramanian P, Stemmler TL, Argüello JM, Rosenzweig AC. Sinorhizobium meliloti Nia is a P(1B-5)-ATPase expressed in the nodule during plant symbiosis and is involved in Ni and Fe transport. Metallomics 2013; 5:1614-1623. [PMID: 24056637 DOI: 10.1039/c3mt00195d] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
The P1B-ATPases are a ubiquitous family of metal transporters. These transporters are classified into subfamilies on the basis of substrate specificity, which is conferred by conserved amino acids in the last three transmembrane domains. Five subfamilies have been identified to date, and representative members of four (P1B-1 to P1B-4) have been studied. The fifth family (P1B-5), of which some members contain a C-terminal hemerythrin (Hr) domain, is less well characterized. The S. meliloti Sma1163 gene encodes for a P1B-5-ATPase, denoted Nia (Nickel-iron ATPase), that is induced by exogenous Fe(2+) and Ni(2+). The nia mutant accumulates nickel and iron, suggesting a possible role in detoxification of these two elements under free-living conditions, as well as in symbiosis, when the highest expression levels are measured. This function is supported by an inhibitory effect of Fe(2+) and Ni(2+) on the pNPPase activity, and by the ability of Nia to bind Fe(2+) in the transmembrane domain. Optical and X-ray absorption spectroscopic studies of the isolated Hr domain confirm the presence of a dinuclear iron center and suggest that this domain might function as an iron sensor.
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Affiliation(s)
- Eliza L Zielazinski
- Departments of Molecular Biosciences and of Chemistry. Northwestern University, Evanston, Illinois, USA.
| | - Manuel González-Guerrero
- Centro de Biotecnología y Genómica de Plantas (CBGP), Universidad Politécnica de Madrid, Campus de Montegancedo, Pozuelo de Alarcón, Madrid, Spain
| | - Poorna Subramanian
- Department of Biochemistry and Molecular Biology and the Cardiovascular Research Institute, Wayne State University, School of Medicine, Detroit, Michigan, USA
| | - Timothy L Stemmler
- Department of Biochemistry and Molecular Biology and the Cardiovascular Research Institute, Wayne State University, School of Medicine, Detroit, Michigan, USA
| | - José M Argüello
- Department of Chemistry and Biochemistry, Worcester Polytechnic Institute, Worcester, Massachusetts, USA.
| | - Amy C Rosenzweig
- Departments of Molecular Biosciences and of Chemistry. Northwestern University, Evanston, Illinois, USA.
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12
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Muratsugu S, Weng Z, Tada M. Surface Functionalization of Supported Mn Clusters to Produce Robust Mn Catalysts for Selective Epoxidation. ACS Catal 2013. [DOI: 10.1021/cs400053f] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Affiliation(s)
- Satoshi Muratsugu
- Institute for Molecular Science, 38 Nishigo-naka, Myodaiji, Okazaki, Aichi 444-8585,
Japan
| | - Zhihuan Weng
- Institute for Molecular Science, 38 Nishigo-naka, Myodaiji, Okazaki, Aichi 444-8585,
Japan
- Department of Applied Physics
and Chemistry, The University of Electro-Communication, Chofu, Tokyo 182-8585, Japan
| | - Mizuki Tada
- Institute for Molecular Science, 38 Nishigo-naka, Myodaiji, Okazaki, Aichi 444-8585,
Japan
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13
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Khajuria R, Syed A, Kumar S, Pandey SK. Spectroscopic, Thermal, Electrochemical, and Antimicrobial Studies of Mononuclear Manganese(II) Ditolyldithiophosphates. Bioinorg Chem Appl 2013; 2013:261731. [PMID: 23983670 PMCID: PMC3747474 DOI: 10.1155/2013/261731] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2013] [Accepted: 06/19/2013] [Indexed: 11/20/2022] Open
Abstract
New complexes of manganese(II) corresponding to [{(ArO)2PS2}2Mn] and [{(ArO)2PS2}2Mn.nL] (Ar = o-, m-, p-CH3C6H4 and p-Cl-m-CH3C6H3; n = 1, L = N2C12H8, N2C10H8; n = 2, L = NC5H5, P(C6H5)3) have been synthesized and characterized by microelemental analyses (C, H, and N), magnetic susceptibility, molar conductance, thermogravimetric, cyclic voltammetry, and spectral analyses including ESI mass spectrometry, IR, and UV-visible. The presence of a four-and-six coordinated Mn atoms has been established in the complexes and adducts, respectively. Antimicrobial screening of the complexes against gram negative bacteria E. coli, K. pneumonia, and P. aeruginosa and fungus S. rolfsii has shown potential bioactivity.
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Affiliation(s)
- Ruchi Khajuria
- Department of Chemistry, University of Jammu, Baba Saheb Ambedkar Road, Jammu and Kashmir 180 006, India
| | - Atiya Syed
- Department of Chemistry, University of Jammu, Baba Saheb Ambedkar Road, Jammu and Kashmir 180 006, India
| | - Sandeep Kumar
- Department of Chemistry, University of Jammu, Baba Saheb Ambedkar Road, Jammu and Kashmir 180 006, India
| | - Sushil K. Pandey
- Department of Chemistry, University of Jammu, Baba Saheb Ambedkar Road, Jammu and Kashmir 180 006, India
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14
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Dai Z, Farquhar ER, Arora DP, Boon EM. Is histidine dissociation a critical component of the NO/H-NOX signaling mechanism? Insights from X-ray absorption spectroscopy. Dalton Trans 2012; 41:7984-93. [PMID: 22430114 PMCID: PMC3671924 DOI: 10.1039/c2dt30147d] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The H-NOX (Heme-Nitric oxide/OXygen binding) family of diatomic gas sensing hemoproteins has attracted great interest. Soluble guanylate cyclase (sGC), the well-characterized eukaryotic nitric oxide (NO) sensor is an H-NOX family member. When NO binds sGC at the ferrous histidine-ligated protoporphyrin-IX, the proximal histidine ligand dissociates, resulting in a 5-coordinate (5c) complex; formation of this 5c complex is viewed as necessary for activation of sGC. Characterization of other H-NOX family members has revealed that while most also bind NO in a 5c complex, some bind NO in a 6-coordinate (6c) complex or as a 5c/6c mixture. To gain insight into the heme pocket structural differences between 5c and 6c Fe(ii)-NO H-NOX complexes, we investigated the extended X-ray absorption fine structure (EXAFS) of the Fe(II)-unligated and Fe(II)-NO complexes of H-NOX domains from three species, Thermoanaerobacter tengcongensis, Shewanella woodyi, and Pseudoalteromonas atlantica. Although the Fe(II)-NO complex of TtH-NOX is formally 6c, we found the Fe-N(His) bond is substantially lengthened. Furthermore, although NO binds to SwH-NOX and PaH-NOX as a 5c complex, consistent with histidine dissociation, the EXAFS data do not exclude a very weakly associated histidine. Regardless of coordination number, upon NO-binding, the Fe-N(porphyrin) bond lengths in all three H-NOXs contract by ~0.07 Å. This study reveals that the overall heme structure of 5c and 6c Fe(II)-NO H-NOX complexes are substantially similar, suggesting that formal histidine dissociation may not be required to trigger NO/H-NOX signal transduction. The study has refined our understanding of the molecular mechanisms underlying NO/H-NOX signaling.
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Affiliation(s)
- Zhou Dai
- Department of Chemistry, Stony Brook University, Stony Brook, New York 11794-3400, USA
| | - Erik R. Farquhar
- Case Western Reserve University Center for Synchrotron Biosciences and Center for Proteomics and Bioinformatics, National Synchrotron Light Source, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - Dhruv P. Arora
- Department of Chemistry, Stony Brook University, Stony Brook, New York 11794-3400, USA
| | - Elizabeth M. Boon
- Department of Chemistry, Stony Brook University, Stony Brook, New York 11794-3400, USA
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15
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16
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Chen Y, Farquhar ER, Chance MR, Palczewski K, Kiser PD. Insights into substrate specificity and metal activation of mammalian tetrahedral aspartyl aminopeptidase. J Biol Chem 2012; 287:13356-70. [PMID: 22356908 DOI: 10.1074/jbc.m112.347518] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Aminopeptidases are key enzymes involved in the regulation of signaling peptide activity. Here, we present a detailed biochemical and structural analysis of an evolutionary highly conserved aspartyl aminopeptidase called DNPEP. We show that this peptidase can cleave multiple physiologically relevant substrates, including angiotensins, and thus may play a key role in regulating neuron function. Using a combination of x-ray crystallography, x-ray absorption spectroscopy, and single particle electron microscopy analysis, we provide the first detailed structural analysis of DNPEP. We show that this enzyme possesses a binuclear zinc-active site in which one of the zinc ions is readily exchangeable with other divalent cations such as manganese, which strongly stimulates the enzymatic activity of the protein. The plasticity of this metal-binding site suggests a mechanism for regulation of DNPEP activity. We also demonstrate that DNPEP assembles into a functionally relevant tetrahedral complex that restricts access of peptide substrates to the active site. These structural data allow rationalization of the enzyme's preference for short peptide substrates with N-terminal acidic residues. This study provides a structural basis for understanding the physiology and bioinorganic chemistry of DNPEP and other M18 family aminopeptidases.
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Affiliation(s)
- Yuanyuan Chen
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106-4965, USA
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Leidel N, Popović-Bijelić A, Havelius KGV, Chernev P, Voevodskaya N, Gräslund A, Haumann M. High-valent [MnFe] and [FeFe] cofactors in ribonucleotide reductases. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2012; 1817:430-44. [PMID: 22222354 DOI: 10.1016/j.bbabio.2011.12.008] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/05/2011] [Revised: 12/13/2011] [Accepted: 12/16/2011] [Indexed: 11/30/2022]
Abstract
Ribonucleotide reductases (RNRs) are essential for DNA synthesis in most organisms. In class-Ic RNR from Chlamydia trachomatis (Ct), a MnFe cofactor in subunit R2 forms the site required for enzyme activity, instead of an FeFe cofactor plus a redox-active tyrosine in class-Ia RNRs, for example in mouse (Mus musculus, Mm). For R2 proteins from Ct and Mm, either grown in the presence of, or reconstituted with Mn and Fe ions, structural and electronic properties of higher valence MnFe and FeFe sites were determined by X-ray absorption spectroscopy and complementary techniques, in combination with bond-valence-sum and density functional theory calculations. At least ten different cofactor species could be tentatively distinguished. In Ct R2, two different Mn(IV)Fe(III) site configurations were assigned either L(4)Mn(IV)(μO)(2)Fe(III)L(4) (metal-metal distance of ~2.75Å, L = ligand) prevailing in metal-grown R2, or L(4)Mn(IV)(μO)(μOH)Fe(III)L(4) (~2.90Å) dominating in metal-reconstituted R2. Specific spectroscopic features were attributed to an Fe(IV)Fe(III) site (~2.55Å) with a L(4)Fe(IV)(μO)(2)Fe(III)L(3) core structure. Several Mn,Fe(III)Fe(III) (~2.9-3.1Å) and Mn,Fe(III)Fe(II) species (~3.3-3.4Å) likely showed 5-coordinated Mn(III) or Fe(III). Rapid X-ray photoreduction of iron and shorter metal-metal distances in the high-valent states suggested radiation-induced modifications in most crystal structures of R2. The actual configuration of the MnFe and FeFe cofactors seems to depend on assembly sequences, bound metal type, valence state, and previous catalytic activity involving subunit R1. In Ct R2, the protonation of a bridging oxide in the Mn(IV)(μO)(μOH)Fe(III) core may be important for preventing premature site reduction and initiation of the radical chemistry in R1.
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Affiliation(s)
- Nils Leidel
- Institut für Experimentalphysik, Freie Universität Berlin, 14195 Berlin, Germany
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Pace RJ, Jin L, Stranger R. What spectroscopy reveals concerning the Mn oxidation levels in the oxygen evolving complex of photosystem II: X-ray to near infra-red. Dalton Trans 2012; 41:11145-60. [DOI: 10.1039/c2dt30938f] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Schoenfeldt NJ, Ni Z, Korinda AW, Meyer RJ, Notestein JM. Manganese Triazacyclononane Oxidation Catalysts Grafted under Reaction Conditions on Solid Cocatalytic Supports. J Am Chem Soc 2011; 133:18684-95. [DOI: 10.1021/ja204761e] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Nicholas J. Schoenfeldt
- Department of Chemical and Biological Engineering, Northwestern University, 2145 Sheridan Road, Technological Institute, Room E136, Evanston, Illinois 60208, United States
| | - Zhenjuan Ni
- Department of Chemical Engineering, University of Illinois at Chicago, 810 South Clinton Street, Chicago, Illinois 60607, United States
| | - Andrew W. Korinda
- Department of Chemical and Biological Engineering, Northwestern University, 2145 Sheridan Road, Technological Institute, Room E136, Evanston, Illinois 60208, United States
| | - Randall J. Meyer
- Department of Chemical Engineering, University of Illinois at Chicago, 810 South Clinton Street, Chicago, Illinois 60607, United States
| | - Justin M. Notestein
- Department of Chemical and Biological Engineering, Northwestern University, 2145 Sheridan Road, Technological Institute, Room E136, Evanston, Illinois 60208, United States
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Jaszewski AR, Petrie S, Pace RJ, Stranger R. Toward the Assignment of the Manganese Oxidation Pattern in the Water-Oxidizing Complex of Photosystem II: A Time-Dependent DFT Study of XANES Energies. Chemistry 2011; 17:5699-713. [DOI: 10.1002/chem.201001996] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2010] [Revised: 12/23/2010] [Indexed: 11/10/2022]
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21
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Jaszewski AR, Stranger R, Pace RJ. Structural and Electronic Models of the Water Oxidizing Complex in the S0 State of Photosystem II: A Density Functional Study. J Phys Chem B 2011; 115:4484-99. [DOI: 10.1021/jp200053n] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Affiliation(s)
- Adrian R. Jaszewski
- Research School of Chemistry, College of Science, Australian National University, Canberra ACT 0200, Australia
| | - Rob Stranger
- Research School of Chemistry, College of Science, Australian National University, Canberra ACT 0200, Australia
| | - Ronald J. Pace
- Research School of Chemistry, College of Science, Australian National University, Canberra ACT 0200, Australia
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Traverso ME, Subramanian P, Davydov R, Hoffman BM, Stemmler TL, Rosenzweig AC. Identification of a hemerythrin-like domain in a P1B-type transport ATPase. Biochemistry 2010; 49:7060-8. [PMID: 20672819 PMCID: PMC2935145 DOI: 10.1021/bi100866b] [Citation(s) in RCA: 22] [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 P(1B)-type ATPases couple the energy of ATP hydrolysis to metal ion translocation across cell membranes. Important for prokaryotic metal resistance and essential metal distribution in eukaryotes, P(1B)-ATPases are divided into subclasses on the basis of their metal substrate specificities. Sequence analysis of putative P(1B-5)-ATPases, for which the substrate has not been identified, led to the discovery of a C-terminal soluble domain homologous to hemerythrin (Hr) proteins and domains. The Hr domain from the Acidothermus cellulolyticus P(1B-5)-ATPase was cloned, expressed, and purified (P(1B-5)-Hr). P(1B-5)-Hr binds two iron ions per monomer and adopts a predominantly helical fold. Optical absorption features of the iron-loaded and azide-treated protein are consistent with features observed for other Hr proteins. Autoxidation to the met form is very rapid, as reported for other prokaryotic Hr domains. The presence of a diiron center was confirmed by electron paramagnetic resonance (EPR) and X-ray absorption spectroscopic (XAS) data. The occurrence of a Hr-like domain in a P-type ATPase is unprecedented and suggests new regulatory mechanisms as well as an expanded function for Hr proteins in biology.
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Affiliation(s)
- Matthew E. Traverso
- Department of Biochemistry, Molecular Biology, and Cell Biology, Northwestern University, Evanston IL 60208
- Department of Chemistry, Northwestern University, Evanston IL 60208
| | - Poorna Subramanian
- Department of Biochemistry and Molecular Biology, Wayne State University, School of Medicine, Detroit MI 48202
| | - Roman Davydov
- Department of Chemistry, Northwestern University, Evanston IL 60208
| | - Brian M. Hoffman
- Department of Biochemistry, Molecular Biology, and Cell Biology, Northwestern University, Evanston IL 60208
- Department of Chemistry, Northwestern University, Evanston IL 60208
| | - Timothy L. Stemmler
- Department of Biochemistry and Molecular Biology, Wayne State University, School of Medicine, Detroit MI 48202
| | - Amy C. Rosenzweig
- Department of Biochemistry, Molecular Biology, and Cell Biology, Northwestern University, Evanston IL 60208
- Department of Chemistry, Northwestern University, Evanston IL 60208
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Stone EM, Glazer ES, Chantranupong L, Cherukuri P, Breece RM, Tierney DL, Curley SA, Iverson BL, Georgiou G. Replacing Mn(2+) with Co(2+) in human arginase i enhances cytotoxicity toward l-arginine auxotrophic cancer cell lines. ACS Chem Biol 2010; 5:333-42. [PMID: 20050660 DOI: 10.1021/cb900267j] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Replacing the two Mn(2+) ions normally present in human Arginase I with Co(2+) resulted in a significantly lowered K(M) value without a concomitant reduction in k(cat). In addition, the pH dependence of the reaction was shifted from a pK(a) of 8.5 to a pK(a) of 7.5. The combination of these effects led to a 10-fold increase in overall catalytic activity (k(cat)/K(M)) at pH 7.4, close to the pH of human serum. Just as important for therapeutic applications, Co(2+) substitution lead to significantly increased serum stability of the enzyme. Our data can be explained by direct coordination of l-Arg to one of the Co(2+) ions during reaction, consistent with previously reported model studies. In vitro cytotoxicity experiments verified that the Co(2+)-substituted human Arg I displays an approximately 12- to 15-fold lower IC(50) value for the killing of human hepatocellular carcinoma and melanoma cell lines and thus constitutes a promising new candidate for the treatment of l-Arg auxotrophic tumors.
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Affiliation(s)
- Everett M. Stone
- Departments of Chemical Engineering, Biomedical Engineering, Molecular Genetics and Microbiology
| | - Evan S. Glazer
- Department of Surgical Oncology, University of Texas, M. D. Anderson Cancer Center, Houston, Texas 77030
| | - Lynne Chantranupong
- Departments of Chemical Engineering, Biomedical Engineering, Molecular Genetics and Microbiology
| | - Paul Cherukuri
- Department of Surgical Oncology, University of Texas, M. D. Anderson Cancer Center, Houston, Texas 77030
| | - Robert M. Breece
- Department of Chemistry and Biochemistry, Miami University, Oxford, Ohio 45056
| | - David L. Tierney
- Department of Chemistry and Biochemistry, Miami University, Oxford, Ohio 45056
| | - Steven A. Curley
- Department of Surgical Oncology, University of Texas, M. D. Anderson Cancer Center, Houston, Texas 77030
| | - Brent L. Iverson
- Institute for Cell and Institute for Molecular and Cell Biology
- Department of Chemistry and Biochemistry, University of Texas, Austin, Texas 78712
| | - George Georgiou
- Departments of Chemical Engineering, Biomedical Engineering, Molecular Genetics and Microbiology
- Institute for Cell and Institute for Molecular and Cell Biology
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25
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26
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Li H, Mapolelo DT, Dingra NN, Naik SG, Lees NS, Hoffman BM, Riggs-Gelasco PJ, Huynh BH, Johnson MK, Outten CE. The yeast iron regulatory proteins Grx3/4 and Fra2 form heterodimeric complexes containing a [2Fe-2S] cluster with cysteinyl and histidyl ligation. Biochemistry 2009; 48:9569-81. [PMID: 19715344 DOI: 10.1021/bi901182w] [Citation(s) in RCA: 173] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The transcription of iron uptake and storage genes in Saccharomyces cerevisiae is primarily regulated by the transcription factor Aft1. Nucleocytoplasmic shuttling of Aft1 is dependent upon mitochondrial Fe-S cluster biosynthesis via a signaling pathway that includes the cytosolic monothiol glutaredoxins (Grx3 and Grx4) and the BolA homologue Fra2. However, the interactions between these proteins and the iron-dependent mechanism by which they control Aft1 localization are unclear. To reconstitute and characterize components of this signaling pathway in vitro, we have overexpressed yeast Fra2 and Grx3/4 in Escherichia coli. We have shown that coexpression of recombinant Fra2 with Grx3 or Grx4 allows purification of a stable [2Fe-2S](2+) cluster-containing Fra2-Grx3 or Fra2-Grx4 heterodimeric complex. Reconstitution of a [2Fe-2S] cluster on Grx3 or Grx4 without Fra2 produces a [2Fe-2S]-bridged homodimer. UV-visible absorption and CD, resonance Raman, EPR, ENDOR, Mossbauer, and EXAFS studies of [2Fe-2S] Grx3/4 homodimers and the [2Fe-2S] Fra2-Grx3/4 heterodimers indicate that inclusion of Fra2 in the Grx3/4 Fe-S complex causes a change in the cluster stability and coordination environment. Taken together, our analytical, spectroscopic, and mutagenesis data indicate that Grx3/4 and Fra2 form a Fe-S-bridged heterodimeric complex with Fe ligands provided by the active site cysteine of Grx3/4, glutathione, and a histidine residue. Overall, these results suggest that the ability of the Fra2-Grx3/4 complex to assemble a [2Fe-2S] cluster may act as a signal to control the iron regulon in response to cellular iron status in yeast.
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Affiliation(s)
- Haoran Li
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208, USA
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27
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Habibi MH, Askari E, Mokhtari R, Montazerozohori M, Suzuki T. Bis{μ-4,4′-dimethoxy-2,2′-[propane-1,2-diylbis(nitrilomethylidyne)]diphenolato}bis({4,4′-dimethoxy-2,2′-[propane-1,2-diylbis(nitrilomethylidyne)]diphenol}manganese(III)) bis(hexafluoridophosphate). Acta Crystallogr Sect E Struct Rep Online 2009; 65:m1004-5. [PMID: 21583304 PMCID: PMC2977226 DOI: 10.1107/s1600536809028591] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2009] [Accepted: 07/20/2009] [Indexed: 11/11/2022]
Abstract
In the title complex, [Mn2(C19H20N2O4)2(C19H22N2O4)2](PF6)2, the MnIII ion is coordinated by two O [Mn—O = 1.855 (2) and 1.887 (2) Å] and two N [Mn—N = 1.982 (3) and 1.977 (3) Å] atoms from the tetradentate Schiff base ligand and a coordinated axial ligand [Mn—O = 2.129 (2) Å]. The centrosymmetric dimer contains two Jahn–Teller-distorted MnIII ions, each in a nearly octahedral geometry, connected through two phenolate bridges from two ligands. There are two stereogenic centers. The methyl group and the H atom attached to the middle propane C atom are disordered over two positions with occupancy factors in the ratio 0.58:0.42. The crystal is therefore a mixture of two diasteroisomers, viz. RS/SR and RR/SS. In the axial ligand, the two benzene rings form a dihedral angle of 56.97 (5)° and the dihedral angle between the two MnNC3O chelate rings is 2.98 (12)°
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Jaszewski AR, Stranger R, Pace RJ. The effect of Mn oxidation state on metal core electron excitations in manganese dimers: a time-dependent density functional investigation. Phys Chem Chem Phys 2009; 11:5634-42. [DOI: 10.1039/b900694j] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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29
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Jaszewski AR, Stranger R, Pace RJ. Time-Dependent DFT Studies of Metal Core-Electron Excitations in Mn Complexes. J Phys Chem A 2008; 112:11223-34. [DOI: 10.1021/jp803286c] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Adrian R. Jaszewski
- Department of Chemistry, Faculty of Science, Australian National University, Canberra ACT 0200, Australia
| | - Rob Stranger
- Department of Chemistry, Faculty of Science, Australian National University, Canberra ACT 0200, Australia
| | - Ronald J. Pace
- Department of Chemistry, Faculty of Science, Australian National University, Canberra ACT 0200, Australia
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Smith SR, Bencze KZ, Russ KA, Wasiukanis K, Benore-Parsons M, Stemmler TL. Investigation of the copper binding site and the role of histidine as a ligand in riboflavin binding protein. Inorg Chem 2008; 47:6867-72. [PMID: 18593109 PMCID: PMC2519956 DOI: 10.1021/ic800431b] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Riboflavin Binding Protein (RBP) binds copper in a 1:1 molar ratio, forming a distinct well-ordered type II site. The nature of this site has been examined using X-ray absorption and pulsed electron paramagnetic resonance (EPR) spectroscopies, revealing a four coordinate oxygen/nitrogen rich environment. On the basis of analysis of the Cambridge Structural Database, the average protein bound copper-ligand bond length of 1.96 A, obtained by extended x-ray absorption fine structure (EXAFS), is consistent with four coordinate Cu(I) and Cu(II) models that utilize mixed oxygen and nitrogen ligand distributions. These data suggest a Cu-O 3N coordination state for copper bound to RBP. While pulsed EPR studies including hyperfine sublevel correlation spectroscopy and electron nuclear double resonance show clear spectroscopic evidence for a histidine bound to the copper, inclusion of a histidine in the EXAFS simulation did not lead to any significant improvement in the fit.
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Affiliation(s)
- Sheila R Smith
- Department of Natural Sciences, University of Michigan-Dearborn, Dearborn, Michigan 48101, USA.
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31
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Zaleski CM, Weng TC, Dendrinou-Samara C, Alexiou M, Kanakaraki P, Hsieh WY, Kampf J, Penner-Hahn JE, Pecoraro VL, Kessissoglou DP. Structural and Physical Characterization of Tetranuclear [MnII3MnIV] and [MnII2MnIII2] Valence-Isomer Manganese Complexes. Inorg Chem 2008; 47:6127-36. [DOI: 10.1021/ic702109c] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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32
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Sproviero EM, McEvoy JP, Gascón JA, Brudvig GW, Batista VS. Computational insights into the O2-evolving complex of photosystem II. PHOTOSYNTHESIS RESEARCH 2008; 97:91-114. [PMID: 18483777 PMCID: PMC2728911 DOI: 10.1007/s11120-008-9307-0] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/09/2007] [Accepted: 04/10/2008] [Indexed: 05/04/2023]
Abstract
Mechanistic investigations of the water-splitting reaction of the oxygen-evolving complex (OEC) of photosystem II (PSII) are fundamentally informed by structural studies. Many physical techniques have provided important insights into the OEC structure and function, including X-ray diffraction (XRD) and extended X-ray absorption fine structure (EXAFS) spectroscopy as well as mass spectrometry (MS), electron paramagnetic resonance (EPR) spectroscopy, and Fourier transform infrared spectroscopy applied in conjunction with mutagenesis studies. However, experimental studies have yet to yield consensus as to the exact configuration of the catalytic metal cluster and its ligation scheme. Computational modeling studies, including density functional (DFT) theory combined with quantum mechanics/molecular mechanics (QM/MM) hybrid methods for explicitly including the influence of the surrounding protein, have proposed chemically satisfactory models of the fully ligated OEC within PSII that are maximally consistent with experimental results. The inorganic core of these models is similar to the crystallographic model upon which they were based, but comprises important modifications due to structural refinement, hydration, and proteinaceous ligation which improve agreement with a wide range of experimental data. The computational models are useful for rationalizing spectroscopic and crystallographic results and for building a complete structure-based mechanism of water-splitting in PSII as described by the intermediate oxidation states of the OEC. This review summarizes these recent advances in QM/MM modeling of PSII within the context of recent experimental studies.
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Thampidas VS, Radhakrishnan T, Pike RD. Bis{μ-2,2'-[1,1'-(ethane-1,2-diyldinitrilo)diethyl-idyne]diphenolato}bis-[(benzoato-κO)manganese(III)] dihydrate. Acta Crystallogr Sect E Struct Rep Online 2007; 64:m150-1. [PMID: 21200504 PMCID: PMC2915092 DOI: 10.1107/s160053680706446x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2007] [Accepted: 11/29/2007] [Indexed: 05/30/2023]
Abstract
The title compound, [Mn(2)(C(18)H(18)N(2)O(2))(2)(C(7)H(5)O(2))(2)]·2H(2)O, was synthesized by the reaction between manganese(II) benzoate and the Schiff base generated in situ by the condensation of ethane-1,2-diamine and o-hydroxy-aceto-phen-one. The Jahn-Teller-distorted manganese(III) ions of the centrosymmetric dimer are connected through phen-oxy bridges. Hydrogen-bonding inter-actions between the uncoord-in-ated C=O of the benzoate and uncoordinated water mol-ecules link the dimers into a chain running parallel to the c axis.
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Affiliation(s)
- V. S Thampidas
- Department of Chemistry, SN College, Varkala, Kerala 695 145, India
| | - T. Radhakrishnan
- Department of Chemistry, University of Kerala, Thiruvananthapuram, Kerala 695 581, India
| | - Robert D. Pike
- Department of Chemistry, College of William and Mary, P. O. Box 8795, Williamsburg, VA 23187-8795, USA
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Singh UP, Tyagi P, Upreti S. Manganese complexes as models for manganese-containing pseudocatalase enzymes: Synthesis, structural and catalytic activity studies. Polyhedron 2007. [DOI: 10.1016/j.poly.2007.03.049] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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35
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Collomb MN, Mantel C, Romain S, Duboc C, Leprêtre JC, Pécaut J, Deronzier A. Redox-Induced μ-Acetato and μ-Oxo Core Interconversions in Dinuclear Manganese Tris(2-methylpyridyl)amine (tpa) Complexes: Isolation and Characterization of [Mn2III(μ-O)(μ-O2CCH3)(tpa)2]3+. Eur J Inorg Chem 2007. [DOI: 10.1002/ejic.200601089] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
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Dubois L, Jacquamet L, Pécaut J, Latour JM. X-ray photoreduction of a di(mu-oxo)Mn(III)Mn(IV) complex occurs at temperatures as low as 20 K. Chem Commun (Camb) 2007:4521-3. [PMID: 17283805 DOI: 10.1039/b609072a] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Full reduction of the Mn(III)(mu-O)2Mn(IV) core to Mn(II)(mu-OH2)2Mn(II) is observed upon irradiation by an X-ray beam at ca. 20 K.
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Affiliation(s)
- Lionel Dubois
- Laboratoire DRDCIPMB, UMR 5155 CEA-CNRS- UJF, CEA-Grenoble, 38054 Grenoble Cedex 9, France
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Lieberman RL, Kondapalli KC, Shrestha DB, Hakemian AS, Smith SM, Telser J, Kuzelka J, Gupta R, Borovik AS, Lippard SJ, Hoffman BM, Rosenzweig AC, Stemmler TL. Characterization of the particulate methane monooxygenase metal centers in multiple redox states by X-ray absorption spectroscopy. Inorg Chem 2006; 45:8372-81. [PMID: 16999437 PMCID: PMC2864602 DOI: 10.1021/ic060739v] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The integral membrane enzyme particulate methane monooxygenase (pMMO) converts methane, the most inert hydrocarbon, to methanol under ambient conditions. The 2.8-A resolution pMMO crystal structure revealed three metal sites: a mononuclear copper center, a dinuclear copper center, and a nonphysiological mononuclear zinc center. Although not found in the crystal structure, solution samples of pMMO also contain iron. We have used X-ray absorption spectroscopy to analyze the oxidation states and coordination environments of the pMMO metal centers in as-isolated (pMMO(iso)), chemically reduced (pMMO(red)), and chemically oxidized (pMMO(ox)) samples. X-ray absorption near-edge spectra (XANES) indicate that pMMO(iso) contains both Cu(I) and Cu(II) and that the pMMO Cu centers can undergo redox chemistry. Extended X-ray absorption fine structure (EXAFS) analysis reveals a Cu-Cu interaction in all redox forms of the enzyme. The Cu-Cu distance increases from 2.51 to 2.65 A upon reduction, concomitant with an increase in the average Cu-O/N bond lengths. Appropriate Cu2 model complexes were used to refine and validate the EXAFS fitting protocols for pMMO(iso). Analysis of Fe EXAFS data combined with electron paramagnetic resonance (EPR) spectra indicates that Fe, present as Fe(III), is consistent with heme impurities. These findings are complementary to the crystallographic data and provide new insight into the oxidation states and possible electronic structures of the pMMO Cu ions.
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Cook JD, Bencze KZ, Jankovic AD, Crater AK, Busch CN, Bradley PB, Stemmler AJ, Spaller MR, Stemmler TL. Monomeric yeast frataxin is an iron-binding protein. Biochemistry 2006; 45:7767-77. [PMID: 16784228 PMCID: PMC2518068 DOI: 10.1021/bi060424r] [Citation(s) in RCA: 104] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Friedreich's ataxia, an autosomal cardio- and neurodegenerative disorder that affects 1 in 50,000 humans, is caused by decreased levels of the protein frataxin. Although frataxin is nuclear-encoded, it is targeted to the mitochondrial matrix and necessary for proper regulation of cellular iron homeostasis. Frataxin is required for the cellular production of both heme and iron-sulfur (Fe-S) clusters. Monomeric frataxin binds with high affinity to ferrochelatase, the enzyme involved in iron insertion into porphyrin during heme production. Monomeric frataxin also binds to Isu, the scaffold protein required for assembly of Fe-S cluster intermediates. These processes (heme and Fe-S cluster assembly) share requirements for iron, suggesting that monomeric frataxin might function as the common iron donor. To provide a molecular basis to better understand frataxin's function, we have characterized the binding properties and metal-site structure of ferrous iron bound to monomeric yeast frataxin. Yeast frataxin is stable as an iron-loaded monomer, and the protein can bind two ferrous iron atoms with micromolar binding affinity. Frataxin amino acids affected by the presence of iron are localized within conserved acidic patches located on the surfaces of both helix-1 and strand-1. Under anaerobic conditions, bound metal is stable in the high-spin ferrous state. The metal-ligand coordination geometry of both metal-binding sites is consistent with a six-coordinate iron-(oxygen/nitrogen) based ligand geometry, surely constructed in part from carboxylate and possibly imidazole side chains coming from residues within these conserved acidic patches on the protein. On the basis of our results, we have developed a model for how we believe yeast frataxin interacts with iron.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Timothy L. Stemmler
- To whom correspondence should be sent: Department of Biochemistry and Molecular Biology, Wayne State University, School of Medicine, 540 E. Canfield Ave., Detroit, MI 48201. Telephone: 313−577−5712, Fax: 313−577−2765, E-mail:
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Hakemian AS, Tinberg CE, Kondapalli KC, Telser J, Hoffman BM, Stemmler TL, Rosenzweig AC. The copper chelator methanobactin from Methylosinus trichosporium OB3b binds copper(I). J Am Chem Soc 2006; 127:17142-3. [PMID: 16332035 PMCID: PMC2864604 DOI: 10.1021/ja0558140] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The oxidation state of copper bound to methanobactin, a small siderophore-like molecule from the methanotroph Methylosinus trichosporium OB3b, was investigated. Purified methanobactin loaded with Cu(II) exhibits a weak EPR signal probably due to adventitious Cu(II). The EPR signal intensity increases significantly upon addition of the strong oxidant nitric acid. Features of the X-ray absorption near edge spectrum, including a 1s --> 4p transition at 8985 eV, further indicate the presence of Cu(I). EXAFS data were best fit using a multiple scattering model generated from previously reported crystallographic parameters. These results establish definitively that M. trichosporium OB3b methanobactin binds Cu(I) and suggest that methanobactin itself reduces Cu(II) to Cu(I).
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Teutloff C, Schäfer KO, Sinnecker S, Barynin V, Bittl R, Wieghardt K, Lendzian F, Lubitz W. High-field EPR investigations of Mn(III)Mn(IV) and Mn(II)Mn(III) states of dimanganese catalase and related model systems. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2005; 43 Spec no.:S51-64. [PMID: 16235205 DOI: 10.1002/mrc.1685] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Multi-frequency EPR experiments at 9, 34 and 94 GHz are reported on the antiferromagnetically coupled mixed valence Mn(II)Mn(III) complex of manganese catalase and on several dinuclear manganese model systems. They are compared with similar experiments obtained earlier for the Mn(III)Mn(IV) states. It is demonstrated how accurate information on the G- and 55Mn hyperfine tensors can be derived from this approach. Furthermore, the effect of oxidation state, planarity of the manganese-oxygen core and the type of ligands bridging the manganese ions on the magnetic resonance parameters and the related electronic structure is investigated. 'Broken-symmetry' density functional calculations on two Mn(III)Mn(IV) complexes, including the superoxidized state of the catalase, are presented. The agreement between calculated and experimental EPR parameters and complex geometries is remarkably good. Implications of these results for the structure and function of the dimanganese catalase are discussed.
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Affiliation(s)
- Christian Teutloff
- Max-Volmer-Laboratory, Institute for Chemistry, PC 14, Technical University Berlin, D-10623 Berlin, Germany
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Sinnecker S, Neese F, Lubitz W. Dimanganese catalase--spectroscopic parameters from broken-symmetry density functional theory of the superoxidized Mn(III)/Mn(IV) state. J Biol Inorg Chem 2005; 10:231-8. [PMID: 15830216 DOI: 10.1007/s00775-005-0633-9] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2004] [Accepted: 02/15/2005] [Indexed: 11/24/2022]
Abstract
Broken-symmetry density functional theory was used to study the catalytic center of manganese catalase in the superoxidized Mn(III)/Mn(IV) state. Heisenberg exchange coupling constants, 55Mn and 14N hyperfine coupling constants (hfcs) and nuclear quadrupole splittings, as well as the electronic g tensors were evaluated for different model systems of the active site after complete geometry optimizations in the high-spin and broken-symmetry states. A comparison of the experimental data with the spectroscopic parameters computed for the models with unprotonated and protonated mu-oxo bridges shows best agreement between theory and experiment for a Mn2(mu-O)2(mu-OAc) core. The calculated Mn-Mn distances and 55Mn hfcs clearly support a dimanganese cluster with unprotonated mu-oxo bridges in the superoxidized state. Furthermore, it is shown that an interchange of the Mn(III) and Mn(IV) oxidation states in this trapped valence system leads to specific changes in the molecular and electronic structure of the manganese clusters.
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Affiliation(s)
- Sebastian Sinnecker
- Max-Planck-Institut für Bioanorganische Chemie, Stiftstrasse 34-36, Mülheim an der Ruhr, 45470, Germany
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Fernández G, Corbella M, Alfonso M, Stoeckli-Evans H, Castro I. A Comparative XAS and X-ray Diffraction Study of New Binuclear Mn(III) Complexes with Catalase Activity. Indirect Effect of the Counteranion on Magnetic Properties. Inorg Chem 2004; 43:6684-98. [PMID: 15476368 DOI: 10.1021/ic0348897] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Four new binuclear Mn(III) complexes with carboxylate bridges have been synthesized: [[Mn(nn)(H(2)O)](2)(mu-ClCH(2)COO)(2)(mu-O)](ClO(4))(2) with nn = bpy (1) or phen (2) and [[Mn(bpy)(H(2)O)](2)(mu-RCOO)(2)(mu-O)](NO(3))(2) with RCOO = ClCH(2)COO (3) or CH(3)COO (4). The characterization by X-ray diffraction (1 and 3) and X-ray absorption spectroscopy (XAS) (1-4) displays the relevance of this spectroscopy to the elucidation of the structural environment of the manganese ions in this kind of compound. Magnetic susceptibility data show an antiferromagnetic coupling for all the compounds: J = -2.89 cm(-1) (for 1), -8.16 cm(-1) (for 2), -0.68 cm(-1) (for 3), and -2.34 cm(-1) (for 4). Compounds 1 and 3 have the same cation complex [[Mn(bpy)(H(2)O)](2)(mu-ClCH(2)COO)(2)(mu-O)](2+), but, while 1 shows an antiferromagnetic coupling, for 3 the magnetic interaction between Mn(III) ions is very weak. The four compounds show catalase activity, and when the reaction stopped, Mn(II) compounds with different nuclearity could be obtained: binuclear [[Mn(phen)(2)](mu-ClCH(2)COO)(2)](ClO(4))(2), trinuclear [Mn(3)(bpy)(2)(mu-ClCH(2)COO)(6)], or mononuclear complexes without carboxylate. Two Mn(II) compounds without carboxylate have been characterized by X-ray diffraction: [Mn(NO(3))(2)(bpy)(2)][Mn(NO(3))(bpy)(2)(H(2)O)]NO(3) (5) and [Mn(bpy)(3)](ClO(4))(2).0.5 C(6)H(4)-1,2-(COOEt)(2).0.5H(2)O (8).
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Affiliation(s)
- Gema Fernández
- Departament de Química Inorgànica, Facultat de Química, Universitat de Barcelona, Martí i Franquès 1-11, 08028-Barcelona, Spain
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Wu AJ, Penner-Hahn JE, Pecoraro VL. Structural, spectroscopic, and reactivity models for the manganese catalases. Chem Rev 2004; 104:903-38. [PMID: 14871145 DOI: 10.1021/cr020627v] [Citation(s) in RCA: 404] [Impact Index Per Article: 20.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Amy J Wu
- Willard H Dow Laboratories, Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109-1055, USA
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Abstract
Ab initio density functional theory (DFT) methods were used to investigate the structural features of the active site of the binuclear enzyme rat liver arginase. Special emphasis was placed on the crucial role of the second shell ligand interactions. These interactions were systematically studied by performing calculations on models of varying size. It was determined that a water molecule, and not hydroxide, is the bridging exogenous ligand. The carboxylate ligands facilitate the close approach of the Mn (II) ions by attenuating the metal-metal electrostatic repulsion. Of the two metals, Mn(A) was shown to carry a larger positive charge. Analysis of the electronic properties of the active site revealed that orbitals involving the terminal Asp234 residue, as well as the flexible micro-1,1 bridging Asp232, lie at high energies, suggesting weaker coordination. This is reflected in certain structural variability present in our models and is also consistent with recent experimental findings. Finally, implications of our findings for the biological function of the enzyme are delineated.
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Affiliation(s)
- Ivaylo Ivanov
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
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Golombek AP, Hendrich MP. Quantitative analysis of dinuclear manganese(II) EPR spectra. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2003; 165:33-48. [PMID: 14568515 DOI: 10.1016/j.jmr.2003.07.001] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
A quantitative method for the analysis of EPR spectra from dinuclear Mn(II) complexes is presented. The complex [(Me(3)TACN)(2)Mn(II)(2)(mu-OAc)(3)]BPh(4) (1) (Me(3)TACN=N, N('),N(")-trimethyl-1,4,7-triazacyclononane; OAc=acetate(1-); BPh(4)=tetraphenylborate(1-)) was studied with EPR spectroscopy at X- and Q-band frequencies, for both perpendicular and parallel polarizations of the microwave field, and with variable temperature (2-50K). Complex 1 is an antiferromagnetically coupled dimer which shows signals from all excited spin manifolds, S=1 to 5. The spectra were simulated with diagonalization of the full spin Hamiltonian which includes the Zeeman and zero-field splittings of the individual manganese sites within the dimer, the exchange and dipolar coupling between the two manganese sites of the dimer, and the nuclear hyperfine coupling for each manganese ion. All possible transitions for all spin manifolds were simulated, with the intensities determined from the calculated probability of each transition. In addition, the non-uniform broadening of all resonances was quantitatively predicted using a lineshape model based on D- and r-strain. As the temperature is increased from 2K, an 11-line hyperfine pattern characteristic of dinuclear Mn(II) is first observed from the S=3 manifold. D- and r-strain are the dominate broadening effects that determine where the hyperfine pattern will be resolved. A single unique parameter set was found to simulate all spectra arising for all temperatures, microwave frequencies, and microwave modes. The simulations are quantitative, allowing for the first time the determination of species concentrations directly from EPR spectra. Thus, this work describes the first method for the quantitative characterization of EPR spectra of dinuclear manganese centers in model complexes and proteins. The exchange coupling parameter J for complex 1 was determined (J=-1.5+/-0.3 cm(-1); H(ex)=-2JS(1).S(2)) and found to be in agreement with a previous determination from magnetization. The phenomenon of exchange striction was found to be insignificant for 1.
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Affiliation(s)
- Adina P Golombek
- Department of Chemistry, Carnegie Mellon University, 4400 Fifth Ave., Pittsburgh, PA 15213, USA
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Pierce BS, Elgren TE, Hendrich MP. Mechanistic implications for the formation of the diiron cluster in ribonucleotide reductase provided by quantitative EPR spectroscopy. J Am Chem Soc 2003; 125:8748-59. [PMID: 12862469 DOI: 10.1021/ja021290h] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The small subunit of Escherichia coli ribonucleotide reductase (R2) is a homodimeric (betabeta) protein, in which each beta-peptide contains a diiron cluster composed of two inequivalent iron sites. R2 is capable of reductively activating O(2) to produce a stable tyrosine radical (Y122*), which is essential for production of deoxyribonucleotides on the larger R1 subunit. In this work, the paramagnetic Mn(II) ion is used as a spectroscopic probe to characterize the assembly of the R2 site with EPR spectroscopy. Upon titration of Mn(II) into samples of apoR2, we have been able to quantitatively follow three species (aquaMn(II), mononuclear Mn(II)R2, and dinuclear Mn(2)(II)R2) and fit each to a sequential two binding site model. As previously observed for Fe(II) binding within apoR2, one of the sites has a greater binding affinity relative to the other, K(1) = (5.5 +/- 1.1) x 10(5) M(-)(1) and K(2) = (3.9 +/- 0.6) x 10(4) M(-)(1), which are assigned to the B and A sites, respectively. In multiple titrations, only one dinuclear Mn(2)(II)R2 site was created per homodimer of R2, indicating that only one of the two beta-peptides of R2 is capable of binding Mn(II) following addition of Mn(II) to apoR2. Under anaerobic conditions, addition of only 2 equiv of Fe(II) to R2 (Fe(2)(II)R2) completely prevented the formation of any bound MnR2 species. Upon reaction of this sample with O(2) in the presence of Mn(II), both Y122* and Mn(2)(II)R2 were produced in equal amounts. Previous stopped-flow absorption spectroscopy studies have indicated that apoR2 undergoes a protein conformational change upon binding of metal (Tong et al. J. Am. Chem. Soc. 1996, 118, 2107-2108). On the basis of these observations, we propose a model for R2 metal incorporation that invokes an allosteric interaction between the two beta-peptides of R2. Upon binding the first equiv of metal to a beta-peptide (beta(I)), the aforementioned protein conformational change prevents metal binding in the adjacent beta-peptide (beta(II)) approximately 25 A away. Furthermore, we show that metal incorporation into beta(II) occurs only during the O(2) activation chemistry of the beta(I)-peptide. This is the first direct evidence of an allosteric interaction between the two beta-peptides of R2. Furthermore, this model can explain the generally observed low Fe occupancy of R2. We also demonstrate that metal uptake and this newly observed allosteric effect are buffer dependent. Higher levels of glycerol cause loss of the allosteric effect. Reductive cycling of samples in the presence of Mn(II) produced a novel mixed metal Fe(III)Mn(III)R2 species within the active site of R2. The magnitude of the exchange coupling (J) determined for both the Mn(2)(II)R2 and Fe(III)Mn(III)R2 species was determined to be -1.8 +/- 0.3 and -18 +/- 3 cm(-)(1), respectively. Quantitative spectral simulations for the Fe(III)Mn(III)R2 and mononuclear Mn(II)R2 species are provided. This work represents the first instance where both X- and Q-band simulations of perpendicular and parallel mode spectra were used to quantitatively predict the concentration of a protein bound mononuclear Mn(II) species.
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Affiliation(s)
- Brad S Pierce
- Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA
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Ashur I, Brandis A, Greenwald M, Vakrat-Haglili Y, Rosenbach-Belkin V, Scheer H, Scherz A. Control of redox transitions and oxygen species binding in Mn centers by biologically significant ligands; model studies with [Mn]-bacteriochlorophyll a. J Am Chem Soc 2003; 125:8852-61. [PMID: 12862482 DOI: 10.1021/ja030170m] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Mn-superoxide dismutase (Mn-SOD), which protects the cell from the toxic potential of superoxide radicals (O(2)(-*)), is the only type of SOD which resides in eukaryotic mitochondria. Up-to-date, the exact catalytic mechanism of the enzyme and the relationship between substrate moieties and the ligands within the active site microenvironment are still not resolved. Here, we set out to explore the possible involvement of hydroperoxyl radicals ((*)OOH) in the catalytic dismutaion by following the interplay of Mn(III)/Mn(II) redox transitions, ligands binding, and evolution or consumption of superoxide radical, using a new model system. The model system encompassed an Mn atom chelated by a bacteriochlorophyll allomer macrocycle (BChl) in aerated aprotic media that contain residual water. The redox states of the Mn ion were monitored by the Q(y) electronic transitions at 774 and 825 nm for [Mn(II)]- and [Mn(III)]-BChl, respectively (Geskes, C.; Hartwich, G.; Scheer, H.; Mantele, W.; Heinze, J. J. Am. Chem. Soc. 1995, 117, 7776) and confirmed by electron spin resonance spectroscopy. Evolution of (*)OOH radicals was monitored by the ESR spin-trap technique using 5,5-dimethyl-1-pyrroline-N-oxide (DMPO). The experimental data suggest that the [Mn]-BChl forms a (HO(-))[Mn(III)]-BChl(OOH) complex upon solvation. Spectrophotometeric titrations with tetrabutylamonnium acetate (TBAA) and 1-methylimidazole (1-MeIm) together with ESI-MS measurements indicated the formation of a 1:1 complex with [Mn]-BChl for both ligands. The coordination of ligands at low concentrations to [Mn(III)]-BChl induced a release of a (*)OOH radical and a [Mn(III)]-BChl --> [Mn(II)]-BChl transition at higher concentrations. The estimated equilibrium constants for the total redox reaction ( )()are 1.9 x 10(4) +/- 1 x 10(3) M(-)(1) and 12.3 +/- 0.6 M(-)(1) for TBAA and 1-MeIm, respectively. The profound difference between the equilibrium constants agrees with the suggested key role of the ligand's basicity in the process. A direct interaction of superoxide radicals with [Mn(III)]-BChl in a KO(2) acetonitrile (AN) solution also resulted in [Mn(III)]-BChl --> [Mn(II)]-BChl transition. Cumulatively, our data show that the Mn(III) center encourages the protonation of the O(2)(-)(*) radical in an aprotic environment containing residual water molecules, while promoting its oxidation in the presence of basic ligands. Similar coordination and stabilization of the (*)OOH radical by the Mn center may be key steps in the enzymatic dismutation of superoxide radicals by Mn-SOD.
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Affiliation(s)
- Idan Ashur
- Department of Plant Sciences, The Weizmann Institute of Science, 76100 Rehovot, Israel and Botanisches Institut der Universität, D-80638 München, Germany
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Kehres DG, Maguire ME. Emerging themes in manganese transport, biochemistry and pathogenesis in bacteria. FEMS Microbiol Rev 2003; 27:263-90. [PMID: 12829271 DOI: 10.1016/s0168-6445(03)00052-4] [Citation(s) in RCA: 206] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022] Open
Abstract
Though an essential trace element, manganese is generally accorded little importance in biology other than as a cofactor for some free radical detoxifying enzymes and in the photosynthetic photosystem II. Only a handful of other Mn2+-dependent enzymes are known. Recent data, primarily in bacteria, suggest that Mn2+-dependent processes may have significantly greater physiological importance. Two major classes of prokaryotic Mn2+ uptake systems have now been described, one homologous to eukaryotic Nramp transporters and one a member of the ABC-type ATPase superfamily. Each is highly selective for Mn2+ over Fe2+ or other transition metal divalent cations, and each can accumulate millimolar amounts of intracellular Mn2+ even when environmental Mn2+ is scarce. In Salmonella enterica serovar Typhimurium, simultaneous mutation of both types of transporter results in avirulence, implying that one or more Mn2+-dependent enzymes is essential for pathogenesis. This review summarizes current literature on Mn2+ transport, primarily in the Bacteria but with relevant comparisons to the Archaea and Eukaryota. Mn2+-dependent enzymes are then discussed along with some speculations as to their role(s) in cellular physiology, again primarily in Bacteria. It is of particular interest that most of the enzymes which interconvert phosphoglycerate, pyruvate, and oxaloacetate intermediates are either strictly Mn2+-dependent or highly stimulated by Mn2+. This suggests that Mn2+ may play an important role in central carbon metabolism. Further studies will be required, however, to determine whether these or other actions of Mn2+ within the cell are the relevant factors in pathogenesis.
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Affiliation(s)
- David G Kehres
- Department of Pharmacology, School of Medicine, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106-4965, USA.
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Fernández G, Corbella M, Mahía J, Maestro M. Polynuclear MnII Complexes with Chloroacetate Bridge − Syntheses, Structure, and Magnetic Properties. Eur J Inorg Chem 2002. [DOI: 10.1002/1099-0682(200209)2002:9<2502::aid-ejic2502>3.0.co;2-v] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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