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Ghiladi RA, Rheingold AL, Siegler MA, Karlin KD. Synthesis and Characterization of New Trinuclear Copper Complexes. Inorganica Chim Acta 2012; 389:131-137. [PMID: 22773847 DOI: 10.1016/j.ica.2012.02.020] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
This report describes our approach towards modelling the copper cluster active sites of nitrous oxide reductase and the multicopper oxidases/oxygenases. We have synthesized two mesitylene-based trinucleating ligands, MesPY1 and MesPY2, which employ bis(2-picolyl)amine (PY1) and bis(2-pyridylethyl)amine (PY2) tridentate copper chelates, respectively. Addition of cuprous salts to these ligands leads to the isolation of tricopper(I) complexes [(Mes-PY1)Cu(I) (3)(CH(3)CN)(3)](ClO(4))(3)·0.25Et(2)O (1) and [(Mes-PY2)Cu(I) (3)](PF(6))(3) (3) Each of the three copper centers in 1 is most likely four-coordinate, with ligated acetonitrile as the fourth ligand; by contrast, the copper centers in 3 are three-coordinate, as determined by X-ray crystallography The synthesis of [(Mes-PY1)Cu(II) (3)(CH(3)CN)(2)(CH(3)OH)(2)](ClO(4))(6)·(CH(3)OH) (2) was accomplished by addition of three equivalents of the copper(II) salt, Cu(ClO(4))(2)·6H(2)O, to the ligand. The structure of 2 shows that two of the copper centers are tetracoordinate (with MeCN solvent ligation), but have additional weak axial (fifth ligand) interactions with the perchlorate anions; the third copper is unique in that it is coordinated by two MeOH solvent molecules, making it overall five-coordinate. For complexes 2 and 3, one copper ion center is located on the opposite side of the mesitylene plane as the other two. These observations, although in the solid state, must be taken into account for future studies where intramolecular tricopper(I)/O(2) (or other small molecules of interest) interactions in solution are desirable.
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Affiliation(s)
- Reza A Ghiladi
- Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218, USA
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2
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Doan PE, Telser J, Barney BM, Igarashi RY, Dean DR, Seefeldt LC, Hoffman BM. 57Fe ENDOR spectroscopy and 'electron inventory' analysis of the nitrogenase E4 intermediate suggest the metal-ion core of FeMo-cofactor cycles through only one redox couple. J Am Chem Soc 2011; 133:17329-40. [PMID: 21980917 DOI: 10.1021/ja205304t] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
N(2) binds to the active-site metal cluster in the nitrogenase MoFe protein, the FeMo-cofactor ([7Fe-9S-Mo-homocitrate-X]; FeMo-co) only after the MoFe protein has accumulated three or four electrons/protons (E(3) or E(4) states), with the E(4) state being optimally activated. Here we study the FeMo-co (57)Fe atoms of E(4) trapped with the α-70(Val→Ile) MoFe protein variant through use of advanced ENDOR methods: 'random-hop' Davies pulsed 35 GHz ENDOR; difference triple resonance; the recently developed Pulse-Endor-SaTuration and REcovery (PESTRE) protocol for determining hyperfine-coupling signs; and Raw-DATA (RD)-PESTRE, a PESTRE variant that gives a continuous sign readout over a selected radiofrequency range. These methods have allowed experimental determination of the signed isotropic (57)Fe hyperfine couplings for five of the seven iron sites of the reductively activated E(4) FeMo-co, and given the magnitude of the coupling for a sixth. When supplemented by the use of sum-rules developed to describe electron-spin coupling in FeS proteins, these (57)Fe measurements yield both the magnitude and signs of the isotropic couplings for the complete set of seven Fe sites of FeMo-co in E(4). In light of the previous findings that FeMo-co of E(4) binds two hydrides in the form of (Fe-(μ-H(-))-Fe) fragments, and that molybdenum has not become reduced, an 'electron inventory' analysis assigns the formal redox level of FeMo-co metal ions in E(4) to that of the resting state (M(N)), with the four accumulated electrons residing on the two Fe-bound hydrides. Comparisons with earlier (57)Fe ENDOR studies and electron inventory analyses of the bio-organometallic intermediate formed during the reduction of alkynes and the CO-inhibited forms of nitrogenase (hi-CO and lo-CO) inspire the conjecture that throughout the eight-electron reduction of N(2) plus 2H(+) to two NH(3) plus H(2), the inorganic core of FeMo-co cycles through only a single redox couple connecting two formal redox levels: those associated with the resting state, M(N), and with the one-electron reduced state, M(R). We further note that this conjecture might apply to other complex FeS enzymes.
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Affiliation(s)
- Peter E Doan
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, USA
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3
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Gupta V, Sendra M, Naik SG, Chahal HK, Huynh BH, Outten FW, Fontecave M, Ollagnier de Choudens S. Native Escherichia coli SufA, coexpressed with SufBCDSE, purifies as a [2Fe-2S] protein and acts as an Fe-S transporter to Fe-S target enzymes. J Am Chem Soc 2009; 131:6149-53. [PMID: 19366265 DOI: 10.1021/ja807551e] [Citation(s) in RCA: 79] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Iron-sulfur (Fe-S) clusters are versatile biological cofactors that require biosynthetic systems in vivo to be assembled. In Escherichia coli, the Isc (iscRSUA-hscBA-fdx-iscX) and Suf (sufABCDSE) pathways fulfill this function. Despite extensive biochemical and genetic analysis of these two pathways, the physiological function of the A-type proteins of each pathway (IscA and SufA) is still unclear. Studies conducted in vitro suggest two possible functions for A-type proteins, as Fe-S scaffold/transfer proteins or as iron donors during cluster assembly. To resolve this issue, SufA was coexpressed in vivo with its cognate partner proteins from the suf operon, SufBCDSE. Native SufA purified anaerobically using this approach was unambiguously demonstrated to be a [2Fe-2S] protein by biochemical analysis and UV-vis, Mossbauer, resonance Raman, and EPR spectroscopy. Furthermore, native [2Fe-2S] SufA can transfer its Fe-S cluster to both [2Fe-2S] and [4Fe-4S] apoproteins. These results clearly show that A-type proteins form Fe-S clusters in vivo and are competent to function as Fe-S transfer proteins as purified. This study resolves the contradictory results from previous in vitro studies and demonstrates the critical importance of providing in vivo partner proteins during protein overexpression to allow correct biochemical maturation of metalloproteins.
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Affiliation(s)
- Vibha Gupta
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208, USA
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4
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Ranquet C, Ollagnier-de-Choudens S, Loiseau L, Barras F, Fontecave M. Cobalt stress in Escherichia coli. The effect on the iron-sulfur proteins. J Biol Chem 2007; 282:30442-51. [PMID: 17642475 DOI: 10.1074/jbc.m702519200] [Citation(s) in RCA: 127] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Cobalt is toxic for cells, but mechanisms of this toxicity are largely unknown. The biochemical and genetic experiments reported here demonstrate that iron-sulfur proteins are greatly affected in cobalt-treated Escherichia coli cells. Exposure of a wild-type strain to intracellular cobalt results in the inactivation of three selected iron-sulfur enzymes, the tRNA methylthio-transferase, aconitase, and ferrichrome reductase. Consistently, mutant strains lacking the [Fe-S] cluster assembly SUF machinery are hypersensitive to cobalt. Last, expression of iron uptake genes is increased in cells treated with cobalt. In vitro studies demonstrated that cobalt does not react directly with fully assembled [Fe-S] clusters. In contrast, it reacts with labile ones present in scaffold proteins (IscU, SufA) involved in iron-sulfur cluster biosynthesis. We propose a model wherein cobalt competes out iron during synthesis of [Fe-S] clusters in metabolically essential proteins.
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Affiliation(s)
- Caroline Ranquet
- Laboratoire de Chimie et Biologie des Métaux, iRTSV/LCBM, Commissariat à l'Energie Atomique/CNRS/Université Joseph Fourier, CEA-Grenoble, UMR 5249, 17 Avenue des Martyrs, 38054 Grenoble Cedex 09, France
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5
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Venkateswara Rao P, Holm RH. Synthetic Analogues of the Active Sites of Iron−Sulfur Proteins. Chem Rev 2004; 104:527-59. [PMID: 14871134 DOI: 10.1021/cr020615+] [Citation(s) in RCA: 412] [Impact Index Per Article: 20.6] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- P Venkateswara Rao
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, USA
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6
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Iwasaki T, Watanabe E, Ohmori D, Imai T, Urushiyama A, Akiyama M, Hayashi-Iwasaki Y, Cosper NJ, Scott RA. Spectroscopic investigation of selective cluster conversion of archaeal zinc-containing ferredoxin from Sulfolobus sp. strain 7. J Biol Chem 2000; 275:25391-401. [PMID: 10827091 DOI: 10.1074/jbc.m909243199] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Archaeal zinc-containing ferredoxin from Sulfolobus sp. strain 7 contains one [3Fe-4S] cluster (cluster I), one [4Fe-4S] cluster (cluster II), and one isolated zinc center. Oxidative degradation of this ferredoxin led to the formation of a stable intermediate with 1 zinc and approximately 6 iron atoms. The metal centers of this intermediate were analyzed by electron paramagnetic resonance (EPR), low temperature resonance Raman, x-ray absorption, and (1)H NMR spectroscopies. The spectroscopic data suggest that (i) cluster II was selectively converted to a cubane [3Fe-4S](1+) cluster in the intermediate, without forming a stable radical species, and that (ii) the local metric environments of cluster I and the isolated zinc site did not change significantly in the intermediate. It is concluded that the initial step of oxidative degradation of the archaeal zinc-containing ferredoxin is selective conversion of cluster II, generating a novel intermediate containing two [3Fe-4S] clusters and an isolated zinc center. At this stage, significant structural rearrangement of the protein does not occur. We propose a new scheme for oxidative degradation of dicluster ferredoxins in which each cluster converts in a stepwise manner, prior to apoprotein formation, and discuss its structural and evolutionary implications.
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Affiliation(s)
- T Iwasaki
- Department of Biochemistry and Molecular Biology, Nippon Medical School, Sendagi, Tokyo, Japan. iwasaki/
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7
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Telser J, Lee HI, Hoffman BM. Investigation of exchange couplings in [Fe3S4]+ clusters by electron spin-lattice relaxation. J Biol Inorg Chem 2000; 5:369-80. [PMID: 10907748 DOI: 10.1007/pl00010666] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
We have studied four proteins containing oxidized 3Fe clusters ([Fe3S4]+, S=1/2, composed of three, antiferromagnetically coupled high-spin ferric ions) by continuous wave (CW) and pulsed EPR techniques: Azotobacter vinelandii ferredoxin I, Desulfovibrio gigas ferredoxin II, and the 3Fe forms of Pyrococcus furiosus ferredoxin and aconitase. The 35 GHz (Q-band) CW EPR signals are simulated to yield experimental g tensors, which either had not been reported, or had been reported only at X-band microwave frequency. Pulsed X- and Q-band EPR techniques are used to determine electron spin-lattice (T1, longitudinal) relaxation times at several positions on the samples' EPR envelope over the temperature range 2-4.2 K. The T1, values vary sharply across the EPR envelope, a reflection of the fact that the envelope results from a distribution in cluster properties, as seen earlier as a distribution in g3 values and in 57 Fe hyperfine interactions, as detected by electron nuclear double resonance spectroscopy. The temperature dependence of 1/T1 is analyzed in terms of the Orbach mechanism, with relaxation dominated by resonant two-phonon transitions to a doublet excited state at approximately 20 cm(-1) above the doublet ground state for all four of these 3Fe proteins. The experimental EPR data are combined with previously reported 57Fe hyperfine data to determine electronic spin exchange-coupling within the clusters, following the model of Kent et al. Their model defines the coupling parameters as follows: J13=J, J12=J(1+epsilon'), J23=J(1+epsilon), where Jij is the isotropic exchange coupling between ferric ions i and j, and epsilon' and epsilon' are measures of coupling inequivalence. We have extended their theory to include the effects of epsilon' not equal to 0 and thus derived an exact expression for the energy of the doublet excited state for any epsilon, epsilon'. This excited state energy corresponds roughly to epsilonJ and is in the range 5-10 cm(-1) for each of these four 3Fe proteins. This magnitude of the product epsilonJ, determined by our time-domain relaxation studies in the temperature range 2-4 K, is the same as that obtained from three other distinct types of study: CW EPR studies of spin relaxation in the range 5.5-50 K, NMR studies in the range 293-303 K, and static susceptibility measurements in the range 1.8-200 K. We suggest that an apparent disagreement as to the individual values of J and epsilon be resolved in favor of the values obtained by susceptibility and NMR (J > or approximately 200 cm(-1) and epsilon> or =0.02 cm(-1)). as opposed to a smaller J and larger r as suggested in CW EPR studies. However, we note that this resolution casts doubt on the accepted theoretical model for describing the distribution in magnetic properties of 3Fe clusters.
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Affiliation(s)
- J Telser
- Department of Chemistry, Northwestern University, Evanston, IL 60208-3113, USA
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8
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Lloyd SJ, Lauble H, Prasad GS, Stout CD. The mechanism of aconitase: 1.8 A resolution crystal structure of the S642a:citrate complex. Protein Sci 1999; 8:2655-62. [PMID: 10631981 PMCID: PMC2144235 DOI: 10.1110/ps.8.12.2655] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
The crystal structure of the S642A mutant of mitochondrial aconitase (mAc) with citrate bound has been determined at 1.8 A resolution and 100 K to capture this binding mode of substrates to the native enzyme. The 2.0 A resolution, 100 K crystal structure of the S642A mutant with isocitrate binding provides a control, showing that the Ser --> Ala replacement does not alter the binding of substrates in the active site. The aconitase mechanism requires that the intermediate product, cis-aconitate, flip over by 180 degrees about the C alpha-C beta double bond. Only one of these two alternative modes of binding, that of the isocitrate mode, has been previously visualized. Now, however, the structure revealing the citrate mode of binding provides direct support for the proposed enzyme mechanism.
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Affiliation(s)
- S J Lloyd
- Department of Molecular Biology, The Scripps Research Institute, La Jolla, California 92037, USA
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9
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Simple and Complex Iron-Sulfur Proteins in Sulfate Reducing Bacteria. ADVANCES IN INORGANIC CHEMISTRY 1999. [DOI: 10.1016/s0898-8838(08)60083-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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10
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Aono S, Nakajima H, Saito K. Site-directed mutagenesis of cysteine to serine in a superoxide responsive transcriptional regulator SoxR. ACTA ACUST UNITED AC 1998. [DOI: 10.1016/s1381-1177(98)00004-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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11
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12
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Lauble H, Kennedy MC, Emptage MH, Beinert H, Stout CD. The reaction of fluorocitrate with aconitase and the crystal structure of the enzyme-inhibitor complex. Proc Natl Acad Sci U S A 1996; 93:13699-703. [PMID: 8942997 PMCID: PMC19395 DOI: 10.1073/pnas.93.24.13699] [Citation(s) in RCA: 80] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/03/1996] [Indexed: 02/03/2023] Open
Abstract
It has been known for many years that fluoroacetate and fluorocitrate when metabolized are highly toxic, and that at least one effect of fluorocitrate is to inactivate aconitase. In this paper we present evidence supporting the hypothesis that the (-)-erythro diastereomer of 2-fluorocitrate acts as a mechanism based inhibitor of aconitase by first being converted to fluoro-cis-aconitate, followed by addition of hydroxide and with loss of fluoride to form 4-hydroxy-trans-aconitate (HTn), which binds very tightly, but not covalently, to the enzyme. Formation of HTn by these reactions is in accord with the working model for the enzyme mechanism. That HTn is the product of fluorocitrate inhibition is supported by the crystal structure of the enzyme-inhibitor complex at 2.05-A resolution, release of fluoride stoichiometric with total enzyme when (-)-erythro-2-fluorocitrate is added, HPLC analysis of the product, slow displacement of HTn by 10(6)-fold excess of isocitrate, and previously published Mössbauer experiments. When (+)-erythro-2-fluorocitrate is added to aconitase, the release of fluoride is stoichiometric with total substrate added, and HPLC analysis of the products indicates the formation of oxalosuccinate, and its derivative alpha-ketoglutarate. This is consistent with the proposed mechanism, as is the formation of HTn from (-)-erythro-2-fluorocitrate. The structure of the inhibited complex reveals that HTn binds like the inhibitor trans-aconitate while providing all the interactions of the natural substrate, isocitrate. The structure exhibits four hydrogen bonds < 2.7 A in length involving HTn, H2O bound to the [4Fe-4S] cluster, Asp-165 and His-167, as well as low temperature factors for these moieties, consistent with the observed very tight binding of the inhibitor.
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Affiliation(s)
- H Lauble
- Universität Stuttgart, Institut für Organische Chemie, Germany
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13
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Beinert H, Kennedy MC, Stout CD. Aconitase as Ironminus signSulfur Protein, Enzyme, and Iron-Regulatory Protein. Chem Rev 1996; 96:2335-2374. [PMID: 11848830 DOI: 10.1021/cr950040z] [Citation(s) in RCA: 422] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Helmut Beinert
- Institute for Enzyme Research, Graduate School, and Department of Biochemistry, College of Agricultural and Life Sciences, University of Wisconsin, Madison, Wisconsin 53705, Department of Biochemistry, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, and Department of Molecular Biology, The Scripps Research Institute, La Jolla, California 92037
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14
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Barclay J, Evans DJ. Amino acid induced iron-sulfur cluster interconversions studied by 1H NMR and Mössbauer spectroscopies. Inorganica Chim Acta 1996. [DOI: 10.1016/0020-1693(95)04953-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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15
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Zhou J, Hu Z, Münck E, Holm RH. The Cuboidal Fe3S4 Cluster: Synthesis, Stability, and Geometric and Electronic Structures in a Non-Protein Environment. J Am Chem Soc 1996. [DOI: 10.1021/ja9537843] [Citation(s) in RCA: 86] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Jian Zhou
- Contribution from the Departments of Chemistry, Harvard University, Cambridge, Massachusetts 02138, and Carnegie-Mellon University, Pittsburgh, Pennsylvania 15213
| | - Zhengguo Hu
- Contribution from the Departments of Chemistry, Harvard University, Cambridge, Massachusetts 02138, and Carnegie-Mellon University, Pittsburgh, Pennsylvania 15213
| | - Eckard Münck
- Contribution from the Departments of Chemistry, Harvard University, Cambridge, Massachusetts 02138, and Carnegie-Mellon University, Pittsburgh, Pennsylvania 15213
| | - R. H. Holm
- Contribution from the Departments of Chemistry, Harvard University, Cambridge, Massachusetts 02138, and Carnegie-Mellon University, Pittsburgh, Pennsylvania 15213
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16
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Noodleman L, Peng C, Case D, Mouesca JM. Orbital interactions, electron delocalization and spin coupling in iron-sulfur clusters. Coord Chem Rev 1995. [DOI: 10.1016/0010-8545(95)07011-l] [Citation(s) in RCA: 561] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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17
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Abstract
Crystal structures of mitochondrial aconitase with alpha-methylisocitrate and with sulfate bound have been solved and refined at 2.0 A resolution with R factors of 18.2 and 16.8%, respectively. The steric factors and conformational effects observed in both new structures support the proposed mechanism for the overall reaction catalyzed by aconitase. The alternate substrate alpha-methylisocitrate is derived from alpha-methyl-cis-aconitate during crystallization and is observed to bind in the active site in a manner very similar to that observed for isocitrate. The methyl group is accommodated by favorable contact with Ile-425. However, the other potential hydration product of alpha-methyl-cis-aconitate, alpha-methylcitrate, cannot be accommodated in the active site due to steric conflict of the methyl group with Asp-165. The results are consistent with the requirement that cis-aconitate must bind in two ways, in the citrate mode and in the isocitrate mode. Crystals of aconitase with sulfate bound are isomorphous to those with isocitrate bound. However, the structure displays significant conformational changes, providing a model for the substrate-free state of enzyme. Three water molecules bind in place of the C alpha- and C beta-hydroxyl and carboxyl groups of isocitrate, while sulfate binds in place of the C gamma-carboxyl group. Side chains of Ser-642 and Arg-447 in the active site rotate to pair with other side chains in the absence of substrate. The new conformation of Arg-447 triggers a concerted set of shifts which transmits conformational change to the surface of the protein, 30 A from the active site. In the absence of substrate, a chain segment containing the [4Fe-4S] ligand Cys-358 also shifts, resulting in the net translation and reorientation of the Fe-S cluster.
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Affiliation(s)
- H Lauble
- Institut für Organische Chemie, Universität Stuttgart, Germany
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18
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Hancock RD, Martell AE. Lewis Acid–Base Behavior in Aqueous Solution: Some Implications for Metal Ions in Biology. ADVANCES IN INORGANIC CHEMISTRY 1995. [DOI: 10.1016/s0898-8838(08)60052-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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19
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Tong J, Feinberg B. Direct square-wave voltammetry of superoxidized [4Fe-4S]3+ aconitase and associated 3Fe/4Fe cluster interconversions. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)31478-3] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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20
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Jensen GM, Warshel A, Stephens PJ. Calculation of the redox potentials of iron-sulfur proteins: the 2-/3-couple of [Fe4S*4Cys4] clusters in Peptococcus aerogenes ferredoxin, Azotobacter vinelandii ferredoxin I, and Chromatium vinosum high-potential iron protein. Biochemistry 1994; 33:10911-24. [PMID: 8086408 DOI: 10.1021/bi00202a010] [Citation(s) in RCA: 92] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Calculations of the redox potentials of the 2-/3-couples of [Fe4S*4Cys4] clusters in the iron-sulfur proteins Peptococcus aerogenes ferredoxin (PaFd), Azotobacter vinelandii ferredoxin I (AvFdI) and Chromatium vinosum high potential iron protein (CvHiPIP) based on the Protein Dipoles Langevin Dipoles (PDLD) method are reported. The structures of these proteins have been determined by X-ray crystallography; in the case of PaFd the structure has recently been revised due to a change in the sequence close to Cluster II. The large differences between the potentials of the [Fe4S*4Cys4] clusters of PaFd and AvFdI and the potential of the [Fe4S*4Cys4] cluster of CvHiPIP are successfully modeled and originate principally in differences in the configuration of main-chain amide groups near the clusters. The small difference between the potentials of PaFd and AvFdI is also satisfactorily modeled in the case of Cluster I of PaFd. Solvent dipoles close to the cluster in PaFd are an important contributor to its higher potential. The two X-ray structures of PaFd yield similar results for Cluster I of PaFd. In contrast, the results for Cluster II differ substantially; for reasons not yet clear, the recently revised structure leads to results in worse agreement with experiment.
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Affiliation(s)
- G M Jensen
- Department of Chemistry, University of Southern California, Los Angeles 90089
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21
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Smith JL, Zaluzec EJ, Wery JP, Niu L, Switzer RL, Zalkin H, Satow Y. Structure of the allosteric regulatory enzyme of purine biosynthesis. Science 1994; 264:1427-33. [PMID: 8197456 DOI: 10.1126/science.8197456] [Citation(s) in RCA: 161] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Multi-wavelength anomalous diffraction (MAD) has been used to determine the structure of the regulatory enzyme of de novo synthesis of purine nucleotides, glutamine 5-phosphoribosyl-1-pyrophosphate (PRPP) amidotransferase, from Bacillus subtilis. This allosteric enzyme, a 200-kilodalton tetramer, is subject to end product regulation by purine nucleotides. The metalloenzyme from B. subtilis is a paradigm for the higher eukaryotic enzymes, which have been refractory to isolation in stable form. The two folding domains of the polypeptide are correlated with functional domains for glutamine binding and for transfer of ammonia to the substrate PRPP. Eight molecules of the feedback inhibitor adenosine monophosphate (AMP) are bound to the tetrameric enzyme in two types of binding sites: the PRPP catalytic site of each subunit and an unusual regulatory site that is immediately adjacent to each active site but is between subunits. An oxygen-sensitive [4Fe-4S] cluster in each subunit is proposed to regulate protein turnover in vivo and is distant from the catalytic site. Oxygen sensitivity of the cluster is diminished by AMP, which blocks a channel through the protein to the cluster. The structure is representative of both glutamine amidotransferases and phosphoribosyltransferases.
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Affiliation(s)
- J L Smith
- Department of Biological Sciences, Purdue University, West Lafayette, IN 47907
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22
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Affiliation(s)
- J J Moura
- Departamento de Quimica, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Portugal
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Abstract
Metalloenzymes effect a variety of important chemical transformations, often involving small molecule substrates or products such as molecular oxygen, hydrogen, nitrogen, and water. A diverse array of ions or metal clusters is observed at the active-site cores, but living systems use basic recurring structures that have been modified or tuned for specific purposes. Inorganic chemists are actively involved in the elucidation of the structure, spectroscopy, and mechanism of action of these biological catalysts, in part through a synthetic modeling approach involving biomimetic studies.
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Affiliation(s)
- K D Karlin
- Department of Chemistry, Johns Hopkins University, Baltimore, MD 21218
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McKee V. Macrocyclic Complexes as Models for Nonporphine Metalloproteins. ADVANCES IN INORGANIC CHEMISTRY 1993. [DOI: 10.1016/s0898-8838(08)60186-5] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Fenton DE, Ōkawa H. Dalton perspectives. The emergence of trinuclear constellations at metallobiosites. ACTA ACUST UNITED AC 1993. [DOI: 10.1039/dt9930001349] [Citation(s) in RCA: 57] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Zheng L, Kennedy MC, Blondin GA, Beinert H, Zalkin H. Binding of cytosolic aconitase to the iron responsive element of porcine mitochondrial aconitase mRNA. Arch Biochem Biophys 1992; 299:356-60. [PMID: 1444477 DOI: 10.1016/0003-9861(92)90287-7] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The 5' end of porcine mitochondrial aconitase mRNA contains an iron responsive element (IRE)-like secondary structure (T. Dandekar, R. Stripecke, N. K. Gray, B. Goosen, A. Constable, H. E. Johansson, and M. W. Hentze (1991) EMBO J. 10, 1903-1909). A protein from a liver extract binds to a mitochondrial aconitase RNA probe and supports the identification of this sequence as an IRE. Purified cytosolic aconitase but not the mitochondrial enzyme binds to this IRE as well as to a ferritin IRE. All forms of cytosolic aconitase, [4Fe-4S] enzyme, [3Fe-4S] enzyme and apoenzyme bind with similar affinity. A Kd of 0.25 nM was calculated for the apoaconitase-IRE interaction from Scatchard analysis. These results support the conclusion that cytosolic aconitase is an IRE-binding protein which may regulate translation of mitochondrial aconitase mRNA.
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Affiliation(s)
- L Zheng
- Department of Biochemistry, Purdue University, West Lafayette, Indiana 47907-1153
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Zhang HY, Faridoon K, Sykes A. Kinetic studies on the dithionite reduction of beef-heart aconitase in the [3Fe–4S]+ inactive form. Inorganica Chim Acta 1992. [DOI: 10.1016/s0020-1693(00)85338-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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