1
|
Mansilla S, Tórtora V, Pignataro F, Sastre S, Castro I, Chiribao ML, Robello C, Zeida A, Santos J, Castro L. Redox sensitive human mitochondrial aconitase and its interaction with frataxin: In vitro and in silico studies confirm that it takes two to tango. Free Radic Biol Med 2023; 197:71-84. [PMID: 36738801 DOI: 10.1016/j.freeradbiomed.2023.01.028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/06/2022] [Revised: 01/11/2023] [Accepted: 01/30/2023] [Indexed: 02/05/2023]
Abstract
Mitochondrial aconitase (ACO2) has been postulated as a redox sensor in the tricarboxylic acid cycle. Its high sensitivity towards reactive oxygen and nitrogen species is due to its particularly labile [4Fe-4S]2+ prosthetic group which yields an inactive [3Fe-4S]+ cluster upon oxidation. Moreover, ACO2 was found as a main oxidant target during aging and in pathologies where mitochondrial dysfunction is implied. Herein, we report the expression and characterization of recombinant human ACO2 and its interaction with frataxin (FXN), a protein that participates in the de novo biosynthesis of Fe-S clusters. A high yield of pure ACO2 (≥99%, 22 ± 2 U/mg) was obtained and kinetic parameters for citrate, isocitrate, and cis-aconitate were determined. Superoxide, carbonate radical, peroxynitrite, and hydrogen peroxide reacted with ACO2 with second-order rate constants of 108, 108, 105, and 102 M-1 s-1, respectively. Temperature-induced unfolding assessed by tryptophan fluorescence of ACO2 resulted in apparent melting temperatures of 51.1 ± 0.5 and 43.6 ± 0.2 °C for [4Fe-4S]2+ and [3Fe-4S]+ states of ACO2, sustaining lower thermal stability upon cluster oxidation. Differences in protein dynamics produced by the Fe-S cluster redox state were addressed by molecular dynamics simulations. Reactivation of [3Fe-4S]+-ACO2 by FXN was verified by activation assays and direct iron-dependent interaction was confirmed by protein-protein interaction ELISA and fluorescence spectroscopic assays. Multimer modeling and protein-protein docking predicted an ACO2-FXN complex where the metal ion binding region of FXN approaches the [3Fe-4S]+ cluster, supporting that FXN is a partner for reactivation of ACO2 upon oxidative cluster inactivation.
Collapse
Affiliation(s)
- Santiago Mansilla
- Centro de Investigaciones Biomédicas, Facultad de Medicina, Universidad de la República, Montevideo, Uruguay; Departamento de Métodos Cuantitativos, Facultad de Medicina, Universidad de la República, Montevideo, Uruguay
| | - Verónica Tórtora
- Centro de Investigaciones Biomédicas, Facultad de Medicina, Universidad de la República, Montevideo, Uruguay; Departamento de Educación Médica, Facultad de Medicina, Universidad de la República, Montevideo, Uruguay
| | - Florencia Pignataro
- Instituto de Biociencias, Biotecnología y Biología traslacional, Facultad de Ciencias Exactas, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Santiago Sastre
- Centro de Investigaciones Biomédicas, Facultad de Medicina, Universidad de la República, Montevideo, Uruguay; Departamento de Biofísica, Facultad de Medicina, Universidad de la República, Montevideo, Uruguay
| | - Ignacio Castro
- Instituto de Biociencias, Biotecnología y Biología traslacional, Facultad de Ciencias Exactas, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Ma Laura Chiribao
- Centro de Investigaciones Biomédicas, Facultad de Medicina, Universidad de la República, Montevideo, Uruguay; Departamento de Bioquímica, Facultad de Medicina, Universidad de la República, Montevideo, Uruguay; Laboratorio de Interacciones Hospedero-Patógeno, Institut Pasteur de Montevideo, Uruguay
| | - Carlos Robello
- Centro de Investigaciones Biomédicas, Facultad de Medicina, Universidad de la República, Montevideo, Uruguay; Departamento de Bioquímica, Facultad de Medicina, Universidad de la República, Montevideo, Uruguay; Laboratorio de Interacciones Hospedero-Patógeno, Institut Pasteur de Montevideo, Uruguay
| | - Ari Zeida
- Centro de Investigaciones Biomédicas, Facultad de Medicina, Universidad de la República, Montevideo, Uruguay; Departamento de Bioquímica, Facultad de Medicina, Universidad de la República, Montevideo, Uruguay
| | - Javier Santos
- Instituto de Biociencias, Biotecnología y Biología traslacional, Facultad de Ciencias Exactas, Universidad de Buenos Aires, Buenos Aires, Argentina.
| | - Laura Castro
- Centro de Investigaciones Biomédicas, Facultad de Medicina, Universidad de la República, Montevideo, Uruguay; Departamento de Bioquímica, Facultad de Medicina, Universidad de la República, Montevideo, Uruguay.
| |
Collapse
|
2
|
Abstract
We propose a new model for prochirality that satisfies all known examples: the prochiral plane. This plane contains the prochiral carbon and defines two separate faces for chemical modification. We extend this to enzyme catalysis, replacing the "three point attachment" hypothesis and its variants. Once a prochiral substrate is fixed on an enzyme surface, the asymmetry of the enzyme provides reactants exclusively on one side of the prochiral plane, producing an enantiomerically pure chiral product. The aconitase reaction is detailed as an example, using molecular modeling and its known enzymatic mechanism. We show that the prochiral substrate for this enzyme is not citrate, but rather cis-aconitate. The number of interaction points of cis-aconitate is not relevant to prochirality, but rather to substrate specificity. A second detailed example is the enzyme fumarase; here the substrate fumarate has only two binding sites, but is nonetheless fixed onto the enzyme and has a defined prochiral plane. We also provide a literature survey of more prochiral substrates, all of which have sp2 hybridized carbon and contain a prochiral plane. An example of a prochiral unnatural substrate for sphingosine kinase 2, fingolimod, has an sp3 hybridized prochiral carbon and also contains a prochiral plane. Finally, we provide an intuitive example of a prochiral physical object, a coffee cup, interacting with one hand and lip.
Collapse
Affiliation(s)
- Raymond S Ochs
- Department of Pharmaceutical Sciences, College of Pharmacy and Health Sciences, St. John's University, 8000 Utopia Parkway, Queens, NY, 11439, USA.
| | - Tanaji T Talele
- Department of Pharmaceutical Sciences, College of Pharmacy and Health Sciences, St. John's University, 8000 Utopia Parkway, Queens, NY, 11439, USA
| |
Collapse
|
3
|
Scarcia P, Gorgoglione R, Messina E, Fiermonte G, Blank LM, Wierckx N, Palmieri L, Agrimi G. Mitochondrial carriers of
Ustilago maydis
and
Aspergillus terreus
involved in itaconate production: same physiological role but different biochemical features. FEBS Lett 2019; 594:728-739. [DOI: 10.1002/1873-3468.13645] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2019] [Revised: 10/08/2019] [Accepted: 10/09/2019] [Indexed: 11/10/2022]
Affiliation(s)
- Pasquale Scarcia
- Department of Biosciences, Biotechnologies and Biopharmaceutics University of Bari ALDO MORO Italy
| | - Ruggiero Gorgoglione
- Department of Biosciences, Biotechnologies and Biopharmaceutics University of Bari ALDO MORO Italy
| | - Eugenia Messina
- Department of Biosciences, Biotechnologies and Biopharmaceutics University of Bari ALDO MORO Italy
| | - Giuseppe Fiermonte
- Department of Biosciences, Biotechnologies and Biopharmaceutics University of Bari ALDO MORO Italy
| | - Lars Mathias Blank
- Institute of Applied Microbiology‐iAMB Aachen Biology and Biotechnology‐ABBt RWTH Aachen University Germany
| | - Nick Wierckx
- Institute of Bio‐ and Geosciences IBG‐1: Biotechnology Forschungszentrum Jülich Germany
| | - Luigi Palmieri
- Department of Biosciences, Biotechnologies and Biopharmaceutics University of Bari ALDO MORO Italy
- CNR Institute of Biomembranes, Bioenergetics and Molecular Biotechnologies (IBIOM) Bari Italy
| | - Gennaro Agrimi
- Department of Biosciences, Biotechnologies and Biopharmaceutics University of Bari ALDO MORO Italy
| |
Collapse
|
4
|
The PrpF protein of Shewanella oneidensis MR-1 catalyzes the isomerization of 2-methyl-cis-aconitate during the catabolism of propionate via the AcnD-dependent 2-methylcitric acid cycle. PLoS One 2017; 12:e0188130. [PMID: 29145506 PMCID: PMC5690661 DOI: 10.1371/journal.pone.0188130] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2017] [Accepted: 11/01/2017] [Indexed: 11/23/2022] Open
Abstract
The 2-methylcitric acid cycle (2-MCC) is a common route of propionate catabolism in microorganisms. In Salmonella enterica, the prpBCDE operon encodes most of the 2-MCC enzymes. In other organisms, e.g., Shewanella oneidensis MR-1, two genes, acnD and prpF replace prpD, which encodes 2-methylcitrate dehydratase. We showed that together, S. oneidensis AcnD and PrpF (SoAcnD, SoPrpF) compensated for the absence of PrpD in a S. enterica prpD strain. We also showed that SoAcnD had 2-methylcitrate dehydratase activity and that PrpF has aconitate isomerase activity. Here we report in vitro evidence that the product of the SoAcnD reaction is an isomer of 2-methyl-cis-aconitate (2-MCA], the product of the SePrpD reaction. We show that the SoPrpF protein isomerizes the product of the AcnD reaction into the PrpD product (2-MCA], a known substrate of the housekeeping aconitase (AcnB]. Given that SoPrpF is an isomerase, that SoAcnD is a dehydratase, and the results from in vivo and in vitro experiments reported here, it is likely that 4-methylaconitate is the product of the AcnD enzyme. Results from in vivo studies using a S. enterica prpD strain show that SoPrpF variants with substitutions of residues K73 or C107 failed to support growth with propionate as the sole source of carbon and energy. High-resolution (1.22 Å) three-dimensional crystal structures of PrpFK73E in complex with trans-aconitate or malonate provide insights into the mechanism of catalysis of the wild-type protein.
Collapse
|
5
|
Decreased transport restores growth of a Salmonella enterica apbC mutant on tricarballylate. J Bacteriol 2011; 194:576-83. [PMID: 22101844 DOI: 10.1128/jb.05988-11] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Mutants of Salmonella enterica lacking apbC have nutritional and biochemical properties indicative of defects in iron-sulfur ([Fe-S]) cluster metabolism. An apbC mutant is unable to grow on tricarballylate as a carbon source. Based on the ability of ApbC to transfer an [Fe-S] cluster to an apoprotein, this defect was attributed to poor loading of the [Fe-S] cluster-containing TcuB enzyme. Consistent with these observations, a previous study showed that overexpression of iscU, which encodes an [Fe-S] cluster molecular scaffold, suppressed the tricarballylate growth defect of an apbC mutant (J. M. Boyd, J. A. Lewis, J. C. Escalante-Semerena, and D. M. Downs, J. Bacteriol. 190:4596-4602, 2008). In this study, tcuC mutations that suppress the growth defect of an apbC mutant by decreasing the intracellular concentration of tricarballylate are described. Collectively, the suppressor analyses support a model in which reduced TcuB activity prevents growth on tricarballylate by (i) decreasing catabolism and (ii) allowing levels of tricarballylate that are toxic to the cell to accumulate. The apbC tcuC mutant strains described here reveal that the balance of the metabolic network can be altered by the accumulation of deleterious metabolites.
Collapse
|
6
|
Baumgart M, Bott M. Biochemical characterisation of aconitase from Corynebacterium glutamicum. J Biotechnol 2011; 154:163-70. [DOI: 10.1016/j.jbiotec.2010.07.002] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2010] [Accepted: 07/01/2010] [Indexed: 10/19/2022]
|
7
|
|
8
|
Lewis JA, Escalante-Semerena JC. The FAD-dependent tricarballylate dehydrogenase (TcuA) enzyme of Salmonella enterica converts tricarballylate into cis-aconitate. J Bacteriol 2006; 188:5479-86. [PMID: 16855237 PMCID: PMC1540016 DOI: 10.1128/jb.00514-06] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Tricarballylate is the causative agent of grass tetany, a ruminant disease characterized by acute magnesium deficiency. Tricarballylate toxicity has been attributed to its ability to chelate magnesium and to inhibit aconitase, a Krebs cycle enzyme. Neither the ruminant nor the normal rumen flora can catabolize tricarballylate to ameliorate its toxic effects. However, the gram-negative enterobacterium Salmonella enterica can use tricarballylate as a carbon and energy source, providing an opportunity to study the genes and enzymes required for tricarballylate catabolism. The tricarballylate utilization (tcu) genes are organized into two transcriptional units, i.e., tcuR and tcuABC. Here, we report the initial biochemical analysis of TcuA. TcuA catalyzed the oxidation of tricarballylate to cis-aconitate. The apparent K(m) of TcuA for tricarballylate was 3.8 +/- 0.4 mM, with a V(max) of 7.9 +/- 0.3 mM min(-1), turnover number (k(cat)) of 6.7 x 10(-2) s(-1), and a catalytic efficiency (k(cat)/K(m)) of 17.8 M(-1) s(-1). Optimal activity was measured at pH 7.5 and 30 degrees C. The enzyme was inactivated at 45 degrees C. One mole of FAD was present per mole of TcuA. We propose a role for TcuB as an electron shuttle protein responsible for oxidizing FADH(2) back to FAD in TcuA.
Collapse
Affiliation(s)
- Jeffrey A Lewis
- Department of Bacteriology, University of Wisconsin-Madison, 1710 University Avenue, Madison, WI 53726-4087, USA
| | | |
Collapse
|
9
|
Pitula JS, Deck KM, Clarke SL, Anderson SA, Vasanthakumar A, Eisenstein RS. Selective inhibition of the citrate-to-isocitrate reaction of cytosolic aconitase by phosphomimetic mutation of serine-711. Proc Natl Acad Sci U S A 2004; 101:10907-12. [PMID: 15263083 PMCID: PMC503718 DOI: 10.1073/pnas.0404308101] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2004] [Indexed: 11/18/2022] Open
Abstract
Iron-regulatory protein 1 (IRP1) is a dual-function protein with mutually exclusive roles as a posttranscriptional regulator of animal-cell iron metabolism or as the cytosolic isoform of the iron-sulfur enzyme aconitase (c-acon). Much effort has focused on the role of IRP1 in posttranscriptional gene regulation and in factors that influence its interconversion with c-acon, but little is known about the metabolic function and regulation of c-acon. The role of PKC-dependent phosphorylation of S711 on IRP1/c-acon function was examined. Phosphorylation state-specific antibodies revealed that S711 is phosphorylated by PKC in vitro and in human embryonic kidney cells treated with a PKC activator. In aco1 yeast, the phosphomimetic mutants S711D and S711E exhibited severely impaired aconitase function, whereas S711A and S711T were unaffected relative to the WT protein. Aconitase activity in yeast extracts displayed a similar pattern when assayed for capacity to convert citrate to isocitrate: WT, S711A, and S711T were active, but S711D and S711E activity was undetectable. In contrast, when measured by the conversion of isocitrate to cis-aconitate, S711D and S711E displayed substantial activity, indicating that phosphorylation impairs the citrate but not isocitrate mode of aconitase function. This possibility was confirmed in vivo by demonstrating that S711D and S711E specifically antagonized the requirement for isocitrate in two metabolic scenarios. Iron-responsive element RNA-binding affinity was unaffected by S711 mutations. Our results show that S711 is a target of phosphorylation capable of conferring distinct effects on c-acon function potentially dictating changes in cytosolic citrate/isocitrate metabolism.
Collapse
Affiliation(s)
- Joseph S Pitula
- Department of Nutritional Sciences, University of Wisconsin, Madison, 53706, USA
| | | | | | | | | | | |
Collapse
|
10
|
Lewis JA, Horswill AR, Schwem BE, Escalante-Semerena JC. The Tricarballylate utilization (tcuRABC) genes of Salmonella enterica serovar Typhimurium LT2. J Bacteriol 2004; 186:1629-37. [PMID: 14996793 PMCID: PMC355976 DOI: 10.1128/jb.186.6.1629-1637.2004] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The genes of Salmonella enterica serovar Typhimurium LT2 encoding functions needed for the utilization of tricarballylate as a carbon and energy source were identified and their locations in the chromosome were established. Three of the tricarballylate utilization (tcu) genes, tcuABC, are organized as an operon; a fourth gene, tcuR, is located immediately 5' to the tcuABC operon. The tcuABC operon and tcuR gene share the same direction of transcription but are independently transcribed. The tcuRABC genes are missing in the Escherichia coli K-12 chromosome. The tcuR gene is proposed to encode a regulatory protein needed for the expression of tcuABC. The tcuC gene is proposed to encode an integral membrane protein whose role is to transport tricarballylate across the cell membrane. tcuC function was sufficient to allow E. coli K-12 to grow on citrate (a tricarballylate analog) but not to allow growth of this bacterium on tricarballylate. E. coli K-12 carrying a plasmid with wild-type alleles of tcuABC grew on tricarballylate, suggesting that the functions of the TcuABC proteins were the only ones unique to S. enterica needed to catabolize tricarballylate. Analyses of the predicted amino acid sequences of the TcuAB proteins suggest that TcuA is a flavoprotein, and TcuB is likely anchored to the cell membrane and probably contains one or more Fe-S centers. The TcuB protein is proposed to work in concert with TcuA to oxidize tricarballylate to cis-aconitate, which is further catabolized via the Krebs cycle. The glyoxylate shunt is not required for growth of S. enterica on tricarballylate. A model for tricarballylate catabolism in S. enterica is proposed.
Collapse
Affiliation(s)
- Jeffrey A Lewis
- Department of Bacteriology, University of Wisconsin--Madison, 53726-4087, USA
| | | | | | | |
Collapse
|
11
|
Grimek TL, Escalante-Semerena JC. The acnD genes of Shewenella oneidensis and Vibrio cholerae encode a new Fe/S-dependent 2-methylcitrate dehydratase enzyme that requires prpF function in vivo. J Bacteriol 2004; 186:454-62. [PMID: 14702315 PMCID: PMC305763 DOI: 10.1128/jb.186.2.454-462.2004] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2003] [Accepted: 10/10/2003] [Indexed: 11/20/2022] Open
Abstract
The propionate utilization operons of several bacteria differ from each other in the occurrence of two genes, acnD and prpF, in place of or in addition to the prpD gene encoding an Fe/S-independent 2-methylcitrate dehydratase enzyme. We cloned the acnD and prpF genes from two organisms, Shewanella oneidensis and Vibrio cholerae, and found that, together, the AcnD and PrpF proteins restored the ability of a prpD mutant strain of Salmonella enterica to grow on propionate as a source of carbon and energy. However, neither acnD nor prpF alone was able to substitute for prpD. The AcnD and PrpF proteins were isolated and biochemically analyzed. The AcnD protein required reconstitution of an Fe/S cluster for activity. All detectable AcnD activity was lost after incubation with iron-chelating agents, and no AcnD activity was observed after attempted reconstitution without iron. Nuclear magnetic resonance spectroscopy and in vitro activity assay data showed that AcnD dehydrated 2-methylcitrate and citrate to 2-methyl-cis-aconitate and cis-aconitate, respectively; AcnD also hydrated cis-aconitate. However, 2-methylisocitrate and isocitrate were not substrates for AcnD, indicating that AcnD only catalyzes the first half of the aconitase-like dehydration reactions. No aconitase-like activity was found for PrpF. It is hypothesized that, in vivo, PrpF is an accessory protein required to prevent oxidative damage of the Fe/S center of active AcnD enzyme or that it may be involved in synthesis or repair of the Fe/S cluster present in AcnD.
Collapse
Affiliation(s)
- Tracey L Grimek
- Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin 53726-4087, USA
| | | |
Collapse
|
12
|
Uhrigshardt H, Walden M, John H, Anemüller S. Purification and characterization of the first archaeal aconitase from the thermoacidophilicSulfolobus acidocaldarius. ACTA ACUST UNITED AC 2003. [DOI: 10.1046/j.1432-1327.2001.02049.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
|
13
|
García-Martín ML, García-Espinosa MA, Ballesteros P, Bruix M, Cerdán S. Hydrogen turnover and subcellular compartmentation of hepatic [2-(13)C]glutamate and [3-(13)C]aspartate as detected by (13)C NMR. J Biol Chem 2002; 277:7799-807. [PMID: 11744718 DOI: 10.1074/jbc.m107501200] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
(13)C NMR monitored the dynamics of exchange from specific hydrogens of hepatic [2-(13)C]glutamate and [3-(13)C]aspartate with deuterons from intracellular heavy water providing information on alpha-ketoglutarate/glutamate exchange and subcellular compartmentation. Mouse livers were perfused with [3-(13)C]alanine in buffer containing or not 50% (2)H(2)O for increasing periods of time (1 min < t < 30 min). Liver extracts prepared at the end of the perfusions were analyzed by high resolution (13)C NMR (150.13 MHz) with (1)H decoupling only and with simultaneous (1)H and (2)H decoupling. (13)C-(2)H couplings and (2)H-induced isotopic shifts observed in the glutamate C2 resonance, allowed to estimate the apparent rate constants (forward, reverse; min(-1)) for (i) the reversible exchange of [2-(13)C]glutamate H2 as catalyzed mainly by aspartate aminotransferase (0.32, 0.56), (ii) the reversible exchange of [2-(13)C]glutamate H3(proS) as catalyzed by NAD(P) isocitrate dehydrogenase (0.1, 0.05), and (iii) the irreversible exchanges of glutamate H3(proR) and H3(proS) as catalyzed by the sequential activities of mitochondrial aconitase and NAD isocitrate dehydrogenase of the tricarboxylic acid cycle (0.035), respectively. A similar approach allowed to determine the rates of (1)H-(2)H exchange for the H2 (0.4, 0.5) or H3(proR) (0.3, 0.2) or the H2 and H3(proS) hydrogens (0.20, 0.23) of [3-(13)C]aspartate isotopomers. The ubiquitous subcellular localization of (1)H-(2)H exchange enzymes and the exclusive mitochondrial localization of pyruvate carboxylase and the tricarboxylic acid cycle resulted in distinctive kinetics of deuteration in the H2 and either or both H3 hydrogens of [2-(13)C]glutamate and [3-(13)C]aspartate, allowing to follow glutamate and aspartate trafficking through cytosol and mitochondria.
Collapse
Affiliation(s)
- María L García-Martín
- Instituto de Investigaciones Biomédicas C.S.I.C., c/Arturo Duperier 4, E-28029 Madrid, Spain
| | | | | | | | | |
Collapse
|
14
|
|
15
|
Huynen MA, Snel B. Gene and context: integrative approaches to genome analysis. ADVANCES IN PROTEIN CHEMISTRY 2000; 54:345-79. [PMID: 10829232 DOI: 10.1016/s0065-3233(00)54010-8] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/04/2022]
Affiliation(s)
- M A Huynen
- European Molecular Biology Laboratory, Heidelberg, Germany
| | | |
Collapse
|
16
|
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.
Collapse
Affiliation(s)
- S J Lloyd
- Department of Molecular Biology, The Scripps Research Institute, La Jolla, California 92037, USA
| | | | | | | |
Collapse
|
17
|
Horswill AR, Escalante-Semerena JC. Salmonella typhimurium LT2 catabolizes propionate via the 2-methylcitric acid cycle. J Bacteriol 1999; 181:5615-23. [PMID: 10482501 PMCID: PMC94080 DOI: 10.1128/jb.181.18.5615-5623.1999] [Citation(s) in RCA: 121] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We previously identified the prpBCDE operon, which encodes catabolic functions required for propionate catabolism in Salmonella typhimurium. Results from (13)C-labeling experiments have identified the route of propionate breakdown and determined the biochemical role of each Prp enzyme in this pathway. The identification of catabolites accumulating in wild-type and mutant strains was consistent with propionate breakdown through the 2-methylcitric acid cycle. Our experiments demonstrate that the alpha-carbon of propionate is oxidized to yield pyruvate. The reactions are catalyzed by propionyl coenzyme A (propionyl-CoA) synthetase (PrpE), 2-methylcitrate synthase (PrpC), 2-methylcitrate dehydratase (probably PrpD), 2-methylisocitrate hydratase (probably PrpD), and 2-methylisocitrate lyase (PrpB). In support of this conclusion, the PrpC enzyme was purified to homogeneity and shown to have 2-methylcitrate synthase activity in vitro. (1)H nuclear magnetic resonance spectroscopy and negative-ion electrospray ionization mass spectrometry identified 2-methylcitrate as the product of the PrpC reaction. Although PrpC could use acetyl-CoA as a substrate to synthesize citrate, kinetic analysis demonstrated that propionyl-CoA is the preferred substrate.
Collapse
Affiliation(s)
- A R Horswill
- Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin 53706-1567, USA
| | | |
Collapse
|
18
|
Böhm HJ. Prediction of binding constants of protein ligands: a fast method for the prioritization of hits obtained from de novo design or 3D database search programs. J Comput Aided Mol Des 1998; 12:309-23. [PMID: 9777490 DOI: 10.1023/a:1007999920146] [Citation(s) in RCA: 352] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
A dataset of 82 protein-ligand complexes of known 3D structure and binding constant Ki was analysed to elucidate the important factors that determine the strength of protein-ligand interactions. The following parameters were investigated: the number and geometry of hydrogen bonds and ionic interactions between the protein and the ligand, the size of the lipophilic contact surface, the flexibility of the ligand, the electrostatic potential in the binding site, water molecules in the binding site, cavities along the protein-ligand interface and specific interactions between aromatic rings. Based on these parameters, a new empirical scoring function is presented that estimates the free energy of binding for a protein-ligand complex of known 3D structure. The function distinguishes between buried and solvent accessible hydrogen bonds. It tolerates deviations in the hydrogen bond geometry of up to 0.25 A in the length and up to 30 degrees in the hydrogen bond angle without penalizing the score. The new energy function reproduces the binding constants (ranging from 3.7 x 10(-2) M to 1 x 10(-14) M, corresponding to binding energies between -8 and -80 kJ/mol) of the dataset with a standard deviation of 7.3 kJ/mol corresponding to 1.3 orders of magnitude in binding affinity. The function can be evaluated very fast and is therefore also suitable for the application in a 3D database search or de novo ligand design program such as LUDI. The physical significance of the individual contributions is discussed.
Collapse
Affiliation(s)
- H J Böhm
- BASF AG, Central Research, Ludwigshafen, Germany
| |
Collapse
|
19
|
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
| | | | | |
Collapse
|
20
|
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.
Collapse
Affiliation(s)
- H Lauble
- Institut für Organische Chemie, Universität Stuttgart, Germany
| | | |
Collapse
|
21
|
Mookhtiar K, Kalinowski S, Zhang D, Poulter C. Yeast squalene synthase. A mechanism for addition of substrates and activation by NADPH. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(19)78111-3] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
|
22
|
Goodsell DS, Lauble H, Stout CD, Olson AJ. Automated docking in crystallography: analysis of the substrates of aconitase. Proteins 1993; 17:1-10. [PMID: 8234239 DOI: 10.1002/prot.340170104] [Citation(s) in RCA: 71] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Automated docking of substrates to proteins of known structure aids the process of crystallographic analysis in two ways. First, automated docking can be used to generate a small number of starting models for substrates using only protein coordinates from an early stage of refinement. Second, automated docking provides a method for exploring aspects of catalysis that are inaccessible to crystallography by postulating binding modes of catalytic intermediates. This paper describes the use of automated docking to explore the binding of substrates to aconitase. The technique starts with a substrate molecule in an arbitrary configuration and position and finds favorable docked configurations in a (static) protein active site based on a molecular mechanics type force field. Using protein coordinates from an early stage of refinement of an aconitase-isocitrate complex, we successfully predicted the binding configuration of isocitrate. Four configurations were found, the energetically most favorable of which fit the observed electron density well and was used as a starting model for further refinement. Two configurations were found in citrate docking experiments, the second of which approximates the mode of substrate binding in an aconitase-nitrocitrate complex. We were also able to propose two binding modes of the catalytic intermediate cis-aconitate. These correspond closely to the isocitrate and the citrate binding modes. The relation of these new results to the proposed reaction mechanism is discussed.
Collapse
Affiliation(s)
- D S Goodsell
- Molecular Biology Institute, University of California, Los Angeles 90024
| | | | | | | |
Collapse
|
23
|
Flint DH. Escherichia coli fumarase A catalyzes the isomerization of enol and keto oxalacetic acid. Biochemistry 1993; 32:799-805. [PMID: 8422384 DOI: 10.1021/bi00054a009] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Fumarase A, a product of the fumA gene of Escherichia coli, has been found to catalyze the isomerization of enol to keto oxalacetic acid (OAA) in addition to catalyzing the fumarase reaction. The kcat/Km for the isomerization is almost identical to that for the fumarase reaction. The isomerization reaction apparently takes place at the same active site as the fumarase reaction since both reactions show a similar sensitivity to inactivation by O2, both reactions are strongly inhibited by 2-hydroxy-3-nitropropionate, and the isomerization reaction is inhibited by fumarate and malate. The isomerization requires the presence of a [4Fe-4S] or [3Fe-4S] cluster, perhaps for structural rather than catalytic reasons. Hydration of enol OAA to the gem diol has been ruled out as a possible mechanism of isomerization on the basis of the preservation of the oxygen on carbon 2 and the position of protonation on carbon 3. The isomerization is not stereospecific in the position of protonation at carbon 3 but appears to be stereoselective, with protonation preferentially occurring in the 3-pro-S position. Porcine fumarase, isopropyl malate isomerase, and dihydroxyacid dehydratase do not catalyze this isomerization. Fumarase A and aconitase, two enzymes with 4Fe-4S clusters that bind a linear 4-carbon dicarboxylic acid moiety in the trans conformation during their normal hydro-lyase reaction, do catalyze this isomerization.
Collapse
Affiliation(s)
- D H Flint
- Central Research and Development Department, E. I. du Pont de Nemours and Company, Wilmington, Delaware 19880
| |
Collapse
|
24
|
Lauble H, Kennedy MC, Beinert H, Stout CD. Crystal structures of aconitase with isocitrate and nitroisocitrate bound. Biochemistry 1992; 31:2735-48. [PMID: 1547214 DOI: 10.1021/bi00125a014] [Citation(s) in RCA: 185] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The crystal structures of mitochondrial aconitase with isocitrate and nitroisocitrate bound have been solved and refined to R factors of 0.179 and 0.161, respectively, for all observed data in the range 8.0-2.1 A. Porcine heart enzyme was used for determining the structure with isocitrate bound. The presence of isocitrate in the crystals was corroborated by Mössbauer spectroscopy. Bovine heart enzyme was used for determining the structure with the reaction intermediate analogue nitroisocitrate bound. The inhibitor binds to the enzyme in a manner virtually identical to that of isocitrate. Both compounds bind to the unique Fe atom of the [4Fe-4S] cluster via a hydroxyl oxygen and one carboxyl oxygen. A H2O molecule is also bound, making Fe six-coordinate. The unique Fe is pulled away approximately 0.2 A from the corner of the cubane compared to the position it would occupy in a symmetrically ligated [4Fe-4S] cluster. At least 23 residues from all four domains of aconitase contribute to the active site. These residues participate in substrate recognition (Arg447, Arg452, Arg580, Arg644, Gln72, Ser166, Ser643), cluster ligation and interaction (Cys358, Cys421, Cys424, Asn258, Asn446), and hydrogen bonds supporting active site side chains (Ala74, Asp568, Ser571, Thr567). Residues implicated in catalysis are Ser642 and three histidine-carboxylate pairs (Asp100-His101, Asp165-His147, Glu262-His167). The base necessary for proton abstraction from C beta of isocitrate appears to be Ser642; the O gamma atom is proximal to the calculated hydrogen position, while the environment of O gamma suggests stabilization of an alkoxide (an oxyanion hole formed by the amide and side chain of Arg644). The histidine-carboxylate pairs appear to be required for proton transfer reactions involving two oxygens bound to Fe, one derived from solvent (bound H2O) and one derived from substrate hydroxyl. Each oxygen is in contact with a histidine, and both are in contact with the side chain of Asp165, which bridges the two sites on the six-coordinate Fe.
Collapse
Affiliation(s)
- H Lauble
- Department of Molecular Biology, Scripps Research Institute, La Jolla, California 92037
| | | | | | | |
Collapse
|
25
|
Affiliation(s)
- D J Lowe
- AFRC IPSR Nitrogen Fixation Laboratory, University of Sussex, Brighton, U.K
| |
Collapse
|
26
|
|
27
|
Beinert H, Kennedy MC. 19th Sir Hans Krebs lecture. Engineering of protein bound iron-sulfur clusters. A tool for the study of protein and cluster chemistry and mechanism of iron-sulfur enzymes. EUROPEAN JOURNAL OF BIOCHEMISTRY 1989; 186:5-15. [PMID: 2598939 DOI: 10.1111/j.1432-1033.1989.tb15170.x] [Citation(s) in RCA: 182] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
An increasing number of iron-sulfur (Fe-S) proteins are found in which the Fe-S cluster is not involved in net electron transfer, as it is in the majority of Fe-S proteins. Most of the former are (de)hydratases, of which the most extensively studied is aconitase. Approaches are described and discussed by which the Fe-S cluster of this enzyme could be brought into states of different structure, ligation, oxidation and isotope composition. The species, so obtained, provided the basis for spectroscopic and chemical investigations. Results from studies by protein chemistry, EPR, Mössbauer, 1H, 2H and 57Fe electron-nuclear double resonance spectroscopy are described. Conclusions, which bear on the electronic structure of the Fe-S cluster, enzyme-substrate interaction and the enzymatic mechanism, were derived from a synopsis of the recent work described here and of previous contributions from several laboratories. These conclusions are discussed and summarized in a final section.
Collapse
Affiliation(s)
- H Beinert
- Department of Biochemistry, Medical College of Wisconsin, Milwaukee 53226
| | | |
Collapse
|
28
|
Robbins AH, Stout CD. Structure of activated aconitase: formation of the [4Fe-4S] cluster in the crystal. Proc Natl Acad Sci U S A 1989; 86:3639-43. [PMID: 2726740 PMCID: PMC287193 DOI: 10.1073/pnas.86.10.3639] [Citation(s) in RCA: 209] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
The structure of activated pig heart aconitase [citrate(isocitrate) hydro-lyase, EC 4.2.1.3] containing a [4Fe-4S] cluster has been refined at 2.5-A resolution to a crystallographic residual of 18.2%. Comparison of this structure to the recently determined 2.1-A resolution structure of the inactive enzyme containing a [3Fe-4S] cluster, by difference Fourier analysis, shows that upon activation iron is inserted into the structure isomorphously. The common atoms of the [3Fe-4S] and [4Fe-4S] cores agree within 0.1 A; the three common cysteinyl S gamma ligand atoms agree within 0.25 A. The fourth ligand of the Fe inserted into the [3Fe-4S] cluster is a water or hydroxyl from solvent, consistent with the absence of a free cysteine ligand in the enzyme active site cleft and the isomorphism of the two structures. A water molecule occupies a similar site in the crystal structure of the inactive enzyme.
Collapse
Affiliation(s)
- A H Robbins
- Department of Molecular Biology, Research Institute of Scripps Clinic, La Jolla, CA 92037
| | | |
Collapse
|
29
|
Abstract
The crystal structure of the 80,000 Da Fe-S enzyme aconitase has been solved and refined at 2.1 A resolution. The protein contains four domains; the first three from the N-terminus are closely associated around the [3Fe-4S] cluster with all three cysteine ligands to the cluster being provided by the third domain. Association of the larger C-terminal domain with the first three domains creates an extensive cleft leading to the Fe-S cluster. Residues from all four domains contribute to the active site region, which is defined by the Fe-S cluster and a bound SO4(2-) ion. This region of the structure contains 4 Arg, 3 His, 3 Ser, 2 Asp, 1 Glu, 3 Asn, and 1 Gln residues, as well as several bound water molecules. Three of these side chains reside on a three-turn 3(10) helix in the first domain. The SO4(2-) ion is bound 9.3 A from the center of the [3Fe-4S] cluster by the side chains of 2 Arg and 1 Gln residues. Each of 3 His side chains in the putative active site is paired with Asp or Glu side chains.
Collapse
Affiliation(s)
- A H Robbins
- Research Institute of Scripps Clinic, La Jolla, California 92037
| | | |
Collapse
|
30
|
|
31
|
Woods SA, Schwartzbach SD, Guest JR. Two biochemically distinct classes of fumarase in Escherichia coli. BIOCHIMICA ET BIOPHYSICA ACTA 1988; 954:14-26. [PMID: 3282546 DOI: 10.1016/0167-4838(88)90050-7] [Citation(s) in RCA: 154] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Biochemical studies with strains of Escherichia coli that are amplified for the products of the three fumarase genes, fumA (FUMA), fumB (FUMB) and fumC (FUMC), have shown that there are two distinct classes of fumarase. The Class I enzymes include FUMA, FUMB, and the immunologically related fumarase of Euglena gracilis. These are characteristically thermolabile dimeric enzymes containing identical subunits of Mr 60,000. FUMA and FUMB are differentially regulated enzymes that function in the citric acid cycle (FUMA) or to provide fumarate as an anaerobic electron acceptor (FUMB), and their affinities for fumarate and L-malate are consistent with these roles. The Class II enzymes include FUMC, and the fumarases of Bacillus subtilis, Saccharomyces cerevisiae and mammalian sources. They are thermostable tetrameric enzymes containing identical subunits Mr 48,000-50,000. The Class II fumarases share a high degree of sequence identity with each other (approx. 60%) and with aspartase (approx. 38%) and argininosuccinase (approx. 15%), and it would appear that these are all members of a family of structurally related enzymes. It is also suggested that the Class I enzymes may belong to a wider family of iron-dependent carboxylic acid hydro-lyases that includes maleate dehydratase and aconitase. Apart from one region containing a Gly-Ser-X-X-Met-X-X-Lys-X-Asn consensus sequence, no significant homology was detected between the Class I and Class II fumarases.
Collapse
Affiliation(s)
- S A Woods
- Department of Microbiology, University of Sheffield, U.K
| | | | | |
Collapse
|
32
|
Schweiger G, Dutscho R, Buckel W. Purification of 2-hydroxyglutaryl-CoA dehydratase from Acidaminococcus fermentans. An iron-sulfur protein. EUROPEAN JOURNAL OF BIOCHEMISTRY 1987; 169:441-8. [PMID: 3691501 DOI: 10.1111/j.1432-1033.1987.tb13631.x] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
1. The (R)-2-hydroxyglutaryl-CoA dehydratase system from Acidaminococcus fermentans was separated by chromatography of cell-free extracts on Q-Sepharose into two components, an activator and the actual dehydratase. The latter enzyme was further purified to homogeneity by chromatography on blue-Sepharose. It is an iron-sulfur protein (Mr 210,000) consisting of two different polypeptides (alpha, Mr 55,000, and beta, Mr 42,000) in an alpha 2 beta 2 structure with probably two [4Fe-4S] centers. After activation this purified enzyme catalysed the dehydration of (R)-2-hydroxyglutarate only in the presence of acetyl-CoA and glutaconate CoA-transferase, demonstrating that the thiol ester and not the free acid is the substrate of the dehydration. The result led to a modification of the hydroxyglutarate pathway of glutamate fermentation. 2. The activation of the dehydratase by the flow-through from Q-Sepharose concentrated by ultrafiltration required NADH, MgCl2, ATP and strict anaerobic conditions. This fraction was designated as Ao. Later when the concentration was performed by chromatography on phenyl-Sepharose, an NADH-independent form of the activator, designated as A*, was obtained. This enzyme, which required only ATP for activation of the dehydratase, was purified further by affinity chromatography on ATP-agarose. It contains neither iron nor inorganic sulfur. A*, as well as the activated dehydratase, were irreversibly inactivated by exposure to air within less than 15 min. The activated dehydratase but not A* was also inactivated by 1 mM hydroxylamine or by 0.1 mM 2,4-dinitrophenol. 3. The (R)-2-hydroxyglutaryl-CoA dehydratase system is closely related the that of (R)-lactoyl-CoA dehydratase from Clostridium propionicum as described by R. D. Kuchta and R. H. Abeles [(1985) J. Biol. Chem. 260, 13,181-13,189].
Collapse
Affiliation(s)
- G Schweiger
- Biochemie I, Universität Regensburg, Federal Republic of Germany
| | | | | |
Collapse
|
33
|
Kennedy MC, Werst M, Telser J, Emptage MH, Beinert H, Hoffman BM. Mode of substrate carboxyl binding to the [4Fe-4S]+ cluster of reduced aconitase as studied by 17O and 13C electron-nuclear double resonance spectroscopy. Proc Natl Acad Sci U S A 1987; 84:8854-8. [PMID: 3480514 PMCID: PMC299649 DOI: 10.1073/pnas.84.24.8854] [Citation(s) in RCA: 60] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
The active form of aconitase has a diamagnetic [4Fe-4S]2+ cluster. A specific iron ion (Fea, which is lost during inactivation) is the binding site for substrate, as shown by Mössbauer spectroscopy. We have studied the mode of substrate and analogue binding at equilibrium to the paramagnetic [4Fe-4S]+ cluster of the reduced active form by 17O and 13C electron-nuclear double resonance spectroscopy with specifically labeled substrates. The data show that with substrate, only the carboxyl at C-2 of the propane backbone is strongly bound in addition to H2O or OH- (HxO) from the solvent, whereas in an isocitrate analogue that has a nitro group at C-2, the carboxyl and hydroxyl at C-1 are bound along with solvent HxO. We conclude from these data that, on addition of any one of the three substrates, cis-aconitate is the predominant species bound to Fea of the cluster along with solvent HxO and that cis-aconitate is bound in the citrate mode (carboxyl at C-2). The results with the nitro analogue show that the enzyme can also bind a substrate-like ligand to the cluster in the alternative isocitrate mode (carboxyl at C-1), as is implicit in models proposed for the aconitase reaction.
Collapse
Affiliation(s)
- M C Kennedy
- Department of Biochemistry, Medical College of Wisconsin, Milwaukee 53226
| | | | | | | | | | | |
Collapse
|
34
|
17O electron nuclear double resonance characterization of substrate binding to the [4Fe-4S]1+ cluster of reduced active aconitase. J Biol Chem 1986. [DOI: 10.1016/s0021-9258(19)89181-0] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
|
35
|
Kent TA, Emptage MH, Merkle H, Kennedy MC, Beinert H, Münck E. Mössbauer studies of aconitase. Substrate and inhibitor binding, reaction intermediates, and hyperfine interactions of reduced 3Fe and 4Fe clusters. J Biol Chem 1985. [DOI: 10.1016/s0021-9258(18)88861-5] [Citation(s) in RCA: 78] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
|