1
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Luongo TS, Lambert JP, Yuan A, Zhang X, Gross P, Song J, Shanmughapriya S, Gao E, Jain M, Houser SR, Koch WJ, Cheung JY, Madesh M, Elrod JW. The Mitochondrial Calcium Uniporter Matches Energetic Supply with Cardiac Workload during Stress and Modulates Permeability Transition. Cell Rep 2015; 12:23-34. [PMID: 26119731 DOI: 10.1016/j.celrep.2015.06.017] [Citation(s) in RCA: 279] [Impact Index Per Article: 31.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2015] [Revised: 05/08/2015] [Accepted: 06/04/2015] [Indexed: 12/13/2022] Open
Abstract
Cardiac contractility is mediated by a variable flux in intracellular calcium (Ca(2+)), thought to be integrated into mitochondria via the mitochondrial calcium uniporter (MCU) channel to match energetic demand. Here, we examine a conditional, cardiomyocyte-specific, mutant mouse lacking Mcu, the pore-forming subunit of the MCU channel, in adulthood. Mcu(-/-) mice display no overt baseline phenotype and are protected against mCa(2+) overload in an in vivo myocardial ischemia-reperfusion injury model by preventing the activation of the mitochondrial permeability transition pore, decreasing infarct size, and preserving cardiac function. In addition, we find that Mcu(-/-) mice lack contractile responsiveness to acute β-adrenergic receptor stimulation and in parallel are unable to activate mitochondrial dehydrogenases and display reduced bioenergetic reserve capacity. These results support the hypothesis that MCU may be dispensable for homeostatic cardiac function but required to modulate Ca(2+)-dependent metabolism during acute stress.
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Affiliation(s)
- Timothy S Luongo
- Center for Translational Medicine, Department of Pharmacology, Temple University School of Medicine, Philadelphia, PA 19140, USA
| | - Jonathan P Lambert
- Center for Translational Medicine, Department of Pharmacology, Temple University School of Medicine, Philadelphia, PA 19140, USA
| | - Ancai Yuan
- Center for Translational Medicine, Department of Pharmacology, Temple University School of Medicine, Philadelphia, PA 19140, USA
| | - Xueqian Zhang
- Center for Translational Medicine, Department of Pharmacology, Temple University School of Medicine, Philadelphia, PA 19140, USA
| | - Polina Gross
- Center for Cardiovascular Research, Department of Physiology, Temple University School of Medicine, Philadelphia, PA 19140, USA
| | - Jianliang Song
- Center for Translational Medicine, Department of Pharmacology, Temple University School of Medicine, Philadelphia, PA 19140, USA
| | - Santhanam Shanmughapriya
- Center for Translational Medicine, Department of Pharmacology, Temple University School of Medicine, Philadelphia, PA 19140, USA
| | - Erhe Gao
- Center for Translational Medicine, Department of Pharmacology, Temple University School of Medicine, Philadelphia, PA 19140, USA
| | - Mohit Jain
- Department of Pharmacology, University of California San Diego, La Jolla, CA 92093, USA
| | - Steven R Houser
- Center for Cardiovascular Research, Department of Physiology, Temple University School of Medicine, Philadelphia, PA 19140, USA
| | - Walter J Koch
- Center for Translational Medicine, Department of Pharmacology, Temple University School of Medicine, Philadelphia, PA 19140, USA
| | - Joseph Y Cheung
- Center for Translational Medicine, Department of Pharmacology, Temple University School of Medicine, Philadelphia, PA 19140, USA
| | - Muniswamy Madesh
- Center for Translational Medicine, Department of Pharmacology, Temple University School of Medicine, Philadelphia, PA 19140, USA
| | - John W Elrod
- Center for Translational Medicine, Department of Pharmacology, Temple University School of Medicine, Philadelphia, PA 19140, USA.
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2
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Wu MC, Tian CQ, Cheng HM, Xu L, Wang P, Zhu GP. A Novel Type II NAD+-Specific Isocitrate Dehydrogenase from the Marine Bacterium Congregibacter litoralis KT71. PLoS One 2015; 10:e0125229. [PMID: 25942017 PMCID: PMC4420465 DOI: 10.1371/journal.pone.0125229] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2014] [Accepted: 03/22/2015] [Indexed: 11/29/2022] Open
Abstract
In most living organisms, isocitrate dehydrogenases (IDHs) convert isocitrate into ɑ-ketoglutarate (ɑ-KG). Phylogenetic analyses divide the IDH protein family into two subgroups: types I and II. Based on cofactor usage, IDHs are either NAD+-specific (NAD-IDH) or NADP+-specific (NADP-IDH); NADP-IDH evolved from NAD-IDH. Type I IDHs include NAD-IDHs and NADP-IDHs; however, no type II NAD-IDHs have been reported to date. This study reports a novel type II NAD-IDH from the marine bacterium Congregibacter litoralis KT71 (ClIDH, GenBank accession no. EAQ96042). His-tagged recombinant ClIDH was produced in Escherichia coli and purified; the recombinant enzyme was NAD+-specific and showed no detectable activity with NADP+. The Km values of the enzyme for NAD+ were 262.6±7.4 μM or 309.1±11.2 μM with Mg2+ or Mn2+ as the divalent cation, respectively. The coenzyme specificity of a ClIDH Asp487Arg/Leu488His mutant was altered, and the preference of the mutant for NADP+ was approximately 24-fold higher than that for NAD+, suggesting that ClIDH is an NAD+-specific ancestral enzyme in the type II IDH subgroup. Gel filtration and analytical ultracentrifugation analyses revealed the homohexameric structure of ClIDH, which is the first IDH hexamer discovered thus far. A 163-amino acid segment of CIIDH is essential to maintain its polymerization structure and activity, as a truncated version lacking this region forms a non-functional monomer. ClIDH was dependent on divalent cations, the most effective being Mn2+. The maximal activity of purified recombinant ClIDH was achieved at 35°C and pH 7.5, and a heat inactivation experiment showed that a 20-min incubation at 33°C caused a 50% loss of ClIDH activity. The discovery of a NAD+-specific, type II IDH fills a gap in the current classification of IDHs, and sheds light on the evolution of type II IDHs.
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Affiliation(s)
- Ming-Cai Wu
- Institute of Molecular Biology and Biotechnology, Anhui Normal University, No. 1 Beijing East Road, Wuhu, 241000, Anhui, China
- Anhui Province Key Laboratory of Active Biological Macro-molecules, Wannan Medical College, No. 22 Wenchang West Road, Wuhu, 241002, Anhui, China
| | - Chang-Qing Tian
- Institute of Molecular Biology and Biotechnology, Anhui Normal University, No. 1 Beijing East Road, Wuhu, 241000, Anhui, China
| | - Hong-Mei Cheng
- Institute of Molecular Biology and Biotechnology, Anhui Normal University, No. 1 Beijing East Road, Wuhu, 241000, Anhui, China
| | - Lei Xu
- Institute of Molecular Biology and Biotechnology, Anhui Normal University, No. 1 Beijing East Road, Wuhu, 241000, Anhui, China
- Anhui Province Key Laboratory of Active Biological Macro-molecules, Wannan Medical College, No. 22 Wenchang West Road, Wuhu, 241002, Anhui, China
| | - Peng Wang
- Institute of Molecular Biology and Biotechnology, Anhui Normal University, No. 1 Beijing East Road, Wuhu, 241000, Anhui, China
- * E-mail: (PW); (G-PZ)
| | - Guo-Ping Zhu
- Institute of Molecular Biology and Biotechnology, Anhui Normal University, No. 1 Beijing East Road, Wuhu, 241000, Anhui, China
- * E-mail: (PW); (G-PZ)
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3
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Wang P, Lv C, Zhu G. Novel type II and monomeric NAD+ specific isocitrate dehydrogenases: phylogenetic affinity, enzymatic characterization, and evolutionary implication. Sci Rep 2015; 5:9150. [PMID: 25775177 PMCID: PMC4360740 DOI: 10.1038/srep09150] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2014] [Accepted: 02/23/2015] [Indexed: 11/09/2022] Open
Abstract
NAD(+) use is an ancestral trait of isocitrate dehydrogenase (IDH), and the NADP(+) phenotype arose through evolution as an ancient adaptation event. However, no NAD(+)-specific IDHs have been found among type II IDHs and monomeric IDHs. In this study, novel type II homodimeric NAD-IDHs from Ostreococcus lucimarinus CCE9901 IDH (OlIDH) and Micromonas sp. RCC299 (MiIDH), and novel monomeric NAD-IDHs from Campylobacter sp. FOBRC14 IDH (CaIDH) and Campylobacter curvus (CcIDH) were reported for the first time. The homodimeric OlIDH and monomeric CaIDH were determined by size exclusion chromatography and MALDI-TOF/TOF mass spectrometry. All the four IDHs were demonstrated to be NAD(+)-specific, since OlIDH, MiIDH, CaIDH and CcIDH displayed 99-fold, 224-fold, 61-fold and 37-fold preferences for NAD(+) over NADP(+), respectively. The putative coenzyme discriminating amino acids (Asp326/Met327 in OlIDH, Leu584/Asp595 in CaIDH) were evaluated, and the coenzyme specificities of the two mutants, OlIDH R(326)H(327) and CaIDH H(584)R(595), were completely reversed from NAD(+) to NADP(+). The detailed biochemical properties, including optimal reaction pH and temperature, thermostability, and metal ion effects, of OlIDH and CaIDH were further investigated. The evolutionary connections among OlIDH, CaIDH, and all the other forms of IDHs were described and discussed thoroughly.
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Affiliation(s)
- Peng Wang
- Institute of Molecular Biology and Biotechnology, College of Life Sciences, Anhui Normal University, No.1 Beijing East Road, Wuhu 241000, Anhui, China
| | - Changqi Lv
- Institute of Molecular Biology and Biotechnology, College of Life Sciences, Anhui Normal University, No.1 Beijing East Road, Wuhu 241000, Anhui, China
| | - Guoping Zhu
- Institute of Molecular Biology and Biotechnology, College of Life Sciences, Anhui Normal University, No.1 Beijing East Road, Wuhu 241000, Anhui, China
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4
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Asayama S, Nohara A, Negishi Y, Kawakami H. Plasmid DNA Mono-Ion Complex Stabilized by Hydrogen Bond for In Vivo Diffusive Gene Delivery. Biomacromolecules 2015; 16:1226-31. [DOI: 10.1021/acs.biomac.5b00008] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Shoichiro Asayama
- Department
of Applied Chemistry, Tokyo Metropolitan University, 1-1 minami-Osawa, Hachioji, Tokyo 192-0397, Japan
| | - Atsushi Nohara
- Department
of Applied Chemistry, Tokyo Metropolitan University, 1-1 minami-Osawa, Hachioji, Tokyo 192-0397, Japan
| | - Yoichi Negishi
- Department
of Drug Delivery and Molecular Biopharmaceutics, Tokyo University of Pharmacy and Life Sciences, Horinouchi, Hachioji, Tokyo 192-0392, Japan
| | - Hiroyoshi Kawakami
- Department
of Applied Chemistry, Tokyo Metropolitan University, 1-1 minami-Osawa, Hachioji, Tokyo 192-0397, Japan
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Begara-Morales JC, Chaki M, Sánchez-Calvo B, Mata-Pérez C, Leterrier M, Palma JM, Barroso JB, Corpas FJ. Protein tyrosine nitration in pea roots during development and senescence. JOURNAL OF EXPERIMENTAL BOTANY 2013; 64:1121-34. [PMID: 23362300 PMCID: PMC3580824 DOI: 10.1093/jxb/ert006] [Citation(s) in RCA: 70] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Protein tyrosine nitration is a post-translational modification mediated by reactive nitrogen species (RNS) that is associated with nitro-oxidative damage. No information about this process is available in relation to higher plants during development and senescence. Using pea plants at different developmental stages (ranging from 8 to 71 days), tyrosine nitration in the main organs (roots, stems, leaves, flowers, and fruits) was analysed using immunological and proteomic approaches. In the roots of 71-day-old senescent plants, nitroproteome analysis enabled the identification a total of 16 nitrotyrosine-immunopositive proteins. Among the proteins identified, NADP-isocitrate dehydrogenase (ICDH), an enzyme involved in the carbon and nitrogen metabolism, redox regulation, and responses to oxidative stress, was selected to evaluate the effect of nitration. NADP-ICDH activity fell by 75% during senescence. Analysis showed that peroxynitrite inhibits recombinant cytosolic NADP-ICDH activity through a process of nitration. Of the 12 tyrosines present in this enzyme, mass spectrometric analysis of nitrated recombinant cytosolic NADP-ICDH enabled this study to identify the Tyr392 as exclusively nitrated by peroxynitrite. The data as a whole reveal that protein tyrosine nitration is a nitric oxide-derived PTM prevalent throughout root development and intensifies during senescence.
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Affiliation(s)
- Juan C. Begara-Morales
- Group of Molecular Signaling and Antioxidant Systems in Plants, Associated Unit to Consejo Superior de Investigaciones Científicas (EEZ), Area of Biochemistry and Molecular Biology, University of Jaen, E-23071 Jaén, Spain
| | - Mounira Chaki
- Department of Biochemistry, Molecular and Cellular Biology of Plants, Estación Experimental del Zaidín (EEZ), Consejo Superior de Investigaciones Científicas, E-18080 Granada, Spain
| | - Beatriz Sánchez-Calvo
- Group of Molecular Signaling and Antioxidant Systems in Plants, Associated Unit to Consejo Superior de Investigaciones Científicas (EEZ), Area of Biochemistry and Molecular Biology, University of Jaen, E-23071 Jaén, Spain
| | - Capilla Mata-Pérez
- Group of Molecular Signaling and Antioxidant Systems in Plants, Associated Unit to Consejo Superior de Investigaciones Científicas (EEZ), Area of Biochemistry and Molecular Biology, University of Jaen, E-23071 Jaén, Spain
| | - Marina Leterrier
- Department of Biochemistry, Molecular and Cellular Biology of Plants, Estación Experimental del Zaidín (EEZ), Consejo Superior de Investigaciones Científicas, E-18080 Granada, Spain
| | - José M. Palma
- Department of Biochemistry, Molecular and Cellular Biology of Plants, Estación Experimental del Zaidín (EEZ), Consejo Superior de Investigaciones Científicas, E-18080 Granada, Spain
| | - Juan B. Barroso
- Group of Molecular Signaling and Antioxidant Systems in Plants, Associated Unit to Consejo Superior de Investigaciones Científicas (EEZ), Area of Biochemistry and Molecular Biology, University of Jaen, E-23071 Jaén, Spain
| | - Francisco J. Corpas
- Department of Biochemistry, Molecular and Cellular Biology of Plants, Estación Experimental del Zaidín (EEZ), Consejo Superior de Investigaciones Científicas, E-18080 Granada, Spain
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6
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Leiros HKS, Fedøy AE, Leiros I, Steen IH. The complex structures of isocitrate dehydrogenase from Clostridium thermocellum and Desulfotalea psychrophila suggest a new active site locking mechanism. FEBS Open Bio 2012; 2:159-72. [PMID: 23650595 PMCID: PMC3642140 DOI: 10.1016/j.fob.2012.06.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2012] [Revised: 06/28/2012] [Accepted: 06/28/2012] [Indexed: 11/29/2022] Open
Abstract
Isocitrate dehydrogenase (IDH) catalyzes the oxidative NAD(P)+-dependent decarboxylation of isocitrate into α-ketoglutarate and CO2 and is present in organisms spanning the biological range of temperature. We have solved two crystal structures of the thermophilic Clostridium thermocellum IDH (CtIDH), a native open apo CtIDH to 2.35 Å and a quaternary complex of CtIDH with NADP+, isocitrate and Mg2+ to 2.5 Å. To compare to these a quaternary complex structure of the psychrophilic Desulfotalea psychrophila IDH (DpIDH) was also resolved to 1.93 Å. CtIDH and DpIDH showed similar global thermal stabilities with melting temperatures of 67.9 and 66.9 °C, respectively. CtIDH represents a typical thermophilic enzyme, with a large number of ionic interactions and hydrogen bonds per residue combined with stabilization of the N and C termini. CtIDH had a higher activity temperature optimum, and showed greater affinity for the substrates with an active site that was less thermolabile compared to DpIDH. The uncompensated negative surface charge and the enlarged methionine cluster in the hinge region both of which are important for cold activity in DpIDH, were absent in CtIDH. These structural comparisons revealed that prokaryotic IDHs in subfamily II have a unique locking mechanism involving Arg310, Asp251′ and Arg255 (CtIDH). These interactions lock the large domain to the small domain and direct NADP+ into the correct orientation, which together are important for NADP+ selectivity.
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Key Words
- CtIDH, Clostridium thermocellum IDH
- DSC, differential scanning calorimetry
- DhIDH, Desulfitobacterium hafniense IDH
- Domain movement
- DpIDH, Desulfotalea psychrophila IDH
- EcIDH, Escherichia coli IDH
- HcIDH, human cytosolic IDH
- IDH, isocitrate dehydrogenase
- NADP+ selectivity
- PcIDH, porcine heart mitochondrial IDH
- Psychrophilic
- ScIDH, Saccharomyces cerevesiae mitochondrial IDH
- Temperature adaptation
- Thermophilic
- Tm, apparent melting temperature
- TmIDH, Thermotoga maritima
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Affiliation(s)
- Hanna-Kirsti S Leiros
- The Norwegian Structural Biology Centre (NorStruct), Department of Chemistry, University of Tromsø, N-9037 Tromsø, Norway
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7
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The Role of Mitochondrial NADPH-Dependent Isocitrate Dehydrogenase in Cancer Cells. Int J Cell Biol 2012; 2012:273947. [PMID: 22675360 PMCID: PMC3363418 DOI: 10.1155/2012/273947] [Citation(s) in RCA: 77] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2012] [Accepted: 03/19/2012] [Indexed: 02/07/2023] Open
Abstract
Isocitrate dehydrogenase 2 (IDH2) is located in the mitochondrial matrix. IDH2 acts in the forward Krebs cycle as an NADP+-consuming enzyme, providing NADPH for maintenance of the reduced glutathione and peroxiredoxin systems and for self-maintenance by reactivation of cystine-inactivated IDH2 by glutaredoxin 2. In highly respiring cells, the resulting NAD+ accumulation then induces sirtuin-3-mediated activating IDH2 deacetylation, thus increasing its protective function. Reductive carboxylation of 2-oxoglutarate by IDH2 (in the reverse Krebs cycle direction), which consumes NADPH, may follow glutaminolysis of glutamine to 2-oxoglutarate in cancer cells. When the reverse aconitase reaction and citrate efflux are added, this overall “anoxic” glutaminolysis mode may help highly malignant tumors survive aglycemia during hypoxia. Intermittent glycolysis would hypothetically be required to provide ATP. When oxidative phosphorylation is dormant, this mode causes substantial oxidative stress. Arg172 mutants of human IDH2—frequently found with similar mutants of cytosolic IDH1 in grade 2 and 3 gliomas, secondary glioblastomas, and acute myeloid leukemia—catalyze reductive carboxylation of 2-oxoglutarate and reduction to D-2-hydroxyglutarate, which strengthens the neoplastic phenotype by competitive inhibition of histone demethylation and 5-methylcytosine hydroxylation, leading to genome-wide histone and DNA methylation alternations. D-2-hydroxyglutarate also interferes with proline hydroxylation and thus may stabilize hypoxia-induced factor α.
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Aktas DF, Cook PF. A lysine-tyrosine pair carries out acid-base chemistry in the metal ion-dependent pyridine dinucleotide-linked beta-hydroxyacid oxidative decarboxylases. Biochemistry 2009; 48:3565-77. [PMID: 19281248 DOI: 10.1021/bi8022976] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
This work reviews published structural and kinetic data on the pyridine nucleotide-linked beta-hydroxyacid oxidative decarboxylases. The family of metal ion-dependent pyridine nucleotide-linked beta-hydroxyacid oxidative decarboxylases can be divided into two structural families with the malic enzyme, which has an (S)-hydroxyacid substrate, comprising one subfamily and isocitrate dehydrogenase, isopropylmalate dehydrogenase, homoisocitrate dehydrogenase, and tartrate dehydrogenase, which have an (R)-hydroxyacid substrate, comprising the second subclass. Multiple-sequence alignment of the members of the (R)-hydroxyacid family indicates a high degree of sequence identity with most of the active site residues conserved. The three-dimensional structures of the members of the (R)-hydroxyacid family with structures available superimpose on one another, and the active site structures of the enzymes have a similar overall geometry of residues in the substrate and metal ion binding sites. In addition, a number of residues in the malic enzyme active site are also conserved, and the arrangement of these residues has a similar geometry, although the (R)-hydroxyacid and (S)-hydroxyacid family sites are geometrically mirror images of one another. The active sites of the (R)-hydroxyacid family have a higher positive charge density when compared to those of the (S)-hydroxyacid family, largely due to the number of arginine residues in the vicinity of the substrate alpha-carboxylate and one fewer carboxylate ligand to the divalent metal ion. Data available for all of the enzymes in the family have been considered, and a general mechanism that makes use of a lysine (general base)-tyrosine (general acid) pair is proposed. Differences exist in the mechanism for generating the neutral form of lysine so that it can act as a base.
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Affiliation(s)
- Deniz F Aktas
- Department of Chemistry and Biochemistry, University of Oklahoma, Norman, 73019, USA
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Fedøy AE, Yang N, Martinez A, Leiros HKS, Steen IH. Structural and Functional Properties of Isocitrate Dehydrogenase from the Psychrophilic Bacterium Desulfotalea psychrophila Reveal a Cold-active Enzyme with an Unusual High Thermal Stability. J Mol Biol 2007; 372:130-49. [PMID: 17632124 DOI: 10.1016/j.jmb.2007.06.040] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2007] [Revised: 06/08/2007] [Accepted: 06/13/2007] [Indexed: 11/30/2022]
Abstract
Isocitrate dehydrogenase (IDH) has been studied extensively due to its central role in the Krebs cycle, catalyzing the oxidative NAD(P)(+)-dependent decarboxylation of isocitrate to alpha-ketoglutarate and CO(2). Here, we present the first crystal structure of IDH from a psychrophilic bacterium, Desulfotalea psychrophila (DpIDH). The structural information is combined with a detailed biochemical characterization and a comparative study with IDHs from the mesophilic bacterium Desulfitobacterium hafniense (DhIDH), porcine (PcIDH), human cytosolic (HcIDH) and the hyperthermophilic Thermotoga maritima (TmIDH). DpIDH was found to have a higher melting temperature (T(m)=66.9 degrees C) than its mesophilic homologues and a suboptimal catalytic efficiency at low temperatures. The thermodynamic activation parameters indicated a disordered active site, as seen also for the drastic increase in K(m) for isocitrate at elevated temperatures. A methionine cluster situated at the dimeric interface between the two active sites and a cluster of destabilizing charged amino acids in a region close to the active site might explain the poor isocitrate affinity. On the other hand, DpIDH was optimized for interacting with NADP(+) and the crystal structure revealed unique interactions with the cofactor. The highly acidic surface, destabilizing charged residues, fewer ion pairs and reduced size of ionic networks in DpIDH suggest a flexible global structure. However, strategic placement of ionic interactions stabilizing the N and C termini, and additional ionic interactions in the clasp domain as well as two enlarged aromatic clusters might counteract the destabilizing interactions and promote the increased thermal stability. The structure analysis of DpIDH illustrates how psychrophilic enzymes can adjust their flexibility in dynamic regions during their catalytic cycle without compromising the global stability of the protein.
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Affiliation(s)
- Anita-Elin Fedøy
- Department of Biology, University of Bergen, P.O. Box 7800, Jahnebakken 5, N-5020 Bergen, Norway
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Lee P, Colman RF. Thr373, Asp375, and Lys260 are in the coenzyme site of porcine NADP-dependent isocitrate dehydrogenase. Arch Biochem Biophys 2006; 450:183-90. [PMID: 16712772 DOI: 10.1016/j.abb.2006.04.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2005] [Revised: 03/31/2006] [Accepted: 04/02/2006] [Indexed: 10/24/2022]
Abstract
Thr(373), Lys(374), Asp(375), and Lys(260) were chosen as site-directed mutagenesis targets within porcine NADP-dependent isocitrate dehydrogenase based on structurally corrected sequence alignment among prokaryotic and eukaryotic NADP-isocitrate dehydrogenases. Wild-type and all mutant enzymes were expressed in Escherichia coli and purified to homogeneity. These mutations do not alter the secondary structure or dimerization state of the mutants. The D375N and K260Q mutants exhibit, respectively, a 15- and 28-fold increase in K(m) for NADP, along with marked decreases in V(max) as compared to wild-type enzyme. In contrast, replacing Lys(374), which was previously proposed to contribute to apparent coenzyme affinity, does not change the enzyme's kinetic parameters. T373S exhibits similar kinetic parameters to those of wild-type while T373A and T373V mutations reduce the V(max) values of the resulting enzymes to 1 and 20%, respectively of that of wild-type. We conclude that a hydroxyl group at position 373 is required for effective enzyme function and that Asp(375) and Lys(260) are critical amino acids contributing to coenzyme affinity as well as catalysis by porcine NADP-isocitrate dehydrogenase.
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Affiliation(s)
- Peychii Lee
- Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716, USA
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