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Chen J, Huang SB, Wang X, Huang L, Gao C, Huang XY, Zhao FJ. IAR4 mutation enhances cadmium toxicity by disturbing auxin homeostasis in Arabidopsis thaliana. JOURNAL OF EXPERIMENTAL BOTANY 2024; 75:438-453. [PMID: 37721748 DOI: 10.1093/jxb/erad366] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2022] [Accepted: 09/15/2023] [Indexed: 09/19/2023]
Abstract
Cadmium (Cd) is highly toxic to plants, but the targets and modes of toxicity remain unclear. We isolated a Cd-hypersensitive mutant of Arabidopsis thaliana, Cd-induced short root 2 (cdsr2), in the background of the phytochelatin synthase-defective mutant cad1-3. Both cdsr2 and cdsr2 cad1-3 displayed shorter roots and were more sensitive to Cd than their respective wild type. Using genomic resequencing and complementation, IAR4 was identified as the causal gene, which encodes a putative mitochondrial pyruvate dehydrogenase E1α subunit. cdsr2 showed decreased pyruvate dehydrogenase activity and NADH content, but markedly increased concentrations of pyruvate and alanine in roots. Both Cd stress and IAR4 mutation decreased auxin level in the root tips, and the effect was additive. A higher growth temperature rescued the phenotypes in cdsr2. Exogenous alanine inhibited root growth and decreased auxin level in the wild type. Cadmium stress suppressed the expression of genes involved in auxin biosynthesis, hydrolysis of auxin-conjugates and auxin polar transport. Our results suggest that auxin homeostasis is a key target of Cd toxicity, which is aggravated by IAR4 mutation due to decreased pyruvate dehydrogenase activity. Decreased auxin level in cdsr2 is likely caused by increased auxin-alanine conjugation and decreased energy status in roots.
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Affiliation(s)
- Jie Chen
- State Key Laboratory of Crop Genetics & Germplasm Enhancement and Utilization, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, 210095, China
| | - Shao Bai Huang
- School of Molecular Science and ARC Centre of Excellence in Plant Energy Biology, The University of Western Australia, Crawley, Western Australia 6009, Australia
| | - Xue Wang
- State Key Laboratory of Crop Genetics & Germplasm Enhancement and Utilization, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, 210095, China
| | - LiZhen Huang
- State Key Laboratory of Crop Genetics & Germplasm Enhancement and Utilization, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, 210095, China
| | - Cheng Gao
- State Key Laboratory of Crop Genetics & Germplasm Enhancement and Utilization, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, 210095, China
| | - Xin-Yuan Huang
- State Key Laboratory of Crop Genetics & Germplasm Enhancement and Utilization, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, 210095, China
| | - Fang-Jie Zhao
- State Key Laboratory of Crop Genetics & Germplasm Enhancement and Utilization, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, 210095, China
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2
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Che-Othman MH, Jacoby RP, Millar AH, Taylor NL. Wheat mitochondrial respiration shifts from the tricarboxylic acid cycle to the GABA shunt under salt stress. THE NEW PHYTOLOGIST 2020; 225:1166-1180. [PMID: 30688365 DOI: 10.1111/nph.15713] [Citation(s) in RCA: 90] [Impact Index Per Article: 22.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/08/2019] [Accepted: 01/21/2019] [Indexed: 05/24/2023]
Abstract
Mitochondrial respiration and tricarboxylic acid (TCA) cycle activity are required during salt stress in plants to provide ATP and reductants for adaptive processes such as ion exclusion, compatible solute synthesis and reactive oxygen species (ROS) detoxification. However, there is a poor mechanistic understanding of how salinity affects mitochondrial metabolism, particularly respiratory substrate source. To determine the mechanism of respiratory changes under salt stress in wheat leaves, we conducted an integrated analysis of metabolite content, respiratory rate and targeted protein abundance measurements. Also, we investigated the direct effect of salt on mitochondrial enzyme activities. Salt-treated wheat leaves exhibit higher respiration rate and extensive metabolite changes. The activity of the TCA cycle enzymes pyruvate dehydrogenase complex and the 2-oxoglutarate dehydrogenase complex were shown to be directly salt-sensitive. Multiple lines of evidence showed that the γ-aminobutyric acid (GABA) shunt was activated under salt treatment. During salt exposure, key metabolic enzymes required for the cyclic operation of the TCA cycle are physiochemically inhibited by salt. This inhibition is overcome by increased GABA shunt activity, which provides an alternative carbon source for mitochondria that bypasses salt-sensitive enzymes, to facilitate the increased respiration of wheat leaves.
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Affiliation(s)
- M Hafiz Che-Othman
- ARC Centre of Excellence in Plant Energy Biology, School of Molecular Sciences, The University of Western Australia, Crawley, WA, 6009, Australia
- Centre of Biotechnology and Functional Food, Faculty of Science and Technology, The National University of Malaysia, Bangi, Selangor, 43600, Malaysia
| | - Richard P Jacoby
- ARC Centre of Excellence in Plant Energy Biology, School of Molecular Sciences, The University of Western Australia, Crawley, WA, 6009, Australia
| | - A Harvey Millar
- ARC Centre of Excellence in Plant Energy Biology, School of Molecular Sciences, The University of Western Australia, Crawley, WA, 6009, Australia
| | - Nicolas L Taylor
- ARC Centre of Excellence in Plant Energy Biology, School of Molecular Sciences, The University of Western Australia, Crawley, WA, 6009, Australia
- Institute of Agriculture, The University of Western Australia, Crawley, WA, 6009, Australia
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3
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Wierzbicki MP, Maloney V, Mizrachi E, Myburg AA. Xylan in the Middle: Understanding Xylan Biosynthesis and Its Metabolic Dependencies Toward Improving Wood Fiber for Industrial Processing. FRONTIERS IN PLANT SCIENCE 2019; 10:176. [PMID: 30858858 PMCID: PMC6397879 DOI: 10.3389/fpls.2019.00176] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/09/2018] [Accepted: 02/04/2019] [Indexed: 05/14/2023]
Abstract
Lignocellulosic biomass, encompassing cellulose, lignin and hemicellulose in plant secondary cell walls (SCWs), is the most abundant source of renewable materials on earth. Currently, fast-growing woody dicots such as Eucalyptus and Populus trees are major lignocellulosic (wood fiber) feedstocks for bioproducts such as pulp, paper, cellulose, textiles, bioplastics and other biomaterials. Processing wood for these products entails separating the biomass into its three main components as efficiently as possible without compromising yield. Glucuronoxylan (xylan), the main hemicellulose present in the SCWs of hardwood trees carries chemical modifications that are associated with SCW composition and ultrastructure, and affect the recalcitrance of woody biomass to industrial processing. In this review we highlight the importance of xylan properties for industrial wood fiber processing and how gaining a greater understanding of xylan biosynthesis, specifically xylan modification, could yield novel biotechnology approaches to reduce recalcitrance or introduce novel processing traits. Altering xylan modification patterns has recently become a focus of plant SCW studies due to early findings that altered modification patterns can yield beneficial biomass processing traits. Additionally, it has been noted that plants with altered xylan composition display metabolic differences linked to changes in precursor usage. We explore the possibility of using systems biology and systems genetics approaches to gain insight into the coordination of SCW formation with other interdependent biological processes. Acetyl-CoA, s-adenosylmethionine and nucleotide sugars are precursors needed for xylan modification, however, the pathways which produce metabolic pools during different stages of fiber cell wall formation still have to be identified and their co-regulation during SCW formation elucidated. The crucial dependence on precursor metabolism provides an opportunity to alter xylan modification patterns through metabolic engineering of one or more of these interdependent pathways. The complexity of xylan biosynthesis and modification is currently a stumbling point, but it may provide new avenues for woody biomass engineering that are not possible for other biopolymers.
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Affiliation(s)
| | | | | | - Alexander A. Myburg
- Department of Biochemistry, Genetics and Microbiology, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Pretoria, South Africa
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Hastilestari BR, Lorenz J, Reid S, Hofmann J, Pscheidt D, Sonnewald U, Sonnewald S. Deciphering source and sink responses of potato plants (Solanum tuberosum L.) to elevated temperatures. PLANT, CELL & ENVIRONMENT 2018; 41:2600-2616. [PMID: 29869794 DOI: 10.1111/pce.13366] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/05/2018] [Revised: 05/30/2018] [Accepted: 05/31/2018] [Indexed: 05/07/2023]
Abstract
Potato is an important staple food with increasing popularity worldwide. Elevated temperatures significantly impair tuber yield and quality. Breeding heat-tolerant cultivars is therefore an urgent need to ensure sustainable potato production in the future. An integrated approach combining physiology, biochemistry, and molecular biology was undertaken to contribute to a better understanding of heat effects on source- (leaves) and sink-organs (tubers) in a heat-susceptible cultivar. An experimental set-up was designed allowing tissue-specific heat application. Elevated day and night (29°C/27°C) temperatures impaired photosynthesis and assimilate production. Biomass allocation shifted away from tubers towards leaves indicating reduced sink strength of developing tubers. Reduced sink strength of tubers was paralleled by decreased sucrose synthase activity and expression under elevated temperatures. Heat-mediated inhibition of tuber growth coincided with a decreased expression of the phloem-mobile tuberization signal SP6A in leaves. SP6A expression and photosynthesis were also affected, when only the belowground space was heated, and leaves were kept under control conditions. By contrast, the negative effects on tuber metabolism were attenuated, when only the shoot was subjected to elevated temperatures. This, together with transcriptional changes discussed, indicated a bidirectional communication between leaves and tubers to adjust the source capacity and/or sink strength to environmental conditions.
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Affiliation(s)
- Bernadetta Rina Hastilestari
- Department of Biology, Chair of Biochemistry, Friedrich-Alexander-University Erlangen-Nuremberg, Erlangen, Germany
| | - Julia Lorenz
- Department of Biology, Chair of Biochemistry, Friedrich-Alexander-University Erlangen-Nuremberg, Erlangen, Germany
| | - Stephen Reid
- Department of Biology, Chair of Biochemistry, Friedrich-Alexander-University Erlangen-Nuremberg, Erlangen, Germany
| | - Jörg Hofmann
- Department of Biology, Chair of Biochemistry, Friedrich-Alexander-University Erlangen-Nuremberg, Erlangen, Germany
| | - David Pscheidt
- Department of Biology, Chair of Biochemistry, Friedrich-Alexander-University Erlangen-Nuremberg, Erlangen, Germany
| | - Uwe Sonnewald
- Department of Biology, Chair of Biochemistry, Friedrich-Alexander-University Erlangen-Nuremberg, Erlangen, Germany
| | - Sophia Sonnewald
- Department of Biology, Chair of Biochemistry, Friedrich-Alexander-University Erlangen-Nuremberg, Erlangen, Germany
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5
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Xu W, Li Y, Liu C, Zhao S. Protein lysine acetylation guards metabolic homeostasis to fight against cancer. Oncogene 2013; 33:2279-85. [PMID: 23665675 DOI: 10.1038/onc.2013.163] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2012] [Revised: 03/11/2013] [Accepted: 03/12/2013] [Indexed: 02/07/2023]
Abstract
Properly coordinated metabolism and maintained metabolite homeostasis are important because altered metabolite homeostasis has a causal role in many human diseases, including cancer. Metabolite homeostasis is maintained by fine-tuned coordination of metabolite generation and utilization. Metabolite deregulation has recently been shown to alter the signaling pathways and reprogram epigenetic factors associated with tumorigenesis. Protein lysine acetylation is emerging as a metabolism-coordinating mechanism. Mechanistic studies have shown that acetylation may have roles in nutrient adaptation and in maintaining metabolite homeostasis by exerting regulatory effects on metabolic enzymes, metabolic pathways and metabolic networks. Here we review recent progress in the determination of the role of acetylation regulation in metabolism coordination. In particular, we review links between deregulated acetylation in metabolic enzymes and tumorigenesis. We further hypothesize on applications of the mediation of acetylation to restore deregulated metabolism coordination and thus develop novel means of cancer treatment.
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Affiliation(s)
- W Xu
- 1] Sate Key Laboratory of Genetic Engineering, School of Life Sciences, Fudan University, Shanghai, People's Republic of China [2] Institutes of Biomedical Sciences, Fudan University, Shanghai, People's Republic of China
| | - Y Li
- Sate Key Laboratory of Genetic Engineering, School of Life Sciences, Fudan University, Shanghai, People's Republic of China
| | - C Liu
- Sate Key Laboratory of Genetic Engineering, School of Life Sciences, Fudan University, Shanghai, People's Republic of China
| | - S Zhao
- 1] Sate Key Laboratory of Genetic Engineering, School of Life Sciences, Fudan University, Shanghai, People's Republic of China [2] Institutes of Biomedical Sciences, Fudan University, Shanghai, People's Republic of China
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6
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Yu H, Du X, Zhang F, Zhang F, Hu Y, Liu S, Jiang X, Wang G, Liu D. A mutation in the E2 subunit of the mitochondrial pyruvate dehydrogenase complex in Arabidopsis reduces plant organ size and enhances the accumulation of amino acids and intermediate products of the TCA cycle. PLANTA 2012; 236:387-99. [PMID: 22391856 DOI: 10.1007/s00425-012-1620-3] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/13/2012] [Accepted: 02/22/2012] [Indexed: 05/18/2023]
Abstract
The mitochondrial pyruvate dehydrogenase complex (mtPDC) plays a pivotal role in controlling the entry of carbon into the tricarboxylic acid (TCA) cycle for energy production. This multi-enzyme complex consists of three components: E1, E2, and E3. In Arabidopsis, there are three genes, mtE2-1, mtE2-2, and mtE2-3, which encode the putative mtPDC E2 subunit but how each of them contributes to the total mtPDC activity remains unknown. In this work, we characterized an Arabidopsis mutant, m132, that has abnormal small organs. Molecular cloning indicated that the phenotype of m132 is caused by a mutation in the mtE2-1 gene, which results in a truncation of 109 amino acids at the C-terminus of the encoded protein. In m132, mtPDC activity is only 30% of the WT and ATP production is severely impaired. The mutation in the mtE2-1 gene also leads to the over-accumulation of most intermediate products of the TCA cycle and of all the amino acids for protein synthesis. Our results suggest that, among the three mtE2 genes, mtE2-1 is a major contributor to the function of Arabidopsis mtPDC and that the functional disruption of mtE2-1 profoundly affects plant growth and development, as well as its metabolism.
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MESH Headings
- Adenosine Triphosphate/analysis
- Adenosine Triphosphate/metabolism
- Amino Acids/metabolism
- Arabidopsis/enzymology
- Arabidopsis/genetics
- Arabidopsis/growth & development
- Arabidopsis/ultrastructure
- Chromosome Mapping
- Citric Acid Cycle/genetics
- Cytokinins/analysis
- Cytokinins/metabolism
- Gene Expression Regulation, Enzymologic/genetics
- Gene Expression Regulation, Plant/genetics
- Mitochondria/enzymology
- Mitochondria/genetics
- Mutagenesis, Insertional
- Organ Size/genetics
- Phenotype
- Plant Components, Aerial/enzymology
- Plant Components, Aerial/genetics
- Plant Components, Aerial/growth & development
- Plant Components, Aerial/ultrastructure
- Plants, Genetically Modified
- Protein Structure, Tertiary
- Pyruvate Dehydrogenase Complex/genetics
- Pyruvate Dehydrogenase Complex/metabolism
- Pyruvic Acid/analysis
- Pyruvic Acid/metabolism
- Seedlings/enzymology
- Seedlings/genetics
- Seedlings/growth & development
- Seedlings/ultrastructure
- Seeds/enzymology
- Seeds/genetics
- Seeds/growth & development
- Seeds/ultrastructure
- Sequence Analysis, DNA
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Affiliation(s)
- Hailan Yu
- MOE Key Laboratory of Bioinformatics, School of Life Sciences, Tsinghua University, Beijing, 100084, China
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7
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Ahsan N, Swatek KN, Zhang J, Miernyk JA, Xu D, Thelen JJ. "Scanning mutagenesis" of the amino acid sequences flanking phosphorylation site 1 of the mitochondrial pyruvate dehydrogenase complex. FRONTIERS IN PLANT SCIENCE 2012; 3:153. [PMID: 22811682 PMCID: PMC3397410 DOI: 10.3389/fpls.2012.00153] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/15/2012] [Accepted: 06/19/2012] [Indexed: 06/01/2023]
Abstract
The mitochondrial pyruvate dehydrogenase complex (mtPDC) is regulated by reversible seryl-phosphorylation of the E1α subunit by a dedicated, intrinsic kinase. The phospho-complex is reactivated when dephosphorylated by an intrinsic PP2C-type protein phosphatase. Both the position of the phosphorylated Ser-residue and the sequences of the flanking amino acids are highly conserved. We have used the synthetic peptide-based kinase client (KiC) assay plus recombinant pyruvate dehydrogenase E1α and E1α-kinase to perform "scanning mutagenesis" of the residues flanking the site of phosphorylation. Consistent with the results from "phylogenetic analysis" of the flanking sequences, the direct peptide-based kinase assays tolerated very few changes. Even conservative changes such as Leu, Ile, or Val for Met, or Glu for Asp, gave very marked reductions in phosphorylation. Overall the results indicate that regulation of the mtPDC by reversible phosphorylation is an extreme example of multiple, interdependent instances of co-evolution.
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Affiliation(s)
- Nagib Ahsan
- Department of Biochemistry, University of MissouriColumbia, MO, USA
- Interdisciplinary Plant Group, University of MissouriColumbia, MO, USA
| | - Kirby N. Swatek
- Department of Biochemistry, University of MissouriColumbia, MO, USA
- Interdisciplinary Plant Group, University of MissouriColumbia, MO, USA
| | - Jingfen Zhang
- Interdisciplinary Plant Group, University of MissouriColumbia, MO, USA
- Department of Computer Science, University of MissouriColumbia, MO, USA
| | - Ján A. Miernyk
- Department of Biochemistry, University of MissouriColumbia, MO, USA
- Interdisciplinary Plant Group, University of MissouriColumbia, MO, USA
- Plant Genetics Research Unit, USDA, Agricultural Research Service, University of MissouriColumbia, MO, USA
| | - Dong Xu
- Interdisciplinary Plant Group, University of MissouriColumbia, MO, USA
- Department of Computer Science, University of MissouriColumbia, MO, USA
| | - Jay J. Thelen
- Department of Biochemistry, University of MissouriColumbia, MO, USA
- Interdisciplinary Plant Group, University of MissouriColumbia, MO, USA
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8
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Hirani TA, Tovar-Méndez A, Miernyk JA, Randall DD. Asp295 stabilizes the active-site loop structure of pyruvate dehydrogenase, facilitating phosphorylation of ser292 by pyruvate dehydrogenase-kinase. Enzyme Res 2011; 2011:939068. [PMID: 21318135 PMCID: PMC3034952 DOI: 10.4061/2011/939068] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2010] [Accepted: 11/05/2010] [Indexed: 01/22/2023] Open
Abstract
We have developed an in vitro system for detailed analysis of reversible phosphorylation of the plant mitochondrial pyruvate dehydrogenase complex, comprising recombinant Arabidopsis thalianaα2β2-heterotetrameric pyruvate dehydrogenase (E1) plus A. thaliana E1-kinase (AtPDK). Upon addition of MgATP, Ser292, which is located within the active-site loop structure of E1α, is phosphorylated. In addition to Ser292, Asp295 and Gly297 are highly conserved in the E1α active-site loop sequences. Mutation of Asp295 to Ala, Asn, or Leu greatly reduced phosphorylation of Ser292, while mutation of Gly297 had relatively little effect. Quantitative two-hybrid analysis was used to show that mutation of Asp295 did not substantially affect binding of AtPDK to E1α. When using pyruvate as a variable substrate, the Asp295 mutant proteins had modest changes in kcat, Km, and kcat/Km values. Therefore, we propose that Asp295 plays an important role in stabilizing the active-site loop structure, facilitating transfer of the γ-phosphate from ATP to the Ser residue at regulatory site one of E1α.
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Affiliation(s)
- Tripty A Hirani
- Department of Biochemistry, University of Missouri, Columbia, MO 65211, USA
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9
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Millar AH, Whelan J, Soole KL, Day DA. Organization and regulation of mitochondrial respiration in plants. ANNUAL REVIEW OF PLANT BIOLOGY 2011; 62:79-104. [PMID: 21332361 DOI: 10.1146/annurev-arplant-042110-103857] [Citation(s) in RCA: 385] [Impact Index Per Article: 29.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Mitochondrial respiration in plants provides energy for biosynthesis, and its balance with photosynthesis determines the rate of plant biomass accumulation. We describe recent advances in our understanding of the mitochondrial respiratory machinery of cells, including the presence of a classical oxidative phosphorylation system linked to the cytosol by transporters, discussed alongside nonphosphorylating (and, therefore, non-energy conserving) bypasses that alter the efficiency of ATP synthesis and play a role in oxidative stress responses in plants. We consider respiratory regulation in the context of the contrasting roles mitochondria play in different tissues, from photosynthetic leaves to nutrient-acquiring roots. We focus on the molecular nature of this regulation at transcriptional and post-transcriptional levels that allow the respiratory apparatus of plants to help shape organ development and the response of plants to environmental stress. We highlight the challenges for future research considering spatial and temporal changes of respiration in response to changing climatic conditions.
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Affiliation(s)
- A Harvey Millar
- Australian Research Council Center of Excellence in Plant Energy Biology, University of Western Australia, M316 Crawley, Western Australia 6009, Australia
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10
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Gidda SK, Shockey JM, Rothstein SJ, Dyer JM, Mullen RT. Arabidopsis thaliana GPAT8 and GPAT9 are localized to the ER and possess distinct ER retrieval signals: functional divergence of the dilysine ER retrieval motif in plant cells. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2009; 47:867-79. [PMID: 19539490 DOI: 10.1016/j.plaphy.2009.05.008] [Citation(s) in RCA: 84] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2008] [Revised: 05/14/2009] [Accepted: 05/27/2009] [Indexed: 05/03/2023]
Abstract
Glycerol-3-phosphate acyltransferase (GPAT; EC 2.3.1.15) catalyzes the committed step in the production of glycerolipids, which are major components of cellular membranes, seed storage oils, and epicuticular wax coatings. While the biochemical activities of GPATs have been characterized in detail, the cellular features of these enzymes are only beginning to emerge. Here we characterized the phylogenetic relationships and cellular properties of two GPAT enzymes from the relatively large Arabidopsis thaliana GPAT family, including GPAT8, which is involved in cutin biosynthesis, and GPAT9, which is a new putative GPAT that has extensive homology with a GPAT from mammalian cells involved in storage oil formation and, thus, may have a similar role in plants. Immunofluorescence microscopy of transiently-expressed myc-epitope-tagged GPAT8 and GPAT9 revealed that both proteins were localized to the endoplasmic reticulum (ER), and differential permeabilization experiments indicated that their N- and C-termini were oriented towards the cytosol. However, these two proteins contained distinct types of ER retrieval signals, with GPAT8 possessing a divergent type of dilysine motif (-KK-COOH rather than the prototypic -KKXX-COOH or -KXKXX-COOH motif) and GPAT9 possessing a hydrophobic pentapeptide motif (-phi-X-X-K/R/D/E-phi-; where phi are large hydrophobic amino acid residues). Notably, the divergent dilysine motif in GPAT8 only functioned effectively when additional upstream residues were included to provide the proper protein context. Extensive mutational analyses of the divergent dilysine motif, based upon sequences present in the C-termini of other GPAT8s from various plant species, further expanded the functional definition of this molecular targeting signal, thereby providing insight to the targeting signals in other GPAT family members as well as other ER-resident membrane proteins within plant cells.
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Affiliation(s)
- Satinder K Gidda
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada N1G 2W1
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11
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Millar AH, Small ID, Day DA, Whelan J. Mitochondrial biogenesis and function in Arabidopsis. THE ARABIDOPSIS BOOK 2008; 6:e0111. [PMID: 22303236 DOI: 10.1199/tab.0105] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Mitochondria represent the powerhouse of cells through their synthesis of ATP. However, understanding the role of mitochondria in the growth and development of plants will rely on a much deeper appreciation of the complexity of this organelle. Arabidopsis research has provided clear identification of mitochondrial components, allowed wide-scale analysis of gene expression, and has aided reverse genetic manipulation to test the impact of mitochondrial component loss on plant function. Forward genetics in Arabidopsis has identified mitochondrial involvement in mutations with notable impacts on plant metabolism, growth and development. Here we consider the evidence for components involved in mitochondria biogenesis, metabolism and signalling to the nucleus.
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12
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Millar AH, Small ID, Day DA, Whelan J. Mitochondrial biogenesis and function in Arabidopsis. THE ARABIDOPSIS BOOK 2008; 6:e0111. [PMID: 22303236 PMCID: PMC3243404 DOI: 10.1199/tab.0111] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Mitochondria represent the powerhouse of cells through their synthesis of ATP. However, understanding the role of mitochondria in the growth and development of plants will rely on a much deeper appreciation of the complexity of this organelle. Arabidopsis research has provided clear identification of mitochondrial components, allowed wide-scale analysis of gene expression, and has aided reverse genetic manipulation to test the impact of mitochondrial component loss on plant function. Forward genetics in Arabidopsis has identified mitochondrial involvement in mutations with notable impacts on plant metabolism, growth and development. Here we consider the evidence for components involved in mitochondria biogenesis, metabolism and signalling to the nucleus.
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Affiliation(s)
- A. Harvey Millar
- Australian Research Council (ARC) Centre of Excellence in Plant Energy Biology, The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009
| | - Ian D. Small
- Australian Research Council (ARC) Centre of Excellence in Plant Energy Biology, The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009
| | - David A. Day
- School of Biological Sciences, The University of Sydney 2006, NSW, Australia
| | - James Whelan
- Australian Research Council (ARC) Centre of Excellence in Plant Energy Biology, The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009
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13
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Tovar-Méndez A, Hirani TA, Miernyk JA, Randall DD. Analysis of the catalytic mechanism of pyruvate dehydrogenase kinase. Arch Biochem Biophys 2005; 434:159-68. [PMID: 15629119 DOI: 10.1016/j.abb.2004.10.017] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2004] [Revised: 10/11/2004] [Indexed: 10/26/2022]
Abstract
It has been proposed that "Glu238" within the N-box of pyruvate dehydrogenase kinase (PDK) is a base catalyst. The pH dependence of k(cat) of Arabidopsis thaliana PDK indicates that ionizable groups with pK values of 6.2 and 8.4 are necessary for catalysis, and the temperature dependence of these values suggests that the acidic pK is due to a carboxyl- or imidazole-group. The E238 and K241 mutants had elevated K(m,ATP) values. The acidic pK value of the E238A mutant was shifted to 5.5. The H233A, L234H, and L234A mutants had the same pK values as wild-type AtPDK, contrary to the previous proposal of a "Glu-polarizing" His. Instead, we suggest that the conserved Glu, Lys, and Asn residues of the N-box contribute to coordinating Mg2+ in a position critical for formation of the PDK-MgATP-substrate ternary complex.
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Affiliation(s)
- Alejandro Tovar-Méndez
- Department of Biochemistry, University of Missouri, 117 Schweitzer Hall, Columbia, MO 65211, USA
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14
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LeClere S, Rampey RA, Bartel B. IAR4, a gene required for auxin conjugate sensitivity in Arabidopsis, encodes a pyruvate dehydrogenase E1alpha homolog. PLANT PHYSIOLOGY 2004; 135:989-99. [PMID: 15173569 PMCID: PMC514133 DOI: 10.1104/pp.104.040519] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/04/2004] [Revised: 03/20/2004] [Accepted: 03/21/2004] [Indexed: 05/17/2023]
Abstract
The formation and hydrolysis of indole-3-acetic acid (IAA) conjugates represent a potentially important means for plants to regulate IAA levels and thereby auxin responses. The identification and characterization of mutants defective in these processes is advancing the understanding of auxin regulation and response. Here we report the isolation and characterization of the Arabidopsis iar4 mutant, which has reduced sensitivity to several IAA-amino acid conjugates. iar4 is less sensitive to a synthetic auxin and low concentrations of an ethylene precursor but responds to free IAA and other hormones tested similarly to wild type. The gene defective in iar4 encodes a homolog of the E1alpha-subunit of mitochondrial pyruvate dehydrogenase, which converts pyruvate to acetyl-coenzyme A. We did not detect glycolysis or Krebs-cycle-related defects in the iar4 mutant, and a T-DNA insertion in the IAR4 coding sequence conferred similar phenotypes as the originally identified missense allele. In contrast, we found that disruption of the previously described mitochondrial pyruvate dehydrogenase E1alpha-subunit does not alter IAA-Ala responsiveness or confer any obvious phenotypes. It is possible that IAR4 acts in the conversion of indole-3-pyruvate to indole-3-acetyl-coenzyme A, which is a potential precursor of IAA and IAA conjugates.
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Affiliation(s)
- Sherry LeClere
- Department of Biochemistry and Cell Biology, Rice University, Houston, Texas 77005, USA
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Szurmak B, Strokovskaya L, Mooney BP, Randall DD, Miernyk JA. Expression and assembly of Arabidopsis thaliana pyruvate dehydrogenase in insect cell cytoplasm. Protein Expr Purif 2003; 28:357-61. [PMID: 12699701 DOI: 10.1016/s1046-5928(02)00712-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A vector was constructed for expression of Arabidopsis thaliana mitochondrial pyruvate dehydrogenase (E1) in the cytoplasm of Trichoplusia ni cells. The construct pDDR101 comprises the mature-E1alpha coding sequence under control of the Polh promoter, plus the mature-E1beta coding sequence under control of the p10 promoter. The E1alpha sequence was engineered to include an N-terminal His-tag. When protein samples were subjected to immobilized metal ion affinity chromatography, the alpha- and beta-subunits co-eluted, indicating association. When the recombinant protein sample was analyzed further by gel permeation chromatography, it was demonstrated that a significant amount eluted at a size consistent with assembly into an alpha2beta2 heterotetramer. Recombinant E1 was able to decarboxylate [1-14C]pyruvate and was a substrate for in vitro phosphorylation by E1-kinase.
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Affiliation(s)
- Blanka Szurmak
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawińskiego 5A, 02_106 Warsaw, Poland
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Tovar-Méndez A, Miernyk JA, Randall DD. Regulation of pyruvate dehydrogenase complex activity in plant cells. EUROPEAN JOURNAL OF BIOCHEMISTRY 2003; 270:1043-9. [PMID: 12631264 DOI: 10.1046/j.1432-1033.2003.03469.x] [Citation(s) in RCA: 170] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The pyruvate dehydrogenase complex (PDC) is subjected to multiple interacting levels of control in plant cells. The first level is subcellular compartmentation. Plant cells are unique in having two distinct, spatially separated forms of the PDC; mitochondrial (mtPDC) and plastidial (plPDC). The mtPDC is the site of carbon entry into the tricarboxylic acid cycle, while the plPDC provides acetyl-CoA and NADH for de novo fatty acid biosynthesis. The second level of regulation of PDC activity is the control of gene expression. The genes encoding the subunits of the mt- and plPDCs are expressed following developmental programs, and are additionally subject to physiological and environmental cues. Thirdly, both the mt- and plPDCs are sensitive to product inhibition, and, potentially, to metabolite effectors. Finally, the two different forms of the complex are regulated by distinct organelle-specific mechanisms. Activity of the mtPDC is regulated by reversible phosphorylation catalyzed by intrinsic kinase and phosphatase components. An additional level of sensitivity is provided by metabolite control of the kinase activity. The plPDC is not regulated by reversible phosphorylation. Instead, activity is controlled to a large extent by the physical environment that exists in the plastid stroma.
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Affiliation(s)
- Alejandro Tovar-Méndez
- Department of Biochemistry, University of Missouri and Plant Genetics Research Unit, USDA, Agricultural Research Service, Columbia, MO 65211, USA
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17
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Marillia EF, Micallef BJ, Micallef M, Weninger A, Pedersen KK, Zou J, Taylor DC. Biochemical and physiological studies of Arabidopsis thaliana transgenic lines with repressed expression of the mitochondrial pyruvate dehydrogenase kinase. JOURNAL OF EXPERIMENTAL BOTANY 2003; 54:259-70. [PMID: 12493853 DOI: 10.1093/jxb/erg020] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Pyruvate dehydrogenase kinase (PDHK), a negative regulator of the mitochondrial pyruvate dehydrogenase complex (mtPDC), plays a pivotal role in controlling mtPDC activity, and hence, the TCA cycle and cell respiration. Previously, the cloning of a PDHK cDNA from Arabidopsis thaliana and the effects of constitutively down-regulating its expression on plant growth and development has been reported. The first detailed analyses of the biochemical and physiological effects of partial silencing of the mtPDHK in A. thaliana using antisense constructs driven by both constitutive and seed-specific promoters are reported here. The studies revealed an increased level of respiration in leaves of the constitutive antisense PDHK transgenics; an increase in respiration was also found in developing seeds of the seed-specific antisense transgenics. Both constitutive and seed-specific partial silencing of the mtPDHK resulted in increased seed oil content and seed weight at maturity. Feeding 3-(14)C pyruvate to bolted stems containing siliques (constitutive transgenics), or to isolated siliques or immature seeds (seed-specific transgenics) confirmed a higher rate of incorporation of radiolabel into all seed lipid species, particularly triacylglycerols. Neither constitutive nor seed-specific partial silencing of PDHK negatively affected overall silique and seed development. Instead, oil and seed yield, and overall plant productivity were improved. These findings suggest that a partial reduction of the repression of the mtPDC by antisense PDHK expression can alter carbon flux and, in particular, the contribution of carbon moieties from pyruvate to fatty acid biosynthesis and storage lipid accumulation in developing seeds, implicating a role for mtPDC in fatty acid biosynthesis in seeds.
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Affiliation(s)
- Elizabeth-France Marillia
- National Research Council of Canada, Plant Biotechnology Institute, 110 Gymnasium Place, Saskatoon, Saskatchewan S7N 0W9, Canada
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18
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Lutziger I, Oliver DJ. Characterization of two cDNAs encoding mitochondrial lipoamide dehydrogenase from Arabidopsis. PLANT PHYSIOLOGY 2001. [PMID: 11598235 DOI: 10.1104/pp.010321] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
In contrast to peas (Pisum sativum), where mitochondrial lipoamide dehydrogenase is encoded by a single gene and shared between the alpha-ketoacid dehydrogenase complexes and the Gly decarboxylase complex, Arabidopsis has two genes encoding for two mitochondrial lipoamide dehydrogenases. Northern-blot analysis revealed different levels of RNA expression for the two genes in different organs; mtLPD1 had higher RNA levels in green leaves compared with the much lower level in roots. The mRNA for mtLPD2 shows the inverse pattern. The other organs examined showed nearly equal RNA expressions for both genes. Analysis of etiolated seedlings transferred to light showed a strong induction of RNA expression for mtLPD1 but only a moderate induction of mtLPD2. Based on the organ and light-dependent expression patterns, we hypothesize that mtLPD1 encodes the protein most often associated with the Gly decarboxylase complex, and mtLPD2 encodes the protein incorporated into alpha-ketoacid dehydrogenase complexes. Due to the high level of sequence conservation between the two mtLPDs, we assume that the proteins, once in the mitochondrial matrix, are interchangeable among the different multienzyme complexes. If present at high levels, one mtLPD might substitute for the other. Supporting this hypothesis are results obtained with a T-DNA knockout mutant, mtlpd2, which shows no apparent phenotypic change under laboratory growth conditions. This indicates that mtLPD1 can substitute for mtLPD2 and associate with all these multienzyme complexes.
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Affiliation(s)
- I Lutziger
- 353 Bessey Hall, Department of Botany, Iowa State University, Ames, IA 50011-1020, USA
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19
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Luethy MH, Gemel J, Johnston ML, Mooney BP, Miernyk JA, Randall DD. Developmental expression of the mitochondrial pyruvate dehydrogenase complex in pea (Pisum sativum) seedlings. PHYSIOLOGIA PLANTARUM 2001; 112:559-566. [PMID: 11473717 DOI: 10.1034/j.1399-3054.2001.1120414.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
In order to better understand control of the mitochondrial pyruvate dehydrogenase complex (PDC), total catalytic activity was determined during development of the primary leaves of pea (Pisum sativum L.) seedlings, as well as in each leaf pair of 21-day-old plants. Activity of the PDC in clarified homogenates was highest in the youngest organs and then dropped dramatically as the leaves matured and became photosynthetically competent. As leaves began to senesce, total PDC activity dropped to zero. Steady-state mRNA levels were determined using E1 and E3 cDNA probes. The overall pattern of transcript abundance matched the pattern observed for total PDC activity; transcript levels for E1alpha and E1beta approached zero during senescence. Levels of the E1alpha, E1beta, E2 and E3 subunits of the PDC were analyzed in the same samples, using specific antibodies. Quantitation of the immunoblotting results throughout this developmental series showed a pattern in parallel with that of catalytic activity and mRNA levels, although the relative changes in subunit protein levels were not as extreme as the changes in activity. The exception to the global pattern was that of the E3 subunit: lipoamide dehydrogenase. Expression of this enzyme was highest in mature, fully expanded leaves, which were active in photosynthesis and photorespiration, reflecting the additional role of E3 as a component of glycine decarboxylase.
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Affiliation(s)
- Michael H. Luethy
- Department of Biochemistry and the Interdisciplinary Plant Group, University of Missouri, Columbia, MO 65211, USA; USDA, Agricultural Research Service, Plant Genetics Research Unit, Columbia, MO 65211, USA; Present address: Monsanto, Mystic Location, 62 Maritime Drive, Mystic, CT 06355-1958, USA; Present address: Department of Pediatric Hematology/Oncology, University of Chicago Children's Hospital, 5841 South Maryland Ave., MC4060, Chicago, IL 60637, USA; Present address: PhycoGen, Inc., 4 Moulton Street, Suite 440, Portland, ME 04101-5013, USA
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20
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Moreno JI, David NR, Miernyk JA, Randall DD. Pisum sativum mitochondrial pyruvate dehydrogenase can be assembled as a functional alpha(2)beta(2) heterotetramer in the cytoplasm of Pichia pastoris. Protein Expr Purif 2000; 19:276-83. [PMID: 10873542 DOI: 10.1006/prep.2000.1247] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Pea (Pisum sativum) mitochondrial pyruvate dehydrogenase (E1) was produced by coexpression of the mature alpha and beta subunits in the cytoplasm of the yeast Pichia pastoris. Size-exclusion chromatography of recombinant E1, using a Superose 12 column, yielded a peak at M(r) 160,000 that contained both alpha and beta subunits as well as E1 activity. This corresponds to the size of native alpha(2)beta(2) E1. Recombinant E1 alpha (His(6))-E1 beta was purified by affinity chromatography using immobilized Ni(+), with a yield of 2.8 mg L(-1). The pyruvate-decarboxylating activity of recombinant E1 was dependent upon added Mg(2+) and thiamin-pyrophosphate and was enhanced by the oxidant potassium ferricyanide. Native pea mitochondrial E1-kinase catalyzed phosphorylation of Ser residues in the alpha-subunit of recombinant E1, with concomitant loss of enzymatic activity. Thus, mitochondrial pyruvate dehydrogenase can be assembled in the cytoplasm of P. pastoris into an alpha(2)beta(2) heterotetramer that is both catalytically active and competent for regulatory phosphorylation.
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Affiliation(s)
- J I Moreno
- Department of Biochemistry, University of Missouri, Columbia, Missouri, 65211, USA
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21
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Johnston ML, Miernyk JA, Randall DD. Use of sulfhydryl-directed inhibitors in vitro to distinguish activities of the mitochondrial and plastidic forms of pyruvate dehydrogenase. Arch Biochem Biophys 2000; 378:192-3. [PMID: 10871061 DOI: 10.1006/abbi.2000.1840] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- M L Johnston
- Department of Biochemistry, University of Missouri, Columbia 65211, USA
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22
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Thelen JJ, Miernyk JA, Randall DD. Molecular cloning and expression analysis of the mitochondrial pyruvate dehydrogenase from maize. PLANT PHYSIOLOGY 1999; 119:635-44. [PMID: 9952460 PMCID: PMC32141 DOI: 10.1104/pp.119.2.635] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/1998] [Accepted: 11/02/1998] [Indexed: 05/19/2023]
Abstract
Four cDNAs, one encoding an alpha-subunit and three encoding beta-subunits of the mitochondrial pyruvate dehydrogenase, were isolated from maize (Zea mays L.) libraries. The deduced amino acid sequences of both alpha- and beta-subunits are approximately 80% identical with Arabidopsis and pea (Pisum sativum L.) homologs. The mature N terminus was determined for the beta-subunit by microsequencing the protein purified from etiolated maize shoot mitochondria and was resolved by two-dimensional gel electrophoresis. This single isoelectric species comprised multiple isoforms. Both alpha- and beta-subunits are encoded by multigene families in maize, as determined by Southern-blot analyses. RNA transcripts for both alpha- and beta-subunits were more abundant in roots than in young leaves or etiolated shoots. Pyruvate dehydrogenase activity was also higher in roots (5-fold) compared with etiolated shoots and leaves. Both subunits were present at similar levels in all tissues examined, indicating coordinated gene regulation. The protein levels were highest in heterotrophic organs and in pollen, which contained about 2-fold more protein than any other organ examined. The relative abundance of these proteins in nonphotosynthetic tissues may reflect a high cellular content of mitochondria, a high level of respiratory activity, or an extra plastidial requirement for acetate.
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Affiliation(s)
- J J Thelen
- Department of Biological Sciences, University of Missouri, Columbia, Missouri 65211, USA
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23
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Millar AH, Knorpp C, Leaver CJ, Hill SA. Plant mitochondrial pyruvate dehydrogenase complex: purification and identification of catalytic components in potato. Biochem J 1998; 334 ( Pt 3):571-6. [PMID: 9729464 PMCID: PMC1219725 DOI: 10.1042/bj3340571] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The pyruvate dehydrogenase complex (mPDC) from potato (Solanum tuberosum cv. Romano) tuber mitochondria was purified 40-fold to a specific activity of 5.60 micromol/min per mg of protein. The activity of the complex depended on pyruvate, divalent cations, NAD+ and CoA and was competitively inhibited by both NADH and acetyl-CoA. SDS/PAGE revealed the complex consisted of seven polypeptide bands with apparent molecular masses of 78, 60, 58, 55, 43, 41 and 37 kDa. N-terminal sequencing revealed that the 78 kDa protein was dihydrolipoamide transacetylase (E2), the 58 kDa protein was dihydrolipoamide dehydrogenase (E3), the 43 and 41 kDa proteins were alpha subunits of pyruvate dehydrogenase, and the 37 kDa protein was the beta subunit of pyruvate dehydrogenase. N-terminal sequencing of the 55 kDa protein band yielded two protein sequences: one was another E3; the other was similar to the sequence of E2 from plant and yeast sources but was distinctly different from the sequence of the 78 kDa protein. Incubation of the mPDC with [2-14C]pyruvate resulted in the acetylation of both the 78 and 55 kDa proteins.
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Affiliation(s)
- A H Millar
- Department of Plant Sciences, University of Oxford, South Parks Road, Oxford OX1 3RB, U.K.
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24
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Thelen JJ, Miernyk JA, Randall DD. Partial purification and characterization of the maize mitochondrial pyruvate dehydrogenase complex. PLANT PHYSIOLOGY 1998; 116:1443-50. [PMID: 9536062 PMCID: PMC35052 DOI: 10.1104/pp.116.4.1443] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/24/1997] [Accepted: 12/23/1997] [Indexed: 05/22/2023]
Abstract
The pyruvate dehydrogenase complex was partially purified and characterized from etiolated maize (Zea mays L.) shoot mitochondria. Analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed proteins of 40, 43, 52 to 53, and 62 to 63 kD. Immunoblot analyses identified these proteins as the E1beta-, E1alpha-, E2-, and E3-subunits, respectively. The molecular mass of maize E2 is considerably smaller than that of other plant E2 subunits (76 kD). The activity of the maize mitochondrial complex has a pH optimum of 7.5 and a divalent cation requirement best satisfied by Mg2+. Michaelis constants for the substrates were 47, 3, 77, and 1 &mgr;m for pyruvate, coenzyme A (CoA), NAD+, and thiamine pyrophosphate, respectively. The products NADH and acetyl-CoA were competitive inhibitors with respect to NAD+ and CoA, and the inhibition constants were 15 and 47 &mgr;m, respectively. The complex was inactivated by phosphorylation and was reactivated after the removal of ATP and the addition of Mg2+.
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25
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Johnston ML, Luethy MH, Miernyk JA, Randall DD. Cloning and molecular analyses of the Arabidopsis thaliana plastid pyruvate dehydrogenase subunits. BIOCHIMICA ET BIOPHYSICA ACTA 1997; 1321:200-6. [PMID: 9393637 DOI: 10.1016/s0005-2728(97)00059-5] [Citation(s) in RCA: 51] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Herein we report the first molecular description of the pyruvate dehydrogenase component of the higher plant plastid pyruvate dehydrogenase complex. The full-length cDNAs for the E1 alpha (1530 bp) and E1 beta (1441 bp) subunits of the Arabidopsis thaliana plastid pyruvate dehydrogenase contain open reading frames that encode polypeptides of 428 and 406 amino acids, respectively, with calculated molecular weight values of 47,120 and 44,208. The deduced amino acid sequences for Arabidopsis plastid E1 alpha and E1 beta have 61% and 68% identity to the odpA and odpB genes of the red alga Porphyra purpurea, respectively, but only 31% and 32% identity to the plant mitochondrial counterparts. Results of Southern analyses suggest that each subunit is encoded by a single gene. Northern blot analyses indicate expression of mRNAs of the appropriate size in Arabidopsis leaves.
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Affiliation(s)
- M L Johnston
- Department of Biochemistry, University of Missouri, Columbia 65211, USA
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26
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Buscaglia CA, Pollevick GD, Veloso C, Lorca M, Frasch AC, Sánchez DO. A putative pyruvate dehydrogenase alpha subunit gene from Trypanosoma cruzi. BIOCHIMICA ET BIOPHYSICA ACTA 1996; 1309:53-7. [PMID: 8950176 DOI: 10.1016/s0167-4781(96)00140-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
A full-length DNA clone encoding a putative pyruvate dehydrogenase alpha subunit (E1 alpha) gene was isolated from a Trypanosoma cruzi (RA strain) DNA library. Sequencing of this clone revealed it to encode a 378 amino acid protein (M(r) 42774) with high sequence similarity to E1 alpha obtained from different sources. The highest score is obtained with human E1 alpha: 43,3% similarity. Southern blot analysis is consistent with the existence of a single copy of this putative T. cruzi E1 alpha gene per haploid genome in different parasite strains. Expression of this gene was demonstrated by Northern blot analysis and its trans-splicing acceptor site was identified by Polymerase Chain Reaction-mediated amplification of its cDNA.
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Affiliation(s)
- C A Buscaglia
- Instituto de Investigaciones Bioquímicas Fundación Campomar, Buenos Aires, Argentina
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27
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Zhu PP, Peterkofsky A. Sequence and organization of genes encoding enzymes involved in pyruvate metabolism in Mycoplasma capricolum. Protein Sci 1996; 5:1719-36. [PMID: 8844861 PMCID: PMC2143489 DOI: 10.1002/pro.5560050825] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The region of the genome of Mycoplasma capricolum upstream of the portion encompassing the genes for Enzymes I and IIAglc of the phosphoenolpyruvate:sugar phosphotransferase system (PTS) was cloned and sequenced. Examination of the sequence revealed open reading frames corresponding to numerous genes involved with the oxidation of pyruvate. The deduced gene organization is naox (encoding NADH oxidase)-lplA (encoding lipoate-protein ligase)-odpA (encoding pyruvate dehydrogenase EI alpha)-odpB (encoding pyruvate dehydrogenase EI beta)-odp2(encoding pyruvate dehydrogenase EII)-dldH (encoding dihydrolipoamide dehydrogenase)-pta (encoding phosphotransacetylase)-ack (encoding acetate kinase)-orfA (an unknown open reading frame)-kdtB-ptsI-crr. Analysis of the DNA sequence suggests that the naox and lplA genes are part of a single operon, odpA and odpB constitute an additional operon, odp2 and dldH a third operon, and pta and ack an additional transcription unit. Phylogenetic analyses of the protein products of the odpA and odpB genes indicate that they are most similar to the corresponding proteins from Mycoplasma genitalium, Acholeplasma laidlawii, and Gram-positive organisms. The product of the odp2 gene contains a single lipoyl domain, as is the case with the corresponding proteins from M. genitalium and numerous other organisms. An evolutionary tree places the M. capricolum odp2 gene product in close relationship to the corresponding proteins from A. laidlawii and M.genitalium. The dldH gene encodes an unusual form of dihydrolipoamide dehydrogenase that contains an aminoterminal extension corresponding to a lipoyl domain, a property shared by the corresponding proteins from Alcaligenes eutrophus and Clostridium magnum. Aside from that feature, the protein is related phylogenetically to the corresponding proteins from A. laidlawii and M. genitalium. The phosphotransacetylase from M. capricolum is related most closely to the corresponding protein from M. genitalium and is distinguished easily from the enzymes from Escherichia coli and Haemophilus influenzae by the absence of the characteristic amino-terminal extension. The acetate kinase from M. capricolum is related evolutionarily to the homologous enzyme from M. genitalium. Map position comparisons of genes encoding proteins involved with pyruvate metabolism show that, whereas all the genes are clustered in M. capricolum, they are scattered in M. genitalium.
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Affiliation(s)
- P P Zhu
- Laboratory of Biochemical Genetics, National Heart, Lung and Blood Institute, Bethesda, Maryland 20892, USA
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