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Baird LM, Berndsen CE, Monroe JD. Malate dehydrogenase in plants: evolution, structure, and a myriad of functions. Essays Biochem 2024:EBC20230089. [PMID: 38868915 DOI: 10.1042/ebc20230089] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2024] [Revised: 04/24/2024] [Accepted: 04/29/2024] [Indexed: 06/14/2024]
Abstract
Malate dehydrogenase (MDH) catalyzes the interconversion of oxaloacetate and malate coupled to the oxidation/reduction of coenzymes NAD(P)H/NAD(P)+. While most animals have two isoforms of MDH located in the cytosol and mitochondria, all major groups of land plants have at least six MDHs localized to the cytosol, mitochondria, plastids, and peroxisomes. This family of enzymes participates in important reactions in plant cells including photosynthesis, photorespiration, lipid metabolism, and NH4+ metabolism. MDH also helps to regulate the energy balance in the cell and may help the plant cope with various environmental stresses. Despite their functional diversity, all of the plant MDH enzymes share a similar structural fold and act as dimers. In this review, we will introduce readers to our current understanding of the plant MDHs, including their evolution, structure, and function. The focus will be on the MDH enzymes of the model plant Arabidopsis thaliana.
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Affiliation(s)
- Lisa M Baird
- Department of Biology, University of San Diego, -5998 Alcalá Park, San Diego, CA 92110, U.S.A
| | - Christopher E Berndsen
- Department of Chemistry and Biochemistry, James Madison University, 901 Carrier Dr. MSC 4501, Harrisonburg, VA 22807, U.S.A
| | - Jonathan D Monroe
- Department of Chemistry and Biochemistry, James Madison University, 901 Carrier Dr. MSC 4501, Harrisonburg, VA 22807, U.S.A
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Provost JJ, Cornely KA, Mertz PS, Peterson CN, Riley SG, Tarbox HJ, Narasimhan SR, Pulido AJ, Springer AL. Phosphorylation of mammalian cytosolic and mitochondrial malate dehydrogenase: insights into regulation. Essays Biochem 2024:EBC20230079. [PMID: 38864157 DOI: 10.1042/ebc20230079] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2024] [Revised: 05/21/2024] [Accepted: 05/23/2024] [Indexed: 06/13/2024]
Abstract
Malate dehydrogenase (MDH) is a key enzyme in mammalian metabolic pathways in cytosolic and mitochondrial compartments. Regulation of MDH through phosphorylation remains an underexplored area. In this review we consolidate evidence supporting the potential role of phosphorylation in modulating the function of mammalian MDH. Parallels are drawn with the phosphorylation of lactate dehydrogenase, a homologous enzyme, to reveal its regulatory significance and to suggest a similar regulatory strategy for MDH. Comprehensive mining of phosphorylation databases, provides substantial experimental (primarily mass spectrometry) evidence of MDH phosphorylation in mammalian cells. Experimentally identified phosphorylation sites are overlaid with MDH's functional domains, offering perspective on how these modifications could influence enzyme activity. Preliminary results are presented from phosphomimetic mutations (serine/threonine residues changed to aspartate) generated in recombinant MDH proteins serving as a proof of concept for the regulatory impact of phosphorylation. We also examine and highlight several approaches to probe the structural and cellular impact of phosphorylation. This review highlights the need to explore the dynamic nature of MDH phosphorylation and calls for identifying the responsible kinases and the physiological conditions underpinning this modification. The synthesis of current evidence and experimental data aims to provide insights for future research on understanding MDH regulation, offering new avenues for therapeutic interventions in metabolic disorders and cancer.
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Affiliation(s)
- Joseph J Provost
- Department of Chemistry and Biochemistry, University of San Diego, San Diego CA, U.S.A
| | - Kathleen A Cornely
- Department of Chemistry and Biochemistry, Providence College, Providence RI, U.S.A
| | - Pamela S Mertz
- Department of Chemistry and Biochemistry, St. Mary's College of Maryland, St. Mary's City, MD, U.S.A
| | | | - Sophie G Riley
- Department of Chemistry and Biochemistry, University of San Diego, San Diego CA, U.S.A
| | - Harrison J Tarbox
- Department of Chemistry and Biochemistry, University of San Diego, San Diego CA, U.S.A
| | - Shree R Narasimhan
- Department of Chemistry and Biochemistry, University of San Diego, San Diego CA, U.S.A
| | - Andrew J Pulido
- Department of Chemistry and Biochemistry, University of San Diego, San Diego CA, U.S.A
| | - Amy L Springer
- Department of Biochemistry and Molecular Biology, University of Massachusetts, Amherst, MA, U.S.A
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McCue W, Finzel BC. Structural Characterization of the Human Cytosolic Malate Dehydrogenase I. ACS OMEGA 2022; 7:207-214. [PMID: 35036692 PMCID: PMC8756447 DOI: 10.1021/acsomega.1c04385] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/13/2021] [Accepted: 12/09/2021] [Indexed: 06/14/2023]
Abstract
The first crystal structure of the human cytosolic malate dehydrogenase I (MDH1) is described. Structure determination at a high resolution (1.65 Å) followed production, isolation, and purification of human MDH1 using a bacterial expression system. The structure is a binary complex of MDH1 with only a bound malonate molecule in the substrate binding site. Comparisons of this structure with malate dehydrogenase enzymes from other species confirm that the human enzyme adopts similar secondary, tertiary, and quaternary structures and that the enzyme retains a similar conformation even when nicotinamide adenine dinucleotide (NAD+) is not bound. A comparison to the highly homologous porcine (sus scrofa) MDH1 ternary structures leads to the conclusion that only small conformational differences are needed to accommodate binding by NAD+ or other NAD+ mimetics. Conformational differences observed in the second subunit show that the NAD+ binding elements are nevertheless quite flexible. Comparison of hMDH1 to the human mitochondrial malate dehydrogenase (hMDH2) reveals some key differences in the α7-α8 loop, which lies directly beneath the substrate binding pocket. These differences might be exploited in the structure-assisted design of selective small molecule inhibitors of hMDH1, an emerging target for the development of anticancer therapeutics.
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Kunze M. The type-2 peroxisomal targeting signal. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2019; 1867:118609. [PMID: 31751594 DOI: 10.1016/j.bbamcr.2019.118609] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2019] [Revised: 11/08/2019] [Accepted: 11/13/2019] [Indexed: 12/13/2022]
Abstract
The type-2 peroxisomal targeting signal (PTS2) is one of two peptide motifs destining soluble proteins for peroxisomes. This signal acts as amphiphilic α-helix exposing the side chains of all conserved residues to the same side. PTS2 motifs are recognized by a bipartite protein complex consisting of the receptor PEX7 and a co-receptor. Cargo-loaded receptor complexes are translocated across the peroxisomal membrane by a transient pore and inside peroxisomes, cargo proteins are released and processed in many, but not all species. The components of the bipartite receptor are re-exported into the cytosol by a ubiquitin-mediated and ATP-driven export mechanism. Structurally, PTS2 motifs resemble other N-terminal targeting signals, whereas the functional relation to the second peroxisomal targeting signal (PTS1) is unclear. Although only a few PTS2-carrying proteins are known in humans, subjects lacking a functional import mechanism for these proteins suffer from the severe inherited disease rhizomelic chondrodysplasia punctata.
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Affiliation(s)
- Markus Kunze
- Medical University of Vienna, Center for Brain Research, Department of Pathobiology of the Nervous System, Spitalgasse 4, 1090 Vienna, Austria.
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Moriyama S, Nishio K, Mizushima T. Structure of glyoxysomal malate dehydrogenase (MDH3) from Saccharomyces cerevisiae. Acta Crystallogr F Struct Biol Commun 2018; 74:617-624. [PMID: 30279312 PMCID: PMC6168765 DOI: 10.1107/s2053230x18011895] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2018] [Accepted: 08/22/2018] [Indexed: 11/10/2022] Open
Abstract
Malate dehydrogenase (MDH), a carbohydrate and energy metabolism enzyme in eukaryotes, catalyzes the interconversion of malate to oxaloacetate (OAA) in conjunction with that of nicotinamide adenine dinucleotide (NAD+) to NADH. Three isozymes of MDH have been reported in Saccharomyces cerevisiae: MDH1, MDH2 and MDH3. MDH1 is a mitochondrial enzyme and a member of the tricarboxylic acid cycle, whereas MDH2 is a cytosolic enzyme that functions in the glyoxylate cycle. MDH3 is a glyoxysomal enzyme that is involved in the reoxidation of NADH, which is produced during fatty-acid β-oxidation. The affinity of MDH3 for OAA is lower than those of MDH1 and MDH2. Here, the crystal structures of yeast apo MDH3, the MDH3-NAD+ complex and the MDH3-NAD+-OAA ternary complex were determined. The structure of the ternary complex suggests that the active-site loop is in the open conformation, differing from the closed conformations in mitochondrial and cytosolic malate dehydrogenases.
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Affiliation(s)
- Shu Moriyama
- Picobiology Institute, Graduate School of Life Science, University of Hyogo, 3-2-1 Kouto, Kamigori-cho, Ako-gun, Hyogo 678-1297, Japan
| | - Kazuya Nishio
- Picobiology Institute, Graduate School of Life Science, University of Hyogo, 3-2-1 Kouto, Kamigori-cho, Ako-gun, Hyogo 678-1297, Japan
| | - Tsunehiro Mizushima
- Picobiology Institute, Graduate School of Life Science, University of Hyogo, 3-2-1 Kouto, Kamigori-cho, Ako-gun, Hyogo 678-1297, Japan
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An Y, Cao Y, Xu Y. Purification and characterization of the plastid-localized NAD-dependent malate dehydrogenase from Arabidopsis thaliana. Biotechnol Appl Biochem 2015; 63:490-6. [PMID: 26095832 DOI: 10.1002/bab.1406] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2014] [Accepted: 06/04/2015] [Indexed: 11/11/2022]
Abstract
Malate dehydrogenase (MDH) ubiquitously exists in living organisms and has many isoforms in a single species. MDHs from some classes have been characterized for their catalytic properties, which show significant variations despite that they share high sequence identity for the active sites. One class MDH, the plastid-localized NAD-dependent MDH (plNAD-MDH) is known to be important for plant survival in a dark environment, but its biochemical and enzymatic properties have not been well characterized. This study attempts to fill the gap. plNAD-MDH was expressed in an Escherichia coli system and purified using nickel-affinity chromatography followed by size exclusion chromatography. The N-terminal fusion his-tag was removed by protease cleavage. The gel filtration assay and glutaraldehyde cross-linking results showed that the active enzyme was a homodimer in solution. Further assay indicated that plNAD-MDH is most active at a neutral pH value. The Km values for oxaloacetate and NADH are found in the submillimolar order, a median range for most MDHs. The maximum reaction rate values, however, are dramatically different from other plant MDHs, indicating that plNAD-MDH has different substrate specificity. Moreover, we obtained crystals for this enzyme, which laid the groundwork for further analysis of the enzymatic mechanism from structural stand point.
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Affiliation(s)
- Yan An
- The Nurturing Station for the State Key Laboratory of Subtropical Silviculture, Zhejiang Agriculture and Forestry University, Lin'an, Zhejiang, People's Republic of China
| | - Youzhi Cao
- The Nurturing Station for the State Key Laboratory of Subtropical Silviculture, Zhejiang Agriculture and Forestry University, Lin'an, Zhejiang, People's Republic of China
| | - Yingwu Xu
- The Nurturing Station for the State Key Laboratory of Subtropical Silviculture, Zhejiang Agriculture and Forestry University, Lin'an, Zhejiang, People's Republic of China
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Enzymatic activity analysis and catalytic essential residues identification of Brucella abortus malate dehydrogenase. ScientificWorldJournal 2014; 2014:973751. [PMID: 24895685 PMCID: PMC4033508 DOI: 10.1155/2014/973751] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2014] [Revised: 03/24/2014] [Accepted: 04/09/2014] [Indexed: 12/01/2022] Open
Abstract
Malate dehydrogenase (MDH) plays important metabolic roles in bacteria. In this study, the recombinant MDH protein (His-MDH) of Brucella abortus was purified and its ability to catalyze the conversion of oxaloacetate (OAA) to L-malate (hereon referred to as MDH activity) was analyzed. Michaelis Constant (Km) and Maximum Reaction Velocity (Vmax) of the reaction were determined to be 6.45 × 10−3 M and 0.87 mM L−1 min−1, respectively. In vitro studies showed that His-MDH exhibited maximal MDH activity in pH 6.0 reaction buffer at 40°C. The enzymatic activity was 100%, 60%, and 40% inhibited by Cu2+, Zn2+, and Pb2+, respectively. In addition, six amino acids in the MDH were mutated to investigate their roles in the enzymatic activity. The results showed that the substitutions of amino acids Arg 89, Asp 149, Arg 152, His 176, or Thr 231 almost abolished the activity of His-MDH. The present study will help to understand MDH's roles in B. abortus metabolism.
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Dolze E, Chigri F, Höwing T, Hierl G, Isono E, Vothknecht UC, Gietl C. Calmodulin-like protein AtCML3 mediates dimerization of peroxisomal processing protease AtDEG15 and contributes to normal peroxisome metabolism. PLANT MOLECULAR BIOLOGY 2013; 83:607-24. [PMID: 23943091 PMCID: PMC3830196 DOI: 10.1007/s11103-013-0112-6] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2012] [Accepted: 07/17/2013] [Indexed: 05/22/2023]
Abstract
Matrix enzymes are imported into peroxisomes and glyoxysomes, a subclass of peroxisomes involved in lipid mobilization. Two peroxisomal targeting signals (PTS), the C-terminal PTS1 and the N-terminal PTS2, mediate the translocation of proteins into the organelle. PTS2 processing upon import is conserved in higher eukaryotes, and in watermelon the glyoxysomal processing protease (GPP) was shown to catalyse PTS2 processing. GPP and its ortholog, the peroxisomal DEG protease from Arabidopsis thaliana (AtDEG15), belong to the Deg/HtrA family of ATP-independent serine proteases with Escherichia coli DegP as their prototype. GPP existes in monomeric and dimeric forms. Their equilibrium is shifted towards the monomer upon Ca(2+)-removal and towards the dimer upon Ca(2+)-addition, which is accompanied by a change in substrate specificity from a general protease (monomer) to the specific cleavage of the PTS2 (dimer). We describe the Ca(2+)/calmodulin (CaM) mediated dimerization of AtDEG15. Dimerization is mediated by the CaM-like protein AtCML3 as shown by yeast two and three hybrid analyses. The binding of AtCML3 occurs within the first 25 N-terminal amino acids of AtDEG15, a domain containing a predicted CaM-binding motif. Biochemical analysis of AtDEG15 deletion constructs in planta support the requirement of the CaM-binding domain for PTS2 processing. Phylogenetic analyses indicate that the CaM-binding site is conserved in peroxisomal processing proteases of higher plants (dicots, monocots) but not present in orthologs of animals or cellular slime molds. Despite normal PTS2 processing activity, an atcml3 mutant exhibited reduced 2,4-DB sensitivity, a phenotype previously reported for the atdeg15 mutant, indicating similarly impaired peroxisome metabolism.
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Affiliation(s)
- Esther Dolze
- Institute of Botany, Center of Life and Food Sciences Weihenstephan, TU Munich, Emil-Ramann-Str. 4, 85350 Freising, Germany
| | - Fatima Chigri
- Department of Biology, Center of Integrated Protein Science, LMU Munich, 82152 Martinsried, Germany
| | - Timo Höwing
- Institute of Botany, Center of Life and Food Sciences Weihenstephan, TU Munich, Emil-Ramann-Str. 4, 85350 Freising, Germany
| | - Georg Hierl
- Institute of Botany, Center of Life and Food Sciences Weihenstephan, TU Munich, Emil-Ramann-Str. 4, 85350 Freising, Germany
| | - Erika Isono
- Department of Plant Systems Biology, Center of Life and Food Sciences Weihenstephan, TU Munich, 85350 Freising, Germany
| | - Ute C. Vothknecht
- Department of Biology, Center of Integrated Protein Science, LMU Munich, 82152 Martinsried, Germany
| | - Christine Gietl
- Institute of Botany, Center of Life and Food Sciences Weihenstephan, TU Munich, Emil-Ramann-Str. 4, 85350 Freising, Germany
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Identification and biochemical characterization of a thermostable malate dehydrogenase from the mesophile Streptomyces coelicolor A3(2). Biosci Biotechnol Biochem 2010; 74:2194-201. [PMID: 21071865 DOI: 10.1271/bbb.100357] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
We identified and characterized a malate dehydrogenase from Streptomyces coelicolor A3(2) (ScMDH). The molecular mass of ScMDH was 73,353.5 Da with two 36,675.0 Da subunits as analyzed by matrix-assisted laser-desorption ionization-time-of-flight mass spectrometry (MALDI-TOF-MS). The detailed kinetic parameters of recombinant ScMDH are reported here. Heat inactivation studies showed that ScMDH was more thermostable than most MDHs from other organisms, except for a few extremely thermophile bacteria. Recombinant ScMDH was highly NAD(+)-specific and displayed about 400-fold (k(cat)) and 1,050-fold (k(cat)/K(m)) preferences for oxaloacetate reduction over malate oxidation. Substrate inhibition studies showed that ScMDH activity was inhibited by excess oxaloacetate (K(i)=5.8 mM) and excess L-malate (K(i)=12.8 mM). Moreover, ScMDH activity was not affected by most metal ions, but was strongly inhibited by Fe(2+) and Zn(2+). Taken together, our findings indicate that ScMDH is significantly thermostable and presents a remarkably high catalytic efficiency for malate synthesis.
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Wang ZD, Wang BJ, Ge YD, Pan W, Wang J, Xu L, Liu AM, Zhu GP. Expression and identification of a thermostable malate dehydrogenase from multicellular prokaryote Streptomyces avermitilis MA-4680. Mol Biol Rep 2010; 38:1629-36. [DOI: 10.1007/s11033-010-0273-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2010] [Accepted: 09/02/2010] [Indexed: 01/18/2023]
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Knutson K, Smith J, Nichols P, Wallert MA, Provost JJ. Bringing the excitement and motivation of research to students; Using inquiry and research-based learning in a year-long biochemistry laboratory : Part II-research-based laboratory-a semester-long research approach using malate dehydrogenase as a research model. BIOCHEMISTRY AND MOLECULAR BIOLOGY EDUCATION : A BIMONTHLY PUBLICATION OF THE INTERNATIONAL UNION OF BIOCHEMISTRY AND MOLECULAR BIOLOGY 2010; 38:324-329. [PMID: 21567852 DOI: 10.1002/bmb.20401] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Research-based learning in a teaching environment is an effective way to help bring the excitement and experience of independent bench research to a large number of students. The program described here is the second of a two-semester biochemistry laboratory series. Here, students are empowered to design, execute and analyze their own experiments for the entire semester. This style of laboratory replaces a variety of shorter labs in favor of an in depth research-based learning experience. The concept is to allow students to function in independent research groups. The research projects are focused on a series of wild-type and mutant clones of malate dehydrogenase. A common research theme for the laboratory helps instructors administer the course and is key to delivering a research opportunity to a large number of students. The outcome of this research-based learning laboratory results in students who are much more confident and skilled in critical areas in biochemistry and molecular biology. Students with research experience have significantly higher confidence and motivation than those students without a previous research experience. We have also found that all students performed better in advanced courses and in the workplace.
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Affiliation(s)
- Kristopher Knutson
- Department of Chemistry, Biosciences and the Biochemistry and Biotechnology Program, Minnesota State University Moorhead, Minnesota, Minnesota 56563
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Weidmann S, Rieu A, Rega M, Coucheney F, Guzzo J. Distinct amino acids of the Oenococcus oeni small heat shock protein Lo18 are essential for damaged protein protection and membrane stabilization. FEMS Microbiol Lett 2010; 309:8-15. [PMID: 20546310 DOI: 10.1111/j.1574-6968.2010.01999.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
The small heat shock protein (smHsp) Lo18 from lactic acid bacteria Oenococcus oeni reduces in vitro thermal aggregation of proteins and modulates the membrane fluidity of native liposomes. An absence of information relating to the way in which the smHsp demonstrates a stabilizing effect for both proteins and membranes prompted this study. We expressed three Lo18 proteins with amino acid substitutions in Escherichia coli to investigate their ability to prevent E. coli protein aggregation and their capacity to stabilize E. coli whole-cell membranes. Our results showed that the alanine 123 to serine substitution induces a decrease in chaperone activity in denaturated proteins, and that the tyrosine 107 is required for membrane stabilization. Moreover, this study revealed that the oligomeric structures of proteins with amino acid substitutions do not appear to be modified. Our data strongly suggest that different amino acids are involved in the thermostabilization of proteins and in membrane fluidity regulation and are localized in the alpha-crystallin domain.
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Helm M, Lück C, Prestele J, Hierl G, Huesgen PF, Fröhlich T, Arnold GJ, Adamska I, Görg A, Lottspeich F, Gietl C. Dual specificities of the glyoxysomal/peroxisomal processing protease Deg15 in higher plants. Proc Natl Acad Sci U S A 2007; 104:11501-6. [PMID: 17592111 PMCID: PMC2040927 DOI: 10.1073/pnas.0704733104] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Glyoxysomes are a subclass of peroxisomes involved in lipid mobilization. Two distinct peroxisomal targeting signals (PTSs), the C-terminal PTS1 and the N-terminal PTS2, are defined. Processing of the PTS2 on protein import is conserved in higher eukaryotes. The cleavage site typically contains a Cys at P1 or P2. We purified the glyoxysomal processing protease (GPP) from the fat-storing cotyledons of watermelon (Citrullus vulgaris) by column chromatography, preparative native isoelectric focusing, and 2D PAGE. The GPP appears in two forms, a 72-kDa monomer and a 144-kDa dimer, which are in equilibrium with one another. The equilibrium is shifted on Ca(2+) removal toward the monomer and on Ca(2+) addition toward the dimer. The monomer is a general degrading protease and is activated by denatured proteins. The dimer constitutes the processing protease because the substrate specificity proven for the monomer (Phi-Arg/Lys downward arrow) is different from the processing substrate specificity (Cys-Xxx downward arrow/Xxx-Cys downward arrow) found with the mixture of monomer and dimer. The Arabidopsis genome analysis disclosed three proteases predicted to be in peroxisomes, a Deg-protease, a pitrilysin-like metallopeptidase, and a Lon-protease. Specific antibodies against the peroxisomal Deg-protease from Arabidopsis (Deg15) identify the watermelon GPP as a Deg15. A knockout mutation in the DEG15 gene of Arabidopsis (At1g28320) prevents processing of the glyoxysomal malate dehydrogenase precursor to the mature form. Thus, the GPP/Deg15 belongs to a group of trypsin-like serine proteases with Escherichia coli DegP as a prototype. Nevertheless, the GPP/Deg15 possesses specific characteristics and is therefore a new subgroup within the Deg proteases.
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Affiliation(s)
- Michael Helm
- Lehrstuhl für Botanik, Technische Universität München, Wissenschaftszentrum Weihenstephan, D-85350 Freising, Germany
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