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Durall C, Kanchugal P S, Selmer M, Lindblad P. Oligomerization and characteristics of phosphoenolpyruvate carboxylase in Synechococcus PCC 7002. Sci Rep 2020; 10:3607. [PMID: 32107404 PMCID: PMC7046716 DOI: 10.1038/s41598-020-60249-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2019] [Accepted: 02/10/2020] [Indexed: 11/09/2022] Open
Abstract
Phosphoenolpyruvate carboxylase (PEPc) is an essential enzyme in plants. A photosynthetic form is present both as dimer and tetramer in C4 and CAM metabolism. Additionally, non-photosynthetic PEPcs are also present. The single, non-photosynthetic PEPc of the unicellular cyanobacterium Synechococcus PCC 7002 (Synechococcus), involved in the TCA cycle, was examined. Using size exclusion chromatography (SEC) and small angle X-ray scattering (SAXS), we observed that PEPc in Synechococcus exists as both a dimer and a tetramer. This is the first demonstration of two different oligomerization states of a non-photosynthetic PEPc. High concentration of Mg2+, the substrate PEP and a combination of low concentration of Mg2+ and HCO3- induced the tetramer form of the carboxylase. Using SEC-SAXS analysis, we showed that the oligomerization state of the carboxylase is concentration dependent and that, among the available crystal structures of PEPc, the scattering profile of PEPc of Synechococcus agrees best with the structure of PEPc from Escherichia coli. In addition, the kinetics of the tetramer purified in presence of Mg2+ using SEC, and of the mixed population purified in presence of Mg2+ using a Strep-tagged column were examined. Moreover, the enzyme showed interesting allosteric regulation, being activated by succinate and inhibited by glutamine, and not affected by either malate, 2-oxoglutarate, aspartic acid or citric acid.
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Affiliation(s)
- Claudia Durall
- Microbial Chemistry, Department of Chemistry - Ångström, Uppsala University, P.O. Box 523, SE-751 20, Uppsala, Sweden
| | - Sandesh Kanchugal P
- Department of Cell and Molecular Biology, BMC, Uppsala University, P.O. Box 596, SE-751 24, Uppsala, Sweden
| | - Maria Selmer
- Department of Cell and Molecular Biology, BMC, Uppsala University, P.O. Box 596, SE-751 24, Uppsala, Sweden
| | - Peter Lindblad
- Microbial Chemistry, Department of Chemistry - Ångström, Uppsala University, P.O. Box 523, SE-751 20, Uppsala, Sweden.
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Takai K, Sako Y, Uchida A. ppc, the gene for phosphoenolpyruvate carboxylase from an extremely thermophilic bacterium, Rhodothermus obamensis: cloning, sequencing and overexpression in Escherichia coli. MICROBIOLOGY (READING, ENGLAND) 1998; 144 ( Pt 5):1423-1434. [PMID: 9611816 DOI: 10.1099/00221287-144-5-1423] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The ppc gene, which encodes phosphoenolpyruvate carboxylase (PEPC) of an extremely thermophilic bacterium, Rhodothermus obamensis, was directly sequenced by the thermal asymmetric interlaced (TAIL) PCR method. An ORF for a 937 amino acid polypeptide was found in the gene. The ppc gene had a high G+C content (66.2 mol%) and the third position of the codon exhibited strong preference for G or C usage (85.0 mol%). The calculated molecular mass was 107,848 Da, which was consistent with the molecular mass of the enzyme as determined by SDS-PAGE (100 kDa). The amino acid sequence of R. obamensis PEPC was closely related to that of PEPC from another thermophile, a Thermus sp., and from a mesophile, Corynebacterium glutamicum, exhibiting 45.3% or 37.7% identity and 61.5% or 56.5% similarity, respectively. By Southern analysis, the ppc gene was found to be present in a single copy in the genomic DNA of this organism. The cloned gene was expressed in Escherichia coli using a pET expression vector system and a thermostable recombinant PEPC was obtained. Comparison of the deduced amino acid sequences of the thermophilic and mesophilic PEPCs revealed distinct or common preferences for specific amino acid composition and substitutions in the two thermophilic enzymes.
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Affiliation(s)
- Ken Takai
- Laboratory of Marine Microbiology, Division of Applied Bioscience, Graduate School of Agriculture, Kyoto University, Kyoto 606-8502, Japan
| | - Yoshihiko Sako
- Laboratory of Marine Microbiology, Division of Applied Bioscience, Graduate School of Agriculture, Kyoto University, Kyoto 606-8502, Japan
| | - Aritsune Uchida
- Laboratory of Marine Microbiology, Division of Applied Bioscience, Graduate School of Agriculture, Kyoto University, Kyoto 606-8502, Japan
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Yano M, Izui K. The replacement of Lys620 by serine desensitizes Escherichia coli phosphoenolpyruvate carboxylase to the effects of the feedback inhibitors L-aspartate and L-malate. EUROPEAN JOURNAL OF BIOCHEMISTRY 1997; 247:74-81. [PMID: 9249011 DOI: 10.1111/j.1432-1033.1997.t01-1-00074.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Chemical modification of Escherichia coli phosphoenolpyruvate carboxylase (P-pyruvate carboxylase) by 2,4,6-trinitrobenzene sulfonate, a specific reagent for amino groups, causes desensitization to allosteric inhibitors, L-aspartate and L-malate, as well as inactivation. When L-malate is included in the modification mixture, P-pyruvate carboxylase was markedly protected from both desensitization and inactivation [Naide, A., Izui, K., Yoshinaga, T. & Katsuki, H. (1979) J. Biochem. (Tokyo) 85, 423-432]. To determine the lysine residue(s) involved in allosteric inhibition, the lysine residues that were protected from modification by L-malate were investigated by analyzing trinitrophenylated peptides liberated by digestion with glutamyl endopeptidase (V8-protease). The identified residues were Lys491, Lys620, Lys650, and Lys773. Each of these residues was individually replaced with an alanine or serine residue by site-directed mutagenesis to produce mutant enzymes. The mutant enzyme whose lysine residue was replaced with serine ([Ser620]P-pyruvate carboxylase) showed a marked desensitization to L-aspartate and L-malate, while retaining almost the same maximal catalytic activity as the wild-type P-pyruvate carboxylase. Essentially no changes in enzymatic properties were observed for the [Ala491]- and [Ala650]P-pyruvate carboxylases, while for the [Ala620]- and [Ala773]P-pyruvate carboxylases the polypeptides of the expected size were not significantly accumulated in the transformed E. coli cells, presumably due to intracellular degradation.
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Affiliation(s)
- M Yano
- Department of Chemistry, Faculty of Science, Kyoto University, Sakyo-ku, Japan
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Sako Y, Takai K, Uchida A, Ishida Y. Purification and characterization of phosphoenolpyruvate carboxylase from the hyperthermophilic archaeon Methanothermus sociabilis. FEBS Lett 1996; 392:148-52. [PMID: 8772193 DOI: 10.1016/0014-5793(96)00805-8] [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
Phosphoenolpyruvate carboxylase (PEPC) was purified for the first time from hyperthermophilic archaeon Methanothermus sociabilis, growing autotrophically with an optimum at 88 degrees C. The optimum temperature for enzyme activity was similar to that for growth and was 85 degrees C. The native enzyme was a homotetramer of 240 kDa molecular mass and the subunit displayed an apparent molecular mass of 60 kDa. The archaeal PEPC was insensitive to various metabolites which are known as allosteric effectors for most bacterial and eucaryal counterparts. The enzyme showed extreme thermostability such that there remained 80% of the enzyme activity after incubation for 2 h at 80 degrees C. These results implied that archaeal PEPC was significantly different from bacterial and eucaryal entities.
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Affiliation(s)
- Y Sako
- Laboratory of Marine Microbiology, Department of Applied Bioscience, Graduate School of Agriculture, Kyoto University, Japan
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Rajagopalan AV, Devi MT, Raghavendra AS. Molecular biology of C4 phosphoenolpyruvate carboxylase: Structure, regulation and genetic engineering. PHOTOSYNTHESIS RESEARCH 1994; 39:115-135. [PMID: 24311065 DOI: 10.1007/bf00029380] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/1993] [Accepted: 11/01/1993] [Indexed: 06/02/2023]
Abstract
Three to four families of nuclear genes encode different isoforms of phosphoenolpyruvate (PEP) carboxylase (PEPC): C4-specific, C3 or etiolated, CAM and root forms. C4 leaf PEPC is encoded by a single gene (ppc) in sorghum and maize, but multiple genes in the C4-dicot Flaveria trinervia. Selective expression of ppc in only C4-mesophyll cells is proposed to be due to nuclear factors, DNA methylation and a distinct gene promoter. Deduced amino acid sequences of C4-PEPC pinpoint the phosphorylatable serine near the N-terminus, C4-specific valine and serine residues near the C-terminus, conserved cysteine, lysine and histidine residues and PEP binding/catalytic sites. During the PEPC reaction, PEP and bicarbonate are first converted into carboxyphosphate and the enolate of pyruvate. Carboxyphosphate decomposes within the active site into Pi and CO2, the latter combining with the enolate to form oxalacetate. Besides carboxylation, PEPC catalyzes a HCO3 (-)-dependent hydrolysis of PEP to yield pyruvate and Pi. Post-translational regulation of PEPC occurs by a phosphorylation/dephosphorylation cascade in vivo and by reversible enzyme oligomerization in vitro. The interrelation between phosphorylation and oligomerization of the enzyme is not clear. PEPC-protein kinase (PEPC-PK), the enzyme responsible for phosphorylation of PEPC, has been studied extensively while only limited information is available on the protein phosphatase 2A capable of dephosphorylating PEPC. The C4 ppc was cloned and expressed in Escherichia coli as well as tobacco. The transformed E. coli produced a functional/phosphorylatable C4 PEPC and the transgenic tobacco plants expressed both C3 and C4 isoforms. Site-directed mutagenesis of ppc indicates the importance of His(138), His(579) and Arg(587) in catalysis and/or substrate-binding by the E. coli enzyme, Ser(8) in the regulation of sorghum PEPC. Important areas for further research on C4 PEPC are: mechanism of transduction of light signal during photoactivation of PEPC-PK and PEPC in leaves, extensive use of site-directed mutagenesis to precisely identify other key amino acid residues, changes in quarternary structure of PEPC in vivo, a high-resolution crystal structure, and hormonal regulation of PEPC expression.
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Affiliation(s)
- A V Rajagopalan
- School of Life Sciences, University of Hyderabad, 500 134, Hyderabad, India
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Hermans J, Westhoff P. Homologous genes for the C4 isoform of phosphoenolpyruvate carboxylase in a C3 and a C4 Flaveria species. MOLECULAR & GENERAL GENETICS : MGG 1992; 234:275-84. [PMID: 1508152 DOI: 10.1007/bf00283848] [Citation(s) in RCA: 56] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The C4 isoform of phosphoenolpyruvate carboxylase (PEPCase) in Flaveria trinervia is encoded by the ppcA subgroup of the PEPCase gene family and is abundantly expressed in the mesophyll cells of leaves. The homologous ppcA genes in the C3 plant F pringlei are only weakly expressed and their transcripts do not show the strictly leaf-specific accumulation pattern observed for the F. trinervia genes. Two representative members of the ppcA subfamilies of F. trinervia (C4) and F. pringeli (C3)-named ppcA1-were characterized by Southern blotting, nucleotide sequencing and primer extension analysis. Comparison of the deduced amino acid sequences reveals a close similarity between C4 and C3 isoforms. Only few C4-specific positions can be detected when all known plant PEPCases are included in the comparison. A regulatory domain involved in light-dependent phosphorylation/dephosphorylation of the C4 and crassulacean acid metabolism (CAM) isoforms is present in the ppcA1 gene products of both the C3 and C4 Flaveria. The 5' flanking regions are essentially homologous. The putative promoter regions share several identical sequence motifs (CCAAT, AT-1 and GT-1 box III/III* elements). Additionally, alterations in elements that could contribute to differences in expression rates and light regulation are found. The significance of these findings is discussed with respect to the molecular evolution of C4 photosynthesis in Flaveria.
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Affiliation(s)
- J Hermans
- Institut für Entwicklungs- und Molekularbiologie der Pflanzen, Heinrich-Heine-Universität, Düsseldorf, FRG
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Terada K, Izui K. Site-directed mutagenesis of the conserved histidine residue of phosphoenolpyruvate carboxylase. His138 is essential for the second partial reaction. EUROPEAN JOURNAL OF BIOCHEMISTRY 1991; 202:797-803. [PMID: 1765093 DOI: 10.1111/j.1432-1033.1991.tb16435.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Histidine residues have previously been suggested to be essential for the activity of phosphoenolpyruvate carboxylase as demonstrated by chemical modification of these residues. Although the location of these residues on the primary structure is not known, a comparison of nine phosphoenolpyruvate (P-pyruvate) carboxylases sequenced recently revealed that there are only two conserved histidine residues (His138 and His579, coordinates from the E. coli enzyme). Site-directed mutagenesis of these residues were undertaken with the E. coli P-pyruvate carboxylase and the properties of purified mutant enzymes were investigated. Mutation of His138 to asparagine (H138N) produced a protein which did not show carboxylase activity. However, this mutant enzyme catalyzed the bicarbonate-dependent dephosphorylation (Vmax = 1.4 mumol.min-1.mg-1) of the P-pyruvate. Since this reaction is due to one of the two partial reactions proposed for this enzyme, the results indicate that His138 is obligatory for the second-step reaction, i.e. the carboxylation of the enolate form of pyruvate by carboxyphosphate. Mutation of His579 to asparagine (H579N) produced an enzyme which had 69% of the wild-type carboxylase activity, but its affinity for P-pyruvate was decreased by 24-fold.
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Affiliation(s)
- K Terada
- Department of Chemistry, Faculty of Science, Kyoto University, Japan
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Lepiniec L, Santi S, Keryer E, Amiet V, Vidal J, Gadal P, Crétin C. Complete nucleotide sequence of one member of the Sorghum phosphoenolpyruvate carboxylase gene family. PLANT MOLECULAR BIOLOGY 1991; 17:1077-1079. [PMID: 1840686 DOI: 10.1007/bf00037146] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Affiliation(s)
- L Lepiniec
- URA CNRS D1128, Université Paris Sud, Orsay, France
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Crétin C, Santi S, Keryer E, Lepiniec L, Tagu D, Vidal J, Gadal P. The phosphoenolpyruvate carboxylase gene family of Sorghum: promoter structures, amino acid sequences and expression of genes. Gene X 1991; 99:87-94. [PMID: 2022326 DOI: 10.1016/0378-1119(91)90037-c] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Two different members of the phosphoenolpyruvate carboxylase(PEPC)-encoding multigene family (clones lambda CP21 and lambda CP46) have been isolated from a Sorghum vulgare lambda EMBL4 genomic library. The use of the 3'-noncoding regions to probe Northern blots of RNA from roots, etiolated leaves and green leaves indicated that lambda CP21 and lambda CP46 encode the C3- and C4-type leaf PEPC isoforms, respectively. The lambda CP21 clone is expressed in the three tissues and is not light-regulated, whereas lambda CP46 is only expressed in greening leaves. The nucleotide sequence of the 5'-flanking DNA (520 bp) has been determined for both genes. For lambda CP46, several direct repeats were located in this region with similarities to sequences found in other light-regulated genes, but not in lambda CP21. The deduced amino acid sequences of the two S. vulgare PEPC proteins are 75% identical.
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Affiliation(s)
- C Crétin
- Laboratoire de Physiologie Végétale Moléculaire. Unité Associée CNRS-URA D1128, Université Paris-Sud. Orsay, France
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Jiao JA, Podestá FE, Chollet R, O'Leary MH, Andreo CS. Isolation and sequence of an active-site peptide from maize leaf phosphoenolpyruvate carboxylase inactivated by pyridoxal 5'-phosphate. BIOCHIMICA ET BIOPHYSICA ACTA 1990; 1041:291-5. [PMID: 2268676 DOI: 10.1016/0167-4838(90)90287-p] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
An active-site peptide from maize (Zea mays L.) phosphoenolpyruvate carboxylase has been isolated, sequenced and identified in the primary structure following chemical modification/inactivation of the enzyme by pyridoxal 5'-phosphate and reduction with sodium borohydride. The amino acid sequence of the purified dodecapeptide is Val-Gly-Tyr-Ser-Asp-Ser-Gly-L*ys-Asp-Ala-Gly-Arg, which corresponds exactly to residues 599-610 in the deduced primary sequence of the maize-leaf enzyme. Comparative analysis of the deduced amino acid sequences of the enzyme from Escherichia coli, Anacystis nidulans and C3, C4 and Crassulacean acid metabolism plants indicates that they all contain this specific lysyl group, as well as a high degree of sequence homology flanking this species-invariant residue. This observation suggests a critical role for Lys-606 during catalysis by maize phosphoenolpyruvate carboxylase. This represents the first identification of a specific, species-invariant active-site residue in the enzyme.
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Affiliation(s)
- J A Jiao
- Department of Biochemistry, University of Nebraska-Lincoln 68583-0718
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Jiao JA, Chollet R. Regulatory phosphorylation of serine-15 in maize phosphoenolpyruvate carboxylase by a C4-leaf protein-serine kinase. Arch Biochem Biophys 1990; 283:300-5. [PMID: 2148863 DOI: 10.1016/0003-9861(90)90646-g] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
We have recently reported that the light-induced changes in the enzymatic and regulatory properties of maize leaf phosphoenolpyruvate carboxylase are attributed to the regulatory seryl phosphorylation of this C4-photosynthesis enzyme. In the present study, the darkform target enzyme was phosphorylated/activated in vitro by a maize leaf protein-serine kinase, and the 32P-labeled regulatory site phosphopeptide was purified from a tryptic digest by metal-ion affinity and reversed-phase chromatography. Automated Edman degradation analysis by covalent protein sequencing technology revealed that the amino acid sequence of this phosphoseryl peptide is His-His-Ser(P)-Ile-Asp-Ala-Gln-Leu-Arg. This nonapeptide, which corresponds exactly to residues 13-21 in the deduced primary sequence of the maize leaf carboxylase, is far removed from recently identified active-site cysteine (Cys-553) and lysine (Lys-606) residues in the C-terminal region of the primary structure. Comparative analysis of the deduced N-terminal sequences of C3-, C4-, and Crassulacean acid metabolism (CAM)-leaf phosphoenolpyruvate carboxylases suggests that the motif of Lys/Arg-X-X-Ser is an important structural requirement of the C4- and CAM-leaf protein-serine kinases.
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Affiliation(s)
- J A Jiao
- Department of Biochemistry, University of Nebraska-Lincoln 68583-0718
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A requirement for phosphoenolpyruvate carboxylase in the cyanobacterium Synechococcus PCC 7942. Arch Microbiol 1990. [DOI: 10.1007/bf00245230] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Inoue M, Hayashi M, Sugimoto M, Harada S, Kai Y, Kasai N, Terada K, Izui K. First crystallization of a phosphoenolpyruvate carboxylase from Escherichia coli. J Mol Biol 1989; 208:509-10. [PMID: 2677392 DOI: 10.1016/0022-2836(89)90515-9] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Two different forms of crystal for a phosphoenolpyruvate carboxylase from Escherichia coli were obtained by the hanging-drop vapor diffusion technique, using polyethylene glycol 4000 as precipitant. The hexagonal crystal in space group P6(2)22 (or P6(4)22) has cell dimensions of a = 131 A and c = 325 A, whereas the orthorhombic crystal in space group I222 has a = 119 A, b = 252 A and c = 83 A. A tetrameric molecule (396,244 Mr), a subunit of which contains 883 amino residues, has a crystallographic 2 symmetry in the hexagonal crystal or 222 symmetry in the orthorhombic crystal, respectively.
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Affiliation(s)
- M Inoue
- Department of Applied Chemistry, Faculty of Engineering, Osaka University, Japan
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O'Regan M, Thierbach G, Bachmann B, Villeval D, Lepage P, Viret JF, Lemoine Y. Cloning and nucleotide sequence of the phosphoenolpyruvate carboxylase-coding gene of Corynebacterium glutamicum ATCC13032. Gene 1989; 77:237-51. [PMID: 2666264 DOI: 10.1016/0378-1119(89)90072-3] [Citation(s) in RCA: 51] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
As a first step in determining the importance of the anaplerotic function of phosphoenolpyruvate carboxylase (PEPC) in amino acid biosynthesis, the ppc gene coding for PEPC of Corynebacterium glutamicum ATCC13032 has been cloned by complementation of an Escherichia coli ppc mutant strain. PEPC activity encoded by the cloned gene is not affected by acetyl-CoA under conditions where the E. coli enzyme is strongly activated, whereas acetyl-CoA is able to relieve inhibition by L-aspartate used singly or in combination with alpha-ketoglutarate. Amplification of the ppc gene in a C. glutamicum lysine-excreting strain resulted in increased PEPC-specific activity and lysine productivity. The nucleotide sequence of a DNA fragment of 4885 bp encompassing the ppc gene has been determined. At the amino acid level, PEPC from C. glutamicum presents overall a high degree of similarity with corresponding enzymes from three different organisms. The location of some strictly conserved regions may have important implications for PEPC activity and allostery.
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Affiliation(s)
- M O'Regan
- Degussa AG/Asta Pharma AG, Halle-Kûnsebeck F.R.G
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Rickers J, Cushman JC, Michalowski CB, Schmitt JM, Bohnert HJ. Expression of the CAM-form of phospho(enol)pyruvate carboxylase and nucleotide sequence of a full length cDNA from Mesembryanthemum crystallinum. MOLECULAR & GENERAL GENETICS : MGG 1989; 215:447-54. [PMID: 2710107 DOI: 10.1007/bf00427042] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
We have determined the complete nucleotide sequence of a full length cDNA encoding the Crassulacean acid metabolism (CAM) isogene of phospho(enol)pyruvate carboxylase (PEPCase). The cDNA clone, 3348 bp in length, was obtained from mRNA isolated from Mesembryanthemum crystallinum (common ice plant) which had undergone salt stress and subsequent induction of CAM. The long open reading frame encodes PEPCase (EC 4.1.1.31) with a predicted molecular mass of 110533 daltons. The deduced amino acid sequence of the ice plant PEPCase is most similar to that from maize having an amino acid identity of 74.9%. Sequence identity in corresponding regions of the PEPCase proteins from Escherichia coli and the cyanobacterium Anacystis nidulans are 41.4% and 33.5%, respectively. A compilation of the four amino acid sequences permitted the identification of phylogenetically conserved regions within the proteins which may play a role in the function of this important enzyme in plant metabolism. Gene specific probes from 3' coding and noncoding regions of the cDNA clone used to probe genomic Southern blots established that this PEPCase gene is present in one copy in the nuclear genome of M. crystallinum. Transcripts arising from this gene increase dramatically when M. crystallinum is irrigated with 0.5 M NaCl, a stress which induces this plant to switch the primary fixation of CO2 from C3 (Calvin cycle) to CAM mode. The salt-induced mRNA encodes a PEPCase isoform which is undetectable in plants in the C3 mode as demonstrated by Northern hybridization.
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Affiliation(s)
- J Rickers
- Department of Biochemistry, University of Arizona, Tucson 85721
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