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| Ferrer, J.L.; Ravanel, S.; Robert, M.; Dumas, R.. |
| Cobalamin-independent methionine synthase (MetE) catalyzes the synthesis of methionine by a direct transfer of the methyl group of N5-methyltetrahydrofolate (CH3-H4PteGlun) to the sulfur atom of homocysteine (Hcy). We report here the first crystal structure of this metalloenzyme under different forms, free or complexed with the Hcy and folate substrates. The Arabidopsis thaliana MetE (AtMetE) crystals reveal a monomeric structure built by two (βα)8 barrels making a deep groove at their interface. The active site is located at the surface of the C-terminal domain, facing the large interdomain cleft. Inside the active site, His647, Cys649, and Cys733 are involved in zinc coordination, whereas Asp605, Ile437, and Ser439 interact with Hcy. Opposite the... |
| Tipo: Journal Article |
Palavras-chave: ARABIDOPSIS THALIANA; STRUCTURE TRIDIMENSIONNELLE; SITE ACTIF; HOMOCYSTEINE; FOLATE; SITE DE LIAISON; ZINC; METHIONINE. |
| Ano: 2004 |
URL: http://www.prodinra.inra.fr/prodinra/pinra/doc.xsp?id=PUB0500031912109810&uri=/notices/prodinra1/2010/11/ |
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| Bedhomme, M.; Hoffmann, M.; McCarthy, E.A.; Gambonnet, B.; Moran, R.G.; Rébeillé, F.; Ravanel, S.. |
| The distribution of folates in plant cells suggests a complex traffic of the vitamin between the organelles and the cytosol. The Arabidopsis thaliana protein AtFOLT1 encoded by the At5g66380 gene is the closest homolog of the mitochondrial folate transporters (MFTs) characterized in mammalian cells. AtFOLT1 belongs to the mitochondrial carrier family, but GFP-tagging experiments and Western blot analyses indicated that it is targeted to the envelope of chloroplasts. By using the glycine auxotroph Chinese hamster ovary glyB cell line, which lacks a functional MFT and is deficient in folates transport into mitochondria, we showed by complementation that AtFOLT1 functions as a folate transporter in a hamster background. Indeed, stable transfectants bearing... |
| Tipo: Journal Article |
Palavras-chave: FOLATE; TRANSPORT INTRACELLULAIRE; ENVELOPPE CHLOROPLASTIQUE; TRANSPORTEUR MITOCHONDRIAL; LOCALISATION SUBCELLULAIRE; CHLOROPLASTE; TRANSPORTEUR; EXPRESSION DES GENES. |
| Ano: 2005 |
URL: http://www.prodinra.inra.fr/prodinra/pinra/doc.xsp?id=PUB0500032102110130&uri=/notices/prodinra1/2010/11/ |
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| Klaus, S.M.J.; Kunji, E.R.S.; Bozzo, G.G.; Noiriel, A.; Díaz de la Garza, R.; Basset, G.J.C.; Ravanel, S.; Rébeillé, F.; Gregory III, J.F.; Hanson, A.D.. |
| Cyanobacterial and plant genomes encode proteins with some similarity to the folate and biopterin transporters of the trypanosomatid parasite Leishmania. The Synechocystis slr0642 gene product and its closest Arabidopsis homolog, the At2g32040 gene product, are representative examples. Both have 12 probable transmembrane domains, and the At2g32040 protein has a predicted chloroplast transit peptide. When expressed in Escherichia coli pabA pabB or folE, mutants, which are unable to produce or take up folates, the slr0642 protein and a modified At2g32040 protein (truncated and fused to the N terminus of slr0642) enabled growth on 5-formyltetrahydrofolate or folic acid but not on 5-formyltetrahydrofolate triglutamate, demonstrating that both proteins mediate... |
| Tipo: Journal Article |
Palavras-chave: CYANOBACTERIE; SYNECHOCYSTIS; TRYPANOSOME; LEISHMANIA; FOLATE; TRANSPORT INTRACELLULAIRE; LOCALISATION SUBCELLULAIRE; TRANSPORTEUR; EXPRESSION DES GENES. |
| Ano: 2005 |
URL: http://www.prodinra.inra.fr/prodinra/pinra/doc.xsp?id=PUB0500032100110128&uri=/notices/prodinra1/2010/11/ |
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| Curien, G.; Ravanel, S.; Robert, M.; Dumas, R.. |
| The Arabidopsis genome contains two genes predicted to code for bifunctional aspartate kinase-homoserine dehydrogenase enzymes (isoforms I and II). These two activities catalyze the first and the third steps toward the synthesis of the essential amino acids threonine, isoleucine, and methionine. We first characterized the kinetic and regulatory properties of the recombinant enzymes, showing that they mainly differ with respect to the inhibition of the homoserine dehydrogenase activity by threonine. A systematic search for other allosteric effectors allowed us to identify an additional inhibitor (leucine) and 5 activators (alanine, cysteine, isoleucine, serine, and valine) equally efficient on aspartate kinase I activity (4-fold activation). The six... |
| Tipo: Journal Article |
Palavras-chave: VOIE METABOLIQUE; ACIDE AMINE ESSENTIEL; ASPARTATE KINASE HOMOSERINE DEHYDROGENASE; ISOFORME; EFFECTEUR ALLOSTERIQUE; INHIBITION ENZYMATIQUE; THREONINE; ISOLEUCINE; METHIONINE; ACTIVITE ENZYMATIQUE. |
| Ano: 2005 |
URL: http://www.prodinra.inra.fr/prodinra/pinra/doc.xsp?id=PUB9500032200111312&uri=/notices/prodinra1/2010/11/ |
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| Rébeillé, F.; Jabrin, S.; Bligny, R.; Loizeau, K.; Gambonnet, B.; Van Wilder, V.; Douce, R.; Ravanel, S.. |
| Despite recent progress in elucidating the regulation of methionine (Met) synthesis, little is known about the catabolism of this amino acid in plants. We present here several lines of evidence indicating that the cleavage of Met catalyzed by Met -lyase is the first step in this process. First, we cloned an Arabidopsis cDNA coding a functional Met -lyase (AtMGL), a cytosolic enzyme catalyzing the conversion of Met into methanethiol, α-ketobutyrate (αKB) and ammonia. AtMGL is present in all the Arabidopsis organs and tissues analyzed, except in quiescent dry mature seeds, thus suggesting that AtMGL is involved in the regulation of Met homeostasis in various situations. Also, we demonstrated that the expression of AtMGL was induced in Arabidopsis cells in... |
| Tipo: Journal Article |
Palavras-chave: PLANTE EXPERIMENTALE; SOUFRE; METHIONINE; RESONANCE MAGNETIQUE NUCLEAIRE; RMN METHIONINE GAMMA LYASE. |
| Ano: 2006 |
URL: http://www.prodinra.inra.fr/prodinra/pinra/doc.xsp?id=PROD2007f25a9ec8&uri=/notices/prodinra1/2008/02/ |
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