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Crystal structures of cobalamin-independent methionine synthase complexed with zinc, homocysteine, and methyltetrahydrofolate Inra
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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Identification of six novel allosteric effectors of Arabidopsis thaliana aspartate kinase-homoserine dehydrogenase isoforms. Physiological context sets the specificity Inra
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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Mechanism of control of Arabidopsis thaliana aspartate kinase-homoserine dehydrogenase by threonine Inra
Paris, S.; Viemon, C.; Curien, G.; Dumas, R..
The regulatory domain of the bifunctional threonine-sensitive aspartate kinase homoserine dehydrogenase contains two homologous subdomains defined by a common loop-αhelix-loop-β strand-loop-β strand motif. This motif is homologous with that found in the two subdomains of the biosynthetic threonine-deaminase regulatory domain. Comparisons of the primary and secondary structures of the two enzymes allowed us to predict the location and identity of the amino acid residues potentially involved in two threonine-binding sites ofArabidopsis thaliana aspartate kinase-homoserine dehydrogenase. These amino acids were then mutated and activity measurements were carried out to test this hypothesis. Steady-state kinetic experiments on the wild-type and mutant enzymes...
Tipo: Journal Article Palavras-chave: ASPARTOKINASE; GENE THRA; DESAMINASE; STRUCTURE ENZYMATIQUE; INHIBITION ENZYMATIQUE; SEQUENCE NUCLEOTIDIQUE; THREONINE.
Ano: 2003 URL: http://www.prodinra.inra.fr/prodinra/pinra/doc.xsp?id=PUB0400031090101858&uri=/notices/prodinra1/2010/11/
Registros recuperados: 3
Primeira ... 1 ... Última
 

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