28 research outputs found
Functional characterization of Bacillus subtilis formate dehydrogenases by EPR spectroscopy
De nos jours un des plus grands dĂ©fis environnementaux est la bioremediation du CO2 atmosphĂ©rique. La rĂ©duction biocatalytique de ce dernier en formiate par les formiate dĂ©shydrogĂ©nases microbiennes (FDHs) apparaĂźt trĂšs prometteuse. Dans ce travail est prĂ©sentĂ©e une caractĂ©risation RPE de deux FDHs similaires nommĂ©es ForCE 1 et ForCE 2 issues de la bactĂ©rie du sol Bacillus subtilis. Elles appartiennent Ă la superfamille des enzymes Ă cofacteur de type Mo/W-bisPGD retrouvĂ©es exclusivement chez les procaryotes et catalysant une grande variĂ©tĂ© de rĂ©actions chimiques. Ces deux FDHs sont dâun grand intĂ©rĂȘt scientifique. Les analyses de leurs sĂ©quences rĂ©vĂšlent que leur site actif ne prĂ©sente pas les rĂ©sidus consensuels associĂ©s Ă lâactivitĂ© formiate-dĂ©shydrogĂ©nase, dĂ©finissant une sous-famille de FDHs encore non caractĂ©risĂ©e. Les voies mĂ©taboliques dans lesquelles ces FDHs sâintĂšgrent au sein de cet organisme restent Ă Ă©lucider, ouvrant ainsi la voie Ă dâautres dĂ©couvertes en biologie.Le coeur catalytique des ForCEs est composĂ© de deux sous-unitĂ©s. Les analyses de sequences revĂšlent que la sous-unitĂ© catalytique ForC abriterait cinq centres FeS et un cofacteur de type Mo-bisPGD alors que ForE nâapparait pas hĂ©berger de cofacteur. En combinant potentiomĂ©trie dâoxydorĂ©duction, spectroscopie de rĂ©sonance paramagnĂ©tique Ă©lectronique (RPE) multifrĂ©quence en onde continue et en mode pulsĂ©, nous avons caractĂ©risĂ© les signatures RPE et les propriĂ©tĂ©s redox de plusieurs centres paramagnĂ©tiques dans lâenzyme ForCE1 purifiĂ©e, Ă savoir quatre centres FeS et deux signatures de type Mo(V) associĂ©es au cofacteur Ă molybdĂšne. Un signal radicalaire intense a Ă©galement Ă©tĂ© dĂ©tectĂ©.Nowadays one of the biggest environmental challenges is the bioremediation of atmospheric CO2. The biocatalytic reduction of CO2 to formate by microbial formate dehydrogenases (FDHs) is very promising. We present the EPR characterization of two similar FDHs, named ForCE 1 and ForCE 2, from the soil bacterium Bacillus subtilis. These enzymes belong to the Mo/W-bisPGD (i.e. pyranopterin guanosine dinucleotide) superfamily, which is widespread in prokaryotes. These two FDHs appear to be of great scientific interest for several reasons : sequence analyses reveal that their active site harbours non-consensual residues for formate-dehydrogenase activity, defining a new FDH sub-familly not yet characterised. Moreover, the way in which these enzymes are integrated into the metabolism of this organism remains to be established, leaving the door open for new biological discoveries. The catalytic core of ForCEs is composed of two subunits. From sequence analysis, the larger one (ForC) is thought to coordinate five iron-sulfur clusters and a Mo-bisPGD while ForE does not appear to harbor any cofactor. By combining redox potentiometry, multifrequency continuous wave (CW) and pulsed EPR spectroscopy, we were able to characterize the EPR signatures and redox properties of several paramagnetic cofactors in the purified enzymes including at least four FeS clusters (the fifth was detected by spin quantitation) and two MoV species associated to the molybdenum cofactor. An unexpectedly intense radical signal was also detected and could be attributed to a highly stabilized menasemiquinone species based on its redox and spectroscopic properties determined by a multi-frequency EPR approach
Thiocyanation of N,N-Dialkylhydrazonoyl Bromides: An Entry to Sulfur-Containing 1,2,4-Triazole Derivatives
International audienceA simple and practical one-pot protocol involving sequential C-H bromination and thiocyanation of readily available aldehyde-derived N,N-dialkylhydrazones has been established for the synthesis of 5-thioxo-1,2,4-triazolium inner salts. Applic
Electrochemical Kinetics Support a Second Coordination Sphere Mechanism in MetalâBased Formate Dehydrogenase
International audienceMetal-based formate dehydrogenases are molybdenum or tungsten-dependent enzymes that catalyze the interconversion between formate and CO 2. According to the current consensus, the metal ion of the catalytic center in its active form is coordinated by 6 S (or 5 S and 1 Se) atoms, leaving no free coordination sites to which formate could bind to the metal. Some authors have proposed that one of the active site ligands decoordinates during turnover to allow formate binding. Another proposal is that the oxidation of formate takes place in the second coordination sphere of the metal. Here, we have used electrochemical steady-state kinetics to elucidate the order of the steps in the catalytic cycle of two formate dehydrogenases. Our results strongly support the "second coordination sphere" hypothesis
Cartographie du systĂšme « Source-to-sink » pĂ©ri-PyrĂ©nĂ©endurant le dĂ©but de lâorogenĂšse
National audienceLes connaissances acquises sur lâexhumation de la chaine PyrĂ©nĂ©enne et lâĂ©volution desbassins dâavant-pays adjacents permettent Ă prĂ©sent dâapprĂ©hender ce systĂšmeorogĂ©nique complexe dans une dĂ©marche intĂ©grative dans lâespace et le temps.Cette approche, dite « source-to-sink » sâattache Ă comprendre lâĂ©volution du routagesĂ©dimentaire depuis la Source (relief orogĂ©nique, craton, recyclage de bassin) enpassant par la zone de transfert (pĂ©riphĂ©riques ou internes au bassin) jusquâau rĂ©servoirfinal (bassin flexural, bassin turbiditique profond). Nous proposons, dans le cadre decette nouvelle cartographie, de compiler les donnĂ©es disponibles et nouvellementacquises dans le projet, sur lâensemble du domaine pĂ©ri-pyrĂ©nĂ©en du Golfe du Lion Ă lâEst jusquâau Golfe de Gascogne Ă lâOuest en incluant le Massif Armoricain au Nordjusquâau bassin de Madrid au Sud.La rĂ©alisation de ces cartes sâappuie sur lâutilisation de nombreuses mĂ©thodes et outils,tels que les reconstructions cinĂ©matiques du systĂšme IbĂ©rie-Europe-MĂ©diterranĂ©e, lescoupes restaurĂ©es, lâhistoire dâexhumation par thermochronologie, le traçage dessources, la caractĂ©risation des surfaces dâaltĂ©ration et dâĂ©rosion, la synthĂšse de lâactivitĂ©des accidents structuraux majeurs, les reconstructions palĂ©ogĂ©ographiques, lâanalyse desgĂ©omĂ©tries sĂ©dimentaires et des directions de transport ainsi que la quantification desvolumes prĂ©servĂ©s dans les bassins.Les pas de temps choisis pour ces cartes permettent de rendre compte de diffĂ©rentsstades dâĂ©volution tectono-sĂ©dimentaire du systĂšme pĂ©ri-pyrĂ©nĂ©en au stade dequiescence de lâorogenĂšse (1) Ă 65 Ma, Danien, et aux stades prĂ©coces de lâorogenĂšse(2) ThanĂ©tien terminal (56Ma) et (3) YprĂ©sien (52 Ma). Les compilations effectuĂ©esmettent en regard domaines exhumĂ©s et zone de sĂ©dimentation en termes de flux et devolumes, et permettent de cartographier les systĂšmes de routage et leur Ă©volution aucours dâun cycle de construction dâun orogĂšne.Travaux de recherche financĂ©s et rĂ©alisĂ©s dans le cadre du programme BRGM-TOTALSource-to-Sin
Cartographie du systÚme « Source-to-sink » péri-Pyrénéen
National audienceLes connaissances acquises sur lâexhumation de la chaĂźne pyrĂ©nĂ©enne et lâĂ©volution des bassinsdâavant-pays adjacents permettent Ă prĂ©sent dâapprĂ©hender ce systĂšme orogĂ©nique complexedans une dĂ©marche intĂ©grative dans lâespace et le temps.Cette approche, dite « source-to-sink » sâattache Ă comprendre lâĂ©volution du routagesĂ©dimentaire depuis la Source (relief orogĂ©nique, craton, recyclage de bassin) en passant par lazone de transfert (pĂ©riphĂ©riques ou internes au bassin) jusquâau rĂ©servoir final (bassin flexural,bassin turbiditique profond). Nous proposons, dans le cadre de cette nouvelle cartographie, decompiler les donnĂ©es disponibles et nouvellement acquises dans le projet S2S, sur lâensembledu domaine pĂ©ri-pyrĂ©nĂ©en du Golfe du Lion Ă lâEst jusquâau Golfe de Gascogne Ă lâOuest enincluant le Massif armoricain au Nord jusquâau bassin de Madrid au Sud.La rĂ©alisation de ces cartes sâappuie sur lâutilisation de nombreuses mĂ©thodes et outils, tels queles reconstructions cinĂ©matiques du systĂšme IbĂ©rie-Europe-MĂ©diterranĂ©e, les coupes restaurĂ©es,lâhistoire dâexhumation par thermochronologie, le traçage des sources, la caractĂ©risation dessurfaces dâaltĂ©ration et dâĂ©rosion, la synthĂšse de lâactivitĂ© des accidents structuraux majeurs, lesreconstructions palĂ©ogĂ©ographiques, lâanalyse des gĂ©omĂ©tries sĂ©dimentaires et des directions detransport ainsi que la quantification des volumes prĂ©servĂ©s dans les bassins.Les pas de temps choisis pour ces cartes permettent de rendre compte de diffĂ©rents stadesdâĂ©volution tectono-sĂ©dimentaire du systĂšme pĂ©ri-pyrĂ©nĂ©en au stade prĂ©coce de lâorogĂ©nĂšse -(1) Ă 52 Ma, YprĂ©sien, aux stades dâorogenĂšse mature - (2) Ă 40 Ma, Bartonien et (3) Ă 34 Ma,Priabonien ainsi quâaux pĂ©riodes post-orogĂ©nique - (4) Ă 24 Ma, Chattien et (5) Ă 11 Ma,Tortonien. Les compilations effectuĂ©es mettent en regard domaines exhumĂ©s et zone desĂ©dimentation en termes de flux et de volumes, et permettent de cartographier les systĂšmes deroutage et leur Ă©volution au cours dâun cycle de construction/destruction dâun orogĂšne.Travaux de recherche financĂ©s et rĂ©alisĂ©s dans le cadre du programme BRGM-TOTAL Source6to-Sin
Cartographie du systĂšme « Source-to-sink » pĂ©ri-PyrĂ©nĂ©endurant le dĂ©but de lâorogenĂšse
National audienceLes connaissances acquises sur lâexhumation de la chaine PyrĂ©nĂ©enne et lâĂ©volution desbassins dâavant-pays adjacents permettent Ă prĂ©sent dâapprĂ©hender ce systĂšmeorogĂ©nique complexe dans une dĂ©marche intĂ©grative dans lâespace et le temps.Cette approche, dite « source-to-sink » sâattache Ă comprendre lâĂ©volution du routagesĂ©dimentaire depuis la Source (relief orogĂ©nique, craton, recyclage de bassin) enpassant par la zone de transfert (pĂ©riphĂ©riques ou internes au bassin) jusquâau rĂ©servoirfinal (bassin flexural, bassin turbiditique profond). Nous proposons, dans le cadre decette nouvelle cartographie, de compiler les donnĂ©es disponibles et nouvellementacquises dans le projet, sur lâensemble du domaine pĂ©ri-pyrĂ©nĂ©en du Golfe du Lion Ă lâEst jusquâau Golfe de Gascogne Ă lâOuest en incluant le Massif Armoricain au Nordjusquâau bassin de Madrid au Sud.La rĂ©alisation de ces cartes sâappuie sur lâutilisation de nombreuses mĂ©thodes et outils,tels que les reconstructions cinĂ©matiques du systĂšme IbĂ©rie-Europe-MĂ©diterranĂ©e, lescoupes restaurĂ©es, lâhistoire dâexhumation par thermochronologie, le traçage dessources, la caractĂ©risation des surfaces dâaltĂ©ration et dâĂ©rosion, la synthĂšse de lâactivitĂ©des accidents structuraux majeurs, les reconstructions palĂ©ogĂ©ographiques, lâanalyse desgĂ©omĂ©tries sĂ©dimentaires et des directions de transport ainsi que la quantification desvolumes prĂ©servĂ©s dans les bassins.Les pas de temps choisis pour ces cartes permettent de rendre compte de diffĂ©rentsstades dâĂ©volution tectono-sĂ©dimentaire du systĂšme pĂ©ri-pyrĂ©nĂ©en au stade dequiescence de lâorogenĂšse (1) Ă 65 Ma, Danien, et aux stades prĂ©coces de lâorogenĂšse(2) ThanĂ©tien terminal (56Ma) et (3) YprĂ©sien (52 Ma). Les compilations effectuĂ©esmettent en regard domaines exhumĂ©s et zone de sĂ©dimentation en termes de flux et devolumes, et permettent de cartographier les systĂšmes de routage et leur Ă©volution aucours dâun cycle de construction dâun orogĂšne.Travaux de recherche financĂ©s et rĂ©alisĂ©s dans le cadre du programme BRGM-TOTALSource-to-Sin
Cartographie du systÚme « Source-to-sink » péri-Pyrénéen
National audienceLes connaissances acquises sur lâexhumation de la chaĂźne pyrĂ©nĂ©enne et lâĂ©volution des bassinsdâavant-pays adjacents permettent Ă prĂ©sent dâapprĂ©hender ce systĂšme orogĂ©nique complexedans une dĂ©marche intĂ©grative dans lâespace et le temps.Cette approche, dite « source-to-sink » sâattache Ă comprendre lâĂ©volution du routagesĂ©dimentaire depuis la Source (relief orogĂ©nique, craton, recyclage de bassin) en passant par lazone de transfert (pĂ©riphĂ©riques ou internes au bassin) jusquâau rĂ©servoir final (bassin flexural,bassin turbiditique profond). Nous proposons, dans le cadre de cette nouvelle cartographie, decompiler les donnĂ©es disponibles et nouvellement acquises dans le projet S2S, sur lâensembledu domaine pĂ©ri-pyrĂ©nĂ©en du Golfe du Lion Ă lâEst jusquâau Golfe de Gascogne Ă lâOuest enincluant le Massif armoricain au Nord jusquâau bassin de Madrid au Sud.La rĂ©alisation de ces cartes sâappuie sur lâutilisation de nombreuses mĂ©thodes et outils, tels queles reconstructions cinĂ©matiques du systĂšme IbĂ©rie-Europe-MĂ©diterranĂ©e, les coupes restaurĂ©es,lâhistoire dâexhumation par thermochronologie, le traçage des sources, la caractĂ©risation dessurfaces dâaltĂ©ration et dâĂ©rosion, la synthĂšse de lâactivitĂ© des accidents structuraux majeurs, lesreconstructions palĂ©ogĂ©ographiques, lâanalyse des gĂ©omĂ©tries sĂ©dimentaires et des directions detransport ainsi que la quantification des volumes prĂ©servĂ©s dans les bassins.Les pas de temps choisis pour ces cartes permettent de rendre compte de diffĂ©rents stadesdâĂ©volution tectono-sĂ©dimentaire du systĂšme pĂ©ri-pyrĂ©nĂ©en au stade prĂ©coce de lâorogĂ©nĂšse -(1) Ă 52 Ma, YprĂ©sien, aux stades dâorogenĂšse mature - (2) Ă 40 Ma, Bartonien et (3) Ă 34 Ma,Priabonien ainsi quâaux pĂ©riodes post-orogĂ©nique - (4) Ă 24 Ma, Chattien et (5) Ă 11 Ma,Tortonien. Les compilations effectuĂ©es mettent en regard domaines exhumĂ©s et zone desĂ©dimentation en termes de flux et de volumes, et permettent de cartographier les systĂšmes deroutage et leur Ă©volution au cours dâun cycle de construction/destruction dâun orogĂšne.Travaux de recherche financĂ©s et rĂ©alisĂ©s dans le cadre du programme BRGM-TOTAL Source6to-Sin
Integrated Source to Sink palaeogeological maps at pluri-basins-scale, understandings and predictions
International audience<p>The knowledge acquired on the exhumation of the Pyrenean chain and the evolution of the adjacent foreland basins makes this Alpine-type domain a good laboratory to better constrain a full sediment routing system in a compressive context and to apprehend the driving processes controlling the sediment routing in space and time. This integrated approach aims at enhancing our basin mastering approach as well as improving our predictions of reservoir properties.</p> <p>This Source-to-Sink study seeks to understand the evolution of sedimentary routing from the Source (orogenic relief, craton, basin recycling) through the transfer zone (peripheral or internal to the basin) to the final sink (flexural basin, deep turbiditic margin). Within this new cartography, we propose to compile the data over the entire peri-Pyrenean domain. We produced large scale quantitative and qualitative maps to better observe and interpret the tectonic, climatic and surface processes impacts of the SRS behavior.</p> <p>These maps include kinematic reconstructions of the Iberian-European-Mediterranean system, restored sequential cross-sections, history/magnitude of exhumation by thermochronology, source tracking, characterization of weathering and erosion surfaces, synthesis of the major structures activity, paleogeographic reconstructions, analysis of sedimentary geometries and transport directions as well as the quantification of volumes preserved in the basins. Their interpretation is combined with a time representation along the routing system, linking classical basin wheeler diagram representation to source erosion and lithologies to obtain a continuous view on the sediment journey.</p> <p>The time steps chosen for these 5 maps account for the different stages of tectono-sedimentary evolution of the peri-Pyrenean system at the early-, syn- and post-orogenic stages. The compilations carried out compare exhumed domains and sedimentation zones in terms of fluxes and volumes and make it possible to map the routing systems and point out the main drivers for the surface evolution during the construction/destruction cycle of an orogen.</p> <p>Research work financed and carried out as part of the BRGM-TOTAL Source-to-Sink program</p>
Identification and characterization of a non-canonical menaquinone-linked formate dehydrogenase
International audienceThe Molybdenum/Tungsten-bispyranopterin guanine dinucleotides (Mo/W-bisPGD) family of Formate Dehydrogenases (FDHs) plays roles in several metabolic pathways ranging from carbon fixation to energy harvesting owing to their reaction with a wide variety of redox partners. Indeed, this metabolic plasticity results from the diverse structures, cofactor content, and substrates employed by partner subunits interacting with the catalytic hub. Here, we unveiled two non-canonical FDHs in Bacillus subtilis which are organized into two-subunit complexes with unique features, ForCE1 and ForCE2. We show that the ForC catalytic subunit interacts with an unprecedented partner subunit, ForE, and that its amino acid sequence within the active site deviates from the consensus residues typically associated with FDH activity, as a histidine residue is naturally substituted with a glutamine. The ForE essential subunit mediates the utilization of menaquinone as an electron acceptor as shown by the formate:menadione oxidoreductase activity of both enzymes, their copurification with menaquinone, and the distinctive detection of a protein-bound neutral menasemiquinone radical by multifrequency electron paramagnetic resonance (EPR) experiments on the purified enzymes. Moreover, EPR characterization of both FDHs reveals the presence of several [Fe-S] clusters with distinct relaxation properties and a weakly anisotropic Mo(V) EPR signature, consistent with the characteristic Mo/bisPGD cofactor of this enzyme family. Altogether, this work enlarges our knowledge of the FDH family by identifying a non-canonical FDH, which differs in terms of architecture, amino acid conservation around the Mo cofactor, and reactivity
Pyruvate Aldolases Catalyze Cross-Aldol Reactions between Ketones: Highly Selective Access to Multi-Functionalized Tertiary Alcohols
International audienceTertiary alcohols are widely represented in nature and among bioactive molecules. Their importance is attested by the continuous efforts to meet the challenge of their stereoselective synthesis. In this context, we propose an enzymatic approach, involving class II pyruvate aldolases. These enzymes are shown to catalyze selective cross-aldol reactions between pyruvic acid or derivatives as nucleophiles and a series of ketones as electrophiles. This catalytic activity is exemplified by the highly stereoselective preparation of seven branched ketols with good yields. One of them was readily converted into a constrained 4-hydroxyproline analogue in a multienzymatic one-pot one-step process