References of "Feller, Georges"
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See detailEffectiveness of biostimulation techniques for cleaning of diesel polluted subAntarctic soils (Crozet Archipelago)
Delille, D.; Pelletier, E.; Coulon, F. et al

in Alleman, B. C.; Keley, M. E. (Eds.) In situ bioremediation and on site bioremediation (2005)

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See detailKinetic and structural optimization to catalysis at low temperatures in a psychrophilic cellulase from the Antarctic bacterium Pseudoalteromonas haloplanktis
Garsoux, G.; Lamotte, J.; Gerday, Charles ULiege et al

in Biochemical Journal (2004), 384(Pt 2), 247-253

The cold-adapted cellulase CelG has been purified from the culture supernatant of the Antarctic bacterium Pseudoalteromonas haloplanktis and the gene coding for this enzyme has been cloned, sequenced and ... [more ▼]

The cold-adapted cellulase CelG has been purified from the culture supernatant of the Antarctic bacterium Pseudoalteromonas haloplanktis and the gene coding for this enzyme has been cloned, sequenced and expressed in Escherichia coli. This cellulase is composed of three structurally and functionally distinct regions: an N-terminal catalytic domain belonging to glycosidase family 5 and a C-terminal cellulose-binding domain belonging to carbohydrate-binding module family 5. The linker of 107 residues connecting both domains is one of the longest found in cellulases, and optimizes substrate accessibility to the catalytic domain by drastically increasing the Surface of cellulose available to a bound enzyme molecule. The psychrophilic enzyme is closely related to the cellulase Cel5 from Erwinia chrysanthemi. Both k(cat) and k(cat)/K-m values at 4 degreesC for the psychrophilic cellulase are similar to the values for Cel5 at 30-35 degreesC, suggesting temperature adaptation of the kinetic parameters. The thermodynamic parameters of activation of CelG suggest a heat-labile, relatively disordered active site with low substrate affinity, in agreement with the experimental data. The structure of CelG has been constructed by homology modelling with a molecule of cellotetraose docked into the active site. No structural alteration related to cold-activity can be found in the catalytic cleft, whereas several structural factors in the overall structure can explain the weak thermal stability, suggesting that the loss of stability provides the required active-site mobility at low temperatures. [less ▲]

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See detailExtreme catalysts from low-temperature environments
Hoyoux, A.; Blaise, Vinciane ULiege; Collins, T. et al

in Journal of Bioscience & Bioengineering (2004), 98(5), 317-330

Cold-loving or psychrophilic organisms are widely distributed in nature as a large part of the earth's surface is at temperatures around 0 degrees C. To maintain metabolic rates and to prosper in cold ... [more ▼]

Cold-loving or psychrophilic organisms are widely distributed in nature as a large part of the earth's surface is at temperatures around 0 degrees C. To maintain metabolic rates and to prosper in cold environments, these extremophilic organisms have developed a vast array of adaptations. One main adaptive strategy developed in order to cope with the reduction of chemical reaction rates induced by low temperatures is the synthesis of cold-adapted or psychrophilic enzymes. These enzymes are characterized by a high catalytic activity at low temperatures associated with a low thermal stability. A study of protein adaptation strategies suggests that the high activity of psychrophilic enzymes could be achieved by the destabilization of the active site, allowing the catalytic center to be more flexible at low temperatures, whereas other protein regions may be destabilized or as rigid as their mesophilic counterparts. Due to these particular properties, psychrophilic enzymes offer a high potential not only for fundamental research but also for biotechnological applications. [less ▲]

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See detailA perspective on cold enzymes: Current knowledge and frequently asked questions
Marx, J. C.; Blaise, Vinciane ULiege; Collins, T. et al

in Cellular and Molecular Biology (2004), 50(5), 643-655

Studies on psychrophilic enzymes to determine the structural features important for cold-activity have attracted increased attention in the last few years. This enhanced interest is due to the attractive ... [more ▼]

Studies on psychrophilic enzymes to determine the structural features important for cold-activity have attracted increased attention in the last few years. This enhanced interest is due to the attractive properties of such proteins, i.e. a high specific activity and a low thermal stability, and thus, these enzymes constitute a tremendous potential for fundamental research and biotechnological applications. This review examines the impact of low temperatures on life, the diversity of adaptation to counteract these effects and gives an overview of the features proposed to account for low thermal stability and cold-activity, following the chronological order of the catalytic cycle phases. Moreover, we present an overview of recent techniques used in the analysis of the flexibility of a protein structure which is an important concept in cold-adaptation; an overview of biotechnological potential of psychrophilic enzymes and finally, a few frequently asked questions about cold-adaptation and their possible answers. [less ▲]

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See detailUse of family 8 enzymes with xylanolytic activity in baking
Dutron, Agnes; Georis, Jacques; Genot, Bernard et al

Patent (2004)

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See detailAdenylation-dependent conformation and unfolding pathways of the NAD(+)-dependent DNA ligase from the thermophile Thermus scotoductus
Georlette, D.; Blaise, Vinciane ULiege; Bouillenne, Fabrice ULiege et al

in Biophysical Journal (2004), 86(2), 1089-1104

In the last few years, an increased attention has been focused on NAD(+)-dependent DNA ligases. This is mostly due to their potential use as antibiotic targets, because effective inhibition of these ... [more ▼]

In the last few years, an increased attention has been focused on NAD(+)-dependent DNA ligases. This is mostly due to their potential use as antibiotic targets, because effective inhibition of these essential enzymes would result in the death of the bacterium. However, development of an efficient drug requires that the conformational modifications involved in the catalysis of NAD(+)-dependent DNA ligases are understood. From this perspective, we have investigated the conformational changes occurring in the thermophilic Thermus scotoductus NAD(+)-DNA ligase upon adenylation, as well as the effect of cofactor binding on protein resistance to thermal and chemical (guanidine hydrochloride) denaturation. Our results indicate that cofactor binding induces conformational rearrangement within the active site and promotes a compaction of the enzyme. These data support an induced "open-closure" process upon adenylation, leading to the formation of the catalytically active enzyme that is able to bind DNA. These conformational changes are likely to be associated with the protein function, preventing the formation of nonproductive complexes between deadenylated ligases and DNA. In addition, enzyme adenylation significantly increases resistance of the protein to thermal denaturation and GdmCl-induced unfolding, establishing a thermodynamic link between ligand binding and increased conformational stability. Finally, chemical unfolding of deadenylated and adenylated enzyme is accompanied by accumulation of at least two equilibrium intermediates, the molten globule and premolten globule states. Maximal populations of these intermediates are shifted toward higher GdmCl concentrations in the case of the adenylated ligase. These data provide further insights into the properties of partially folded intermediates. [less ▲]

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See detailSome like it cold: biocatalysis at low temperatures
Georlette, D.; Blaise, Vinciane ULiege; Collins, T. et al

in FEMS Microbiology Reviews (2004), 28(1), 25-42

In the last few years, increased attention has been focused on a class of organisms called psychrophiles. These organisms, hosts of permanently cold habitats, often display metabolic fluxes more or less ... [more ▼]

In the last few years, increased attention has been focused on a class of organisms called psychrophiles. These organisms, hosts of permanently cold habitats, often display metabolic fluxes more or less comparable to those exhibited by mesophilic organisms at moderate temperatures. Psychrophiles have evolved by producing, among other peculiarities, "cold-adapted" enzymes which have the properties to cope with the reduction of chemical reaction rates induced by low temperatures. Thermal compensation in these enzymes is reached, in most cases, through a high catalytic efficiency associated, however, with a low thermal stability. Thanks to recent advances provided by X-ray crystallography, structure modelling, protein engineering and biophysical studies, the adaptation strategies are beginning to be understood. The emerging picture suggests that psychrophilic enzymes are characterized by an improved flexibility of the structural components involved in the catalytic cycle, whereas other protein regions, if not implicated in catalysis, may be even more rigid than their mesophilic counterparts. Due to their attractive properties, i.e., a high specific activity and a low thermal stability, these enzymes constitute a tremendous potential for fundamental research and biotechnological applications. (C) 2003 Federation of European Microbiological Societies. Published by Elsevier B.V. All rights reserved. [less ▲]

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See detailMolecular basis of the amylose-like polymer formation catalyzed by Neisseria polysaccharea amylosucrase
Albenne, C.; Skov, L. K.; Mirza, O. et al

in Journal of Biological Chemistry (2004), 279(1), 726-734

Amylosucrase from Neisseria polysaccharea is a remarkable transglucosidase from family 13 of the glycosidehydrolases that synthesizes an insoluble amylose-like polymer from sucrose in the absence of any ... [more ▼]

Amylosucrase from Neisseria polysaccharea is a remarkable transglucosidase from family 13 of the glycosidehydrolases that synthesizes an insoluble amylose-like polymer from sucrose in the absence of any primer. Amylosucrase shares strong structural similarities with alpha-amylases. Exactly how this enzyme catalyzes the formation of alpha-1,4-glucan and which structural features are involved in this unique functionality existing in family 13 are important questions still not fully answered. Here, we provide evidence that amylosucrase initializes polymer formation by releasing, through sucrose hydrolysis, a glucose molecule that is subsequently used as the first acceptor molecule. Maltooligosaccharides of increasing size were produced and successively elongated at their nonreducing ends until they reached a critical size and concentration, causing precipitation. The ability of amylosucrase to bind and to elongate maltooligosaccharides is notably due to the presence of key residues at the OB1 acceptor binding site that contribute strongly to the guidance ( Arg(415), subsite +4) and the correct positioning (Asp(394) and Arg(446), subsite +1) of acceptor molecules. On the other hand, Arg(226) (subsites +2/+3) limits the binding of maltooligosaccharides, resulting in the accumulation of small products (G to G3) in the medium. A remarkable mutant (R226A), activated by the products it forms, was generated. It yields twice as much insoluble glucan as the wild-type enzyme and leads to the production of lower quantities of by-products. [less ▲]

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See detailHorizontal gene transfer from Eukarya to Bacteria and domain shuffling: the alpha-amylase model
Da Lage, J. L.; Feller, Georges ULiege; Janecek, S.

in Cellular and Molecular Life Sciences : CMLS (2004), 61(1), 97-109

alpha-Amylases are present in all kingdoms of the living world. Despite strong conservation of the tertiary structure, only a few amino acids are conserved in interkingdom comparisons. Animal alpha ... [more ▼]

alpha-Amylases are present in all kingdoms of the living world. Despite strong conservation of the tertiary structure, only a few amino acids are conserved in interkingdom comparisons. Animal alpha-amylases are characterized by several typical motifs and biochemical properties. A few cases of such alpha-amylases have been previously reported in some eubacterial species. We screened the bacterial genomes available in the sequence databases for new occurrences of animal-like alpha-amylases. Three novel cases were found, which belong to unrelated bacterial phyla: Chloroflexus aurantiacus, Microbulbifer degradans, and Thermobifida fusca. All the animal-like alpha-amylases in Bacteria probably result from repeated horizontal gene transfer from animals. The M. degradans genome also contains bacterial-type and plant-type alpha-amylases in addition to the animal-type one. Thus, this species exhibits alpha-amylases of animal, plant, and bacterial origins. Moreover, the similarities in the extra C-terminal domains (different from both the alpha-amylase domain C and the starch-binding domain), when present, also suggest interkingdom as well as intragenomic shuffling. [less ▲]

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See detailA novel family 8 psychrophilic xylanase: fundamentals and applications
Collins, Tony; Gerday, Charles ULiege; Feller, Georges ULiege

Poster (2004)

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See detailActivity-stability relationships in extremophilic enzymes
D'Amico, Salvino; Collins, Tony; Georlette, Daphné et al

Conference (2004)

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See detailStructural adaptations of psychrophilic enzymes
Gerday, Charles ULiege; D'Amico, Salvino; Collins, Tony et al

Conference (2004)

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See detailThe influence of temperature on bacterial assemblages during bioremediation of a diesel fuel contaminated subAntarctic soil
Delille, Daniel; Pelletier, E.; Coulon, F. et al

Conference (2004)

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See detailActivity-stability relationships in extremophilic enzymes
D'Amico, Salvino; Collins, Tony; Marx, Jean Claude et al

Poster (2004)

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See detailCofactor binding modulates the conformational stabilities and unfolding patterns of NAD(+)-dependent DNA ligases from Escherichia coli and Thermus scotoductus
Georlette, D.; Blaise, Vinciane ULiege; Dohmen, C. et al

in Journal of Biological Chemistry (2003), 278(50), 49945-49953

DNA ligases are important enzymes required for cellular processes such as DNA replication, recombination, and repair. NAD(+)-dependent DNA ligases are essentially restricted to eubacteria, thus ... [more ▼]

DNA ligases are important enzymes required for cellular processes such as DNA replication, recombination, and repair. NAD(+)-dependent DNA ligases are essentially restricted to eubacteria, thus constituting an attractive target in the development of novel antibiotics. Although such a project might involve the systematic testing of a vast number of chemical compounds, it can essentially gain from the preliminary deciphering of the conformational stability and structural perturbations associated with the formation of the catalytically active adenylated enzyme. We have, therefore, investigated the adenylation-induced conformational changes in the mesophilic Escherichia coli and thermophilic Thermus scotoductus NAD(+)-DNA ligases, and the resistance of these enzymes to thermal and chemical (guanidine hydrochloride) denaturation. Our results clearly demonstrate that anchoring of the cofactor induces a conformational rearrangement within the active site of both mesophilic and thermophilic enzymes accompanied by their partial compaction. Furthermore, the adenylation of enzymes increases their resistance to thermal and chemical denaturation, establishing a thermodynamic link between cofactor binding and conformational stability enhancement. Finally, guanidine hydrochloride-induced unfolding of NAD(+)-dependent DNA ligases is shown to be a complex process that involves accumulation of at least two equilibrium intermediates, the molten globule and its precursor. [less ▲]

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See detailPsychrophilic enzymes: Hot topics in cold adaptation
Feller, Georges ULiege; Gerday, Charles ULiege

in Nature Reviews Microbiology (2003), 1(3), 200-208

More than three-quarters of the Earth's surface is occupied by cold ecosystems, including the ocean depths, and polar and alpine regions. These permanently cold environments have been successfully ... [more ▼]

More than three-quarters of the Earth's surface is occupied by cold ecosystems, including the ocean depths, and polar and alpine regions. These permanently cold environments have been successfully colonized by a class of extremophilic microorganisms that are known as psychrophiles (which literally means cold-loving). The ability to thrive at temperatures that are close to, or below, the freezing point of water requires a vast array of adaptations to maintain the metabolic rates and sustained growth compatible with life in these severe environmental conditions. [less ▲]

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See detailTemperature adaptation of proteins: Engineering mesophilic-like activity and stability in a cold-adapted alpha-amylase
D'Amico, Salvino ULiege; Gerday, Charles ULiege; Feller, Georges ULiege

in Journal of Molecular Biology (2003), 332(5), 981-988

Two multiple mutants of a psychrophilic alpha-amylase were produced, bearing five mutations (each introducing additional weak interactions found in pig pancreatic (alpha-amylase) with or without an extra ... [more ▼]

Two multiple mutants of a psychrophilic alpha-amylase were produced, bearing five mutations (each introducing additional weak interactions found in pig pancreatic (alpha-amylase) with or without an extra disulfide bond specific to warm-blooded animals. Both multiple mutants display large modifications of stability and activity arising from synergic effects in comparison with single mutations. Newly introduced weak interactions and the disulfide bond confer mesophilic-like stability parameters, as shown by increases in the melting point t(m), in the calorimetric enthalpy DeltaH(cal) and in protection against heat inactivation, as well as by decreases in cooperativity and reversibility of unfolding. In addition, both kinetic and thermodynamic activation parameters of the catalyzed reaction are shifted close to the values of the porcine enzyme. This study confirms the central role of weak interactions in regulating the balance between stability and activity of an enzyme in order to adapt to the environmental temperature. (C) 2003 Elsevier Ltd. All rights reserved. [less ▲]

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See detailStructural and functional adaptations to extreme temperatures in psychrophilic, mesophilic, and thermophilic DNA ligases
Georlette, D.; Damien, B.; Blaise, Vinciane ULiege et al

in Journal of Biological Chemistry (2003), 278(39), 37015-37023

Psychrophiles, host of permanently cold habitats, display metabolic fluxes comparable to those exhibited by mesophilic organisms at moderate temperatures. These organisms have evolved by producing, among ... [more ▼]

Psychrophiles, host of permanently cold habitats, display metabolic fluxes comparable to those exhibited by mesophilic organisms at moderate temperatures. These organisms have evolved by producing, among other peculiarities, cold-active enzymes that have the properties to cope with the reduction of chemical reaction rates induced by low temperatures. The emerging picture suggests that these enzymes display a high catalytic efficiency at low temperatures through an improved flexibility of the structural components involved in the catalytic cycle, whereas other protein regions, if not implicated in catalysis, may be even more rigid than their mesophilic counterparts. In return, the increased flexibility leads to a decreased stability of psychrophilic enzymes. In order to gain further advances in the analysis of the activity/flexibility/stability concept, psychrophilic, mesophilic, and thermophilic DNA ligases have been compared by three-dimensional-modeling studies, as well as regards their activity, surface hydrophobicity, structural permeability, conformational stabilities, and irreversible thermal unfolding. These data show that the cold-adapted DNA ligase is characterized by an increased activity at low and moderate temperatures, an overall destabilization of the molecular edifice, especially at the active site, and a high conformational flexibility. The opposite trend is observed in the mesophilic and thermophilic counterparts, the latter being characterized by a reduced low temperature activity, high stability and reduced flexibility. These results strongly suggest a complex relationship between activity, flexibility and stability. In addition, they also indicate that in cold-adapted enzymes, the driving force for denaturation is a large entropy change. [less ▲]

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