References of "Feller, Georges"
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See detailA novel family 8 psychrophilic xylanase: fundamentals and applications
Collins, Tony; Gerday, Charles ULg; Feller, Georges ULg

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 ULg; 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 ULg; 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 ULg; Gerday, Charles ULg

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 ULg; Gerday, Charles ULg; Feller, Georges ULg

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 ULg 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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See detailMoritella cold-active dihydrofolate reductase: Are there natural limits to optimization of catalytic efficiency at low temperature?
Xu, Y.; Feller, Georges ULg; Gerday, Charles ULg et al

in Journal of Bacteriology (2003), 185(18), 5519-5526

Adapting metabolic enzymes of microorganisms to low temperature environments may require a difficult compromise between velocity and affinity. We have investigated catalytic efficiency in a key metabolic ... [more ▼]

Adapting metabolic enzymes of microorganisms to low temperature environments may require a difficult compromise between velocity and affinity. We have investigated catalytic efficiency in a key metabolic enzyme (dihydrofolate reductase) of Moritella profunda sp. nov., a strictly psychrophilic bacterium with a maximal growth rate at 2degreesC or less. The enzyme is monomeric (M-r = 18,291), 55% identical to its Escherichia coli counterpart, and displays T-m and denaturation enthalpy changes much lower than E. coli and Thermotoga maritima homologues. Its stability curve indicates a maximum stability above the temperature range of the organism, and predicts cold denaturation below 0degreesC. At mesophilic temperatures the apparent K-m value for dihydrofolate is 50- to 80-fold higher than for E. coli, Lactobacillus casei, and T. maritima dihydrofolate reductases, whereas the apparent K-m value for NADPH, though higher, remains in the same order of magnitude. At 5degreesC these values are not significantly modified. The enzyme is also much less sensitive than its E. coli counterpart to the inhibitors methotrexate and trimethoprim. The catalytic efficiency (k(cat)/K-m) with respect to dihydrofolate is thus much lower than in the other three bacteria. The higher affinity for NADPH could have been maintained by selection since NADPH assists the release of the product tetrahydrofolate. Dihydrofolate reductase adaptation to low temperature thus appears to have entailed a pronounced trade-off between affinity and catalytic velocity. The kinetic features of this psychrophilic protein suggest that enzyme adaptation to low temperature may be constrained by natural limits to optimization of catalytic efficiency. [less ▲]

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See detailThe precursor of a psychrophilic alpha-amylase: structural characterization and insights into cold adaptation
Claverie, P.; Vigano, C.; Ruysschaert, J. M. et al

in Biochimica et Biophysica Acta-Proteins and Proteomics (2003), 1649(2), 119-122

The alpha-amylase precursor from the bacterium Pseudoalteromonas haloplanktis possesses a propeptide at the C-terminus possibly responsible for outer membrane translocation. Unlike the predicted beta ... [more ▼]

The alpha-amylase precursor from the bacterium Pseudoalteromonas haloplanktis possesses a propeptide at the C-terminus possibly responsible for outer membrane translocation. Unlike the predicted beta-barrel of autotransporters, this C-terminal propeptide displays a noticeable alpha-helix content. It is connected to the enzyme by a disordered linker and has no significant interaction with the catalytic domain. The microcalorimetric pattern of the precursor also demonstrates that the stability of protein domains may evolve differently. (C) 2003 Elsevier B.V. All rights reserved. [less ▲]

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See detailCold adaptation of a psychrophilic chitinase: a mutagenesis study
Mavromatis, K.; Feller, Georges ULg; Kokkinidis, M. et al

in Protein Engineering (2003), 16(7), 497-503

The gene encoding chitinase ArChiB from the Antarctic Arthrobacter sp. TAD20 has been expressed in Escherichia coli and the recombinant enzyme purified to homogeneity. In an effort to engineer cold ... [more ▼]

The gene encoding chitinase ArChiB from the Antarctic Arthrobacter sp. TAD20 has been expressed in Escherichia coli and the recombinant enzyme purified to homogeneity. In an effort to engineer cold-adapted biocatalysts through rational redesign to operate at elevated temperatures, we performed several mutations aiming to increase the rigidity of the molecular edifice of the selected psychrophilic chitinase. The mutations were designed on the basis of a homology-based three-dimensional model of the enzyme, and included an attempt to introduce a salt bridge (mutant N198K) and replacements of selected Gly residues by either Pro (mutants G93P, G254P) or Gln (G406Q). Mutant N198K resulted in a more stable protein (DeltaT(m)=0.6degreesC). Mutant G93P exhibited a DeltaT(m) of 1.2degreesC, while mutants G254P and G406Q exhibited decreased stability. We conclude that the effect of mutating Gly residues on enzyme stability is rather complex and can only be understood in the context of the structural environment. Kinetic and spectroscopic analysis of these enzyme variants revealed that the kinetic parameters k(cat) and K-m have been significantly modified. [less ▲]

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See detailExpression, purification, crystallization and preliminary X-ray crystallographic studies of a psychrophilic cellulase from Pseudoalteromonas haloplanktis
Violot, S.; Haser, R.; Sonan, G. et al

in Acta Crystallographica Section D-Biological Crystallography (2003), 59(Part 7), 1256-1258

The Antarctic psychrophile Pseudoalteromonas haloplanktis produces a cold-active cellulase. To date, a three-dimensional structure of a psychrophilic cellulase has been lacking. Crystallographic studies ... [more ▼]

The Antarctic psychrophile Pseudoalteromonas haloplanktis produces a cold-active cellulase. To date, a three-dimensional structure of a psychrophilic cellulase has been lacking. Crystallographic studies of this cold-adapted enzyme have therefore been initiated in order to contribute to the understanding of the molecular basis of the cold adaptation and the high catalytic efficiency of the enzyme at low and moderate temperatures. The catalytic core domain of the psychrophilic cellulase CelG from P. haloplanktis has been expressed, purified and crystallized and a complete diffraction data set to 1.8 Angstrom has been collected. The space group was found to be P2(1)2(1)2(1), with unit-cell parameters a = 135.1, b = 78.4, c = 44.1 Angstrom. A molecular-replacement solution, using the structure of the mesophilic counterpart Cel5A from Erwinia chrysanthemi as a search model, has been found. [less ▲]

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See detailActivity, stability and flexibility in Glycosidases adapted to extreme thermal environments
Collins, T.; Meuwis, Marie-Alice ULg; Gerday, Charles ULg et al

in Journal of Molecular Biology (2003), 328(2), 419-428

To elucidate the strategy of low temperature adaptation for a cold-adapted family 8 xylanase, the thermal and chemical stabilities, thermal inactivation, thermodependence of activity and conformational ... [more ▼]

To elucidate the strategy of low temperature adaptation for a cold-adapted family 8 xylanase, the thermal and chemical stabilities, thermal inactivation, thermodependence of activity and conformational flexibility, as well as the thermodynamic basis of these processes, were compared with those of a thermophilic homolog. Differential scanning calorimetry, fluorescence monitoring of guanidine hydrochloride unfolding and fluorescence quenching were used, among other techniques, to show that the cold-adapted enzyme is characterized by a high activity at low temperatures, a poor stability and a high flexibility. In contrast, the thermophilic enzyme is shown to have a reduced low temperature activity, high stability and a reduced flexibility. These findings agree with the hypothesis that cold-adapted enzymes overcome the quandary imposed by low temperature environments via a global or local increase in the flexibility of their molecular edifice, with this in turn leading to a reduced stability. Analysis of the guanidine hydrochloride unfolding, as well as the thermodynamic parameters of irreversible thermal unfolding and thermal inactivation shows that the driving force for this denaturation and inactivation is a large entropy change while a low enthalpy change is implicated in the low temperature activity. A reduced number of salt-bridges are believed to be responsible for both these effects. Guanidine hydrochloride unfolding studies also indicate that both family 8 enzymes unfold via an intermediate prone to aggregation. (C) 2003 Elsevier Science Ltd. All rights reserved. [less ▲]

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See detailMetabolic enzymes from psychrophilic bacteria: Challenge of adaptation to low temperatures in ornithine carbamoyltransferase from Moritella abyssi
Xu, Y.; Feller, Georges ULg; Gerday, Charles ULg et al

in Journal of Bacteriology (2003), 185(7), 2161-2168

The enzyme ornithine carbamoyltransferase (OTCase) of Motitella abyssi (OTCase(Mab)), a new, strictly psychrophilic and piezophilic bacterial species, was purified. OTCase(Mab) displays maximal activity ... [more ▼]

The enzyme ornithine carbamoyltransferase (OTCase) of Motitella abyssi (OTCase(Mab)), a new, strictly psychrophilic and piezophilic bacterial species, was purified. OTCase(Mab) displays maximal activity at rather low temperatures (23 to 25degreesC) compared to other cold-active enzymes and is much less thermoresistant than its homologues from Escherichia coli or thermophilic procaryotes. In vitro the enzyme is in equilibrium between a trimeric state and a dodecameric, more stable state. The melting point and denaturation enthalpy changes for the two forms are considerably lower than the corresponding values for the dodecameric Pyrococcus furiosus OTCase and for a thermolabile trimeric mutant thereof. OTCase(Mab) displays higher K-m values for ornithine and carbamoyl phosphate than mesophilic and thermophilic OTCases and is only weakly inhibited by the bisubstrate analogue delta-N-phosphonoacetyl-L-ornithine (PALO). OTCase(Mab) differs from other, nonpsychrophilic OTCases by substitutions in the most conserved motifs, which probably contribute to the comparatively high K-m values and the lower sensitivity to PALO. The K. for ornithine, however, is substantially lower at low temperatures. A survey of the catalytic efficiencies (k(cat)/K-m) of OTCases adapted to different temperatures showed that OTCase(Mab) activity remains suboptimal at low temperature despite the 4.5-fold decrease in the K-m value for ornithine observed when the temperature is brought from 20 to 5degreesC. OTCase(Mab) adaptation to cold indicates a trade-off between affinity and catalytic velocity, suggesting that optimization of key metabolic enzymes at low temperatures may be constrained by natural limits. [less ▲]

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See detailMolecular adaptations to cold in psychrophilic enzymes
Feller, Georges ULg

in Cellular and Molecular Life Sciences : CMLS (2003), 60(4), 648-662

Psychrophiles or cold-loving organisms successfully colonize cold environments of the Earth's biosphere. To cope with the reduction of chemical reaction rates induced by low temperatures, these organisms ... [more ▼]

Psychrophiles or cold-loving organisms successfully colonize cold environments of the Earth's biosphere. To cope with the reduction of chemical reaction rates induced by low temperatures, these organisms synthesize enzymes characterized by a high catalytic activity at low temperatures associated, however, with low thermal stability. Thanks to recent advances provided by Xray crystallography, protein engineering and biophysical studies, we are beginning to understand the molecular adaptations responsible for these properties which appear to be relatively diverse. The emerging picture suggests that psychrophilic enzymes utilize an improved flexibility of the structures involved in the catalytic cycle, whereas other protein regions if not implicated in catalysis may or may not be subjected to genetic drift. [less ▲]

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See detailActivity-stability relationships in extremophilic enzymes
D'Amico, Salvino ULg; Marx, J. C.; Gerday, Charles ULg et al

in Journal of Biological Chemistry (2003), 278(10), 7891-7896

Psychrophilic, mesophilic, and thermophilic alpha-amylases have been studied as regards their conformational stability, heat inactivation, irreversible unfolding, activation parameters of the reaction ... [more ▼]

Psychrophilic, mesophilic, and thermophilic alpha-amylases have been studied as regards their conformational stability, heat inactivation, irreversible unfolding, activation parameters of the reaction, properties of the enzyme in complex with a transition state analog, and structural permeability. These data allowed us to propose an energy landscape for a family of extremophilic enzymes based on the folding funnel model, integrating the main differences in conformational energy, cooperativity of protein unfolding, and temperature dependence of the activity. In particular, the shape of the funnel bottom, which depicts the stability of the native state ensemble, also accounts for the thermodynamic parameters of activation that characterize these extremophilic enzymes, therefore providing a rational basis for stability-activity relationships in protein adaptation to extreme temperatures. [less ▲]

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See detailThe structure of a cold-adapted family 8 xylanase at 1.3 angstrom resolution - Structural adaptations to cold and investigation of the active site
Van Petegem, F.; Collins, T.; Meuwis, Marie-Alice ULg et al

in Journal of Biological Chemistry (2003), 278(9), 7531-7539

Enzymes from psychrophilic organisms differ from their mesophilic counterparts in having a lower thermo-stability and a higher specific activity at low and moderate temperatures. The current consensus is ... [more ▼]

Enzymes from psychrophilic organisms differ from their mesophilic counterparts in having a lower thermo-stability and a higher specific activity at low and moderate temperatures. The current consensus is that they have an increased flexibility, enhancing accommodation and transformation of the substrates at low energy costs. Here we describe the structure of the xylanase from the Antarctic bacterium Pseudoalteromonas haloplanktis at 1.3 Angstrom resolution. Xylanases are usually grouped into glycosyl hydrolase families 10 and 11, but this enzyme belongs to family 8. The fold differs from that of other known xylanases and can be described as an (alpha/alpha)(6) barrel. Various parameters that may explain the cold-adapted properties were examined and indicated that the protein has a reduced number of salt bridges and an increased exposure of hydrophobic residues. The crystal structures of a complex with xylobiose and of mutant D144N were obtained at 1.2 and 1.5 A resolution, respectively. Analysis of the various substrate binding sites shows that the +3 and -3 subsites are rearranged as compared to those of a family 8 homolog, while the xylobiose complex suggests the existence of a +4 subsite. A decreased acidity of the substrate binding cleft and an increased flexibility of aromatic residues lining the subsites may enhance the rate at which substrate is bound. [less ▲]

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