References of "Feller, Georges"
     in
Bookmark and Share    
Full Text
Peer Reviewed
See detailA novel family 8 xylanase, functional and physicochemical characterization
Collins, T.; Meuwis, Marie-Alice ULg; Stals, I. et al

in Journal of Biological Chemistry (2002), 277(38), 35133-35139

Detailed reference viewed: 7 (0 ULg)
Full Text
Peer Reviewed
See detailCrystallization and preliminary X-ray analysis of a xylanase from the psychrophile Pseudoalteromonas haloplanktis
Van Petegem, F.; Collins, T.; Meuwis, Marie-Alice ULg et al

in Acta Crystallographica Section D-Biological Crystallography (2002), 58(Part 9), 1494-1496

The 46 kDa xylanase from the Antarctic microorganism Pseudoalteromonas haloplanktis is an enzyme that efficiently catalyzes reactions at low temperatures. Here, the crystallization of both the native ... [more ▼]

The 46 kDa xylanase from the Antarctic microorganism Pseudoalteromonas haloplanktis is an enzyme that efficiently catalyzes reactions at low temperatures. Here, the crystallization of both the native protein and the SeMet-substituted enzyme and data collection from both crystals using synchrotron radiation are described. The native data showed that the crystals diffract to 1.3 Angstrom resolution and belong to space group P2(1)2(1)2(1), with unit-cell parameters a = 50.87, b = 90.51, c = 97.23 Angstrom. SAD data collected at the peak of the selenium absorption edge proved to be sufficient to determine the heavy-atom configuration and to obtain electron density of good quality. [less ▲]

Detailed reference viewed: 8 (1 ULg)
Full Text
Peer Reviewed
See detailMolecular basis of cold adaptation
D'Amico, Salvino ULg; Claverie, P.; Collins, T. et al

in Philosophical Transactions of the Royal Society of London Series B-Biological Sciences (2002), 357(1423), 917-924

Cold-adapted, or psychrophilic, organisms are able to thrive at low temperatures in permanently cold environments, which in fact characterize the greatest proportion of our planet. Psychrophiles include ... [more ▼]

Cold-adapted, or psychrophilic, organisms are able to thrive at low temperatures in permanently cold environments, which in fact characterize the greatest proportion of our planet. Psychrophiles include both prokaryotic and eukaryotic organisms and thus represent a significant proportion of the living world. These organisms produce cold-evolved enzymes that are partially able to cope with the reduction in chemical reaction rates induced by low temperatures. As a rule, cold-active enzymes display a high catalytic efficiency, associated however, with a low thermal stability. In most cases, the adaptation to cold is achieved through a reduction in the activation energy that possibly originates from an increased flexibility of either a selected area or of the overall protein structure. This enhanced plasticity seems in turn to be induced by the weak thermal stability of psychrophilic enzymes. The adaptation strategies are beginning to be understood thanks to recent advances in the elucidation of the molecular characteristics of cold-adapted enzymes derived from X-ray crystallography, protein engineering and biophysical methods. Psychrophilic organisms and their enzymes have, in recent years, increasingly attracted the attention of the scientific community due to their peculiar properties that render them particularly useful in investigating the possible relationship existing between stability, flexibility and specific activity and as valuable tools for biotechnological purposes. [less ▲]

Detailed reference viewed: 23 (2 ULg)
Full Text
Peer Reviewed
See detailStructural basis of alpha-amylase activation by chloride
Aghajari, N.; Feller, Georges ULg; Gerday, Charles ULg et al

in Protein Science : A Publication of the Protein Society (2002), 11(6), 1435-1441

To further investigate the mechanism and function of allosteric activation by chloride in some alpha-amylases, the structure of the bacterial alpha-amylase from the psychrophilic micro-organism ... [more ▼]

To further investigate the mechanism and function of allosteric activation by chloride in some alpha-amylases, the structure of the bacterial alpha-amylase from the psychrophilic micro-organism Pseudoalteromonas haloplanktis in complex with nitrate has been solved at 2.1 Angstrom, as well as the structure of the mutants Lys300Gln (2.5 Angstrom) and Lys300Arg (2.25 Angstrom). Nitrate binds strongly to alpha-amylase but is a weak activator. Mutation of the critical chloride ligand Lys300 into Gln results in a chloride-independent enzyme, whereas the mutation into Arg mimics the binding site as is found in animal alpha-amylases with, however, a lower affinity for chloride. These structures reveal that the triangular conformation of the chloride ligands and the nearly equatorial coordination allow the perfect accommodation of planar trigonal monovalent anions such as NO3-, explaining their unusual strong binding. It is also shown that a localized negative charge such as that of Cl-, rather than a delocalized charge as in the case of nitrate, is essential for maximal activation. The chloride-free mutant Lys300Gln indicates that chloride is not mandatory for the catalytic mechanism but strongly increases the reactivity at the active site. Disappearance of the putative catalytic water molecule in this weakly active mutant supports the view that chloride helps to polarize the hydrolytic water molecule and enhances the rate of the second step in the catalytic reaction. [less ▲]

Detailed reference viewed: 41 (0 ULg)
Full Text
Peer Reviewed
See detailA colorimetric method for the determination of lipase activity in soil
Margesin, R.; Feller, Georges ULg; Hammerle, M. et al

in Biotechnology Letters (2002), 24(1), 27-33

A colorimetric method for the determination of lipase activity in soil has been developed. Using p-nitrophenyl butyrate as substrate, soil samples are incubated at 30 degreesC and pH 7.25 for 10 min ... [more ▼]

A colorimetric method for the determination of lipase activity in soil has been developed. Using p-nitrophenyl butyrate as substrate, soil samples are incubated at 30 degreesC and pH 7.25 for 10 min. After cooling on ice and centrifugation, the released p-nitrophenol is determined at 400 nm. To allow for the adsorption of p-nitrophenol onto soil, a calibration curve is prepared in the presence of soil. [less ▲]

Detailed reference viewed: 129 (0 ULg)
See detailCold adapted endoglucanase from Antarctic bacteria
Sonan, Guillaume; Feller, Georges ULg; Gerday, Charles ULg

Poster (2002)

Detailed reference viewed: 5 (0 ULg)
See detailSimilarities and partial characterization of cold adapted alpha-amylases from Antarctic and Arctic bacteria.
Gratia, Emmanuelle; D'Amico, Salvino; Yilmaz, N. et al

Poster (2002)

Detailed reference viewed: 4 (0 ULg)
Peer Reviewed
See detailA cellulase from a psychrophilic microorganism: 3D structures of its native form and its complex with cellobiose
Violot, S.; Gouet, P.; Haser, Richard et al

Poster (2002)

Detailed reference viewed: 5 (0 ULg)
Peer Reviewed
See detailCloning, biochemical and structural studies of an alcohol dehydrogenase from the Antarctic bacterium Moraxella sp. TAE 123
Tsigos, I.; Georlette, Daphné; Papanikolau, Y. et al

Poster (2002)

Detailed reference viewed: 6 (0 ULg)
Peer Reviewed
See detailCalorimetric characterization of cold-adapted enzymes
Georlette, Daphné; D'Amico, Salvino; Feller, Georges ULg et al

Poster (2002)

Detailed reference viewed: 5 (0 ULg)
Full Text
See detailCold-adapted microorganisms: adaptation strategies and biotechnological potential
Margesin, R.; Feller, Georges ULg; Gerday, Charles ULg et al

in Bitton, G. (Ed.) The Encyclopedia of Environmental Microbiology, vol. 2 (2002)

Detailed reference viewed: 81 (3 ULg)
See detailLife in the cold: psychrophilic enzymes
Collins, T.; Claverie, P.; D'Amico, Salvino ULg et al

in Recent Res. Devl. Proteins vol. 1 (2002)

Detailed reference viewed: 29 (2 ULg)
Full Text
Peer Reviewed
See detailStructural determinants of cold adaptation and stability in a psychrophilic alpha-amylase
D'Amico, Salvino ULg; Gerday, Charles ULg; Feller, Georges ULg

in Biologia (2002), 57(Suppl. 11), 213-219

The heat-labile alpha-amylase from an Antarctic bacterium is the largest known protein that unfolds reversibly according to a two-state transition, as shown by differential scanning calorimetry. Mutants ... [more ▼]

The heat-labile alpha-amylase from an Antarctic bacterium is the largest known protein that unfolds reversibly according to a two-state transition, as shown by differential scanning calorimetry. Mutants of this enzyme were produced, carrying intended additional weak interactions of a type found in thermostable alpha-amylases. It is shown that single amino acid side chain substitutions can significantly modify the melting point T-m, the calorimetric enthalpy DeltaH(cal), the cooperativity and reversibility of unfolding, the thermal inactivation rate constant, and the kinetic parameters k(cat) and K-m. Although all mutations were located far from the active site, their overall trend is to decrease both k(cat) and K-m, probably by making the molecule more rigid, but this protects mutants against thermal inactivation. [less ▲]

Detailed reference viewed: 14 (3 ULg)
Full Text
See detailCatalysis and Low Temperature: Molecular adaptations
Feller, Georges ULg; Gerday, Charles ULg

in EOLSS (Ed.) Encyclopedia of Life Support Systems (2002)

Detailed reference viewed: 7 (2 ULg)
Full Text
Peer Reviewed
See detailDid Psychrophilic Enzymes Really Win the Challenge?
Zecchinon, Laurent ULg; Claverie, P.; Collins, T. et al

in Extremophiles : Life Under Extreme Conditions (2001), 5(5), 313-21

Organisms living in permanently cold environments, which actually represent the greatest proportion of our planet, display at low temperatures metabolic fluxes comparable to those exhibited by mesophilic ... [more ▼]

Organisms living in permanently cold environments, which actually represent the greatest proportion of our planet, display at low temperatures metabolic fluxes comparable to those exhibited by mesophilic organisms at moderate temperatures. They produce cold-evolved enzymes partially able to cope with the reduction in chemical reaction rates and the increased viscosity of the medium induced by low temperatures. In most cases, the adaptation is achieved through a reduction in the activation energy, leading to a high catalytic efficiency, which possibly originates from an increased flexibility of either a selected area of or the overall protein structure. This enhanced plasticity seems in return to be responsible for the weak thermal stability of cold enzymes. These particular properties render cold enzymes particularly useful in investigating the possible relationships existing between stability, flexibility, and specific activity and make them potentially unrivaled for numerous biotechnological tasks. In most cases, however, the adaptation appears to be far from being fully achieved. [less ▲]

Detailed reference viewed: 22 (0 ULg)
Full Text
Peer Reviewed
See detailStructural Determinants of Cold Adaptation and Stability in a Large Protein
D'Amico, Salvino ULg; Gerday, Charles ULg; Feller, Georges ULg

in Journal of Biological Chemistry (2001), 276(28), 25791-6

The heat-labile alpha-amylase from an antarctic bacterium is the largest known protein that unfolds reversibly according to a two-state transition as shown by differential scanning calorimetry. Mutants of ... [more ▼]

The heat-labile alpha-amylase from an antarctic bacterium is the largest known protein that unfolds reversibly according to a two-state transition as shown by differential scanning calorimetry. Mutants of this enzyme were produced, carrying additional weak interactions found in thermostable alpha-amylases. It is shown that single amino acid side chain substitutions can significantly modify the melting point T(m), the calorimetric enthalpy Delta H(cal), the cooperativity and reversibility of unfolding, the thermal inactivation rate constant, and the kinetic parameters k(cat) and K(m). The correlation between thermal inactivation and unfolding reversibility displayed by the mutants also shows that stabilizing interactions increase the frequency of side reactions during refolding, leading to intramolecular mismatches or aggregations typical of large proteins. Although all mutations were located far from the active site, their overall trend is to decrease both k(cat) and K(m) by rigidifying the molecule and to protect mutants against thermal inactivation. The effects of these mutations indicate that the cold-adapted alpha-amylase has lost a large number of weak interactions during evolution to reach the required conformational plasticity for catalysis at low temperatures, thereby producing an enzyme close to the lowest stability allowing maintenance of the native conformation. [less ▲]

Detailed reference viewed: 5 (1 ULg)
Full Text
Peer Reviewed
See detailModular Structure, Local Flexibility and Cold-Activity of a Novel Chitobiase from a Psychrophilic Antarctic Bacterium
Lonhienne, T.; Zoidakis, J.; Vorgias, C. E. et al

in Journal of Molecular Biology (2001), 310(2), 291-7

The gene archb encoding for the cell-bound chitobiase from the Antarctic Gram-positive bacterium Arthrobacter sp. TAD20 was cloned and expressed in Escherichia coli in a soluble form. The mature ... [more ▼]

The gene archb encoding for the cell-bound chitobiase from the Antarctic Gram-positive bacterium Arthrobacter sp. TAD20 was cloned and expressed in Escherichia coli in a soluble form. The mature chitobiase ArChb possesses four functionally independent domains: a catalytic domain stabilized by Ca(2+), a galactose-binding domain and an immunoglobulin-like domain followed by a cell-wall anchorage signal, typical of cell-surface proteins from Gram-positive bacteria. Binding of saccharides was analyzed by differential scanning calorimetry, allowing to distinguish unequivocally the catalytic domain from the galactose-binding domain and to study binding specificities. The results suggest that ArChb could play a role in bacterium attachment to natural hosts. Kinetic parameters of ArChb demonstrate perfect adaptation to catalysis at low temperatures, as shown by a low activation energy associated with unusually low K(m) and high k(cat) values. Thermodependence of these parameters indicates that discrete amino acid substitutions in the catalytic center have optimized the thermodynamic properties of weak interactions involved in substrate binding at low temperatures. Microcalorimetry also reveals that heat-lability, a general trait of psychrophilic enzymes, only affects the active site domain of ArChb. [less ▲]

Detailed reference viewed: 10 (0 ULg)