References of "Feller, Georges"
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See detailInsights into bacterial cellulose biosynthesis by functional metagenomics on Antarctic soil samples.
Berlemont, Renaud ULg; Delsaute, Maud ULg; Pipers, Delphine ULg et al

in ISME Journal (The) (2009), 3(9), 1070-1081

In this study, the mining of an Antarctic soil sample by functional metagenomics allowed the isolation of a cold-adapted protein (RBcel1) that hydrolyzes only carboxymethyl cellulose. The new enzyme is ... [more ▼]

In this study, the mining of an Antarctic soil sample by functional metagenomics allowed the isolation of a cold-adapted protein (RBcel1) that hydrolyzes only carboxymethyl cellulose. The new enzyme is related to family 5 of the glycosyl hydrolase (GH5) protein from Pseudomonas stutzeri (Pst_2494) and does not possess a carbohydrate-binding domain. The protein was produced and purified to homogeneity. RBcel1 displayed an endoglucanase activity, producing cellobiose and cellotriose, using carboxymethyl cellulose as a substrate. Moreover, the study of pH and the thermal dependence of the hydrolytic activity shows that RBcel1 was active from pH 6 to pH 9 and remained significantly active when temperature decreased (18% of activity at 10 degrees C). It is interesting that RBcel1 was able to synthetize non-reticulated cellulose using cellobiose as a substrate. Moreover, by a combination of bioinformatics and enzyme analysis, the physiological relevance of the RBcel1 protein and its mesophilic homologous Pst_2494 protein from P. stutzeri, A1501, was established as the key enzymes involved in the production of cellulose by bacteria. In addition, RBcel1 and Pst_2494 are the two primary enzymes belonging to the GH5 family involved in this process.The ISME Journal advance online publication, 21 May 2009; doi:10.1038/ismej.2009.48. [less ▲]

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See detailA nondetergent sulfobetaine improves protein unfolding reversibility in microcalorimetric studies
D'Amico, Salvino ULg; Feller, Georges ULg

in Analytical Biochemistry (2009), 385(2), 389-91

A nondetergent sulfobetaine (NDSB) was found to improve unfolding reversibility of several proteins by inhibiting heat-induced aggregation. As a consequence, DeltaH(cal)/DeltaH(vH) ratios were also ... [more ▼]

A nondetergent sulfobetaine (NDSB) was found to improve unfolding reversibility of several proteins by inhibiting heat-induced aggregation. As a consequence, DeltaH(cal)/DeltaH(vH) ratios were also improved to values close to 1 for a two-state unfolding. NDSB is effective in a wide range of pH values and especially at acidic pH generally used to calculate DeltaC(p) values by the Kirchhoff relation. The sulfobetaine also allows recording protein refolding by protecting the heat-induced unfolded state against aggregation. [less ▲]

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See detailSelection of a cold-adapted bacterium for bioremediation of wastewater at low temperatures
Gratia, E.; Weekers, F.; Margesin, R. et al

in Extremophiles : Life Under Extreme Conditions (2009), 13(5), 763-8

Amongst more than 1000 isolates collected in various cold environments, the strain Arthrobacter psychrolactophilus Sp 31.3 has been selected for its ability to grow and to produce exoenzymes at low ... [more ▼]

Amongst more than 1000 isolates collected in various cold environments, the strain Arthrobacter psychrolactophilus Sp 31.3 has been selected for its ability to grow and to produce exoenzymes at low temperatures, its inability to grow at 37 degrees C, its non-halophilic character and its growth versatility on various media. This non-pathogenic strain displays a strong resistance to desiccation and storage at room temperature and is suitable for the production of freeze-dried bacterial starters. When grown in a synthetic wastewater at 10 degrees C, the strain induces a complete clarification of the turbid medium and efficiently hydrolyses proteins, starch and lipids in the broth. Furthermore, this strain has a remarkable capacity to improve the biodegradability of organic compounds in wastewater as indicated by a BOD(5)/COD ratio of 0.7. [less ▲]

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See detailThe Noncatalytic Triad of Alpha-Amylases: A Novel Structural Motif Involved in Conformational Stability
Marx, J. C.; Poncin, J.; Simorre, J. P. et al

in Proteins (2008), 70(2), 320-328

Chloride-activated alpha-amylases contain a noncatalytic triad, independent of the glycosidic active site, perfectly mimicking the catalytic triad of serine-proteases and of other active serine hydrolytic ... [more ▼]

Chloride-activated alpha-amylases contain a noncatalytic triad, independent of the glycosidic active site, perfectly mimicking the catalytic triad of serine-proteases and of other active serine hydrolytic enzymes. Mutagenesis of Glu, His, and Ser residues in various alpha-amylases shows that this pattern is a structural determinant of the enzyme conformation that cannot be altered without losing the intrinsic stability of the protein. (1)H-(15)N NMR spectra of a bacterial alpha-amylase reveal proton signals that are identical with the NMR signature of catalytic triads and especially a deshielded proton involving a protonated histidine and displaying properties similar to that of a low barrier hydrogen bond. It is proposed that the H-bond between His and Glu of the noncatalytic triad is an unusually strong interaction, responsible for the observed NMR signal and for the weak stability of the triad mutants. Furthermore, a stringent template-based search of the Protein Data Bank demonstrated that this motif is not restricted to alpha-amylases, but is also found in 80 structures from 33 different proteins, amongst which SH2 domain-containing proteins are the best representatives. [less ▲]

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See detailProtein synthesis and folding is a rate limiting step for bacterial growth at low temperatures.
Piette, Florence; D'Amico, Salvino; Leprince, Pierre ULg et al

Poster (2008)

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See detailIsolation of novel hydrolytic genes from an Antarctic metagenomic library
Pipers, D.; Berlemont, R.; Power, P. et al

Poster (2008)

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See detailA blue oxidase from the white continent
Roulling, Fredéric; Verté, F.; Feller, Georges ULg

Poster (2008)

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See detailProtein synthesis and folding is a rate limiting step for bacterial growth at low temperatures.
Piette, Florence; D'Amico, Salvino; Leprince, Pierre ULg et al

Poster (2008)

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See detailThe cold-adapted trigger factor from the Antarctic bacterium Pseudoalteromonas haloplanktis.
D'Amico, Salvino; Piette, Florence; Leprince, Pierre ULg et al

Poster (2008)

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See detailCrystal structure of a cold-adapted class C beta-lactamase.
Michaux, Catherine; Massant, Jan; Kerff, Frédéric ULg et al

in FEBS Journal (2008), 275(8), 1687-97

In this study, the crystal structure of a class C beta-lactamase from a psychrophilic organism, Pseudomonas fluorescens, has been refined to 2.2 A resolution. It is one of the few solved crystal ... [more ▼]

In this study, the crystal structure of a class C beta-lactamase from a psychrophilic organism, Pseudomonas fluorescens, has been refined to 2.2 A resolution. It is one of the few solved crystal structures of psychrophilic proteins. The structure was compared with those of homologous mesophilic enzymes and of another, modeled, psychrophilic protein. The elucidation of the 3D structure of this enzyme provides additional insights into the features involved in cold adaptation. Structure comparison of the psychrophilic and mesophilic beta-lactamases shows that electrostatics seems to play a major role in low-temperature adaptation, with a lower total number of ionic interactions for cold enzymes. The psychrophilic enzymes are also characterized by a decreased number of hydrogen bonds, a lower content of prolines, and a lower percentage of arginines in comparison with lysines. All these features make the structure more flexible so that the enzyme can behave as an efficient catalyst at low temperatures. [less ▲]

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See detailDirected evolution on the cold adapted properties of TAB5 alkaline phosphatase
Koutsioulis, D.; Wang, E.; Tzanodaskalaki, M. et al

in Protein Engineering, Design & Selection (2008), 21(5), 319-27

Psychrophilic alkaline phosphatase (AP) from the Antarctic strain TAB5 was subjected to directed evolution in order to identify the key residues steering the enzyme's cold-adapted activity and stability ... [more ▼]

Psychrophilic alkaline phosphatase (AP) from the Antarctic strain TAB5 was subjected to directed evolution in order to identify the key residues steering the enzyme's cold-adapted activity and stability. A round of random mutagenesis and further recombination yielded three thermostable and six thermolabile variants of the TAB5 AP. All of the isolated variants were characterised by their residual activity after heat treatment, Michaelis-Menten kinetics, activation energy and microcalorimetric parameters of unfolding. In addition, they were modelled into the structure of the TAB5 AP. Mutations which affected the cold-adapted properties of the enzyme were all located close to the active site. The destabilised variants H135E and H135E/G149D had 2- and 3-fold higher kcat, respectively, than the wild-type enzyme. Wild-type AP has a complex heat-induced unfolding pattern while the mutated enzymes loose local unfolding transitions and have large shifts of the Tm values. Comparison of the wild-type and mutated TAB5 APs demonstrates that there is a delicate balance between the enzyme activity and stability and that it is possible to improve the activity and thermostability simultaneously as demonstrated in the case of the H135E/G149D variant compared to H135E. [less ▲]

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See detailCrystal structure of the cold-active aminopeptidase from Colwellia psychrerythraea, a close structural homologue of the human bifunctional leukotriene A4 hydrolase
Bauvois, Cédric; Jacquamet, Lilian; Huston, Adrienne L. et al

in Journal of Biological Chemistry (2008), 283(34), 23315-25

The crystal structure of a cold-active aminopeptidase (ColAP) from Colwellia psychrerythraea strain 34H has been determined, extending the number of crystal structures of the M1 metallopeptidase family to ... [more ▼]

The crystal structure of a cold-active aminopeptidase (ColAP) from Colwellia psychrerythraea strain 34H has been determined, extending the number of crystal structures of the M1 metallopeptidase family to four among the 436 members currently identified. In agreement with their sequence similarity, the overall structure of ColAP displayed a high correspondence with leukotriene A4 hydrolase (LTA4H), a human bifunctional enzyme that converts leukotriene A4 (LTA4) in the potent chemoattractant leukotriene B4. Indeed, both enzymes are composed of three domains, an N-terminal saddle-like domain, a catalytic thermolysin-like domain, and a less conserved C-terminal alpha-helical flat spiral domain. Together, these domains form a deep cavity harboring the zinc binding site formed by residues included in the conserved HEXXHX(18)H motif. A detailed structural comparison of these enzymes revealed several plausible determinants of ColAP cold adaptation. The main differences involve specific amino acid substitutions, loop content and solvent exposure, complexity and distribution of ion pairs, and differential domain flexibilities. Such elements may act synergistically to allow conformational flexibility needed for an efficient catalysis in cold environments. Furthermore, the region of ColAP corresponding to the aminopeptidase active site of LTA4H is much more conserved than the suggested LTA4 substrate binding region. This observation supports the hypothesis that this region of the LTA4H active site has evolved in order to fit the lipidic substrate. [less ▲]

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See detailEnzyme function at low temperatures in psychrophiles
Feller, Georges ULg

in Thomas, T.; Siddiqui, K. S. (Eds.) Protein Adaptation in Extremophiles (2008)

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See detailCold adaptation of enzymes: structural, kinetic and microcalorimetric characterizations of an aminopeptidase from the Arctic psychrophile Colwellia psychrerythraea and of human leukotriene A(4) hydrolase
Huston, A. L.; Haeggstrom, J. Z.; Feller, Georges ULg

in Biochimica et Biophysica Acta (2008), 1784(11), 1865-72

The relationships between structure, activity, stability and flexibility of a cold-adapted aminopeptidase produced by a psychrophilic marine bacterium have been investigated in comparison with a ... [more ▼]

The relationships between structure, activity, stability and flexibility of a cold-adapted aminopeptidase produced by a psychrophilic marine bacterium have been investigated in comparison with a mesophilic structural and functional human homolog. Differential scanning calorimetry, fluorescence monitoring of thermal- and guanidine hydrochloride-induced unfolding and fluorescence quenching were used to show that the cold-adapted enzyme is characterized by a high activity at low temperatures, a low structural stability versus thermal and chemical denaturants and a greater structural permeability to a quenching agent relative to the mesophilic homolog. These findings support the hypothesis that cold-adapted enzymes maintain their activity at low temperatures as a result of increased global or local structural flexibility, which results in low stability. Analysis of the thermodynamic parameters of irreversible thermal unfolding suggests that entropy-driven factors are responsible for the fast unfolding rate of the cold-adapted aminopeptidase. A reduced number of proline residues, a lower degree of hydrophobic residue burial and a decreased surface accessibility of charged residues may be responsible for this effect. On the other hand, the reduction in enthalpy-driven interactions is the primary determinant of the weak conformational stability. [less ▲]

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See detailFundamentals of Cold-Adapted Enzymes
Collins, T.; Roulling, Frédéric ULg; Piette, Florence ULg et al

in Margesin, R.; Schinner, F.; Gerday, Charles (Eds.) et al Psychrophiles: from Biodiversity to Biotechnology (2008)

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See detailIntrinsic halotolerance of the psychrophilic alpha-amylase from Pseudoalteromonas haloplanktis
Srimathi, S.; Jayaraman, G.; Feller, Georges ULg et al

in Extremophiles : Life Under Extreme Conditions (2007), 11(3), 505-515

The halotolerance of a cold adapted alpha-amylase from the psychrophilic bacterium Pseudoalteromonas haloplanktis (AHA) was investigated. AHA exhibited hydrolytic activity over a broad range of NaCl ... [more ▼]

The halotolerance of a cold adapted alpha-amylase from the psychrophilic bacterium Pseudoalteromonas haloplanktis (AHA) was investigated. AHA exhibited hydrolytic activity over a broad range of NaCl concentrations (0.01-4.5 M). AHA showed 28% increased activity in 0.5-2.0 M NaCl compared to that in 0.01 M NaCl. In contrast, the corresponding mesophilic (Bacillus amyloliquefaciens) and thermostable (B. licheniformis) alpha-amylases showed a 39 and 46% decrease in activity respectively. Even at 4.5 M NaCl, 80% of the initial activity was detected for AHA, whereas the mesophilic and thermostable enzymes were inactive. Besides an unaltered fluorescence emission and secondary structure, a 10 degrees C positive shift in the temperature optimum, a stabilization factor of > 5 for thermal inactivation and a Delta T-m of 8.3 degrees C for the secondary structure melting were estimated in 2.7 M NaCl. The higher activation energy, half-life time and T-m indicated reduced conformational dynamics and increased rigidity in the presence of higher NaCl concentrations. A comparison with the sequences of other halophilic alpha-amylases revealed that AHA also contains higher proportion of small hydrophobic residues and acidic residues resulting in a higher negative surface potential. Thus, with some compromise in cold activity, psychrophilic adaptation has also manifested halotolerance to AHA that is comparable to the halophilic enzymes. [less ▲]

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See detailLife at low temperatures: is disorder the driving force?
Feller, Georges ULg

in Extremophiles : Life Under Extreme Conditions (2007), 11(2), 211-216

The thermodynamic characterization of various biological systems from psychrophiles points to a larger entropic contribution when compared to the corresponding mesophilic or (hyper) thermophilic ... [more ▼]

The thermodynamic characterization of various biological systems from psychrophiles points to a larger entropic contribution when compared to the corresponding mesophilic or (hyper) thermophilic counterparts, either at the level of the macromolecules (thermodynamic and kinetic stabilities) or of their function (ligand binding, catalytic activity). It is suggested here that in an environment characterized by a low heat content (enthalpy) and at temperatures that strongly slowdown molecular motions, the cold-adapted biological systems rely on a larger disorder to maintain macromolecular dynamics and function. Such pre-eminent involvement of entropy is observed in the experimental results and, from a macroscopic point of view, is also reflected for instance by the steric hindrances introduced by cis-unsaturated and branched lipids to maintain membrane fluidity, by the loose conformation of psychrophilic proteins or by the local destabilization of tRNA by dihydrouridine in psychrophilic bacteria. [less ▲]

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See detailCold-Adapted Enzymes
Collins, T.; D'Amico, Salvino ULg; Marx, J. C. et al

in Gerday, Charles; Glansdorff, N. (Eds.) Physiology and biochemistry of extremophiles (2007)

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See detailAdaptation strategies and uses of cold adapted enzymes in biotechnological processes
Gerday, Charles ULg; D'Amico, Salvino ULg; Collins, T. et al

in JAMSTEC ERC (Ed.) Proceedings of the International Symposium on Extremophiles and their Applications 2005 (2007)

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See detailA novel family 8 psychrophilic xylanase: fundamentals and application
Collins, T.; Hoyoux, A.; Van Petegem, F. et al

in JAMSTEC E.R.C (Ed.) Proceedings of the International Symposium on Extremophiles and their Applications 2005 (2007)

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