Showing results 21 to 29 of 29
  The structure of a cold-adapted family 8 xylanase at 1.3 angstrom resolution - Structural adaptations to cold and investigation of the active site; ; Meuwis, Marie-Alice  et alin 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 ▲] Detailed reference viewed: 4 (1 ULg)A novel family 8 xylanase, functional and physicochemical characterization; Meuwis, Marie-Alice ; et alin Journal of Biological Chemistry (2002), 277(38), 35133-35139 Detailed reference viewed: 7 (0 ULg) Crystallization and preliminary X-ray analysis of a xylanase from the psychrophile Pseudoalteromonas haloplanktis; ; Meuwis, Marie-Alice et alin 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)Molecular basis of cold adaptationD'Amico, Salvino ; ; et alin 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: 8 (2 ULg)Life in the cold: psychrophilic enzymes; ; D'Amico, Salvino et alin Recent Res. Devl. Proteins vol. 1 (2002) Detailed reference viewed: 25 (2 ULg)Did Psychrophilic Enzymes Really Win the Challenge?Zecchinon, Laurent ; ; et alin 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)Cold-adapted enzymes: an unachieved symphonyD'Amico, Salvino ; ; et alin Storey, K. B.; Storey, J. M. (Eds.) Cell and Molecular Responses to Stress vol.2. Protein adaptations and signal transduction, (2001) Detailed reference viewed: 24 (3 ULg)Cold-adapted enzymes; ; et al in Bulte, J.; DeCuyper, M. (Eds.) Focus on Biotechnology – Physics and Chemistry Basis for Biotechnology (2001) Detailed reference viewed: 18 (2 ULg)Cold-Adapted Enzymes: From Fundamentals to BiotechnologyGerday, Charles ; ; et alin Trends in Biotechnology (2000), 18(3), 103-7 Psychrophilic enzymes produced by cold-adapted microorganisms display a high catalytic efficiency and are most often, if not always, associated with high thermosensitivity. Using X-ray crystallography ... [more ▼] Psychrophilic enzymes produced by cold-adapted microorganisms display a high catalytic efficiency and are most often, if not always, associated with high thermosensitivity. Using X-ray crystallography, these properties are beginning to become understood, and the rules governing their adaptation to cold appear to be relatively diverse. The application of these enzymes offers considerable potential to the biotechnology industry, for example, in the detergent and food industries, for the production of fine chemicals and in bioremediation processes. [less ▲] Detailed reference viewed: 50 (1 ULg)
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