Reference : Modular Structure, Local Flexibility and Cold-Activity of a Novel Chitobiase from a Psyc...
Scientific journals : Article
Life sciences : Biochemistry, biophysics & molecular biology
http://hdl.handle.net/2268/16035
Modular Structure, Local Flexibility and Cold-Activity of a Novel Chitobiase from a Psychrophilic Antarctic Bacterium
English
Lonhienne, T. [> > > >]
Zoidakis, J. [> > > >]
Vorgias, C. E. [> > > >]
Feller, Georges mailto [Université de Liège - ULg > Département des sciences de la vie > Labo de biochimie >]
Gerday, Charles mailto [Université de Liège - ULg > Services généraux (Faculté des sciences) > Relations académiques et scientifiques (Sciences) >]
Bouriotis, V. [> > > >]
6-Jul-2001
Journal of Molecular Biology
310
2
291-7
Yes (verified by ORBi)
International
0022-2836
[en] 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.
http://hdl.handle.net/2268/16035
10.1006/jmbi.2001.4774

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