Τίτλος:
Modular structure, local flexibility and cold-activity of a novel
chitobiase from a psychrophilic Antarctic bacterium
Γλώσσες Τεκμηρίου:
Αγγλικά
Περίληψη:
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 Ca2+, 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
su,,est 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. (C) 2001 Academic Press.
Συγγραφείς:
Lonhienne, T
Zoidakis, J
Vorgias, CE
Feller, G
Gerday, C
and Bouriotis, V
Περιοδικό:
JOURNAL OF MOLECULAR BIOLOGY
Εκδότης:
ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD
Λέξεις-κλειδιά:
chitobiase; glycosyl hydrolase; microcalorimetry; psychrophile;
extremophile
DOI:
10.1006/jmbi.2001.4774
