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Internet Electronic Journal of Molecular Design - IEJMD, ISSN 1538-6414, CODEN IEJMAT
| ABSTRACT - Internet Electron. J. Mol. Des. December 2003, Volume 2, Number 12, 835-851 |
Structural Contributions for Thermostability of a New Endo-1,4-β-xylanase
from the Fungus Humicola grisea
Sonia M. De Freitas, Werner L. Treptow, Fabricia P. De Faria, Maristela De O. Azevedo, and Bernard Maigret
Internet Electron. J. Mol. Des. 2003, 2, 835-851
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Abstract:
The Humicola grisea var. thermoidea is known as a good
producer of hydrolytic enzymes. The H. grisea endo-1,4-β-xylanase
gene (xyn2) was isolated and its sequence was
translated into a predicted protein coding for a xylanase of 23
kDa. A structural model of H. grisea endo-1,4-β-xylanase
(XYN2) was built by homology modeling based on the database
search results of related proteins, belonging to Glycoside
Hydrolase Family 11 (GH11). The inactive/active conformation
transition of the XYN2 model active site is pH sensitive as
revealed by independent molecular dynamics simulations at
different pH. The active conformation exhibits the common
structural β-sheet twisted architecture of the GH11. The active
site is formed by a large cleft containing the catalytic residues
(E84 and E175), and is stabilized by hydrogen bond network
involving the Q134, Y75, Y88, W77, and Y169. Additionally,
the structural properties described by the model explain the
observed thermostability of the XYN2 protein. According to our
results, the thermostability of XYN2 protein, compared to
mesophilic xylanases, can be explained by an additional
electrostatic network and extra aromatic exposed residues.
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