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Exo-beta-1,3-glucanase (EC 3.2.1.58) successively hydrolyse O-glycosidic linkage of beta-1,3-linked
glucans from their nonreducing terminus to subsequently yield glucose. In this paper, we present the
3D structure prediction and validation of novel bacterial exo-beta-1, 3-glucanase of GH family 17
from Psychroflexus torquis ATCC700755/ACAM623-a psychrophilic bacteria. This is the first
attempt to model this enzyme with a GH family 17 fold in bacteria. All known exo-beta-1, 3-
glucanase of GH family 17 are of plant and fungal origin. Validation of the stereochemistry of the
predicted model using the Rampage sever for Ramachandran plot indicates 97.1% of residues
located in favoured and allowed regions while the remaining are in outlier region. This model also
obtained an ERRAT score of 93.17% which is well above the 50% critical value for a good model.
As a way of further evaluation, we generated profile files of the model and template by the
‘asses_dope’ command of MODELLER 9.15 programme. These profile files were used in gnuplot
4.6 ploting software to produce a comparative plot of Discrete Optimized Protein Energy (DOPE)
per residue of the template and model. This model obtained an overall DOPE value better than the
template.
Key words: Psychroflexus torques, O-glycosidic, Exo-beta-1,3-glucanase