4XB3 image
Entry Detail
PDB ID:
4XB3
Keywords:
Title:
Structure of dextran glucosidase
Biological Source:
Host Organism:
PDB Version:
Deposition Date:
2014-12-16
Release Date:
2015-08-26
Method Details:
Experimental Method:
Resolution:
2.09 Å
R-Value Free:
0.21
R-Value Work:
0.17
R-Value Observed:
0.18
Space Group:
P 21 21 21
Macromolecular Entities
Polymer Type:polypeptide(L)
Description:Glucan 1,6-alpha-glucosidase
Mutations:E236Q, N536L
Chain IDs:A
Chain Length:536
Number of Molecules:1
Biological Source:Streptococcus mutans UA159
Primary Citation
Structural insights into the catalytic reaction that is involved in the reorientation of Trp238 at the substrate-binding site in GH13 dextran glucosidase
Febs Lett. 589 484 489 (2015)
PMID: 25595454 DOI: 10.1016/j.febslet.2015.01.005

Abstact

Streptococcus mutans dextran glucosidase (SmDG) belongs to glycoside hydrolase family 13, and catalyzes both the hydrolysis of substrates such as isomaltooligosaccharides and subsequent transglucosylation to form α-(1→6)-glucosidic linkage at the substrate non-reducing ends. Here, we report the 2.4Å resolution crystal structure of glucosyl-enzyme intermediate of SmDG. In the obtained structure, the Trp238 side-chain that constitutes the substrate-binding site turned away from the active pocket, concurrently with conformational changes of the nucleophile and the acid/base residues. Different conformations of Trp238 in each reaction stage indicated its flexibility. Considering the results of kinetic analyses, such flexibility may reflect a requirement for the reaction mechanism of SmDG.

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