3WNM: D308A mutant of Bacillus circulans T-3040 cycloisomaltooligosaccharide glucanotransferase complexed with isomaltoheptaose

Citation:
Abstract
Bacillus circulans T-3040 cycloisomaltooligosaccharide glucanotransferase belongs to the glycoside hydrolase family 66 and catalyzes an intramolecular transglucosylation reaction that produces cycloisomaltooligosaccharides from dextran. The crystal structure of the core fragment from Ser-39 to Met-738 of B. circulans T-3040 cycloisomaltooligosaccharide glucanotransferase, devoid of its N-terminal signal peptide and C-terminal nonconserved regions, was determined. The structural model contained one catalytic (beta/alpha)8-barrel domain and three beta-domains. Domain N with an immunoglobulin-like beta-sandwich fold was attached to the N terminus; domain C with a Greek key beta-sandwich fold was located at the C terminus, and a carbohydrate-binding module family 35 (CBM35) beta-jellyroll domain B was inserted between the 7th beta-strand and the 7th alpha-helix of the catalytic domain A. The structures of the inactive catalytic nucleophile mutant enzyme complexed with isomaltohexaose, isomaltoheptaose, isomaltooctaose, and cycloisomaltooctaose revealed that the ligands bound in the catalytic cleft and the sugar-binding site of CBM35. Of these, isomaltooctaose bound in the catalytic site extended to the second sugar-binding site of CBM35, which acted as subsite -8, representing the enzyme.substrate complex when the enzyme produces cycloisomaltooctaose. The isomaltoheptaose and cycloisomaltooctaose bound in the catalytic cleft with a circular structure around Met-310, representing the enzyme.product complex. These structures collectively indicated that CBM35 functions in determining the size of the product, causing the predominant production of cycloisomaltooctaose by the enzyme. The canonical sugar-binding site of CBM35 bound the mid-part of isomaltooligosaccharides, indicating that the original function involved substrate binding required for efficient catalysis.
PDB ID: 3WNMDownload
MMDB ID: 117151
PDB Deposition Date: 2013/12/10
Updated in MMDB: 2017/12
Experimental Method:
x-ray diffraction
Resolution: 2.25  Å
Source Organism:
Similar Structures:
Biological Unit for 3WNM: monomeric; determined by author and by software (PISA)
Molecular Components in 3WNM
Label Count Molecule
Protein (1 molecule)
1
Cycloisomaltooligosaccharide Glucanotransferase
Molecule annotation
Chemicals (22 molecules)
1
1
2
1
3
8
4
1
5
10
6
1
* Click molecule labels to explore molecular sequence information.

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