4AK7 image
Deposition Date 2012-02-21
Release Date 2012-03-14
Last Version Date 2024-05-08
Entry Detail
PDB ID:
4AK7
Keywords:
Title:
Crystal structure of BpGH117_E303Q in complex with neoagarobiose
Biological Source:
Source Organism:
Host Organism:
Method Details:
Experimental Method:
Resolution:
1.80 Å
R-Value Free:
0.20
R-Value Work:
0.15
R-Value Observed:
0.15
Space Group:
P 21 21 21
Macromolecular Entities
Polymer Type:polypeptide(L)
Molecule:ANHYDRO-ALPHA-L-GALACTOSIDASE
Gene (Uniprot):BACPLE_01671
Mutations:YES
Chain IDs:A, B
Chain Length:404
Number of Molecules:2
Biological Source:BACTEROIDES PLEBEIUS
Primary Citation
Analysis of Keystone Enzyme in Agar Hydrolysis Provides Insight Into the Degradation (of a Polysaccharide from) Red Seaweeds.
J.Biol.Chem. 287 13985 ? (2012)
PMID: 22393053 DOI: 10.1074/JBC.M112.345645

Abstact

Agars are abundant polysaccharides from marine red algae, and their chemical structure consists of alternating D-galactose and 3,6-anhydro-L-galactose residues, the latter of which are presumed to make the polymer recalcitrant to degradation by most terrestrial bacteria. Here we study a family 117 glycoside hydrolase (BpGH117) encoded within a recently discovered locus from the human gut bacterium Bacteroides plebeius. Consistent with this locus being involved in agarocolloid degradation, we show that BpGH117 is an exo-acting 3,6-anhydro-α-(1,3)-L-galactosidase that removes the 3,6-anhydrogalactose from the non-reducing end of neoagaro-oligosaccharides. A Michaelis complex of BpGH117 with neoagarobiose reveals the distortion of the constrained 3,6-anhydro-L-galactose into a conformation that favors catalysis. Furthermore, this complex, supported by analysis of site-directed mutants, provides evidence for an organization of the active site and positioning of the catalytic residues that are consistent with an inverting mechanism of catalysis and suggests that a histidine residue acts as the general acid. This latter feature differs from the vast majority of glycoside hydrolases, which use a carboxylic acid, highlighting the alternative strategies that enzymes may utilize in catalyzing the cleavage of glycosidic bonds.

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Primary Citation of related structures