PDBsum entry: 2je8

Hydrolase

PDB id: 2je8

Contents

Protein chains

837 a.a. *

Ligands

B3P ×3

GOL ×9

Metals

_CL ×4

Waters ×1856

* Residue conservation analysis

PDB id:

2je8

Name:

Hydrolase

Title:

Structure of a beta-mannosidase from bacteroides thetaiotaomicron

Structure:

Beta-mannosidase. Chain: a, b. Fragment: residues 26-864. Engineered: yes

Source:

Bacteroides thetaiotaomicron. Organism_taxid: 226186. Strain: vpi-5482. Atcc: 29148. Expressed in: escherichia coli. Expression_system_taxid: 511693. Other_details: directly from atcc

Resolution:

1.7Å R-factor: 0.157 R-free: 0.188

Authors:

L.E.Tailford,V.A.Money,N.L.Smith,C.Dumon,G.J.Davies, H.J.Gilbert

Key ref:

L.E.Tailford et al. (2007). Mannose foraging by Bacteroides thetaiotaomicron: structure and specificity of the beta-mannosidase, BtMan2A. J Biol Chem, 282, 11291-11299. PubMed id: 17287210 DOI: 10.1074/jbc.M610964200

Date:

16-Jan-07 Release date: 06-Feb-07

Protein chains

Q8AAK6  (Q8AAK6_BACTN) -  Beta-mannosidase

Seq: 864 a.a.

Struc: 837 a.a.

 Gene Ontology (GO) functional annotation 

• Biological process: carbohydrate metabolic process (1 term)
• Biochemical function: catalytic activity (3 terms)

DOI no: 10.1074/jbc.M610964200

J Biol Chem 282:11291-11299 (2007)

PubMed id: 17287210

Mannose foraging by Bacteroides thetaiotaomicron: structure and specificity of the beta-mannosidase, BtMan2A.

L.E.Tailford, V.A.Money, N.L.Smith, C.Dumon, G.J.Davies, H.J.Gilbert.

ABSTRACT

The human colonic bacterium Bacteroides thetaiotaomicron, which plays an important role in maintaining human health, produces an extensive array of exo-acting glycoside hydrolases (GH), including 32 family GH2 glycoside hydrolases. Although it is likely that these enzymes enable the organism to utilize dietary and host glycans as major nutrient sources, the biochemical properties of these GH2 glycoside hydrolases are currently unclear. Here we report the biochemical properties and crystal structure of the GH2 B. thetaiotaomicron enzyme BtMan2A. Kinetic analysis demonstrates that BtMan2A is a beta-mannosidase in which substrate binding energy is provided principally by the glycone binding site, whereas aglycone recognition is highly plastic. The three-dimensional structure, determined to a resolution of 1.7 A, reveals a five-domain structure that is globally similar to the Escherichia coli LacZ beta-galactosidase. The catalytic center is housed mainly within a (beta/alpha)8 barrel although the N-terminal domain also contributes to the active site topology. The nature of the substrate-binding residues is quite distinct from other GH2 enzymes of known structure, instead they are similar to other clan GH-A enzymes specific for manno-configured substrates. Mutagenesis studies, informed by the crystal structure, identified a WDW motif in the N-terminal domain that makes a significant contribution to catalytic activity. The observation that this motif is invariant in GH2 mannosidases points to a generic role for these residues in this enzyme class. The identification of GH-A clan and GH2 specific residues in the active site of BtMan2A explains why this enzyme is able to harness substrate binding at the proximal glycone binding site more efficiently than mannan-hydrolyzing glycoside hydrolases in related enzyme families. The catalytic properties of BtMan2A are consistent with the flexible nutrient acquisition displayed by the colonic bacterium.

Selected figure(s)

Figure 1.
FIGURE 1. Mannose foraging by BtMan2A. BtMan2A is able to utilize both undecorated manno-oligosaccharides (A) as a substrate, and also hydrolyzes the Man-GlcNAc disaccharide that may reflect targeting to the Man 1,4-GlcNAc- 1,4-GlcNAc core (B) of N-glycans. The mannosidase displays weak activity against manno-oligosaccharides that are substituted at the O-6 position of the first (R[1] = -Gal) or second (R[2] = -Gal) aglycone sugar.

Figure 5.
FIGURE 5. Active site of BtMan2A. The figure depicts a divergent (wall-eyed) stereo of an overlay of the -1 subsite of BtMan2A and CmMan5A. Residues in the TIM barrel (green) and 1st domain (blue) of BtMan2A are overlaid with the equivalent residues of the exo-mannanase CmMan5A (gray) in complex with isofagominelactam (IFL) that is also depicted in gray (11). The residue numbers in parentheses refer to CmMan5A.

The above figures are reprinted by permission from the ASBMB: J Biol Chem (2007, 282, 11291-11299) copyright 2007.

Figures were selected by an automated process.