PDBsum entry 4nrs

Hydrolase

PDB id: 4nrs

Contents

Protein chains

416 a.a.

Ligands

MAN-BMA ×2

Waters ×227

PDB id:

4nrs

Name:

Hydrolase

Title:

Crystal structure of glycoside hydrolase family 5 mannosidase (e202a mutant) from rhizomucor miehei in complex with mannobiose

Structure:

Exo-beta-1,4-mannosidase. Chain: a, b. Engineered: yes. Mutation: yes

Source:

Rhizomucor miehei. Organism_taxid: 4839. Strain: cau432. Expressed in: escherichia coli. Expression_system_taxid: 562

Resolution:

2.57Å R-factor: 0.198 R-free: 0.243

Authors:

Z.Q.Jiang,P.Zhou,S.Q.Yang,Y.Liu,Q.J.Yan

Key ref:

P.Zhou et al. (2014). Structural insights into the substrate specificity and transglycosylation activity of a fungal glycoside hydrolase family 5 β-mannosidase. Acta Crystallogr D Biol Crystallogr, 70, 2970-2982. PubMed id: 25372687 DOI: 10.1107/S1399004714019762

Date:

27-Nov-13 Release date: 19-Nov-14

Protein chains

A0A075C6T6  (A0A075C6T6_RHIMI) -  mannan endo-1,4-beta-mannosidase from Rhizomucor miehei

Seq: 450 a.a.

Struc: 416 a.a.*

* PDB and UniProt seqs differ at 4 residue positions (black crosses)

Enzyme reactions

• Enzyme class: E.C.3.2.1.78 - mannan endo-1,4-beta-mannosidase.
• Reaction: Random hydrolysis of 1,4-beta-D-mannosidic linkages in mannans, galactomannans, glucomannans, and galactoglucomannans.

DOI no: 10.1107/S1399004714019762

Acta Crystallogr D Biol Crystallogr 70:2970-2982 (2014)

PubMed id: 25372687

Structural insights into the substrate specificity and transglycosylation activity of a fungal glycoside hydrolase family 5 β-mannosidase.

P.Zhou, Y.Liu, Q.Yan, Z.Chen, Z.Qin, Z.Jiang.

ABSTRACT

β-Mannosidases are exo-acting glycoside hydrolases (GHs) that catalyse the removal of the nonreducing end β-D-mannose from manno-oligosaccharides or mannoside-substituted molecules. They play important roles in fundamental biological processes and also have potential applications in various industries. In this study, the first fungal GH family 5 β-mannosidase (RmMan5B) from Rhizomucor miehei was functionally and structurally characterized. RmMan5B exhibited a much higher activity against manno-oligosaccharides than against p-nitrophenyl β-D-mannopyranoside (pNPM) and had a transglycosylation activity which transferred mannosyl residues to sugars such as fructose. To investigate its substrate specificity and transglycosylation activity, crystal structures of RmMan5B and of its inactive E202A mutant in complex with mannobiose, mannotriose and mannosyl-fructose were determined at resolutions of 1.3, 2.6, 2.0 and 2.4 Å, respectively. In addition, the crystal structure of R. miehei β-mannanase (RmMan5A) was determined at a resolution of 2.3 Å. Both RmMan5A and RmMan5B adopt the (β/α)8-barrel architecture, which is globally similar to the other members of GH family 5. However, RmMan5B shows several differences in the loop around the active site. The extended loop between strand β8 and helix α8 (residues 354-392) forms a `double' steric barrier to `block' the substrate-binding cleft at the end of the -1 subsite. Trp119, Asn260 and Glu380 in the β-mannosidase, which are involved in hydrogen-bond contacts with the -1 mannose, might be essential for exo catalytic activity. Moreover, the structure of RmMan5B in complex with mannosyl-fructose has provided evidence for the interactions between the β-mannosidase and D-fructofuranose. Overall, the present study not only helps in understanding the catalytic mechanism of GH family 5 β-mannosidases, but also provides a basis for further enzymatic engineering of β-mannosidases and β-mannanases.