4AD0 image
Entry Detail
PDB ID:
4AD0
Keywords:
Title:
Structure of the GH99 endo-alpha-mannosidase from Bacteriodes thetaiotaomicron in complex with BIS-TRIS-Propane
Biological Source:
Host Organism:
PDB Version:
Deposition Date:
2011-12-21
Release Date:
2012-02-01
Method Details:
Experimental Method:
Resolution:
2.09 Å
R-Value Free:
0.23
R-Value Work:
0.18
R-Value Observed:
0.18
Space Group:
P 1 21 1
Macromolecular Entities
Polymer Type:polypeptide(L)
Description:ENDO-ALPHA-MANNOSIDASE
Chain IDs:A, B, C, D
Chain Length:382
Number of Molecules:4
Biological Source:BACTEROIDES THETAIOTAOMICRON
Primary Citation
Structural and Mechanistic Insight Into N-Glycan Processing by Endo-Alpha-Mannosidase.
Proc.Natl.Acad.Sci.USA 109 781 ? (2012)
PMID: 22219371 DOI: 10.1073/PNAS.1111482109

Abstact

N-linked glycans play key roles in protein folding, stability, and function. Biosynthetic modification of N-linked glycans, within the endoplasmic reticulum, features sequential trimming and readornment steps. One unusual enzyme, endo-α-mannosidase, cleaves mannoside linkages internally within an N-linked glycan chain, short circuiting the classical N-glycan biosynthetic pathway. Here, using two bacterial orthologs, we present the first structural and mechanistic dissection of endo-α-mannosidase. Structures solved at resolutions 1.7-2.1 Å reveal a (β/α)(8) barrel fold in which the catalytic center is present in a long substrate-binding groove, consistent with cleavage within the N-glycan chain. Enzymatic cleavage of authentic Glc(1/3)Man(9)GlcNAc(2) yields Glc(1/3)-Man. Using the bespoke substrate α-Glc-1,3-α-Man fluoride, the enzyme was shown to act with retention of anomeric configuration. Complexes with the established endo-α-mannosidase inhibitor α-Glc-1,3-deoxymannonojirimycin and a newly developed inhibitor, α-Glc-1,3-isofagomine, and with the reducing-end product α-1,2-mannobiose structurally define the -2 to +2 subsites of the enzyme. These structural and mechanistic data provide a foundation upon which to develop new enzyme inhibitors targeting the hijacking of N-glycan synthesis in viral disease and cancer.

Legend

Protein

Chemical

Disease

Primary Citation of related structures