Open AccessStructural bases for N‐glycan processing by mannoside phosphorylase
Author(s) -
Ladevèze Simon,
Cioci Gianluca,
Roblin Pierre,
Mourey Lionel,
Tranier Samuel,
PotockiVéronèse Gabrielle
Publication year - 2015
Publication title -
acta crystallographica section d
Language(s) - English
Resource type - Journals
ISSN - 1399-0047
DOI - 10.1107/s1399004715006604
Subject(s) - glycan , chitobiose , chemistry , glycoside hydrolase , biochemistry , mannose , stereochemistry , glycosylation , glycome , enzyme , subfamily , carbohydrate conformation , glycogen phosphorylase , polysaccharide , glycoprotein , gene , chitin , chitosan
The first crystal structure of Uhgb_MP, a β‐1,4‐mannopyranosyl‐chitobiose phosphorylase belonging to the GH130 family which is involved in N‐glycan degradation by human gut bacteria, was solved at 1.85 Å resolution in the apo form and in complex with mannose and N ‐acetylglucosamine. SAXS and crystal structure analysis revealed a hexameric structure, a specific feature of GH130 enzymes among other glycoside phosphorylases. Mapping of the −1 and +1 subsites in the presence of phosphate confirmed the conserved Asp104 as the general acid/base catalytic residue, which is in agreement with a single‐step reaction mechanism involving Man O 3 assistance for proton transfer. Analysis of this structure, the first to be solved for a member of the GH130_2 subfamily, revealed Met67, Phe203 and the Gly121–Pro125 loop as the main determinants of the specificity of Uhgb_MP and its homologues towards the N‐glycan core oligosaccharides and mannan, and the molecular bases of the key role played by GH130 enzymes in the catabolism of dietary fibre and host glycans.