title: Bacterial chitobiase structure provides insight into catalytic mechanism and the basis of Tay-Sachs disease.
abstract: Chitin, the second most abundant polysaccharide on earth, is degraded by chitinases and chitobiases. The structure of Serratia marcescens chitobiase has been refined at 1.9 A resolution. The mature protein is folded into four domains and its active site is situated at the C-terminal end of the central (beta alpha)8-barrel. Based on the structure of the complex with the substrate disaccharide chitobiose, we propose an acid-base reaction mechanism, in which only one protein carboxylate acts as catalytic acid, while the nucleophile is the polar acetamido group of the sugar in a substrate-assisted reaction. The structural data lead to the hypothesis that the reaction proceeds with retention of anomeric configuration. The structure allows us to model the catalytic domain of the homologous hexosaminidases to give a structural rationale to pathogenic mutations that underlie Tay-Sachs and Sandhoff disease.
authors.affiliation: European Molecular Biology Laboratory, Hamburg, Germany.
authors.forename: I
authors.initials: I
authors.lastname: Tews
authors.forename: A
authors.initials: A
authors.lastname: Perrakis
authors.forename: A
authors.initials: A
authors.lastname: Oppenheim
authors.forename: Z
authors.initials: Z
authors.lastname: Dauter
authors.forename: K S
authors.initials: KS
authors.lastname: Wilson
authors.forename: C E
authors.initials: CE
authors.lastname: Vorgias
mesh_terms: D000118:Acetylglucosaminidase / Q000737:chemistry*; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry*; D002384:Catalysis; D018360:Crystallography, X-Ray; D006801:Humans; D006860:Hydrogen Bonding; D008961:Models, Structural; D008969:Molecular Sequence Data; D017354:Point Mutation; D011487:Protein Conformation; D011994:Recombinant Proteins; D012497:Sandhoff Disease / Q000209:etiology; D013379:Substrate Specificity; D013661:Tay-Sachs Disease / Q000209:etiology*; D001619:beta-N-Acetylhexosaminidases / Q000737:chemistry
chemical_list: D001426:Bacterial Proteins; D011994:Recombinant Proteins; D000118:Acetylglucosaminidase; D001619:beta-N-Acetylhexosaminidases