title: Structural basis of sialyltransferase activity in trypanosomal sialidases.
abstract: The intracellular parasite Trypanosoma cruzi, the etiological agent of Chagas disease, sheds a developmentally regulated surface trans-sialidase, which is involved in key aspects of parasite-host cell interactions. Although it shares a common active site architecture with bacterial neuraminidases, the T.cruzi enzyme behaves as a highly efficient sialyltransferase. Here we report the crystal structure of the closely related Trypanosoma rangeli sialidase and its complex with inhibitor. The enzyme folds into two distinct domains: a catalytic beta-propeller fold tightly associated with a lectin-like domain. Comparison with the modeled structure of T.cruzi trans-sialidase and mutagenesis experiments allowed the identification of amino acid substitutions within the active site cleft that modulate sialyltransferase activity and suggest the presence of a distinct binding site for the acceptor carbohydrate. The structures of the Trypanosoma enzymes illustrate how a glycosidase scaffold can achieve efficient glycosyltransferase activity and provide a framework for structure-based drug design.
authors.affiliation: Unité de Biochimie Structurale, Institut Pasteur, 25 rue du Dr Roux, 75724 Paris.
authors.forename: A
authors.initials: A
authors.lastname: Buschiazzo
authors.forename: G A
authors.initials: GA
authors.lastname: Tavares
authors.forename: O
authors.initials: O
authors.lastname: Campetella
authors.forename: S
authors.initials: S
authors.lastname: Spinelli
authors.forename: M L
authors.initials: ML
authors.lastname: Cremona
authors.forename: G
authors.initials: G
authors.lastname: París
authors.forename: M F
authors.initials: MF
authors.lastname: Amaya
authors.forename: A C
authors.initials: AC
authors.lastname: Frasch
authors.forename: P M
authors.initials: PM
authors.lastname: Alzari
mesh_terms: D000818:Animals; D001665:Binding Sites; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D009439:Neuraminidase / Q000235:genetics / Q000378:metabolism*; D011487:Protein Conformation; D012799:Sialyltransferases / Q000235:genetics / Q000378:metabolism*; D014345:Trypanosoma / Q000201:enzymology* / Q000235:genetics
chemical_list: D012799:Sialyltransferases; D009439:Neuraminidase