Crystal structures of Toxoplasma gondii HGXPRTase reveal the catalytic role of a long flexible loop.

Journal Article (Journal Article)

Crystal structures of substrate-free and XMP-soaked hypoxanthine-guanine-xanthine phosphoribosyltransferase (HGXPRTase) of the opportunistic pathogen Toxoplasma gondii have been determined to 2.4 and 2.9 A resolution, respectively. HGXPRTase displays the conserved PRTase fold. In the structure of the enzyme bound to its product, a long flexible loop (residues 115-126) is located away from the active site. Comparison to the substrate-free structure reveals a striking relocation of the loop, which is poised to cover the catalytic pocket, thus providing a mechanism by which the HG(X)PRTases shield their oxocarbonium transition states from nucleophilic attack by the bulk solvent. The conserved Ser 117-Tyr 118 dipeptide within the loop is brought to the active site, completing the ensemble of catalytic residues.

Full Text

Duke Authors

Cited Authors

  • Schumacher, MA; Carter, D; Roos, DS; Ullman, B; Brennan, RG

Published Date

  • October 1996

Published In

Volume / Issue

  • 3 / 10

Start / End Page

  • 881 - 887

PubMed ID

  • 8836106

International Standard Serial Number (ISSN)

  • 1072-8368

Digital Object Identifier (DOI)

  • 10.1038/nsb1096-881


  • eng

Conference Location

  • United States