Download MendeleyCrystal structures of Toxoplasma gondii HGXPRTase reveal the catalytic role of a long flexible loop.
Schumacher, M.A., Carter, D., Ross, D.S., Ullman, B., Brennan, R.G.(1996) Nat Struct Biol 3: 881-887
- PubMed: 8836106
- DOI: https://doi.org/10.1038/nsb1096-881
- Primary Citation of Related Structures:
1DBR - PubMed Abstract:
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.
Organizational Affiliation:
Department of Biochemistry and Molecular Biology, Oregon Health Sciences University, Portland 97201-3098, USA.
