| Title | Inhibition and structure of toxoplasma gondii purine nucleoside phosphorylase |
| Publication Type | Journal Article |
| Year of Publication | 2014 |
| Authors | Donaldson, T.M., Cassera M.B., Ho M.-C., Zhan C., Merino E.F., Evans G.B., Tyler P.C., Almo S.C., Schramm V.L., and Kim K. |
| Journal | Eukaryotic Cell |
| Volume | 13 |
| Issue | 5 |
| Pagination | 572 - 579 |
| Date Published | 2014 |
| ISSN | 15359778 (ISSN) |
| Keywords | antagonists and inhibitors, catalysis, Catalytic Domain, chemistry, Crystallography, X-Ray, enzyme active site, enzyme inhibitor, Enzyme Inhibitors, enzyme specificity, enzymology, forodesine, genetics, Kinetics, metabolism, protozoal protein, Protozoan Proteins, purine nucleoside, Purine nucleoside phosphorylase, Purine Nucleosides, Purine-Nucleoside Phosphorylase, pyrimidinone derivative, Pyrimidinones, Substrate Specificity, Toxoplasma, X ray crystallography |
| Abstract | The intracellular pathogen Toxoplasma gondii is a purine auxotroph that relies on purine salvage for proliferation. We have optimized T. gondii purine nucleoside phosphorylase (TgPNP) stability and crystallized TgPNP with phosphate and immucillin-H, a transition-state analogue that has high affinity for the enzyme. Immucillin-H bound to TgPNP with a dissociation constant of 370 pM, the highest affinity of 11 immucillins selected to probe the catalytic site. The specificity for transition-state analogues indicated an early dissociative transition state for TgPNP. Compared to Plasmodium falciparum PNP, large substituents surrounding the 5′-hydroxyl group of inhibitors demonstrate reduced capacity for TgPNP inhibition. Catalytic discrimination against large 5′ groups is consistent with the inability of TgPNP to catalyze the phosphorolysis of 5′-methylthioinosine to hypoxanthine. In contrast to mammalian PNP, the 2′-hydroxyl group is crucial for inhibitor binding in the catalytic site of TgPNP. This first crystal structure of TgPNP describes the basis for discrimination against 5′-methylthioinosine and similarly 5′-hydroxy-substituted immucillins; structural differences reflect the unique adaptations of purine salvage pathways of Apicomplexa. © 2014, American Society for Microbiology. All Rights Reserved. |
| URL | http://www.scopus.com/inward/record.url?eid=2-s2.0-84899949323&partnerID=40&md5=13455536977d7568e15455492bce683f |
| DOI | 10.1128/EC.00308-13 |
