3MB8

Crystal structure of purine nucleoside phosphorylase from toxoplasma gondii in complex with immucillin-H

Summary for 3MB8

• Entry DOI: 10.2210/pdb3mb8/pdb
• Descriptor: Purine nucleoside phosphorylase, 1,4-DIDEOXY-4-AZA-1-(S)-(9-DEAZAHYPOXANTHIN-9-YL)-D-RIBITOL, PHOSPHATE ION, ... (5 entities in total)
• Functional Keywords: pnp, purine nucleoside phosphorylase, immucillin h, immh, transferase
• Biological source: Toxoplasma gondii
• Total number of polymer chains: 2
• Total formula weight: 62258.84

Authors

Ho, M.,Almo, S.C.,Schramm, V.L. (deposition date: 2010-03-25, release date: 2011-04-06, Last modification date: 2024-05-22)

Primary citation

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.,Kim, K.
Inhibition and Structure of Toxoplasma gondii Purine Nucleoside Phosphorylase.
Eukaryot Cell, 13:572-579, 2014

PubMed 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.

PubMed: 24585883
DOI: 10.1128/EC.00308-13

Experimental method

X-RAY DIFFRACTION (1.9 Å)