1nw4
Crystal Structure of Plasmodium falciparum Purine Nucleoside Phosphorylase in complex with ImmH and Sulfate
Structural highlights
FunctionPNPH_PLAF7 As part of the purine salvage pathway, catalyzes the phosphorolytic breakdown of the N-glycosidic bond in the beta-(deoxy)ribonucleoside molecules, with the formation of the corresponding free purine bases and pentose-1-phosphate (PubMed:18957439, PubMed:14982926, PubMed:16131758, PubMed:19575810, PubMed:24416224, PubMed:29440412). Preferentially acts on inosine and guanosine, and to a lesser extent on 2'-deoxyguanosine and guanosine (PubMed:14982926, PubMed:16131758, PubMed:19575810). Also catalyzes the phosphorylation of S-methyl-5'-thioinosine (MTI) to hypoxanthine; MTI is produced by adenosine deaminase (ADA)-mediated breakdown of S-methyl-5'-thioadenosine (MTA), a major by-product of polyamine biosynthesis (PubMed:18957439, PubMed:14982926, PubMed:24416224). Generates hypoxanthine from both the purine salvage pathway and from polyamine metabolism which is required for nucleic acids synthesis (PubMed:18957439, PubMed:14982926, PubMed:24416224). Has no activity towards adenosine (By similarity).[UniProtKB:Q8T9Z7][1] [2] [3] [4] [5] [6] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedPurine nucleoside phosphorylase from Plasmodium falciparum (PfPNP) is an anti-malarial target based on the activity of Immucillins. The crystal structure of PfPNP.Immucillin-H (ImmH).SO(4) reveals a homohexamer with ImmH and SO(4) bound at each catalytic site. A solvent-filled cavity close to the 5'-hydroxyl group of ImmH suggested that PfPNP can accept additional functional groups at the 5'-carbon. Assays established 5'-methylthioinosine (MTI) as a substrate for PfPNP. MTI is not found in human metabolism. These properties of PfPNP suggest unusual purine pathways in P. falciparum and provide structural and mechanistic foundations for the design of malaria-specific transition state analogue inhibitors. 5'-Methylthio-Immucillin-H (MT-ImmH) was designed to resemble the transition state of PfPNP and binds to PfPNP and human-PNP with K(d) values of 2.7 and 303 nm, respectively, to give a discrimination factor of 112. MT-ImmH is the first inhibitor that favors PfPNP inhibition. The structure of PfPNP.MT-ImmH.SO(4) shows that the hydrophobic methylthio group inserts into a hydrophobic region adjacent to the more hydrophilic 5'-hydroxyl binding site of ImmH. The catalytic features of PfPNP indicate a dual cellular function in purine salvage and polyamine metabolism. Combined metabolic functions in a single enzyme strengthen the rationale for targeting PfPNP in anti-malarial action. Plasmodium falciparum purine nucleoside phosphorylase: crystal structures, immucillin inhibitors, and dual catalytic function.,Shi W, Ting LM, Kicska GA, Lewandowicz A, Tyler PC, Evans GB, Furneaux RH, Kim K, Almo SC, Schramm VL J Biol Chem. 2004 Apr 30;279(18):18103-6. Epub 2004 Feb 23. PMID:14982926[7] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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