2bsx
Crystal structure of the Plasmodium falciparum purine nucleoside phosphorylase complexed with inosine
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:14982926, PubMed:16131758, PubMed:18957439, 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:14982926, PubMed:18957439, PubMed:24416224). Generates hypoxanthine from both the purine salvage pathway and from polyamine metabolism which is required for nucleic acids synthesis (PubMed:14982926, PubMed:18957439, 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 metabolism in the parasite Plasmodium has been identified as a promising target for antimalarial therapies. Purine nucleoside phosphorylase (PNP) is part of a salvage pathway for the biosynthesis of purines, which are essential for parasite survival. Two crystal structures of PNP from Plasmodium falciparum (PfPNP) in two space groups, each with a single subunit in the asymmetric unit, are described here. One structure, refined to 2.4 A, has an empty nucleoside-binding site and a sulfate ion bound in the phosphate-binding pocket. The second structure, refined to 2.0 A, has the substrate inosine bound to the active centre. Structure comparison reveals alterations in the active site upon ligand binding. The new structures presented here specifically highlight the likely roles of Asp206 and two loops flanking the active site: the beta7-alpha6 loop (residues approximately 161-169) and the beta9-alpha8 loop (residues approximately 208-223). Comparison with PNP in complex with transition-state inhibitors suggests that the purine substrate moves towards the phosphate substrate, rather than vice versa, upon forming the transition state. The single-substrate-containing PfPNP structures also appear to be more flexible than PfPNP bound to inhibitors. Together, these structures serve as a basis for better understanding of ligand binding and mechanism that can be further exploited to optimize the specificity of anti-PfPNP drugs. Structures of Plasmodium falciparum purine nucleoside phosphorylase complexed with sulfate and its natural substrate inosine.,Schnick C, Robien MA, Brzozowski AM, Dodson EJ, Murshudov GN, Anderson L, Luft JR, Mehlin C, Hol WG, Brannigan JA, Wilkinson AJ Acta Crystallogr D Biol Crystallogr. 2005 Sep;61(Pt 9):1245-54. Epub 2005, Aug 16. PMID:16131758[7] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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