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| {{STRUCTURE_1bd3| PDB=1bd3 | SCENE= }} | | {{STRUCTURE_1bd3| PDB=1bd3 | SCENE= }} |
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| '''STRUCTURE OF THE APO URACIL PHOSPHORIBOSYLTRANSFERASE, 2 MUTANT C128V'''
| | ===STRUCTURE OF THE APO URACIL PHOSPHORIBOSYLTRANSFERASE, 2 MUTANT C128V=== |
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| ==Overview==
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| Uracil phosphoribosyltransferase (UPRTase) catalyzes the transfer of a ribosyl phosphate group from alpha-D-5-phosphoribosyl-1-pyrophosphate to the N1 nitrogen of uracil. The UPRTase from the opportunistic pathogen Toxoplasma gondii is a rational target for antiparasitic drug design. To aid in structure-based drug design studies against toxoplasmosis, the crystal structures of the T.gondii apo UPRTase (1.93 A resolution), the UPRTase bound to its substrate, uracil (2.2 A resolution), its product, UMP (2.5 A resolution), and the prodrug, 5-fluorouracil (2.3 A resolution), have been determined. These structures reveal that UPRTase recognizes uracil through polypeptide backbone hydrogen bonds to the uracil exocyclic O2 and endocyclic N3 atoms and a backbone-water-exocyclic O4 oxygen hydrogen bond. This stereochemical arrangement and the architecture of the uracil-binding pocket reveal why cytosine and pyrimidines with exocyclic substituents at ring position 5 larger than fluorine, including thymine, cannot bind to the enzyme. Strikingly, the T. gondii UPRTase contains a 22 residue insertion within the conserved PRTase fold that forms an extended antiparallel beta-arm. Leu92, at the tip of this arm, functions to cap the active site of its dimer mate, thereby inhibiting the escape of the substrate-binding water molecule.
| | The line below this paragraph, {{ABSTRACT_PUBMED_9628859}}, adds the Publication Abstract to the page |
| | (as it appears on PubMed at http://www.pubmed.gov), where 9628859 is the PubMed ID number. |
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| | {{ABSTRACT_PUBMED_9628859}} |
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| ==About this Structure== | | ==About this Structure== |
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| [[Category: Transferase]] | | [[Category: Transferase]] |
| [[Category: Uprtase]] | | [[Category: Uprtase]] |
| ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 11:21:30 2008'' | | |
| | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Mon Jun 30 18:52:13 2008'' |
