3qpb | pdb_00003qpb

Crystal Structure of Streptococcus Pyogenes Uridine Phosphorylase Reveals a Subclass of the NP-I Superfamily

spinqualitylabelsall models 3qpb, resolution 1.82Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 3qpb is a 18 chain structure with sequence from Streptococcus pyogenes serotype m6. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Ligands: R1P, URA Gene: M6_Spy1599 (Streptococcus pyogenes serotype M6) Activity: Uridine phosphorylase, with EC number 2.4.2.3 Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function [Q5XA29_STRP6] Catalyzes the reversible phosphorylytic cleavage of uridine and deoxyuridine to uracil and ribose- or deoxyribose-1-phosphate. The produced molecules are then utilized as carbon and energy sources or in the rescue of pyrimidine bases for nucleotide synthesis.[RuleBase:RU361131] Publication Abstract from PubMed Uridine phosphorylase (UP), a key enzyme in the pyrimidine salvage pathway, catalyzes the reversible phosphorolysis of uridine or 2'-deoxyuridine to uracil and ribose 1-phosphate or 2'-deoxyribose 1-phosphate. This enzyme belongs to the nucleoside phosphorylase I superfamily whose members show diverse specificity for nucleoside substrates. Phylogenetic analysis shows Streptococcus pyogenes uridine phosphorylase (SpUP) is found in a distinct branch of the pyrimidine subfamily of nucleoside phosphorylases. To further characterize SpUP, we determined the crystal structure in complex with the products, ribose 1-phosphate and uracil, at 1.8 A resolution. Like Escherichia coli UP (EcUP), the biological unit of SpUP is a hexamer with an alpha/beta monomeric fold. A novel feature of the active site is the presence of His169, which structurally aligns with Arg168 of the EcUP structure. A second active site residue, Lys162, is not present in previously determined UP structures and interacts with O2 of uracil. Biochemical studies of wild-type SpUP showed that its substrate specificity is similar to that of EcUP, while EcUP is approximately 7-fold more efficient than SpUP. Biochemical studies of SpUP mutants showed that mutations of His169 reduced activity, while mutation of Lys162 abolished all activity, suggesting that the negative charge in the transition state resides mostly on uracil O2. This is in contrast to EcUP for which transition state stabilization occurs mostly at O4. The Crystal Structure of Streptococcus pyogenes Uridine Phosphorylase Reveals a Distinct Subfamily of Nucleoside Phosphorylases.,Tran TH, Christoffersen S, Allan PW, Parker WB, Piskur J, Serra I, Terreni M, Ealick SE Biochemistry. 2011 Aug 2;50(30):6549-6558. Epub 2011 Jul 8. PMID:21707079 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See Also Uridine phosphorylase 3D structures

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