3ova

How the CCA-adding Enzyme Selects Adenine over Cytosine in Position 76 of tRNA

spinqualitylabelsall models 3ova, resolution 1.98Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 3ova is a 2 chain structure with sequence from Archaeoglobus fulgidus. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Ligands: APC, EDO, MG, SO4 Related: 3ouy, 3ov7, 3ovb, 3ovs Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function [CCA_ARCFU] Catalyzes the addition and repair of the essential 3'-terminal CCA sequence in tRNAs without using a nucleic acid template. Adds these three nucleotides in the order of C, C, and A to the tRNA nucleotide-73, using CTP and ATP as substrates and producing inorganic pyrophosphate. Publication Abstract from PubMed CCA-adding enzymes [ATP(CTP):tRNA nucleotidyltransferases] add CCA onto the 3' end of transfer RNA (tRNA) precursors without using a nucleic acid template. Although the mechanism by which cytosine (C) is selected at position 75 of tRNA has been established, the mechanism by which adenine (A) is selected at position 76 remains elusive. Here, we report five cocrystal structures of the enzyme complexed with both a tRNA mimic and nucleoside triphosphates under catalytically active conditions. These structures suggest that adenosine 5'-monophosphate is incorporated onto the A76 position of the tRNA via a carboxylate-assisted, one-metal-ion mechanism with aspartate 110 functioning as a general base. The discrimination against incorporation of cytidine 5'-triphosphate (CTP) at position 76 arises from improper placement of the alpha phosphate of the incoming CTP, which results from the interaction of C with arginine 224 and prevents the nucleophilic attack by the 3' hydroxyl group of cytidine75. How the CCA-adding enzyme selects adenine over cytosine at position 76 of tRNA.,Pan B, Xiong Y, Steitz TA Science. 2010 Nov 12;330(6006):937-40. PMID:21071662 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See Also CCA-adding enzyme Transfer RNA (tRNA)

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