2ago

Fidelity of Dpo4: effect of metal ions, nucleotide selection and pyrophosphorolysis

spinqualitylabelsall models 2ago, resolution 2.85Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 2ago is a 3 chain structure with sequence from Saccharolobus solfataricus. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: X-ray diffraction, Resolution 2.85Å Ligands: CA, MG, POP Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function DPO4_SACS2 Poorly processive, error-prone DNA polymerase involved in untargeted mutagenesis. Copies undamaged DNA at stalled replication forks, which arise in vivo from mismatched or misaligned primer ends. These misaligned primers can be extended by PolIV. Exhibits no 3'-5' exonuclease (proofreading) activity. It is involved in translesional synthesis. 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 PubMed We report the crystal structures of a translesion DNA polymerase, Dpo4, complexed with a matched or mismatched incoming nucleotide and with a pyrophosphate product after misincorporation. These structures suggest two mechanisms by which Dpo4 may reject a wrong incoming nucleotide with its preformed and open active site. First, a mismatched replicating base pair leads to poor base stacking and alignment of the metal ions and as a consequence, inhibits incorporation. By replacing Mg2+ with Mn2+, which has a relaxed coordination requirement and tolerates misalignment, the catalytic efficiency of misincorporation increases dramatically. Mn2+ also enhances translesion synthesis by Dpo4. Subtle conformational changes that lead to the proper metal ion coordination may, therefore, be a key step in catalysis. Second, the slow release of pyrophosphate may increase the fidelity of Dpo4 by stalling mispaired primer extension and promoting pyrophosphorolysis that reverses the polymerization reaction. Indeed, Dpo4 has robust pyrophosphorolysis activity and degrades the primer strand in the presence of pyrophosphate. The correct incoming nucleotide allows DNA synthesis to overcome pyrophosphorolysis, but an incorrect incoming nucleotide does not. Fidelity of Dpo4: effect of metal ions, nucleotide selection and pyrophosphorolysis.,Vaisman A, Ling H, Woodgate R, Yang W EMBO J. 2005 Sep 7;24(17):2957-67. Epub 2005 Aug 18. PMID:16107880 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See Also DNA polymerase 3D structures

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