3tag

5-fluorocytosine paired with dAMP in RB69 gp43

spinqualitylabelsall models 3tag, resolution 2.95Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 3tag is a 12 chain structure with sequence from Escherichia phage RB69 and Synthetic construct. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: X-ray diffraction, Resolution 2.95Å Ligands: C37, SO4 Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function DPOL_BPR69 This polymerase possesses two enzymatic activities: DNA synthesis (polymerase) and an exonucleolytic activity that degrades single stranded DNA in the 3'- to 5'-direction. Publication Abstract from PubMed 5-Hydroxycytosine (5-OHC) is a stable oxidation product of cytosine associated with an increased frequency of C --> T transition mutations. When this lesion escapes recognition by the base excision repair pathway and persists to serve as a templating base during DNA synthesis, replicative DNA polymerases often misincorporate dAMP at the primer terminus, which can lead to fixation of mutations and subsequent disease. To characterize the dynamics of DNA synthesis opposite 5-OHC, we initiated a comparison of unmodified dCMP to 5-OHC, 5-fluorocytosine (5-FC), and 5-methylcytosine (5-MEC) in which these bases act as templates in the active site of RB69 gp43, a high-fidelity DNA polymerase sharing homology with human replicative DNA polymerases. This study presents the first crystal structure of any DNA polymerase binding this physiologically important premutagenic DNA lesion, showing that while dGMP is stabilized by 5-OHC through normal Watson-Crick base pairing, incorporation of dAMP leads to unstacking and instability in the template. Furthermore, the electronegativity of the C5 substituent appears to be important in the miscoding potential of these cytosine-like templates. While dAMP is incorporated opposite 5-OHC approximately 5 times more efficiently than opposite unmodified dCMP, an elevated level of incorporation is also observed opposite 5-FC but not 5-MEC. Taken together, these data imply that the nonuniform templating by 5-OHC is due to weakened stacking capabilities, which allows dAMP incorporation to proceed in a manner similar to that observed opposite abasic sites. The Miscoding Potential of 5-Hydroxycytosine Arises Due to Template Instability in the Replicative Polymerase Active Site.,Zahn KE, Averill A, Wallace SS, Doublie S Biochemistry. 2011 Nov 3. PMID:22026756 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See Also DNA polymerase 3D structures

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