4f5p
Open ternary mismatch complex of R283K DNA polymerase beta with a dATP analogOpen ternary mismatch complex of R283K DNA polymerase beta with a dATP analog
Structural highlights
FunctionDPOLB_HUMAN Repair polymerase that plays a key role in base-excision repair. Has 5'-deoxyribose-5-phosphate lyase (dRP lyase) activity that removes the 5' sugar phosphate and also acts as a DNA polymerase that adds one nucleotide to the 3' end of the arising single-nucleotide gap. Conducts 'gap-filling' DNA synthesis in a stepwise distributive fashion rather than in a processive fashion as for other DNA polymerases.[1] [2] [3] [4] Publication Abstract from PubMedDNA polymerase and substrate conformational changes are essential for high-fidelity DNA synthesis. Structures of DNA polymerase (pol) beta in complex with DNA show the enzyme in an "open" conformation. Subsequent to binding the nucleotide, the polymerase "closes" around the nascent base pair with two metals positioned for chemistry. However, structures of substrate/active site intermediates prior to closure are lacking. By destabilizing the closed complex, we determined unique ternary complex structures of pol beta with correct and incorrect incoming nucleotides bound to the open conformation. These structures reveal that Watson-Crick hydrogen bonding is assessed upon initial complex formation. Importantly, nucleotide-bound states representing intermediate metal coordination states occur with active site assembly. The correct, but not incorrect, nucleotide maintains Watson-Crick hydrogen bonds during interconversion of these states. These structures indicate that the triphosphate of the incoming nucleotide undergoes rearrangement prior to closure, providing an opportunity to deter misinsertion and increase fidelity. Structures of dNTP Intermediate States during DNA Polymerase Active Site Assembly.,Freudenthal BD, Beard WA, Wilson SH Structure. 2012 Nov 7;20(11):1829-37. doi: 10.1016/j.str.2012.08.008. Epub 2012, Sep 6. PMID:22959623[5] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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