4rq3
From Proteopedia
Precatalytic ternary complex of Human DNA Polymerase Beta With Gapped DNA Containing an 8-oxo-7,8-dihydro-Guanine (8-oxoG) and dATP in the presence of CaCl2
Structural highlights
Function[DPOLB_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 PubMedOne common oxidative DNA lesion, 8-oxo-7,8-dihydro-2'-deoxyguanine (8-oxoG), is highly mutagenic in vivo due to its anti-conformation forming a Watson-Crick base pair with correct deoxycytidine 5'-triphosphate (dCTP) and its syn-conformation forming a Hoogsteen base pair with incorrect deoxyadenosine 5'-triphosphate (dATP). Here, we utilized time-resolved X-ray crystallography to follow 8-oxoG bypass by human DNA polymerase beta (hPolbeta). In the 12 solved structures, both Watson-Crick (anti-8-oxoG:anti-dCTP) and Hoogsteen (syn-8-oxoG:anti-dATP) base pairing were clearly visible and were maintained throughout the chemical reaction. Additionally, a third Mg2+ appeared during the process of phosphodiester bond formation and was located between the reacting alpha- and beta-phosphates of the dNTP, suggesting its role in stabilizing reaction intermediates. After phosphodiester bond formation, hPolbeta reopened its conformation, pyrophosphate was released, and the newly incorporated primer 3'-terminal nucleotide stacked, rather than base paired, with 8-oxoG. These structures provide the first real-time pictures, to our knowledge, of how a polymerase correctly and incorrectly bypasses a DNA lesion. Viewing Human DNA Polymerase beta Faithfully and Unfaithfully Bypass an Oxidative Lesion by Time-Dependent Crystallography.,Vyas R, Reed AJ, Tokarsky EJ, Suo Z J Am Chem Soc. 2015 Apr 9. PMID:25825995[5] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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