3rjh
From Proteopedia
Ternary complex of DNA Polymerase Beta with a gapped DNA containing (syn)8odG:dA at primer terminus and dG:dCMP(CF2)PPin the active site
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 PubMedOxidation of genomic DNA forms the guanine lesion 7,8-dihydro-8-oxoguanine (8-oxoG). When in the template base position during DNA synthesis the 8-oxoG lesion has dual coding potential by virtue of its anti- and syn-conformations, base pairing with cytosine and adenine, respectively. This impacts mutagenesis, because insertion of adenine opposite template 8-oxoG can result in a G to T transversion. DNA polymerases vary by orders of magnitude in their preferences for mutagenic vs. error-free 8-oxoG lesion bypass. Yet, the structural basis for lesion bypass specificity is not well understood. The DNA base excision repair enzyme DNA polymerase (pol) beta is presented with gap-filling synthesis opposite 8-oxoG during repair and has similar insertion efficiencies for dCTP and dATP. We report the structure of pol beta in binary complex with template 8-oxoG in a base excision repair substrate. The structure reveals both the syn- and anti-conformations of template 8-oxoG in the confines of the polymerase active site, consistent with the dual coding observed kinetically for this enzyme. A ternary complex structure of pol beta with the syn-8-oxoG:anti-A Hoogsteen base pair in the closed fully assembled preinsertion active site is also reported. The syn-conformation of 8-oxoG is stabilized by minor groove hydrogen bonding between the side chain of Arg283 and O8 of 8-oxoG. An adjustment in the position of the phosphodiester backbone 5'-phosphate enables 8-oxoG to adopt the syn-conformation. Binary complex crystal structure of DNA polymerase beta reveals multiple conformations of the templating 8-oxoguanine lesion.,Batra VK, Shock DD, Beard WA, McKenna CE, Wilson SH Proc Natl Acad Sci U S A. 2012 Jan 3;109(1):113-8. Epub 2011 Dec 16. PMID:22178760[5] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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