3pnc
Ternary crystal structure of a polymerase lambda variant with a GT mispair at the primer terminus and sodium at catalytic metal siteTernary crystal structure of a polymerase lambda variant with a GT mispair at the primer terminus and sodium at catalytic metal site
Structural highlights
Function[DPOLL_HUMAN] Repair polymerase. Involved in base excision repair (BER) responsible for repair of lesions that give rise to abasic (AP) sites in DNA. Has both DNA polymerase and terminal transferase activities. Has a 5'-deoxyribose-5-phosphate lyase (dRP lyase) activity.[1] [2] Publication Abstract from PubMedIn describing the DNA double helix, Watson and Crick suggested that "spontaneous mutation may be due to a base occasionally occurring in one of its less likely tautomeric forms." Indeed, among many mispairing possibilities, either tautomerization or ionization of bases might allow a DNA polymerase to insert a mismatch with correct Watson-Crick geometry. However, despite substantial progress in understanding the structural basis of error prevention during polymerization, no DNA polymerase has yet been shown to form a natural base-base mismatch with Watson-Crick-like geometry. Here we provide such evidence, in the form of a crystal structure of a human DNA polymerase lambda variant poised to misinsert dGTP opposite a template T. All atoms needed for catalysis are present at the active site and in positions that overlay with those for a correct base pair. The mismatch has Watson-Crick geometry consistent with a tautomeric or ionized base pair, with the pH dependence of misinsertion consistent with the latter. The results support the original idea that a base substitution can originate from a mismatch having Watson-Crick geometry, and they suggest a common catalytic mechanism for inserting a correct and an incorrect nucleotide. A second structure indicates that after misinsertion, the now primer-terminal G*T mismatch is also poised for catalysis but in the wobble conformation seen in other studies, indicating the dynamic nature of the pathway required to create a mismatch in fully duplex DNA. Replication infidelity via a mismatch with Watson-Crick geometry.,Bebenek K, Pedersen LC, Kunkel TA Proc Natl Acad Sci U S A. 2011 Jan 13. PMID:21233421[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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