The I260Q variant of DNA polymerase β extends mispaired primer termini due to its increased affinity for deoxynucleotide triphosphate substrates

Shibani Dalal, Daniela Starcevic, Joachim Jaeger, Joann B. Sweasy

Research output: Contribution to journalArticlepeer-review

10 Scopus citations

Abstract

DNA polymerase β plays a key role in base excision repair. We have previously shown that the hydrophobic hinge region of polymerase β, which is distant from its active site, plays a critical role in the fidelity of DNA synthesis by this enzyme. The I260Q hinge variant of polymerase β misincorporates nucleotides with a significantly higher catalytic efficiency than the wild-type enzyme. In the study described here, we show that I260Q extends mispaired primer termini. The kinetic basis for extension of mispairs is defective discrimination by I260Q at the level of ground-state binding of the dNTP substrate. Our results suggest that the hydrophobic hinge region influences the geometry of the dNTP binding pocket exclusively. Because the DNA forms part of the binding pocket, our data are also consistent with the interpretation that the mispaired primer terminus affects the geometry of the dNTP binding pocket such that the I260Q variant has a higher affinity for the incoming dNTP than wild-type polymerase β.

Original languageEnglish (US)
Pages (from-to)12118-12125
Number of pages8
JournalBiochemistry
Volume47
Issue number46
DOIs
StatePublished - Nov 18 2008
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry

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