Varied Active-Site Constraints in the Klenow Fragment of E. coli DNA Polymerase I and the Lesion-Bypass Dbh DNA Polymerase

Cramer, Janina; Rangam, Gopinath; Marx, Andreas; Restle, Tobias

Varied Active-Site Constraints in the Klenow Fragment of E. coli DNA Polymerase I and the Lesion-Bypass Dbh DNA Polymerase

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Datum

2008

Autor:innen

Cramer, Janina

Rangam, Gopinath

Marx, Andreas

Restle, Tobias

Publikationstyp

Zeitschriftenartikel

Publikationsstatus

Published

Erschienen in

ChemBioChem. 2008, 9(8), pp. 1243-1250. ISSN 1439-4227. eISSN 1439-7633. Available under: doi: 10.1002/cbic.200700634

Zusammenfassung

We report on comparative pre-steady-state kinetic analyses of exonuclease-deficient Escherichia coli DNA polymerase I (Klenow fragment, KF-) and the archaeal Y-family DinB homologue (Dbh) of Sulfolobus solfataricus. We used size-augmented sugar-modified thymidine-5-triphosphate (TRTP) analogues to test the effects of steric constraints in the active sites of the polymerases. These nucleotides serve as models for study of DNA polymerases exhibiting both relatively high and low intrinsic selectivity. Substitution of a hydrogen atom at the 4-position in the nucleotide analogue by a methyl group reduces the maximum rate of nucleotide incorporation by about 40-fold for KF- and about twelvefold for Dbh. Increasing the size to an ethyl group leads to a further twofold reduction in the rates of incorporation for both enzymes. Interestingly, the affinity of KF- for the modified nucleotides is only marginally affected, which would indicate no discrimination during the binding step. Dbh even has a higher affinity for the modified analogues than it does for the natural substrate. Misincorporation of either TTP or TMeTP opposite a G template causes a drastic decline in incorporation rates for both enzymes. At the same time, the binding affinities of KF- for these nucleotides drop by about 16- and fourfold, respectively, whereas Dbh shows only a twofold reduction. Available structural data for ternary complexes of relevant DNA polymerases indicate that both enzymes make close contacts with the sugar moiety of the dNTP. Thus, the varied proficiencies of the two enzymes in processing the size-augmented probes indicate varied flexibility of the enzymes' active sites and support the notion of active site tightness being a criterion for DNA polymerase selectivity.

Fachgebiet (DDC)

540 Chemie

Schlagwörter

DNA polymerases, DNA replication, DNA, pre-steady-state kinetics, sugar-modified dNTP analogues

Zitieren

ISO 690

CRAMER, Janina, Gopinath RANGAM, Andreas MARX, Tobias RESTLE, 2008. Varied Active-Site Constraints in the Klenow Fragment of E. coli DNA Polymerase I and the Lesion-Bypass Dbh DNA Polymerase. In: ChemBioChem. 2008, 9(8), pp. 1243-1250. ISSN 1439-4227. eISSN 1439-7633. Available under: doi: 10.1002/cbic.200700634

BibTex

@article{Cramer2008Varie-1084,
  year={2008},
  doi={10.1002/cbic.200700634},
  title={Varied Active-Site Constraints in the Klenow Fragment of E. coli DNA Polymerase I and the Lesion-Bypass Dbh DNA Polymerase},
  number={8},
  volume={9},
  issn={1439-4227},
  journal={ChemBioChem},
  pages={1243--1250},
  author={Cramer, Janina and Rangam, Gopinath and Marx, Andreas and Restle, Tobias}
}

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