Mechanism of DNA polymerase I: exonuclease/polymerase activity switch and DNA sequence dependence of pyrophosphorolysis and misincorporation reactions

Proc Natl Acad Sci U S A. 1986 Aug;83(16):5769-73. doi: 10.1073/pnas.83.16.5769.


Mechanistic features of several processes involved in the idling-turnover reaction catalyzed by the large (Klenow) fragment of Escherichia coli DNA polymerase I have been established. The exonuclease----polymerase activity switch involved in the excision/incorporation mode of idling-turnover occurs without an intervening dissociation of the enzyme from its DNA substrate. Comparative studies on the pyrophosphorolysis kinetics of related DNA substrates indicate a significant dependence of the reaction rate upon the DNA sequence within the duplex region upstream of the primer-template junction. Finally, a gel electrophoretic analysis of the products of the idling-turnover reaction has provided direct evidence for an alternative DNA sequence-dependent misincorporation/excision pathway.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Base Sequence
  • DNA Polymerase I / metabolism*
  • Diphosphates / metabolism
  • Escherichia coli / enzymology*
  • Exodeoxyribonucleases / metabolism*
  • Kinetics
  • Substrate Specificity


  • Diphosphates
  • DNA Polymerase I
  • Exodeoxyribonucleases