Mechanism of the idling-turnover reaction of the large (Klenow) fragment of Escherichia coli DNA polymerase I

Proc Natl Acad Sci U S A. 1986 Jan;83(2):231-5. doi: 10.1073/pnas.83.2.231.


The mechanism of the idling-turnover reaction catalyzed by the large (Klenow) fragment of Escherichia coli DNA polymerase I has been investigated. The reaction cycle involved is one of excision/incorporation, in which the 3' deoxynucleotide residue of the primer DNA strand is partitioned into its 5'-mono- and 5'-triphosphate derivatives, respectively. Mechanistic studies suggest the 5'-monophosphate product is formed in the first step by simple 3'----5' exonucleolytic cleavage. Rapid polymerization follows with the concomitant release of inorganic pyrophosphate. In the second step, the 5'-triphosphate product is generated by a pyrophosphorolysis reaction, which, despite the low concentration of pyrophosphate that has accumulated, occurs at a rate that is comparable with that of the parallel 3'----5' hydrolysis reaction.

Publication types

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

MeSH terms

  • DNA Polymerase I / metabolism*
  • Deoxyadenine Nucleotides / metabolism
  • Deoxyguanine Nucleotides / metabolism
  • Escherichia coli / enzymology*
  • Kinetics
  • Peptide Fragments / metabolism*


  • Deoxyadenine Nucleotides
  • Deoxyguanine Nucleotides
  • Peptide Fragments
  • DNA Polymerase I