NaF and mononucleotides as inhibitors of 3'-5'-exonuclease activity and stimulators of polymerase activity of E. coli DNA polymerase I Klenow fragment

FEBS Lett. 1990 Dec 17;277(1-2):109-11. doi: 10.1016/0014-5793(90)80820-9.


It has been shown that, in the absence of dATP in the poly(dT).oligo(dA) template-primer complex, the rate of primer cleavage by the E. coli DNA polymerase I Klenow fragment equals 4% of polymerization rate, while in the presence of dATP it equals as much as 50-60%. NaF and NMP taken separately inhibit exonuclease cleavage of oligo(dA) both with and without dATP. The addition of NaF (5-10 mM) or NMP (5-20 mM) increases the absolute increment of polymerization rate 5-9-fold relative to the absolute decrement of the rate of nuclease hydrolysis of primer. This proves the assumption that not more than 10-20% of primer molecules, interacting with the exonuclease center of polymerase, are cleaved by the enzyme. Presumably, NaF and nucleotides disturb the coupling of the 3'-end of oligonucleotide primer to the exonuclease center of the enzyme. As the primers mostly form complexes with the polymerizing center, the reaction of polymerization is activated.

MeSH terms

  • DNA Polymerase I / antagonists & inhibitors*
  • DNA Polymerase I / metabolism*
  • Deoxyadenine Nucleotides / pharmacology
  • Deoxyribonucleotides / pharmacology
  • Exodeoxyribonucleases / antagonists & inhibitors*
  • In Vitro Techniques
  • Sodium Fluoride / pharmacology*
  • Templates, Genetic


  • Deoxyadenine Nucleotides
  • Deoxyribonucleotides
  • Sodium Fluoride
  • DNA Polymerase I
  • Exodeoxyribonucleases