Mechanism of 3' to 5' exonuclease associated with phage T5-induced DNA polymerase: processiveness and template specificity

Nucleic Acids Res. 1980 Feb 11;8(3):657-71. doi: 10.1093/nar/8.3.657.


T5-induced DNA polymerase has an associated 3' to 5' exonuclease activity. Both single-stranded and duplex DNA are hydrolyzed by this enzyme in a quasi-processive manner. This is indicated by the results of polymer-challenge experiments utilizing product analysis techniques. Due to the quasi-processive mode of hydrolysis, the kinetics of label release from the 3'-terminally labeled oligonucleotide substrates, annealed to complementary homopolymers, show an initial high rate of hydrolysis. In the case of both single-stranded and duplex DNA substrates, hydrolysis seems to continue, at best, up to the point where the enzyme is five or six nucleotides away from the 5-end. The enzyme carries out mismatch repair, as evidenced by experiments with primer molecules containing improper base residues at the 3'-OH terminus. Control experiments with complementary base residues at the 3'-end indicate that extensive removal of terminal residue takes place in the presence of dNTP's only when such residues are "improper" in the Watson-Crick sense.

Publication types

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

MeSH terms

  • DNA, Single-Stranded / metabolism
  • DNA-Directed DNA Polymerase / metabolism*
  • Exonucleases / metabolism*
  • Hydrolysis
  • Mutation
  • T-Phages / enzymology*
  • Templates, Genetic


  • DNA, Single-Stranded
  • DNA-Directed DNA Polymerase
  • Exonucleases