A DNA polymerase from Ustilago maydis. Evidence of proof-reading by the associated 3' leads to 5' deoxyribonuclease activity

Eur J Biochem. 1977 Aug 1;77(3):521-7. doi: 10.1111/j.1432-1033.1977.tb11694.x.


The 3' leads to 5' deoxyribonuclease activity associated with an Ustilago maydis DNA polymerase hydrolysed non-complementary 3'-primer termini about 12 times more rapidly than complementary termini. An analysis of its substrate specificity suggested that, although it was unable to hydrolyse fully single-stranded polynucleotides, it could hydrolyse such regions less than about four nucleotides in length covalently bound to a primer molecule which was base-paired to a complementary template strand. Template-primer combinations containing complementary or non-complementary primer termini both supported polynucleotide synthesis, but whereas the former were conserved, the latter were hydrolysed during the reaction thus allowing synthesis to occur. No addition of nucleotides onto a conserved non-complementary 3'-primer terminus was detected. The deoxyribonuclease activity therefore fulfilled a proof-reading function during DNA synthesis in vitro.

MeSH terms

  • Basidiomycota / enzymology*
  • DNA-Directed DNA Polymerase / metabolism*
  • Deoxyribonucleases / metabolism*
  • Kinetics
  • Polydeoxyribonucleotides
  • Structure-Activity Relationship
  • Templates, Genetic
  • Ustilago / enzymology*


  • Polydeoxyribonucleotides
  • DNA-Directed DNA Polymerase
  • Deoxyribonucleases