Effect of manganese ions on the incorporation of dideoxynucleotides by bacteriophage T7 DNA polymerase and Escherichia coli DNA polymerase I

Proc Natl Acad Sci U S A. 1989 Jun;86(11):4076-80. doi: 10.1073/pnas.86.11.4076.


Incorporation of dideoxynucleotides by T7 DNA polymerase and Escherichia coli DNA polymerase I is more efficient when Mn2+ rather than Mg2+ is used for catalysis. Substituting Mn2+ for Mg2+ reduces the discrimination against dideoxynucleotides approximately 100-fold for DNA polymerase I and 4-fold for T7 DNA polymerase. With T7 DNA polymerase and Mn2+, dideoxynucleotides and deoxynucleotides are incorporated at virtually the same rate. Mn2+ also reduces the discrimination against other analogs with modifications in the furanose moiety, the base, and the phosphate linkage. A metal buffer, isocitrate, expands the MnCl2 concentration range effective in catalyzing DNA synthesis. The lack of discrimination against dideoxynucleoside triphosphates using T7 DNA polymerase and Mn2+ results in uniform terminations of DNA sequencing reactions, with the intensity of adjacent bands on polyacrylamide gels varying in most instances by less than 10%.

Publication types

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

MeSH terms

  • DNA Polymerase I / metabolism*
  • DNA-Directed DNA Polymerase / metabolism*
  • Deoxyribonucleotides / metabolism*
  • Escherichia coli / enzymology*
  • Kinetics
  • Magnesium / pharmacology
  • Manganese / pharmacology*
  • Substrate Specificity
  • T-Phages / enzymology*


  • Deoxyribonucleotides
  • Manganese
  • DNA Polymerase I
  • DNA-Directed DNA Polymerase
  • Magnesium