Identification and properties of the catalytic domain of mammalian DNA polymerase beta

Biochemistry. 1990 Aug 7;29(31):7156-9. doi: 10.1021/bi00483a002.


Rat DNA polymerase beta (beta-pol) is a 39-kDa protein organized in two tightly folded domains, 8-kDa N-terminal and 31-kDa C-terminal domains, connected by a short protease-sensitive region. The 8-kDa domain contributes template binding to the intact protein, and we now report that the 31-kDa C-terminal domain contributes catalytic activity. Our results show that this domain as a purified proteolytic fragment conducts DNA synthesis under appropriate conditions but the kcat is lower and primer extension properties are different from those of the intact enzyme. A proteolytic truncation of the 31-kDa catalytic domain fragment, to remove a 60-residue segment from the NH2-terminal end, results in nearly complete loss of activity, suggesting the importance of this segment. Overall, these results indicate that the domains of beta-pol have distinct functional roles, template binding and nucleotidyltransferase, respectively; yet, the intact protein is more active for each function than the isolated individual domain fragment.

MeSH terms

  • Animals
  • Binding Sites
  • Catalysis
  • DNA Polymerase I / chemistry*
  • DNA Polymerase I / metabolism
  • DNA, Single-Stranded / metabolism
  • DNA, Viral / metabolism
  • Molecular Structure
  • Protein Binding
  • Protein Conformation
  • Rats
  • Templates, Genetic


  • DNA, Single-Stranded
  • DNA, Viral
  • DNA Polymerase I