A new form of DNA polymerase 3 and a copolymerase replicate a long, single-stranded primer-template

Proc Natl Acad Sci U S A. 1973 Jun;70(6):1764-7. doi: 10.1073/pnas.70.6.1764.


A new form of DNA polymerase III, termed Pol III star (Pol III(*)), has been purified to homogeneity from Escherichia coli. Pol III(*) is temperature sensitive when isolated from a thermo-sensitive dnaE mutant, as had been described for Pol III. Pol III(*) and Pol III are separable by gel filtration. Pol III(*) utilizes a duplex template containing short gaps with the same catalytic properties as Pol III. However, Pol III(*) is able to replicate long, singlestranded templates such as homopolymer chains and viral circles of M13 and varphiX174 if provided with the following: spermidine, a primer fragment, and a new protein, termed copolymerase III(*) (Copol III(*)). The latter, purified to homogeneity, has no known independent enzymatic activity and supports synthesis by Pol III(*) but not by Pol I, Pol II, or Pol III.

MeSH terms

  • Centrifugation, Density Gradient
  • Chemical Precipitation
  • Chromatography
  • Chromatography, DEAE-Cellulose
  • Chromatography, Gel
  • Coenzymes / isolation & purification
  • Coenzymes / metabolism*
  • Coliphages / metabolism
  • DNA Nucleotidyltransferases / isolation & purification
  • DNA Nucleotidyltransferases / metabolism*
  • DNA Replication*
  • DNA, Single-Stranded / biosynthesis
  • DNA, Viral / biosynthesis*
  • Electrophoresis, Disc
  • Escherichia coli / enzymology*
  • Spermidine
  • Templates, Genetic*


  • Coenzymes
  • DNA, Single-Stranded
  • DNA, Viral
  • DNA Nucleotidyltransferases
  • Spermidine