Mechanism of T5-induced DNA polymerase. II. Characterization of the dead-end complex

J Biol Chem. 1977 Dec 10;252(23):8708-12.


We have shown that bacteriophage T5-induced DNA polymerase replicates short primer-templates (400 to 600 nucleotides long) at a rapid rate initially, followed by a slower rate sustained for much longer periods (Das, S. K., and Fujimura, R. K. (1977) J. Biol. Chem. 252, 8700-8707). In order to explain the slower steady rate and the results of polymer-challenge experiments, we conjectured the presence of a "dead-end complex" formed by the enzyme with the primer-template at the end of the primer elongation process. In this communication we present evidence which indicates that the presumed complex shows a first order kinetics of decay with a half-life of 3.5 min at 37 degrees. Energies of activation for the steady phase of synthesis and the decay of the dead-end complex were both found to be about 23 kcal/mol. This indicates that the dissociation of the aforesaid complex might be the rate-limiting step during the steady phase of synthesis. Correlation between the salt-induced reduction in the half-life of the complex and the increase in the steady rate of synthesis is in agreement with the above mentioned possibility.

Publication types

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

MeSH terms

  • Ammonium Sulfate / pharmacology
  • Coliphages / enzymology*
  • DNA Replication / drug effects
  • DNA-Directed DNA Polymerase / metabolism*
  • Edetic Acid / pharmacology
  • Escherichia coli / enzymology*
  • Kinetics
  • Magnesium / pharmacology
  • Templates, Genetic


  • Edetic Acid
  • DNA-Directed DNA Polymerase
  • Magnesium
  • Ammonium Sulfate