The beta subunit dissociates readily from the Escherichia coli DNA polymerase III holoenzyme

J Biol Chem. 1987 Feb 5;262(4):1720-4.


Purified DNA polymerase III holoenzyme (holoenzyme) was separated by glycerol gradient sedimentation into the beta subunit and the subassembly that lacks it (pol III). In the presence of ATP, beta subunit dimer dissociated from holoenzyme with a KD of 1 nM; in the absence of ATP, the KD was greater than 5 nM. The beta subunit was known to remain tightly associated in the holoenzyme upon formation of an initiation complex with a primed template and during the course of replication. With separation from the template, holoenzyme dissociated into beta and pol III. Cycling to a new template depended on the reformation of holoenzyme. Holoenzyme was in equilibrium with pol III and the beta subunit in crude enzyme fractions as well as in pure preparations.

Publication types

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

MeSH terms

  • Adenosine Triphosphate / metabolism
  • Centrifugation, Density Gradient
  • DNA Polymerase III / metabolism*
  • DNA Replication
  • DNA-Directed DNA Polymerase / metabolism*
  • Escherichia coli / enzymology*
  • Kinetics


  • Adenosine Triphosphate
  • DNA Polymerase III
  • DNA-Directed DNA Polymerase