Dynamics of loading the Escherichia coli DNA polymerase processivity clamp

Crit Rev Biochem Mol Biol. 2006 May-Jun;41(3):179-208. doi: 10.1080/10409230600648751.


Sliding clamps and clamp loaders are processivity factors required for efficient DNA replication. Sliding clamps are ring-shaped complexes that tether DNA polymerases to DNA to increase the processivity of synthesis. Clamp loaders assemble these ring-shaped clamps onto DNA in an ATP-dependent reaction. The overall process of clamp loading is dynamic in that protein-protein and protein-DNA interactions must actively change in a coordinated fashion to complete the mechanical clamp-loading reaction cycle. The clamp loader must initially have a high affinity for both the clamp and DNA to bring these macromolecules together, but then must release the clamp on DNA for synthesis to begin. Evidence is presented for a mechanism in which the clamp-loading reaction comprises a series of binding reactions to ATP, the clamp, DNA, and ADP, each of which promotes some change in the conformation of the clamp loader that alters interactions with the next component of the pathway. These changes in interactions must be rapid enough to allow the clamp loader to keep pace with replication fork movement. This review focuses on the measurement of dynamic and transient interactions required to assemble the Escherichia coli sliding clamp on DNA.

Publication types

  • Research Support, N.I.H., Extramural
  • Review

MeSH terms

  • Adenosine Diphosphate / metabolism
  • Adenosine Triphosphate / metabolism
  • DNA Replication / genetics*
  • DNA, Bacterial / genetics*
  • DNA, Bacterial / metabolism
  • DNA-Binding Proteins / metabolism
  • DNA-Directed DNA Polymerase / metabolism*
  • Escherichia coli / genetics*
  • Escherichia coli / metabolism
  • Escherichia coli Proteins / metabolism
  • Humans
  • Models, Genetic


  • DNA, Bacterial
  • DNA-Binding Proteins
  • Escherichia coli Proteins
  • Adenosine Diphosphate
  • Adenosine Triphosphate
  • DNA-Directed DNA Polymerase