Nucleotide-induced conformational changes in an isolated Escherichia coli DNA polymerase III clamp loader subunit

Structure. 2003 Mar;11(3):253-63. doi: 10.1016/s0969-2126(03)00027-3.


Sliding clamps are loaded onto DNA by ATP-driven clamp loader complexes. The structure of the E. coli clamp loader in a nucleotide-free state has been determined previously. We now report crystal structures of a truncated form of the isolated gamma-ATPase subunit, gamma(1-243), of the E. coli clamp loader, in nucleotide-free and bound forms. The gamma subunit adopts a defined conformation when empty, in which the nucleotide binding site is blocked. The binding of either ATPgammaS or ADP, which are shown to bind with equal affinity to gamma(1-243), induces a change in the relative orientation of the two domains such that nucleotides can be accommodated. This change would break one of the gamma:gamma interfaces seen in the empty clamp loader complex, and may represent one step in the activation process.

Publication types

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

MeSH terms

  • Adenosine Triphosphatases / metabolism
  • DNA / metabolism*
  • DNA Polymerase III / metabolism*
  • Escherichia coli / enzymology*
  • Protein Conformation
  • Protein Structure, Quaternary
  • Pyrococcus furiosus / enzymology


  • DNA
  • DNA Polymerase III
  • Adenosine Triphosphatases

Associated data

  • PDB/1NJF
  • PDB/1NJG