The sliding clamp tethers the endonuclease domain of MutL to DNA

Nucleic Acids Res. 2015 Dec 15;43(22):10746-59. doi: 10.1093/nar/gkv918. Epub 2015 Sep 17.


The sliding clamp enhances polymerase processivity and coordinates DNA replication with other critical DNA processing events including translesion synthesis, Okazaki fragment maturation and DNA repair. The relative binding affinity of the sliding clamp for its partners determines how these processes are orchestrated and is essential to ensure the correct processing of newly replicated DNA. However, while stable clamp interactions have been extensively studied; dynamic interactions mediated by the sliding clamp remain poorly understood. Here, we characterize the interaction between the bacterial sliding clamp (β-clamp) and one of its weak-binding partners, the DNA mismatch repair protein MutL. Disruption of this interaction causes a mild mutator phenotype in Escherichia coli, but completely abrogates mismatch repair activity in Bacillus subtilis. We stabilize the MutL-β interaction by engineering two cysteine residues at variable positions of the interface. Using disulfide bridge crosslinking, we have stabilized the E. coli and B. subtilis MutL-β complexes and have characterized their structures using small angle X-ray scattering. We find that the MutL-β interaction greatly stimulates the endonuclease activity of B. subtilis MutL and supports this activity even in the absence of the N-terminal region of the protein.

Publication types

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

MeSH terms

  • Adenosine Triphosphatases / chemistry*
  • Adenosine Triphosphatases / genetics
  • Adenosine Triphosphatases / metabolism
  • Bacillus subtilis / genetics
  • Bacterial Proteins / chemistry*
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism
  • Binding Sites
  • Cysteine / genetics
  • DNA / metabolism
  • DNA Polymerase III / chemistry*
  • DNA Polymerase III / genetics
  • DNA Polymerase III / metabolism
  • Endodeoxyribonucleases / chemistry*
  • Endodeoxyribonucleases / metabolism
  • Escherichia coli / genetics
  • Escherichia coli Proteins / chemistry*
  • Escherichia coli Proteins / genetics
  • Escherichia coli Proteins / metabolism
  • Models, Molecular
  • MutL Proteins
  • Protein Binding
  • Protein Structure, Tertiary


  • Bacterial Proteins
  • Escherichia coli Proteins
  • MutL protein, E coli
  • DNA
  • beta subunit, DNA polymerase III
  • DNA Polymerase III
  • Endodeoxyribonucleases
  • Adenosine Triphosphatases
  • MutL Proteins
  • Cysteine