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Binding of the regulatory domain of MutL to the sliding β-clamp is species specific

Ahmad W Almawi1, Michelle K Scotland2,3, Justin R Randall4

  • 1Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON, Canada.

Nucleic Acids Research
|March 28, 2019
PubMed

Insights

The β-clamp protein interaction with MutL differs between bacteria. Structural and functional studies reveal distinct binding modes, impacting DNA repair mechanisms and MutL endonuclease activity.

Area of Science:

  • Molecular Biology
  • Biochemistry
  • Genetics

Background:

  • The β-clamp is a crucial protein hub for DNA replication and fork management.
  • Interactions with the β-clamp are typically studied using short peptides, limiting understanding of complex protein domain binding.
  • The mismatch repair protein MutL interacts with the β-clamp, with varying functional significance across organisms.

Purpose of the Study:

  • To determine the structures of *E. coli* and *B. subtilis* MutL regulatory domains bound to their respective β-clamps.
  • To elucidate the molecular mechanisms and functional implications of MutL-β-clamp interactions.
  • To propose a model for MutL endonuclease activation in specific bacterial lineages.

Main Methods:

  • X-ray crystallography to determine protein-ligand complex structures.
  • Biochemical assays to characterize protein-protein interactions and enzyme activity.
  • Comparative analysis of MutL-β-clamp binding modes in different bacterial species.

Main Results:

  • Distinct binding modes of *E. coli* and *B. subtilis* MutL to the β-clamp were revealed through structural determination.
  • The clamp-binding motif within the MutL regulatory domain is essential for interaction, but additional motifs may enhance binding stability.
  • Functional differences in MutL-β-clamp interaction correlate with organism-specific DNA mismatch repair pathways.

Conclusions:

  • β-clamp binding to MutL is a multi-step process involving specific motifs within structured domains.
  • Understanding these interactions provides insights into the regulation of DNA repair and MutL endonuclease activity.
  • The findings offer a model for MutL activation in bacteria lacking methyl-directed mismatch repair.

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