Structure and Function of B. subtilis MutL

Abstract

Maintaining genomic integrity is important for any organism. DNA mismatch repair (MMR) serves to correct errors that occur during DNA replication and recombination, such as unpaired bases or mismatched bases. Mutl is a key player and serves to coordinate protein-protein interactions. Recently it has been shown that human Mutl functions as an endonuclease and that this activity is imperative for functioning MMR. In this work, the X-ray crystal structure of the C-terminal endonuclease domain of Bacillus subtilis Mutl (BsMutL-CTD) is presented. Diffraction quality crystals of BsMutL-CTD were grown using vapor diffusion. The crystal structure of BsMutL-CTD was solved using multiwavelength anomalous diffraction. The structure reveals a putative metal binding site which clusters closely in space with endonuclease motif. Using the structure and sequence homology, several mutations were made and an investigation into the endonuclease activity of BsMutL was performed. BsMutL was confirmed to be a manganese-dependent endonuclease and key residues which contribute to endonuclease function were identified.