ABSTRACT
Escherichia coli protein Vsr is a sequence-specific, mismatch-specific endonuclease that is involved in the maintenance of cytosine methylation in DNA and mutation avoidance. This chapter surveys what is known about the structure of this protein, how it finds the substrate TG mismatch in DNA and its catalytic mechanism. A summary is also presented concerning how two accessory proteins, MutS and MutL, may help Vsr perform its nuclease function and help prevent mutations.
