Bacterial EndoMS/NucS acts as a clamp-mediated mismatch endonuclease to prevent asymmetric accumulation of replication errors.

Mismatch repair (MMR) systems based on MutS eliminate mismatches originating from replication errors. Despite extensive conservation of mutS homologues throughout the three domains of life, Actinobacteria and some archaea do not have genes homologous to mutS. Here, we report that EndoMS/NucS of Corynebacterium glutamicum is the mismatch-specific endonuclease that functions cooperatively with a sliding clamp.