This protein is involved in the repair of mismatches in DNA. It is possible that it carries out the mismatch recognition step. This protein has a weak ATPase activity (By similarity). Overexpression of mutSL partially suppresses the high spontaneous mutation frequency of a ytkD/mutM/mutY triple disruption which lacks the system required to prevent damage by oxidized guanine (8-oxo-dGTP). This suggests that MutSL also functions to repair mismatches due to oxidative stress in both growing and stationary phase cells. Cells lacking this gene have a 225-fold increased spontaneous mutation frequency. Double or triple disruptions with mutL/nth do not change the frequency. Belongs to the DNA mismatch repair MutS family.