Important for mitochondrial DNA (mtDNA) stability and repair. Recognizes and binds to base-base and small insertion-deletion mismatches in mtDNA. ATP binding and hydrolysis is crucial for function. Binding to a mismatched base pair attenuates ATP hydrolysis. Also involved in proper sorting of mtDNA during mtDNA transmission. Homodimer. Present with 1670 molecules/cell in log phase SD medium. Belongs to the DNA mismatch repair MutS family.