Mismatch repair. DNA mismatch repair in E. coli is initiated by the interplay of MutS, MutL, and MutH proteins. A G—T mismatch is recognized by MutS. MutH cleaves the backbone in the vicinity of the mismatch. A segment of the DNA strand containing the erroneous T is removed by exonuclease I and synthesized anew by DNA polymerase III.

[Information from R. F. Service, Science 263:1559–1560, 1994.]