Table 1.
Distribution of MMR proteins.
| Molecular function | Thermus thermophilus | Escherichia coli | Saccharomyces cerevisiae | Homo sapiens |
|---|---|---|---|---|
| Mismatch recognition | MutS | MutS | MutSα (MSH2/MSH6) MutSβ (MSH2/MSH3) | MutSα (MSH2/MSH6) MutSβ (MSH2/MSH3) |
| Strand incision | β-clamp∗1 | — | PCNA | PCNA |
| clamp-loader∗1 | RFC | RFC | ||
| MutL | MutLα (MLH1/PMS1) MutLγ ∗2 (MLH1/MLH3) | MutLα (MLH1/PMS2) MutLγ ∗2 (MLH1/MLH3) | ||
| Strand incision | — | MutH | — | — |
| Match making | MutL | MutL | MutLα (MLH1/PMS1) MutLβ (MLH1/MLH2) MutLγ (MLH1/MLH3) | MutLα (MLH1/PMS2) MutLβ (MLH1/PMS1) MutLγ (MLH1/MLH3) |
| Strand excision (single-stranded DNA-binding) | SSB | SSB | RPA | RPA |
| Strand excision (exonuclease) |
RecJ ExoI |
RecJ ExoI ExoVII ExoX |
EXO1∗3 | EXO1∗3 |
| Strand excision (helicase) | UvrD |
UvrD |
— | — |
| Repair synthesis | DNA polymerase III | DNA polymerase III | DNA polymerase δ | DNA polymerase δ |
∗1The involvement of bacterial clamp and clamp-loader in the strand incision reaction has not yet been confirmed. ∗2It is demonstrated that the endonuclease motif in MLH3 is responsible for in vivo MMR [83]; however, the endonuclease activity of MutLγ has not yet been confirmed biochemically. ∗3In yeast and human, EXO1 has the 5′-flap endonuclease activity in addition to 5′–3′ exonuclease activity.