DNA mismatch repair

• Optimum confrontation of active site and incoming nucleotide allows catalysis of correct base pair
• Proofreading: DNA polymerase II detects mistake and uses 3-5 exonuclease activity to remove recent mismatched nucleotides and replace with correct nucleotide
• DNA mismatch repair covers for replication errors not corrected by proofreading
• DNA binding protein MutS and MutL recognize mismatch damage
• MutH endonuclease nicks daughter strand several nucleotides away from mismatch
• Exo1 5-3 exonuclease removes region of daughter strand surrounding mismatch so DNA polymerase III can repair it and fill the gap before DNA ligase seals the nick