Meta-Biol

• Pathways

LIG1 (DNA ligase I) catalyzes the formation of a phosphodiester bond between a 3' hydroxyl group and a 5' phosphate group to form an intact DNA strand (Bhat and Grossman 1986). ATP is hydrolyzed to AMP and pyrophosphate in a reaction mechanism that involves adenylylation of a lysine residue of the enzyme, transfer of the adenylyl group to the 5' phosphate of DNA, and nick sealing by nucleophilic attack of the 3' hydroxyl group on the adenylylated 5' phosphate (Taylor et al. 2011, reviewed in Tomkinson et al. 2006). RPA stimulates the activity of LIG1 about 15-fold (Ranalli et al. 2002). LIG1 is recruited to repair sites by interaction with PCNA (Mortusewicz et al. 2006). Ligation is the final step in mismatch repair (Zhang et al. 2005, Constantin et al. 2005).