N-terminal domain of Escherichia coli Fpg1/MutM and related bacterial DNA glycosylases
This family contains the N-terminal domain of Escherichia coli Fpg1/MutM and related bacterial DNA glycosylases. It belongs to the FpgNei_N, [N-terminal domain of Fpg (formamidopyrimidine-DNA glycosylase, MutM)_Nei (endonuclease VIII)] domain superfamily. DNA glycosylases maintain genome integrity by recognizing base lesions created by ionizing radiation, alkylating or oxidizing agents, and endogenous reactive oxygen species. They initiate the base-excision repair process, which is completed with the help of enzymes such as phosphodiesterases, AP endonucleases, DNA polymerases and DNA ligases. DNA glycosylases cleave the N-glycosyl bond between the sugar and the damaged base, creating an AP (apurinic/apyrimidinic) site. Most FpgNei DNA glycosylases use their N-terminal proline residue as the key catalytic nucleophile, and the reaction proceeds via a Schiff base intermediate. Escherichia coli Fpg mainly recognizes and excises damaged purines such as 8-oxo-7,8-dihydroguanine (8-oxoG) and 2,6-diamino-4-hydroxy-5-formamidopyrimidine (FapyG). It is bifunctional, having both a DNA glycosylase (recognition activity) and a AP lyase activity. In addition to this EcFpg-like_N domain, enzymes belonging to this family contain a helix-two turn-helix (H2TH) domain and a zinc-finger motif, which also contribute residues to the active site.