Uncharacterized bacterial subgroup of the N-terminal domain of Fpg (formamidopyrimidine-DNA glycosylase, MutM)_Nei (endonuclease VIII) base-excision repair DNA glycosylases
This family is an uncharacterized bacterial subgroup of the FpgNei_N 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. One exception is mouse Nei-like glycosylase 3 (Neil3) which forms a Schiff base intermediate via its N-terminal valine. In this family the N-terminal proline is replaced by an isoleucine or valine. Escherichia coli Fpg prefers 8-oxo-7,8-dihydroguanine (8-oxoG) and oxidized purines and Escherichia coli Nei recognizes oxidized pyrimidines. However, neither Escherichia coli Fpg or Nei belong to this family. In addition to this BaFpgNei_N_3 domain, enzymes belonging to this family contain a helix-two turn-helix (H2TH) domain and a zinc-finger motif.