N-terminal domain of the actinomycetal Nei2 and related DNA glycosylases
This family contains the N-terminal domain of the actinomycetal Nei2 and related 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. This family contains mostly actinomycetes and includes Mycobacterium tuberculosis Nei2 (MtuNei2). Complementation experiments in repair-deficient Escherichia coli (fpg mutY nei triple and nei nth double mutants), support that MtuNei2 is functionally active in vivo and recognizes both guanine and cytosine oxidation products. In addition to this AcNei2_N domain, enzymes belonging to this family contain a helix-two turn-helix (H2TH) domain and a zinc-finger motif.