Antitoxin component of a hybrid type II/IV toxin-antitoxin (TA) system. De-ADP-ribosylates DNA (probably) modified on thymidine by its cognate toxin DarT, which neutralizes the activity of DarT (PubMed:27939941). Experiments in which DarG levels are depleted lead to cell death; expression of wild-type DarG protein from M.tuberculosis or T.aquaticus restores growth. Cells depleted of DarG are more sensitive to bedaquilline (targets respiration), DNA-damaging drugs (mitomycin C, netropsin) and transcription-targeted drugs (rifabutin and rifampicin). When depleted, a DNA-damage response is induced and mutability is increased (PubMed:32634279). In E.coli the macrodomain alone neutralizes DarT toxin from non-cognate T.aquaticus. The same domain de-ADP-ribosylates genomic DNA (PubMed:34408320). an N-(ADP-alpha-D-ribosyl)-thymidine in DNA + H2O = a thymidine in DNA + ADP-D-ribose Forms a complex with cognate toxin DarT; this complex neutralizes the toxic effect of DarT (PubMed:32634279). Co-immunoprecipitates with a number proteins known to be involved in DNA metabolism, in the presence and absence of darT; includes alkA, dnaB, dnaE1, dnaG, dus, embR, mtrA, nrdE, nrdR, polA, recA, recB, recF, xerD, Rv2258c (PubMed:32634279). Part of the dnaB-darT-darG operon. The macro domain alone is sufficient to neutralize DarT from non-cognate T.aquaticus in E.coli, DarT in M.bovis, and to de-ADP-ribosylate DNA in vitro. Cells lacking this gene display impaired growth (PubMed:12657046). A double darT-darG deletion shows no change in growth in culture, upon infection of mice, or upon exposure to a variety of stresses (PubMed:32634279). Another group finds the double knockout gives a competitive advantage over wild-type cells in liquid culture growth experiments. Knock-down of darG expression leads to increased RecA expression, ADP-ribosylation of OriC and growth arrest (PubMed:34408320). As expression of DarT is bactericidal (rather than bacteriostatic as are most TA systems in this bacteria), inactivation of DarG may be an attractive drug target. Belongs to the DarG ADP-ribosyl glycohydrolase family.