Antitoxin component of a hybrid type II/IV toxin-antitoxin (TA) system. De-ADP-ribosylates DNA modified by its cognate toxin DarT, which neutralizes the activity of cognate toxin DarT. Neutralizes DarT in vivo in 2 ways, by reversing the ADP-ribosylation via the DarG macro domain and by interacting with (and presumably sequestering) DarT via the DarG C-terminal domain (PubMed:32023456). In vivo the macrodomain alone neutralizes DarT toxin from non-cognate T.aquaticus. The same domain de-ADP-ribosylates gDNA (PubMed:34408320). an N-(ADP-alpha-D-ribosyl)-thymidine in DNA + H2O = a thymidine in DNA + ADP-D-ribose Interacts with DarT (shown using mutant G49E), primarily via the C-terminus of DarG, which probably sequesters DarT and inhibits it. The macro domain (residues 1-16 joined to 112-330) alone is able to de-ADP-ribosylate substrate in vitro and is almost as effective at neutralizing DarT in growth experiments as full-length protein. The C-terminal domain has no de-ADP-ribosylation activity, but is able to neutralize DarT mutant G49D and interacts with DarT mutant G49D. Belongs to the DarG ADP-ribosyl glycohydrolase family. Truncated N-terminus.