Part of the dpd cluster involved in the insertion of 7-deazaguanine derivatives in DNA (PubMed:26929322, PubMed:30159947). DpdA may insert 7-cyano-7-deazaguanine (preQ0) into DNA with the help of DpdB (PubMed:30159947). DpdA and dpdB are necessary and sufficient to synthesize 2'-deoxy-7-cyano-7-deazaguanosine (dPreQ0) (PubMed:30159947). Binds 1 zinc ion per subunit. Mutant lacking the whole dpd gene cluster does not contain dPreQ0 and 2'-deoxy-7-amido-7-deazaguanosine (dADG) in DNA (PubMed:26929322). DpdA deletion mutant (in a dpdD mutant background) lacks both dPreQ0 and dADG (PubMed:30159947). Belongs to the DNA-guanine transglycosylase family.