3'-5' exonuclease acting on single-stranded DNA (ssDNA) and RNA (ssRNA) substrates. Displays ssDNA-stimulated ATPase activity, but lacks helicase activity. The nuclease activity is inhibited by ATP or ADP. kcat is 25 min(-1) for ATPase activity in the absence of DNA. kcat is 78 min(-1) for ATPase activity in the presence of ssDNA. Monomer in solution. Changes in the ATP-binding site of the helicase domain can affect the activity of the nuclease domain. Belongs to the helicase family. DinG subfamily. Type 2 sub-subfamily.