An exodeoxyribonuclease that degrades linear or supercoiled dsDNA from 5'-3'. Nicks and linearizes circular DNA. Activity is not stimulated by ATP or AMP-PNP, although it has DNA-stimulated ATPase activity. Exonucleolytic cleavage in the 5'- to 3'-direction to yield nucleoside 5'-phosphates. Probably binds 2 metal cations. In vitro during a short incubation, Mn(2+) is most efficient on linear or supercoiled dsDNA, nicks but only poorly digests dsDNA with Co(2+), Ni(2+) or Zn(2+). When purified from E.coli Ca(2+) and Mg(2+) are the most abundant metals. kcat is 0.44 min(-1) for ATPase at 65 degrees Celsius. Optimum temperature is 65 degrees Celsius for the ATPase activity. Homodimer. The ATPase domain dimerizes on its own via its dimerization region, the Toprim (topoisomerase/primase) domain does not. The Toprim domain has Mn(2+)-dependent nuclease activity on linear and supercoiled dsDNA. It faces away from the dimerization domain. Belongs to the class 1 OLD nuclease family.