The toprim domain is found in a wide variety of enzymes involved in nucleic acid manipulation [1].

1: Toprim--a conserved catalytic domain in type IA and II topoisomerases, DnaG-type primases, OLD family nucleases and RecR proteins. Aravind L, Leipe DD, Koonin EV; Nucleic Acids Res 1998;26:4205-4213. PMID:9722641