This topoisomerase-primase (Toprim) nucleotidyl transferase/hydrolase domain is found in the type II topoisomerase VIA and Spo11, which structurally related. Spo11 is a meiosis-specific protein that is responsible for the initiation of recombination through the formation of DNA double-strand breaks by a type II DNA topoisomerase-like activity. Topoisomerase VI is a type IIB enzyme that breaks double-stranded DNA and assembles as a heterotetramer, consisting of two A subunits required for DNA cleavage and two B subunits required for ATP hydrolysis [1-3].

1: Structure and function of an archaeal topoisomerase VI subunit with homology to the meiotic recombination factor Spo11. Nichols MD, DeAngelis K, Keck JL, Berger JM; EMBO J 1999;18:6177-6188. PMID:10545127

2: Holoenzyme assembly and ATP-mediated conformational dynamics of topoisomerase VI. Corbett KD, Benedetti P, Berger JM; Nat Struct Mol Biol. 2007;14:611-619. PMID:17603498

3: Crystal structure of an intact type II DNA topoisomerase: insights into DNA transfer mechanisms. Graille M, Cladiere L, Durand D, Lecointe F, Gadelle D, Quevillon-Cheruel S, Vachette P, Forterre P, van Tilbeurgh H; Structure. 2008;16:360-370. PMID:18334211