Type II topoisomerase (PubMed:27060564, PubMed:25463606). Processively relaxes supercoiled DNA (PubMed:27060564). Displays DNA-supercoiling activity only when associated with the viral histone-like protein (PubMed:28381576). ATP-dependent breakage, passage and rejoining of double-stranded DNA. Binds two Mg(2+) per subunit. The magnesium ions form salt bridges with both the protein and the DNA. Can also accept other divalent metal cations, such as Mn(2+) or Ca(2+). Localizes throughout the cytoplasmic viral factories at 16 hpi. Expressed in the early phase of the viral replicative cycle (PubMed:32075923). It is transcribed early, under the control of an early promoter, but its transcript levels are maintained and still present during late infection (Probable). Belongs to the type II topoisomerase family.