Topoisomerase IV is essential for chromosome segregation. It relaxes supercoiled DNA (PubMed:22916023). Performs the decatenation events required during the replication of a circular DNA molecule. 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+). Heterotetramer composed of ParC and ParE. Belongs to the type II topoisomerase family. ParE type 1 subfamily.