The amino terminus of eukaryotic and prokaryotic DNAtopoisomerase II are similar, but they have a different carboxylterminus. The amino-terminal portion of the DNA gyrase B protein is thought to catalyse the ATP-dependent super-coilingof DNA. See Pfam:PF00204. The carboxyl-terminal end supportsthe complexation with the DNA gyrase A protein and theATP-independent relaxation. This family also containsTopoisomerase IV. This is a bacterial enzyme that is closelyrelated to DNA gyrase, [1].