DNA gyrase negatively supercoils closed circular double-stranded DNA in an ATP-dependent manner and also catalyzes the interconversion of other topological isomers of double-stranded DNA rings, including catenanes and knotted rings. 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+). Pyrrolopyrimidines inhibit both GyrB and its paralog in topoisomerase IV (parE) (PubMed:23352267). Heterotetramer, composed of two GyrA and two GyrB chains. Within the heterotetramer, GyrA contains the active site tyrosine that forms a covalent intermediate with the DNA, while GyrB contributes the cofactor binding sites and catalyzes ATP hydrolysis. Belongs to the type II topoisomerase family.