A type II topoisomerase that negatively supercoils closed circular double-stranded (ds) DNA in an ATP-dependent manner to maintain chromosomes in an underwound state, while in the absence of ATP it relaxes supercoiled dsDNA (PubMed:15047530. PubMed:16876125, PubMed:19060136, PubMed:16377674, PubMed:18426901, PubMed:22844097, PubMed:19596812, PubMed:20805881). Also catalyzes the interconversion of other topological isomers of dsDNA rings, including catenanes (PubMed:16876125, PubMed:19060136, PubMed:22457352). Gyrase from M.tuberculosis has higher decatenation than supercoiling activity compared to E.coli; as M.tuberculosis only has 1 type II topoisomerase, gyrase has to fulfill the decatenation function of topoisomerase IV as well (PubMed:16876125, PubMed:22457352, PubMed:23869946). At comparable concentrations M.tuberculosis gyrase cannot introduce as many negative supercoils into DNA as the E.coli enzyme, and its ATPase activity is lower, perhaps because it does not couple DNA wrapping and ATP binding as well as E.coli (PubMed:22457352, PubMed:24015710). Negative supercoiling favors strand separation, and DNA replication, transcription, recombination and repair, all of which involve strand separation. Type II topoisomerases break and join 2 DNA strands simultaneously in an ATP-dependent manner. ATP-dependent breakage, passage and rejoining of double-stranded DNA. Mg(2+) required for DNA supercoiling, DNA relaxation, DNA cleavage and DNA decatenation, Mn(2+) substitutes for relaxation but not supercoiling or cleavage activity (PubMed:16876125). Ca(2+) does not substitute for supercoiling activity (PubMed:22844097). DNA supercoiling inhibited by (fluoro)quinoline antibiotics such as sparfloxacin and levofloxacin, which usually act on GyrA subunit (PubMed:15047530). DNA supercoiling inhibited by the coumarin antibiotic novobiocin which acts on GyrB (PubMed:16876125). Quinolones lead to gyrase-mediated dsDNA cleavage while preventing reclosure (PubMed:15047530, PubMed:16876125, PubMed:23869946). DNA supercoiling activity inhibited by aminopyrazinamide and pyrrolamide derivatives, probably via effects on the GyrB subunit (PubMed:23268609, PubMed:24126580). DNA relaxation inhibited by ATP and its analogs (PubMed:16876125). DNA supercoiling, relaxation, decatenation and quinolone-promoted DNA cleavage are inhibited by MfpA (50% inhibition occurs at 2 uM), inhibition of gyrase activities is enhanced in a concentration-dependent manner by MfpA (PubMed:19060136). Heterotetramer, composed of two GyrA and two GyrB chains (PubMed:15047530). In the heterotetramer, GyrA contains the active site tyrosine that forms a transient covalent intermediate with DNA, while GyrB binds cofactors and catalyzes ATP hydrolysis. The B' domain (residues 448-675, Toprim plus a tail domain) forms a dimer; when reconstituted with intact GyrA the complex has ATP-independent DNA relaxation activity (PubMed:19596812). The same fragment (also called TopBK) when reconstituted with intact GyrA or the N-terminus of GyrA (residues 1-502) can catalyze quinolone-mediated DNA breaks (PubMed:20805881). When the enzyme transiently cleaves DNA a phosphotyrosine bond is formed between GyrA and DNA (PubMed:15047530). In the presence of quinolones this intermediate can be trapped and is used as an indicator of drug toxicity (PubMed:16377674, PubMed:16876125, PubMed:23869946). DNA gyrase is intrinsically more resistant to fluoroquinolone drugs than in E.coli, mutating it to resemble E.coli increases its susceptibility to fluoroquinolones (most quinolone-resistant mutations are in the GyrA subunit) (PubMed:18426901). Gyrase from M.tuberculosis is usually assayed in the presence of potassium glutamate (KGlu); KGlu stimulates supercoiling but inhibits DNA relaxation activity, and has concentration-dependent effects on GyrA-box mutants (PubMed:16876125, PubMed:23869946). Few gyrases are as efficient as E.coli at forming negative supercoils. Not all organisms have 2 type II topoisomerases; in organisms with a single type II topoisomerase this enzyme also has to decatenate newly replicated chromosomes. Belongs to the type II topoisomerase GyrB family. Extended N-terminus.