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:16377674, PubMed:16876125, PubMed:17015625, PubMed:18426901, PubMed:19060136, PubMed:22844097, 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). 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. May bind up to 2 Ca(2+) per subunit, Ca(2+) does not substitute for supercoiling activity, but is required for relaxation, probably by an interaction with this subunit (PubMed:22844097). This subunit has altered protease sensitivity in the presence of Ca(2+), which might reflect regulation (PubMed:22844097). DNA supercoiling inhibited by (fluoro)quinoline antibiotics such as sparfloxacin and levofloxacin, which usually act on GyrA (PubMed:15047530, PubMed:17015625). 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. 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 (PubMed:15047530). The N-terminal domain (residues 1-502, also called GA57BK) forms a dimer; when reconstituted with intact GyrB or the C-terminus of GyrB (residues 448-675) can catalyze quinolone-mediated DNA breaks (PubMed:20805881). The C-terminal domain (CTD, residues 514-838) contains 6 tandemly repeated subdomains known as blades, each of which is composed of a 4-stranded antiparallel beta-sheet (PubMed:22457352, PubMed:23869946). The blades form a circular-shaped beta-pinwheel fold arranged in a spiral around a screw axis, which binds DNA (PubMed:22457352, PubMed:23869946). Unlike in E.coli, isolated CTD both binds and wraps DNA and is able to introduce writhe into DNA, but the holoenzyme in M.tuberculosis is missing the GyrA acidic tail found in E.coli and thus does not couple DNA wrapping and ATP binding as well as E.coli (PubMed:22457352). There are 2 GyrA-boxes in the CTD; mutations in GyrA-box (residues 537-543, the canonical box) affect supercoiling but not decatenation, those in GyrA-box-1 (residues 743-749, conserved in some Actinobacteria) affect both, suggesting there is a novel DNA-binding pathway in M.tuberculosis compared to E.coli (PubMed:23869946). 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: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 this 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). Belongs to the type II topoisomerase GyrA/ParC subunit family.