A type II topoisomerase that negatively supercoils closed circular double-stranded (ds) DNA in an ATP-dependent manner to modulate DNA topology and maintain chromosomes in an underwound state (PubMed:23804759, PubMed:11850422). It probably also catalyzes the interconversion of other topological isomers of double-stranded DNA rings, including catenanes (PubMed:11850422). Relaxes negatively supercoiled DNA in an ATP-independent manner (PubMed:23804759, PubMed:11850422). At comparable concentrations T.thermophilus gyrase does not introduce as many negative supercoils into DNA as the E.coli enzyme (PubMed:23804759). 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. Optimum temperature is 65 degrees Celsius (PubMed:23804759, PubMed:11850422). Active between 25 and 77 degrees Celsius (PubMed:11850422). Heterotetramer, composed of two GyrA and two GyrB chains (PubMed:23804759). The two subunits form an intertwined dimer where the GyrB ATPase transducer helix of 1 subunit connects to the Toprim domain of the other GyrB subunit through a 10 residue linker (PubMed:23804759). In the heterotetramer, GyrA contains the active site tyrosine that forms a transient covalent intermediate with the DNA, while GyrB binds cofactors and catalyzes ATP hydrolysis. For the electron microscopy studies a GyrB-GyrA fusion protein was made with a Gly-Asp-Leu linker between the 2 subunits. It forms the expected dimer (PubMed:23804759). 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 GyrA/ParC subunit family.