Bacterial DNA topoisomerase II

Bacterial DNA topoisomerase II refers primarily to two essential enzymes found in bacteria—**DNA gyrase** and **topoisomerase IV**. Both are classified as type IIA topoisomerases. These enzymes catalyze changes in the topology of double-stranded DNA by introducing transient double-strand breaks, allowing them to manage supercoiling and untangle intertwined chromosomes during vital cellular processes such as replication, transcription, recombination, and chromosome segregation. DNA gyrase is unique among type II enzymes because it can introduce negative supercoils into bacterial chromosomal DNA—a function critical for maintaining proper chromosome structure. Topoisomerase IV specializes mainly in decatenating daughter chromosomes after replication but can also relax positive supercoils. Both enzymes are validated targets for antibacterial chemotherapy due to their essential roles in bacterial cell survival. Several classes of antibiotics—including fluoroquinolones and aminocoumarins—target these enzymes by either inhibiting their ATP-binding sites or stabilizing the intermediate cleavage complexes they form with DNA, ultimately leading to lethal double-strand breaks. Resistance can arise through point mutations within the genes encoding these proteins or through other mechanisms that reduce drug binding affinity. The continued emergence of resistant strains has driven research into novel inhibitors with distinct mechanisms or improved efficacy against resistant bacteria[2][4][6].

Other names

DNA gyrase (for one subtype)Topoisomerase IV (for another subtype)Type II topoisomeraseType IIA topoisomerase (when referring to the main bacterial forms)

Inhibition of ATP binding/hydrolysis site to block enzyme activity; Stabilization of the cleavage complex leading to double-stranded breaks in bacterial DNA ("topoisomerase poisons")