DNA gyrase

The DNA gyrase is one of the DNA topoisomerases that acts during DNA replication to reduce the molecular strain caused by supercoiling. DNA gyrase produces double-stranded cuts and they are then joined by ligases. It acts as a highly dangerous molecule.

DNA gyrase, as a topoisomerase, has a very important role in modulating the topological state of DNA, since it regulates its superhelical structure. Unlike DNA gyrase, topoisomerase 1 cuts only one of the two strands of the DNA double helix; and acts in the transcription of DNA. Meanwhile, DNA gyrase (or topoisomerase 2) cuts both DNA strands to alleviate supercoiling, and works during DNA replication.

DNA gyrase molecules move along the DNA ahead of the replication fork and remove positive supercoils. DNA gyrase performs this task by cutting the two strands of the duplex DNA; a segment of DNA passes through the double-strand break to the other side and the breaks are then ligated again, a process carried out by the release of energy during ATP (adenosine triphosphate) hydrolysis.