DNAgiraasi

DNAgiraasi is a bacterial enzyme that plays a crucial role in DNA replication and repair. It belongs to the type II topoisomerase family, enzymes that are essential for managing the topological state of DNA. Specifically, DNA gyrase introduces negative supercoils into DNA, a process that is vital for unwinding the double helix during replication and for transcription. It achieves this by making a transient double-strand break in the DNA, passing another segment of DNA through the break, and then resealing the break. This action reduces the torsional stress that builds up ahead of the replication fork.

The enzyme is composed of two subunits, GyrA and GyrB, each present in two copies. GyrA is responsible for the DNA breakage and rejoining activity, while GyrB binds ATP and provides the energy for the strand passage. DNA gyrase is a primary target for several clinically important antibiotics, such as the quinolones. These drugs inhibit the enzyme's activity by stabilizing the complex formed between DNA gyrase and its cleaved DNA substrate, leading to an accumulation of double-strand breaks and cell death. Because DNA gyrase is found in bacteria but not in human cells, it represents an excellent target for selective antibacterial therapy. Its essentiality for bacterial survival makes it a critical component in the fight against bacterial infections.