DNAgyrase

DNA gyrase is a type II topoisomerase found in bacteria. Its primary function is to introduce negative supercoils into DNA. This process is essential for several critical DNA transactions, including replication, transcription, and recombination. DNA gyrase achieves supercoiling by creating a transient double-strand break in the DNA, passing another segment of DNA through the break, and then resealing the break.

The enzyme is a heterotetramer composed of two GyrA subunits and two GyrB subunits. The GyrA subunits are responsible for binding to the DNA and creating the double-strand break, while the GyrB subunits possess ATPase activity that provides the energy required for the DNA passage and resealing steps.

DNA gyrase is a vital target for many antibacterial drugs, such as the fluoroquinolones. These drugs inhibit the activity of DNA gyrase by trapping the enzyme-DNA complex after the double-strand break has been made but before it is resealed. This leads to the accumulation of lethal DNA breaks and ultimately cell death. Due to its essential role in bacterial survival and its susceptibility to antibiotics, DNA gyrase is a well-studied enzyme in molecular biology and pharmacology. Its existence and function are critical for maintaining the topological state of bacterial DNA.