DNA gyrase, also known as gyrase, is an enzyme found in bacteria that plays a crucial role in DNA replication and maintenance.
DNA gyrase is a tetrameric enzyme composed of two GyrA (A) and two GyrB (B) subunits.
The complex has three pairs of “gates” that open and close during its activity.
N-gates (formed by ATPase domains of GyrB) close upon ATP binding, while C-gates (formed by GyrA subunits) play a role in DNA cleavage and reunion.
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Prokaryotic topoisomerase II, also known as DNA gyrase & introduces negative supercoils during dna replication process.
The thermophilic bacterium Sulfolobus produced DNA gyrase, a “reverse gyrase” that adds positive superhelical twists to DNA in the presence of ATP
Gyrase reduces topological strain in double-stranded DNA during processes like transcription and replication.
It actively introduces negative supercoils into DNA, which is essential for maintaining free negative supercoils in bacterial DNA.
Gyrase can also relax positive supercoils, allowing replication to continue smoothly.
Mechanism:
• Gyrase binds to DNA, forming the “Gyrase-DNA” state.
• It competes between DNA wrapping and dissociation.
• Increasing DNA tension enhances dissociation probability.
• ATP hydrolysis drives the process.
Supercoiling Regulation:
• DNA gyrase introduces negative supercoils into bacterial DNA.
• These supercoils help maintain proper DNA topology for essential processes like transcription and replication.
• Without functional gyrase, supercoiling becomes unregulated, affecting gene expression and replication.
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Antibiotic Target:
• DNA gyrase is an attractive target for antibiotics.
• Inhibiting gyrase disrupts bacterial growth.
• Interestingly, DNA gyrase is absent in higher eukaryotes, making it a specific bacterial target.
Archaeal Context:
• While ubiquitous in bacteria, DNA gyrase has a patchy distribution in Archaea.
• Recent research suggests horizontal gene transfers introduced gyrase into certain archaeal lineages.
• Co-evolution with another enzyme, Topoisomerase VI, helps manage topological constraints in Archaea.
• In summary, we can say that bacterial growth relies on functional DNA gyrase for proper DNA supercoiling and essential cellular processes.