DNA gyrase, often referred to simply as gyrase, is an enzyme that relieves strain while double-strand DNA is being unwound by helicase.
This causes negative supercoiling of the DNA.
Bacterial DNA gyrase is the target of many antibiotics, including nalidixic acid, novobiocin, and ciprofloxacin.
It supercoils (or relaxes positive supercoils) into DNA by looping the template so as to form a crossing, then cutting one of the double helices and passing the other through it before releasing the break, changing the linking number by two in each enzymatic step.
This process occurs in prokaryotes (in particular, in bacteria), whose single circular DNA is cut by DNA gyrase and the two ends are then twisted around each other to form supercoils. Very recently, gyrase has been found in the apicoplast of the malarial parasite Plasmodium falciparum, a unicellular eukaryote.
The unique ability of gyrase to introduce negative supercoils into DNA is what allows bacterial DNA to have free negative supercoils.
The ability of gyrase to relax positive supercoils comes into play during DNA replication and prokaryotic transcription.
The right-handed nature of the DNA double helix causes positive supercoils to accumulate ahead of a translocating enzyme, in the case of DNA replication, a DNA polymerase.
The ability of gyrase (and topoisomerase IV) to relax positive supercoils allows superhelical tension ahead of the polymerase to be released so that replication can continue.
DNA gyrase, often referred to simply as gyrase, is an enzyme that relieves strain while double-strand DNA is being unwound by helicase.
This causes negative supercoiling of the DNA.
Bacterial DNA gyrase is the target of many antibiotics, including nalidixic acid, novobiocin, and ciprofloxacin.
It supercoils (or relaxes positive supercoils) into DNA by looping the template so as to form a crossing, then cutting one of the double helices and passing the other through it before releasing the break, changing the linking number by two in each enzymatic step.
This process occurs in prokaryotes (in particular, in bacteria), whose single circular DNA is cut by DNA gyrase and the two ends are then twisted around each other to form supercoils. Very recently, gyrase has been found in the apicoplast of the malarial parasite Plasmodium falciparum, a unicellular eukaryote.
The unique ability of gyrase to introduce negative supercoils into DNA is what allows bacterial DNA to have free negative supercoils.
The ability of gyrase to relax positive supercoils comes into play during DNA replication and prokaryotic transcription.
The right-handed nature of the DNA double helix causes positive supercoils to accumulate ahead of a translocating enzyme, in the case of DNA replication, a DNA polymerase.
The ability of gyrase (and topoisomerase IV) to relax positive supercoils allows superhelical tension ahead of the polymerase to be released so that replication can continue.
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