What is the difference between topoisomerase and DNA gyrase?

DNA gyrase and topoisomerase IV are the two type II topoisomerases present in bacteria. Gyrase is involved primarily in supporting nascent chain elongation during replication of the chromosome, whereas topoisomerase IV separates the topologically linked daughter chromosomes during the terminal stage of DNA replication.

What is DNA topoisomerase IV?

Topoisomerase IV (Topo IV), an essential ATP-dependent bacterial type II topoisomerase, transports one segment of DNA through a transient double-strand break in a second segment of DNA. In vivo, Topo IV unlinks catenated chromosomes before cell division and relaxes positive supercoils generated during DNA replication.

What is the role for the topoisomerase IV in DNA replication?

The primary cellular functions of topoisomerase IV are to unlink daughter chromosomes following DNA replication and to resolve DNA knots that are formed during recombination. Recently, it was found that topoisomerase IV removes positive supercoils from DNA more efficiently than it removes negative supercoils.

What is the function of DNA gyrase topoisomerase?

DNA gyrase is an essential bacterial enzyme that catalyzes the ATP-dependent negative super-coiling of double-stranded closed-circular DNA. Gyrase belongs to a class of enzymes known as topoisomerases that are involved in the control of topological transitions of DNA.

What causes supercoiling of DNA?

Supercoiling occurs when the molecule relieves the helical stress by twisting around itself. The hydrogen bonds (holding together complementary bases) break and part of the double helix separates. Strand separation is required for transcription (copying DNA to RNA) and replication (copying DNA to DNA).

What is meant by Supercoiling?

Abstract. DNA supercoiling describes a higher-order DNA structure. The double-helical structure of DNA entails the interwinding of two complementary strands around one another and around a common helical axis. The writhing of this helical axis in space defines the DNA superhelical structure (DNA tertiary structure).

What is negative supercoiling of DNA?

Positive supercoiling of DNA occurs when the right-handed, double-helical conformation of DNA is twisted even tighter (twisted in a right-handed fashion) until the helix begins to distort and “knot.” Negative supercoiling, on the other hand, involves twisting against the helical conformation (twisting in a left-handed …

Does topoisomerase cut DNA?

The topoisomerases act by transiently cutting one or both strands of the DNA. Topoisomerase type I cuts one strand whereas topoisomerase type II cuts both strands of the DNA to relax the coil and extend the DNA molecule.

What is the difference between Type 1 and Type 2 topoisomerase?

Type I topoisomerases relax DNA (i.e., remove supercoils) by nicking and closing one strand of duplex DNA (see Figure 12-14). Type II topoisomerases change DNA topology by breaking and rejoining double-stranded DNA. Both replicated circular and linear DNA chromosomes are separated by type II topoisomerases.

What happens if topoisomerase is not functional?

Topoisomerase alleviates supercoiling downstream of the origin of replication. In the absence of topoisomerase, supercoiling tension would increase to the point where DNA could fragment. DNA replication could not be initiated because there would be no RNA primer. DNA strands would not be ligated together.

What is meant by supercoiling?

Why is supercoiling bad?

With the exception of extreme thermophiles, supercoiling has a negative sign, which means that the torsional tension diminishes the DNA helicity and facilitates strand separation.

What does DNA gyrase do?

Jump to navigation Jump to search. DNA gyrase, or simply gyrase, is an enzyme within the class of topoisomerase and is a subclass of Type II topoisomerases that reduces topological strain in an ATP dependent manner while double-stranded DNA is being unwound by elongating RNA-polymerase or by helicase in front of the progressing replication fork.

What does DNA topoisomerases, type II, bacterial mean?

DNA gyrase is a bacterial topoisomerase that introduces negative supercoils into DNA . Because it cuts both strands of DNA, it is considered to be a Class II topoisomerase. Type II topoisomerases are divided into two subfamilies: IIA and IIB.

What does DNA topoisomerase IV mean?

Topoisomerase IV is one of two Type II topoisomerases in bacteria, the other being DNA gyrase . Like gyrase, topoisomerase IV is able to pass one double-strand of DNA through another double-strand of DNA, thereby changing the linking number of DNA by two in each enzymatic step.

Is DNA gyrase in eukaryotes?

Gyrase is also found in eukaryotic plastids: it has been found in the apicoplast of the malarial parasite Plasmodium falciparum and in chloroplasts of several plants. Bacterial DNA gyrase is the target of many antibiotics, including nalidixic acid, novobiocin, and ciprofloxacin.