Both DNA gyrase and topoisomerase are enzymes that are essential for controlling DNA topology and structure within cells. The replication, transcription, and recombination of DNA are only a few of the functions that they are crucial for in the cell.
Bacteria and some archaea include the type II topoisomerase known as DNA gyrase. It is in charge of giving DNA molecules negative supercoils, which aid in relieving the torsional strain that accumulates before the replication fork during DNA replication. This procedure is necessary for the DNA helicase to unwind the DNA double helix effectively.
In order to accomplish this, DNA gyrase briefly separates the DNA double helix, inserts a different piece of DNA into the space left open, and then rejoins the DNA strands. The supercoiling of the DNA is altered by this process, becoming more compact and enabling separation.
Enzymes called topoisomerases modify the supercoiling, knotting, and linking of DNA to change its topological features. Type I and type II topoisomerases are the two primary types.
Topoisomerases of type I DNA can rotate around the unbroken strand thanks to these enzymes’ temporary single-strand breaks in one of the double helix’s strands. This procedure modifies the DNA molecule’s linking number and lowers torsional stress.
Negative supercoils are typically relaxed and DNA integrity is maintained by type I topoisomerases.
DNA gyrase is one of the type II topoisomerases. Both strands of the DNA double helix can be broken by type II topoisomerases, allowing a section of DNA to flow through before the breaks are repaired.
Unlike type I topoisomerases, this mechanism is more intricate and has the potential to cause both positive and negative supercoiling. Bacterial type II topoisomerase DNA gyrase introduces negative supercoiling specifically.
Inhibiting DNA gyrase and other topoisomerases can be a target for antibiotics and other medications because they are both crucial for numerous cellular activities. For instance, some antibiotics, such as fluoroquinolones, specifically target DNA gyrase and other bacterial topoisomerases, causing them to malfunction and preventing bacterial DNA replication and transcription.
|
S.No. |
Aspects |
DNA Gyrase |
Topoisomerase |
|
1 |
Type of Enzyme |
Type II topoisomerase |
Type I or Type II topoisomerase |
|
2 |
Function |
Introduces negative supercoils in DNA |
Alters DNA topology by breaking and rejoining strands |
|
3 |
Target DNA |
Acts on double-stranded DNA |
Acts on both single-stranded and double-stranded DNA |
|
4 |
Catalytic Subunits |
Typically composed of two subunits (A2B2) |
Can have various subunit compositions |
|
5 |
Energy Requirement |
Utilizes ATP for its function |
Some types utilize ATP, while others do not |
|
6 |
Supercoiling Direction |
Introduces negative supercoils (relaxes DNA) |
Can introduce negative or positive supercoils |
|
7 |
DNA Relaxation |
Introduces negative supercoiling to relax overwound DNA |
Relaxes supercoiled DNA by cutting and rejoining |
|
8 |
DNA Cleavage Mechanism |
Creates double-strand breaks via cleavage in both strands |
Creates single-strand breaks via cleavage |
|
9 |
DNA Strand Separation |
Separates the two DNA strands before cleavage |
Does not require strand separation before action |
|
10 |
DNA Unwinding |
Induces DNA unwinding as it relaxes supercoils |
Can induce DNA unwinding as it alters topology |
|
11 |
Topological Isomerism |
Reduces positive supercoiling and introduces negative supercoiling |
Alters the number of supercoils in DNA |
|
12 |
DNA Topology Change |
Changes the linking number of DNA strands |
Can change the linking number and twist of DNA |
|
13 |
Reactions Involved |
Undergoes ATP hydrolysis in cleavage and ligation reactions |
Can involve ATP or other nucleotide cofactors |
|
14 |
Role in DNA Replication |
Relieves supercoiling ahead of replication fork |
May participate in replication and repair |
|
15 |
Target of Antibiotics |
Targeted by antibiotics like quinolones |
Targeted by various antibiotics |
|
16 |
Subunit Functions |
Subunit A (DNA cleavage) and Subunit B (ATP hydrolysis) |
Various subunits have distinct functions |
|
17 |
Inhibitors |
Affected by quinolone antibiotics |
Inhibited by a variety of compounds and drugs |
|
18 |
Role in Topological Problems |
Resolves topological problems like DNA knots and tangles |
Resolves topological problems such as knots and tangles |
|
19 |
Activity during Transcription |
Can alleviate positive supercoiling generated during transcription |
Participates in transcription by altering DNA topology |
|
20 |
Role in DNA Compaction |
Plays a role in DNA compaction in bacterial nucleoids |
May contribute to DNA compaction in chromatin |
|
21 |
Essential for Cell Viability |
Essential in most bacteria for survival |
Essential for many cellular processes in all organisms |
|
22 |
Enzyme Family |
Part of the type II topoisomerase family |
Belongs to either type I or type II topoisomerase family |
|
23 |
Action at Specific Sites |
Acts at specific DNA sequences called gyrase binding sites |
Can act at various DNA sequences and structures |
|
24 |
DNA Replication Regulation |
Regulates DNA replication by alleviating torsional stress |
Can regulate DNA replication and repair processes |
|
25 |
Activity in Chromosome Condensation |
Involved in chromosome condensation in prokaryotes |
May play a role in chromosome condensation in eukaryotes |
Frequently Asked Questions (FAQ’S)
1. What is DNA gyrase's purpose?
The torsional stress that accumulates in front of the replication fork during DNA replication is lessened by DNA gyrase. It accomplishes this by creating negative supercoils into DNA, which facilitates more effective DNA strand unwinding and permits replication to proceed without interruption.
2. How does the DNA gyrase function?
In order to function, DNA gyrase catalyzes a reversible double-strand break in the DNA molecule. A subsequent DNA segment is then passed through the break and the break is subsequently repaired. Negative supercoiling and a change in DNA architecture are brought about by this process.
3. What function do topoisomerases serve in the replication of DNA?
Topoisomerases, such as DNA gyrase, aid in controlling the topological alterations to DNA that take place during replication. They do this by causing brief gaps in the DNA strands, allowing them to untangle or relax, which prevents DNA tangling and supercoiling. This is essential for the efficient development of cellular functions such as replication.
4. Can antibiotic resistance be caused by DNA gyrase mutations?
Yes, mutations in the gyrA and gyrB genes, which encode DNA gyrase subunits, can lead to fluoroquinolone antibiotic resistance. These changes may change the binding location of the enzyme, decreasing the antibiotic’s potency and enabling bacteria to resist treatment.
5. Do all creatures contain DNA gyrase?
The majority of archaea and certain bacteria include DNA gyrase. Topoisomerase II, also known as DNA topoisomerase II, is a distinct type II topoisomerase found in eukaryotic creatures like humans. It performs similar tasks to DNA gyrase but differs somewhat in structure and mechanism.
