The key difference between prokaryotic and eukaryotic topoisomerase is the cellular origin of the topoisomerase. Prokaryotic topoisomerases are present in the cells of prokaryotic cellular origin while eukaryotic topoisomerases are present among organisms with eukaryotic cellular origin. Furthermore, they differ in the distribution as well. Prokaryotic topoisomerases are present in the cytoplasm of the cell while eukaryotic topoisomerases are distributed in the nucleus.
An isomerase is a group of enzymes which catalyze the structural rearrangement of molecules. Topoisomerase is one type of isomerases. It modifies the topology of the DNA molecule by regulating DNA supercoiling. It cuts and reseals one or both strands of the DNA duplex. Therefore, DNA is able to undergo replication, transcription, repair and chromosomal segregation. There are two types of topoisomerases namely topoisomerase I and II.
CONTENTS
1. Overview and Key Difference
2. What is Prokaryotic Topoisomerase
3. What is Eukaryotic Topoisomerase
4. Similarities Between Prokaryotic and Eukaryotic Topoisomerase
5. Side by Side Comparison – Prokaryotic vs Eukaryotic Topoisomerase in Tabular Form
6. Summary
What is Prokaryotic Topoisomerase?
Prokaryotic DNA Topoisomerases are the enzymes required during prokaryotic DNA replication. They relieve the stress during DNA supercoiling by causing single-stranded and double-stranded breaks.
Types of Prokaryotic Topoisomerases
Type I topoisomerases are responsible for single-stranded breaks whereas Type II topoisomerases cause double-stranded breaks. Topo IA, Topo IC, and Reverse Gyrase are the main three types of prokaryotic topoisomerases that are mostly present in bacteria and archaea. Type IIA and Type IIB are type II topoisomerases present in prokaryotes.
Camptothecin and non-Camptothecin inhibit the action of prokaryotic topoisomerase type I, and they are well-known drugs for anti-cancer therapies.
What is Eukaryotic Topoisomerase?
Eukaryotic Topoisomerases take part in eukaryotic DNA replication. They help in removing positive and negative supercoils during the unwinding of the double helix at the initiation phase of replication
Types of Eukaryotic Topoisomerases
Eukaryotes carry both type I and type II topoisomerases. Similar to prokaryotes, type I topoisomerases break single strands of DNA. In contrast, type II topoisomerases cause double-stranded breaks. Type I topoisomerases in eukaryotes are the subgroups of type IB topoisomerase, whereas type IIA subclasses including type IIα are present in higher eukaryotes such as mammals. Yeast has special topoisomerases.
Figure 01: Topoisomerase Action in Eukaryotes
Camptothecin and non-camptothecin drugs can inhibit eukaryotic topoisomerases as well. Thus, they are useful as anti-cancer agents to prevent the proliferation of cancer cells by inhibiting the replication process.
What are the Similarities Between Prokaryotic and Eukaryotic Topoisomerase?
- Both topoisomerases cause single stranded or double stranded breaks to relieve the stress during supercoiling.
- They are essential for DNA replication.
- They can remove both positive and negative supercoils.
- Both topoisomerases are in two types as type I and type II.
- Camptothecin and non-camptothecin drugs inhibit the action of both topoisomerases.
What is the Difference Between Prokaryotic and Eukaryotic Topoisomerase?
Prokaryotic topoisomerases are present in the cytoplasm of bacteria and archaea. In contrast, Eukaryotic topoisomerases are present in the nucleus. Topo IA, Topo IC, and Reverse Gyrase are type I prokaryotic topoisomerase while type I eukaryotic topoisomerase include subgroups of type IB topoisomerase. Type II prokaryotic topoisomerase include Type IIA and Type IIB while type II eukaryotic topoisomerase include type IIA subclasses.
Summary – Prokaryotic vs Eukaryotic Topoisomerase
DNA topoisomerases are the enzymes that involve in removing the positive and negative supercoils formed during the unwinding process of DNA replication. The difference between prokaryotic and eukaryotic topoisomerase depends on their cellular origin of the enzyme and the distribution.
Reference:
1.Champoux, J J. “DNA Topoisomerases: Structure, Function, and Mechanism.” Advances in Pediatrics., U.S. National Library of Medicine, Available here.
Image Courtesy:
1. “Figure 14 04 01” By CNX OpenStax – (CC BY 4.0) via Commons Wikimedia