Topoisomerase is responsible for relaxing DNA to begin DNA replication. They relax the DNA by making cuts in the DNA. 

University of Wisconsin - Madison

While eukaryotes and prokaryotes have some differences between their processes of DNA replication, they share many of the same proteins needed for replication. These are: 

- DNA Polymerase
- Helicase
- Topoisomerase
- Sliding Clamp
- Primase
- Single-stranded binding protein
- Ligase

Enzymes Involved in DNA Replication

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DNA replication in bacteria occurs rapidly at approximately 1000 nucleotides per second, which is approximately ten times the speed of eukaryotes. It also occurs at a single origin to begin replication.

DNA Replication in Prokaryotes

Helicase separates the DNA strands by severing the hydrogen bonds between the DNA base pairs at the origin of replication. This requires ATP for energy. This creates the replication fork which are at each end of the replicating DNA.

Helicase

The sliding clamp protein keeps DNA polymerase in place while it synthesizes DNA.

Sliding Clamp

DNA ligase joins the Okazaki fragments on the newly synthesized DNA of the lagging strand by forming the phosphodiester linkages between the DNA fragments.

DNA ligase

RNA Primase adds a primer to the DNA to begin replication. This is necessary because DNA polymerase requires a 3'-hydroxyl group to add nucleotides for DNA replication. RNA Primase provides this 3'-hydroxyl by adding a short strand of RNA with a 3'-hydroxyl end to the single stranded DNA. 

RNA Primase

Single-stranded binding proteins (SSBs) coat the single-stranded DNA to ensure it does not prematurely rewind into a helix during DNA replication. 

Single-stranded binding proteins (SSBs)

Topoisomerase

There are several kinds of DNA Polymerases in eukaryotes and prokaryotes. DNA Polymerase adds nucleotides to DNA strands in replication.This process requires energy.

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