DNA Polymerase

DNA Polymerase belongs to the family of enzymes that initiate the synthesis of DNA molecules in the body by assembling the nucleotides, known as the building blocks of DNA or Deoxyribonucleic acid. DNA polymerase acts as an essential enzyme for DNA replication in the body. The enzymes work in a group to create two equivalent DNA duplexes from a single strand of the original DNA duplex. During the process of replicating the DNA duplexes, these enzymes read and inspect the original DNA strand to create two replicas that match the original strand of DNA. 

The enzyme act as a catalyst in the chemical reaction to replicate DNA duplexes. Now, let’s discuss the functions, structure, and types of DNA polymerase.

History of DNA Polymerase

The history of DNA polymerase can be traced back to 1956 when Arthur Kornberg and his colleagues discovered the enzyme in Escherichia Coli. Arthur Kornberg named the enzyme as DNA Polymerase I and described the DNA replication process, where these enzymes were involved in creating two replica DNA strands from the original. Later in 1970, Thomas Kornberg (son of Arthur Kornberg) and his colleague Malcolm E. Gefter discovered DNA polymerase II. They also described the role of DNA polymerase I and II in DNA replication.

DNA Polymerase Structure

All the known DNA Polymerases have highly conserved structures, which means that each catalytic subunit of the enzyme varies from the other in different species, independent of their original structures. The highly conserved DNA polymerase structure indicates the essential and irreplaceable functions of the cells. We can describe the shape of the DNA polymerase as the right hand with the only thumb, finger, and palm domains. 

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DNA Polymerase Function

We can divide the role of DNA Polymerase under three significant heads. Let’s discuss each head in detail.

• Replication of DNA: The primary function of every DNA polymerase enzyme is to initiate the DNA synthesis and replication in organisms by assembling the nucleotides. These enzymes act as a catalyst in the chemical process of DNA replication. The DNA polymerase enzymes work in clusters or groups to replicate the original DNA strand into two DNA duplexes.  

• Repairing: The replication of the DNA strand is a critical function, and it helps maintain the originality of the Genome. During the process of replication, the DNA strand incurs much damage. The DNA polymerase continuously repairs and rectifies the error in each DNA strand to maintain its integrity. 

• Proofreading: Proofreading is another crucial role of DNA Polymerase, where the enzyme checks all the nucleotides being added to duplicate the DNA strand. During the replication process, many errors occur in the replication of nucleotides, and each incorrect nucleotide should be removed to maintain the integrity of the genome. Hence, the DNA polymerase inspects each nucleotide and eliminates the incorrect ones. 

DNA Polymerase Types

The DNA Polymerase types can be divided into two groups - The Prokaryotic and the Eukaryotic. Each group and polymerase enzymes differ in their structure and functions. Let’s discuss each type and its functions.

Prokaryotic DNA Polymerase Types

There are generally five types of Prokaryotic DNA Polymerase that were identified in the Escherichia Coli. Below we have mentioned all the types with their functions.

• DNA Polymerase I: Polymerase I is coded by pol A genome. It consists of a single strand of polypeptide and plays an essential role in the recreation and repairs of the nucleotide during the replication process. 

• DNA Polymerase II: This polymerase is coded by the pol B genome. It consists of 7 catalytic subunits and helps in the repair of nucleotides during the replication process. The polymerase also backs up the DNA Polymerase III. 

• DNA Polymerase III: It is considered the primary enzyme for the replication process in Escherichia Coli. The polymerase III is coded by the pol C genome. It consists of 13 main catalytic subunits. 

• DNA Polymerase IV: Polymerase IV is coded by the din B genome and is primarily responsible for the DNA repair during SOS response. 

• DNA Polymerase V: Polymerase V is the primary enzyme involved in the SOS response and DNA repair during the replication process. 

Eukaryotic DNA Polymerase Types 

Like the prokaryotic cells, eukaryotic cells also contain DNA polymerase that helps synthesise and replicate DNA. Below, we have mentioned the crucial Eukaryotic DNA polymerase types:

• DNA Polymerase Delta 𝛅: The polymerase delta is the primary enzyme for DNA replication in the eukaryotes, and it is involved in the proofreading process during DNA replication.

• DNA Polymerase 𝜶: It is another vital polymerase in the eukaryotes and helps synthesise primer for the Okazaki fragments.

• DNA Polymerase ∈: The polymerase ∈ is primarily involved in repairing the DNA strands and removes primer from the lagging strands.

• DNA Polymerase ү: The polymerase ү acts as the main replicating enzyme for mitochondrial DNA replication.

Above, we discussed DNA polymerase, its structure, types, and functions, and we hope it would help gain in-depth knowledge about the subject. You can also read a DNA Polymerase ppt for more details.