POLYMERASE

What is Polymerase ?

According to Faraza (2017), polymerases are collectively referred as the groups of enzymes that catalyze nucleic acid molecules’ synthesis. It is customary to use the name of the nucleic acid template on which the polymerase acts. And Polymerases are enzymes that catalyze the production of complementary DNA or RNA polymers to the original template, as defined by Watson-Crick base pairing. However, at the time of Watson and Crick's conception of the double-helical DNA structure, the deoxynucleotide precursors of DNA were unknown, and many people thought of DNA synthesis as a "vital" process that was inextricably linked to the live cell. Kornberg would prove them incorrect by finding DNA polymerase, the need for a DNA template in addition to deoxynucleotides and primers, and the DNA polymerase I's 3′-5′ error-correcting mechanism

Arthur Kornberg discovered that nicotinamide adenine dinucleotide (NAD), a coenzyme found in all living cells, could be synthesized using an enzyme derived from potatoes (nucleotide pyrophosphatase). He began researching if other enzymes might assemble the numerous nucleotides that make up the chains of nucleic acids, notably RNA, in 1950. Kornberg and his postdoctoral associate, Uri Littauer, demonstrated in 1954 that the probable nucleotide building blocks were produced and activated in cells. Mariane Grunberg-Manago, a postdoctoral fellow in Severo Ochaoa's group, announced the discovery of polynucleotide phosphorylase, a novel enzyme capable of generating RNA in a test tube from simple nucleotides.

Kornberg and his colleagues isolated DNA polymerase from E coli (The first polymerase crystal structure solved by Thomas Steitz in 1985.) samples in 1956, assisted by the department's recent installation of a fermentor. They were able to obtain a few thousandfold purified but not yet homogenous formulation of DNA polymerase using chromatography. The insertion of DNA as a primer facilitated in this DNA synthesis. Many more E. coli DNA polymerases have been isolated. coli since the 1950s, including Taq DNA polymerase, which was isolated in 1976 from the bacteria Thermus aquaticus.

Polymerase does not generate a brand-new DNA strand. Instead, it creates a new DNA strand from the template of two existing DNA strands. This is accomplished with the assistance of another enzyme known as helicase, which unwinds the double helix structure of the DNA molecule into two single DNA strands. Polymerases require a primer in addition to a template strand to work. This is a nucleic acid fragment that acts as the beginning point for DNA replication. The primer, which is usually a short strand of RNA, must be complementary to the template.

The DNA polymerase enzyme is considered to be capable of replicating 749 nucleotides per second. By the completion of the replication process, two new DNA molecules will have been produced, each identical to the other as well as the original parent molecule. Such precise replication is aided by the fact that DNA polymerase has the ability to identify and rectify any errors it produces throughout the replication process. The fundamental purpose of DNA polymerases is to replicate genomic DNA. Once the DNA has been correctly copied, the cell can divide, with each daughter cell inheriting the whole genetic code of the organism. Polymerases, which are responsible for DNA replication, are sophisticated multiprotein machines that can create DNA at high speeds, with high processivity, and with great fidelity.

The three critical polymerases

  • DNA-dependent DNA polymerase that replicates DNA from DNA.
  • RNA-dependent DNA polymerase (reverse transcriptase) that transcribes DNA from RNA.
  • DNA-dependent RNA polymerase that transcribes RNA from DNA

TYPES OF DNA POLYMERASE (EUKARYOTE AND PROKARYOTE)

PROKARYOTES

  • DNA Polymerase I is coded by polA gene, a single polypeptide and has a role in recombination and repair.
  • DNA Polymerase II is coded by polB gene, made up of 7 subunits, main role is repair and a backup of DNA polymerase III.
  • DNA Polymerase III is the main enzyme for replication in E. coli., coded by polC gene.
  • DNA Polymerase IV is coded by dinB gene, main role is in DNA repair during SOS response, when DNA replication is stalled at the replication fork.
  • DNA Polymerase V is also involved in translesion synthesis during SOS response and DNA repair.

EUKARYOTE

  • DNA polymerase 𝝳 – for replication in eukaryotes
  • DNA polymerase 𝜶 – to synthesize primers
  • DNA polymerase 𝟄 – to repair DNA
  • DNA polymerase 𝝲 – the replicative enzyme for mitochondrial DNA

STRUCTURE With DNA polymerase, it has a conserved structure, establishing its critical role in cell function.

  • It consists of subdomains that resemble the palm, fingers, and thumb of an open right hand.
  • The active sites of the palm include catalytic necessary amino acids. The fingers play an important role in nucleotide identification and binding. The thumb is for DNA substrate binding.

Since their discovery, DNA polymerases have paved the door for fresh insights into how DNA is duplicated and transcribed. They were also critical in the invention of DNA sequencing and PCR, which are the foundations of most modern biotechnology. Polymerases are now the most important tools for DNA tagging, sequencing, and amplification. DNA polymerases are also necessary for the development of molecular diagnostics for customized treatment. They are at the forefront of ways to discover genetic abnormalities that might cause illnesses like cancer or lead people to have harmful medication responses, for example.

Edit Report
Pub: 28 Mar 2023 06:35 UTC
Edit: 29 Mar 2023 08:32 UTC
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