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DNA polymerase I (or Pol I) is an enzyme that participates in the process of prokaryotic DNA replication. Discovered by Arthur Kornberg in 1956, [1] it was the first known DNA polymerase (and the first known of any kind of polymerase). It was initially characterized in E. coli and is ubiquitous in prokaryotes.
DNA polymerase's rapid catalysis due to its processive nature. Processivity is a characteristic of enzymes that function on polymeric substrates. In the case of DNA polymerase, the degree of processivity refers to the average number of nucleotides added each time the enzyme binds a template.
Structure of Taq DNA polymerase. In biochemistry, a polymerase is an enzyme (EC 2.7.7.6/7/19/48/49) that synthesizes long chains of polymers or nucleic acids. DNA polymerase and RNA polymerase are used to assemble DNA and RNA molecules, respectively, by copying a DNA template strand using base-pairing interactions or RNA by half ladder replication.
Taq polymerase is a thermostable DNA polymerase I named after the thermophilic eubacterial microorganism Thermus aquaticus, from which it was originally isolated by Chinese scientist Alice Chien et al. in 1976. [1] Its name is often abbreviated to Taq or Taq pol.
The Klenow fragment is a large protein fragment produced when DNA polymerase I from E. coli is enzymatically cleaved by the protease subtilisin.First reported in 1970, [1] it retains the 5' → 3' polymerase activity and the 3’ → 5’ exonuclease activity for removal of precoding nucleotides and proofreading, but loses its 5' → 3' exonuclease activity.
Along the DNA template, primase intersperses RNA primers that DNA polymerase uses to synthesize DNA from in the 5′→3′ direction. [1] Another example of primers being used to enable DNA synthesis is reverse transcription. Reverse transcriptase is an enzyme that uses a template strand of RNA to synthesize a complementary strand of DNA. The ...
An evolutionary divergence (about 0.25 to 1.2 billion years ago), appears to have been associated with the separation of the DNA polymerase gene function from the 3’ to 5’ exonuclease editing gene function in the lineage that led to E. coli and S. typhimurium. [11]
Thus, a proposed mechanism follows: after a PCNA-DNA polymerase δ complex synthesizes Okazaki fragments, the DNA polymerase δ is released. Then, DNA ligase I binds to the PCNA, which is clamped to the nicks of the lagging strand, and catalyzes the formation of phosphodiester bonds. [12] [13] [14]