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The discovery of DNA Polymerase I is credited to Arthur Kornberg in 1955. Kornberg and his colleagues isolated RNA pol I from E. coli extracts through a DNA assay. SOURCE This enzyme was the first DNA polymerase discovered, and was therefore given the name DNA Polymerase I. It plays a key role in prokaryotic DNA replication.
Function
DNA Polymerase I has the ability to manipulate DNA in three separate ways. It is similar to DNA Polymerase III, as it has 5' to 3' polymerase activity to elongate the replicated DNA strand along with 3' to 5' exonuclease activity for proofreading and editing the new DNA. Both of the active sites for these functions are found in the Klenow Fragment. Clip thing
Its primary role is removing the RNA primers initially laid down by the RNA polymerase primase and replacing those nucleotides with dNTPs. The initial step of excising RNA nucleotides on the replicated strand is made possible due to its 5' to 3' exonuclease activity. The enzyme will remove then add on DNA nucleotides 5' to 3' and connect these nucleotides by phosphodiester bonds.
Its function is parallel to the eukaryotic DNA polymerase BLANK.
DNA polymerase I will bind to .
Structure
DNA Polymerase I is a hetero trimer comprised of six chains with three distinct sequences. Each of the sequences is repeated twice within the molecule. Two of the six chains are polypeptide chains, each comprised of 580 amino acids. They have identical secondary structures consisting of 31 alpha helices and 20 beta pleated sheets. Another distinct sequence found in DNA Polymerase is a short polypeptide chain that is 9 amino acids in length. The final distinct sequence is a DNA sequence that is 12 nucleotides in length. Each lengthy DNA chain has a condensed tertiary structure. A short polypeptide chain and a DNA chain burrow into the center of the condensed DNA strand, creating the quaternary structure of the molecule. The two condensed chains form a disulfide bond and form a parallel structure.
DNA Polymerase I is composed of 3 major domains. The first domain is the A-terminus domain. The second domain is the Klenow fragment. The final domain is the ==DNA Polymerase I==
.
Sources
Lehman, I. R. (2003). Discovery of DNA polymerase. Journal of Biological Chemistry, 278(37), 34733-34738.
