DNA Polymerase III

Discovered by Thomas Konberg and Malcolm Gefter (1970)

POLYMERASE

Polymerase is a class of enzyme that extends a monomeric unit of

nucleic acid and subsequently forms a polymer.

DNA Polymerase• Cannot initiate the replication process on

its own

• Requires a template.

• Requires a primer with free 3’-OH (which acts as a nucleophile) to start the polymerization activity .

• The fundamental reaction is a phosphoryl group transfer.

• The main reaction is (dNMP)n + dNTP (dNMP)n+1 + PPi Source: www.cas.miamioh.edu

Encoded by dnaE gene, has the polymerase activity

Encoded by dnaQ gene, has 3’->5’ exonuclease activity

Encoded by holE gene, stimulates the ε proof-reading activity

Encoded by dnaX, which acts to dimerize two of the core enzymes (α, ε, and θ subunits).

Encoded by dnaX, which acts as the clamp loader

Encoded by holB, which acts as a clamp loader

Encoded by holA, which acts as a clamp opener

Encoded by holC, which helps in interaction with SSB

Encoded by holD, which helps in the interaction with γ and Χ

Schematic of DNA Polymerase III

Source: www.en.wikipedia.org

Beta-clamp and clamp loading complex

Source: David L. Nelson, Michael M. Cox-Lehninger Principles of Biochemistry, 5th Edition-W. H. Freeman (2008)

Source: David L. Nelson, Michael M. Cox-Lehninger Principles of Biochemistry, 5th Edition-W. H. Freeman (2008)

Source: https://giphy.com/gifs/V1TD7IqBcq4Sc

DNA Polymerase II I

Source:http://sarinasunbeam.deviantart.com/art/Leading-and-Lagging-Strand-in-DNA-GIF-623507478

Source: http://femsre.oxfordjournals.org/content/36/6/1105

Source: https://giphy.com/gifs/V1TD7IqBcq4Sc

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