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
Hope you all had a great time…