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What are the differences between DNA polymerase I and III?

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Wilson2014 | eNotes Employee

Posted April 21, 2013 at 5:56 PM via web

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What are the differences between DNA polymerase I and III?

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orchid101 | College Teacher | (Level 1) Associate Educator

Posted April 23, 2013 at 2:17 PM (Answer #1)

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The Kornberg enzyme, now called polymerase I, is no longer considered to be an essential enzyme for DNA synthesis. Polymerase I is a single polypeptide chin with a molecular weight of 109,000. Thus DNA polymerases are metalloenzymes.

Polymerase III consists of two polypeptide chains having molecular weights of 140,000 and 40,000. Like polymerase II it has 5'-3' polymerization activity and 3'-5' exonuclease activity. Recent work has shown that polymerase III is the main polymerizing enzyme. It can polymerize about 15,000 nucleotides per minute in E.coli. Polymerization is the synthesis of a complementary DNA strand from deoxyribonucleoside triphosphate monomers.

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