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3' to 5' Exonuclease question

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3' to 5' Exonuclease question

Postby NathanielZhu » Thu Jul 07, 2011 2:03 am

The lectures notes of a molecular biology course recorded from Berkley (one of those free online courses where they record the classes) says that "Polymerization is a race between the 3' to 5' exonuclease and polymerase" (probably polymerase III).

What does that mean?
How can it be a race since the DNA Polymerase is a holoenzyme/molecular machine/replisome which pretty much means that all the subunits are connected? That's like if I were to tie a string onto two matchbox cars - if I push one, they other moves along with it. DNA Polymerase + the 3' to 5' exonuclease is the same way so how is it a race?
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Postby JackBean » Tue Aug 02, 2011 11:00 am

I guess they mean the proof-reading function? ;)

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Re: 3' to 5' Exonuclease question

Postby Duc » Mon Aug 08, 2011 4:20 am


This is my first time in this forum.
As I read about DNA Polymerase III in "molecular biology of the cell" the enzyme has both functions of polymerization 5'-3' and exonuclease 3'-5'. They locate in two active site of this enzyme. When a nucleotide is mismatched at polymerase site, the enzyme will stop and the mismatched nucleotide will be removed at exonuclease site. That's also called proof-reading function of DNA Pol III.
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