Polymerase
II
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Pol
II
Polymerase II is a single polypeptide chain with a molecular weight of about 90,000. There are about 40 molecules of polymerase II present in each E. coli cell. Polymerase H shows 5'-->3' polymerization activity, and also contains an associated nuclease digesting in the 3'-->5' direction. Unlike polymerase I, however,it does not show 5'-->3' exonuclease activity.
The polymerization activity of polymerase II is much less than that of polymerase I. Only about 50 nucleotides are polymerized per minute in E. coli. Moreover, polymerase II can synthesize not more than 50 nucleotides of template DNA. The 3'-->5' exonuclease activity of
polymerase II indicates that it may have an 'editing' role in repair replication of ultraviolet induced DNA damage.
