Polymerase III - Pol III

Polymerase III - Pol III

	Polymerase III - Pol III - 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. 5'-->3' exonuclease activity is reported to be absent, although some works indicate that nucleotides can be removed in either 3'-->5' or 5'-->3' direction.Recent work has shown that polymerase III is the main polymerizing enzyme.
It can polymerize about 15,000 nucleotides per minute in E; coli. As in the case of polymerase II, polymerase III also cannot carry out polymerization efficiently if the template DNA strand is long. However, in the presence of ATP and certain protein factors, called I and II, polymerase III can synthesize DNA on long templates.
Synthesis of long templates can also take place in the presence of another polymerase, called DNA polymerase 111, if a factor called co-polymerase 111 is present. Perhaps the protein factor II converts polymerase III into polymerase 111. The activities of polymerase III arc similar to those of polymerase III plus the protein factors I-II.

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Polymerase II - Pol II Polymerase III - Pol III Characteristics of DNA Polymerases Eukaryotic DNA Polymerases Models of Replication Cairns Model of Replication Yoshikawa Model of Replication Rolling Circle Model of Replication Replication in Duplex Rod Prokaryote Chromosome Replication in Eukaryote Chromosome Repair Replication Functions of DNA