Wikipedia:POTD column/December 17, 2006



The assembled human DNA clamp, a trimer of the protein PCNA, is a processivity factor that increases the speed and efficiency of DNA replication. In the assembled replication complex, the clamp encircles the DNA, which passes through the central pore, and binds DNA polymerase to prevent the enzyme from dissociating from the template DNA strand. The DNA clamp protein's presence can increase the rate of DNA synthesis up to 1,000-fold versus a nonprocessive polymerase.

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