Topic summary
Pol I
Extracted from the Wikipedia article DNA polymerase I.
General structure
Pol I mainly functions in the repair of damaged DNA. Structurally, Pol I is a member of the alpha/beta protein superfamily, which encompasses proteins in which α-helices and β-strands occur in irregular sequences. E. coli DNA Pol I consists of multiple domains with three distinct enzymatic activities. Three domains, often referred to as thumb, finger and palm domain work together to sustain DNA polymerase activity. A fourth domain next to the palm domain contains an exonuclease active site that removes incorrectly incorporated nucleotides in a 3' to 5' direction in a process known as proofreading. A fifth domain contains another exonuclease active site that removes DNA or RNA in a 5' to 3' direction and is essential for RNA primer removal during DNA replication or DNA during DNA repair processes.