The three distinct enzymatic functions of DNA pol I are segregated to the three domains. This multi-domain organisation insures that the three activities involved in DNA replication can be carried out efficiently, in the required order and that they are present in equivalent quantities in the cell. The Klenow fragment produced from DNA pol I by proteolytic cleavage corresponds to the two C-terminal domains which have 3'-5' exonuclease and DNA polymerase activities
A few examples:
1. Klenow fragment of the E. coli DNA polymerase I; C-alpha atoms only 1dpi (53Kb) [Bbk|BNL|ExP|Waw|Hal]
back to roles of protein domains