AN ACTIVE FRAGMENT OF DNA POLYMERASE PRODUCED BY PROTEOLYTIC CLEAVAGE

DNA polymerase from Escherichia coli was cleaved by limited proteolytic action into two fragments of 76, 000 and 34, 000 molecular weight. The cleaved enzyme is still an active polymerase but has a reduced 5′→3′ nuclease activity. The fragments were separated by gel filtration. The isolated larger fragment retains the polymerizing activity and the 3′→5′ nuclease activity present in the native enzyme, but not the 5′→3′ nuclease. This specific proteolytic cleavage was catalyzed most effectively by an extract from Bacillus subtilis or by trypsin. © 1969.