Purification of the Bacteriophage T4 Type II DNA Topoisomerase

Bacteriophage T4 encodes a type II topoisomerase with properties more similar to those of the eukaryotic class of enzymes than to those of the bacterial DNA gyrase (1 ,2 ). Indeed, the discovery of the T4 topoisomerase provided the first example of an ATP-dependent relaxing enzyme (3 ,4 ), and an understanding of the properties of the T4 enzyme rapidly led to the discovery of similar enzymes from eukaryotic cells (5 -7 ).