J.L. Keck and J.M. Berger are in the Department of
Molecular and Cell Biology, University of California at Berkeley,
229 Stanley Hall-#3206, Berkeley, California
94720, USA.
DNA topoisomerases are proteins that regulate DNA topology in cells through
selective cycles of DNA cleavage, manipulation, and religation. Two papers
describe an ensemble of different protein conformations and nucleotide−protein
complexes of Escherichia coli topoisomerase. These results lead to
new insights about how this enzyme recognizes DNA and catalyzes supercoil
relaxation.
