Enzymology

Type II topoisomerases alter the topological state of DNA in a reaction that involves at least seven discrete steps. The ability to analyze specific steps of this catalytic cycle has contributed greatly to our understanding of enzyme function and the interaction of type II topoisomerases with anticancer and antibacterial drugs.

We utilize several techniques for assessing enzyme activity, including assays that specifically monitor catalytic activity, DNA cleavage, DNA re-ligation, and the persistence of enzyme-DNA cleavage complexes. We have also used rapid-quench and single-molecule systems to observe reactions in real time. We are also interested in determining how DNA geometry influences the activities of human and bacterial topoisomerases during DNA cleavage and strand passage reactions.

CURRENT PROJECTS ON ENZYME MECHANISM:

• Determining how type II topoisomerases recognize supercoil handedness during DNA cleavage, catenation and decatenation.
• Determining how the sites of DNA cleavage affect type II topoisomerase activity.
• Understanding how gyrase utilizes a unique mechanism of DNA wrapping to achieve different topological outcomes.
• Determining how different bacterial species use different type II topoisomerases to regulate DNA topology.