Exploration of topoisomerase IA gate dynamics reveals an additional widened state

Abstract

E. coli topoisomerase I, a type IA topoisomerase, is believed to be the main enzyme responsible forrelaxing negative supercoils in-vivo via a strand passage mechanism. Additionally, in-vitro studies haveestablished that the enzyme in also able to (de)catenate two double stranded DNA molecules via thesame mechanism, provided that one of them contains a nick. Despite the fact that all evidence pointedtowards the existence of a protein-mediated gate as a transition state, the actual gate opening eventwas only recently directly observed, allowing access to the study of the gate dynamics.