Conformational transitions during FtsK translocase activation of individual XerCD-dif recombination complexes

Abstract

Threesingle-moleculetechniqueshavebeenusedsimultaneouslyand in tandem to track the formation in vitro of single XerCD-dif recombination complexes.We observed the arrival of the FtsK translocase at individual preformed synaptic complexes and demonstrated the conformational change that occurs during their activation. We then followed the reaction intermediate transitions as Holliday junctions formedthroughcatalysisbyXerD, isomerized, andwere convertedby XerC to reaction products, which then dissociated. These observations, along with the calculated intermediate lifetimes, inform the reactionmechanism,which plays a key role in chromosome unlinking in most bacteria with circular chromosomes.