Convergent evolution of MutS and topoisomerase II for clamping DNA crossovers and stacked Holliday junctions

This study shows that topoisomerase II and MutS proteins share a structural motif that has, in its dimeric form, a suitable geometry for clamping the two arms of either right-handed DNA crossovers or their isostructural stack ed Holliday junctions. This defines a new protein family selected by conver gent evolution for sensing DNA topology and binding recombination intermedi ates. This study also proposes that MutS binding on 2-fold right-handed cro ssover provides a mechanism for strand discrimination during DNA translocat ion.