Elements in the co-evolution of relaxases and their origins of transfer

The central elements in the conjugative mobilization of most plasmids are the relaxase and its cognate origin of transfer (oriT). The relaxase of the plasmid R1162, together with its oriT, belong to a large and widely distributed family of related relaxase/oriT pairs. Several of the properties of these elements are considered for R1162 and for other members of this family with a view to understanding how systems for mobilization might have evolved.