... toxin–antitoxin system of plasmid R1 – basic contributions, biotechnological applications and relationships with closely-related toxin–antitoxin systems Elizabeth Diago-Navarro1, Ana M. Hernandez-Arriaga1, ... stability potential of the parD system was compared with that of the ccd system of plasmid F, as well as that of the parDETA system of plasmid RK2 ⁄ RP4 and hok-sok of plas-mid R1. In this analysis, ... parD of R1 and the ccd system of F whosetoxins belong to the same superfamily. We often referto the pem system, which is identical to parD of R1 and was identified in plasmid R10 0 [20], and to...