CLPX AND CLPP ARE ESSENTIAL FOR THE EFFICIENT ACQUISITION OF GENES SPECIFYING TYPE IA AND IB RESTRICTION SYSTEMS

Efficient acquisition of genes that encode a restriction and modificat ion (R-NI) system with specificities different from any already presen t in the recipient bacterium requires the sequential production of the new modification enzyme followed by the restriction activity in order that the chromosome of the recipient bacterium is protected against a ttack by the restriction endonuclease. We show that ClpX and ClpP, the components of ClpXP protease, are necessary for the efficient transmi ssion of the genes encoding EcoKI and EcoAl, representatives of two fa milies of type I R-M systems, thus implicating ClpXP in the modulation of restriction activity. Loss of ClpX imposed a bigger barrier than l oss of ClpP, consistent with a dual role for ClpX, possibly as a chape rone and as a component of the ClpXP protease. Transmission of genes s pecifying EcoKI was more dependent on ClpX and ClpP than transmission of the genes for EcoAl. Sensitivity to absence of the protease was als o influenced by the mode of gene transfer; conjugative transfer and tr ansformation were more dependent on ClpXP than transduction. In the ab sence of either ClpX or ClpP transfer of the EcoKI genes by P1-mediate d transduction was impaired, transfer of the EcoAl genes was not.