The isolation and characteristics of plasmids derived from the insertion of MupAp1 into pML2: Their behavior during transposition

Abstract

Three independent insertions of the phage Mu variant MupAp1 into the ColE1 derivative pML2 have been isolated. From one of these hybrid plasmids (pSU1), two mini-Mu plasmids have been generated. These have lost internal regions of the Mu genome but retain the ends of the prophage. In pSU17 all but one kilobase pair of the early region and most of the late region have been deleted whereas in pSU123 most of the early region is still present but the deletion covers nearly all the late region. Mu immunity, host killing, and transposition functions are located in the DNA present in pSU123 but absent from pSU17. Transposition of Mu and the mini-Mu from the hybrid plasmids to the sex factor R388 is usually associated with the formation of cointegrates between the two parental plasmids.