Plasmid pKUN9, a versatile vector for the selective packaging of both DNA strands into single-stranded DNA-containing phage-like particles.

A versatile vector plasmid, pKUN9, has been constructed which, simply by infecting cells harboring this plasmid with either bacteriophage IKe or Ff (M13, fd, and fl), permits the selective packaging of both of its DNA strands into, single-stranded (ss) DNA-containing, phage-like particles. The plasmid, which is a derivative of plasmid pUC9 [Vieira and Messing, Gene 19 (1982) 269-276], contains in opposite orientations the replication origins and contiguous packaging signals of the distantly related filamentous phages IKe and Ff. As a result of the selective packaging, both strands of a DNA fragment cloned in pKUN9 can be obtained in a single-stranded form and can be sequenced by the dideoxy method using commercially available (+) and (-) sequencing primers. In addition, plasmid pKUN9 possesses all unique properties incorporated in the M13mp phages and the pUC plasmids.