Construction and properties of plasmid pKC30, a pBR322 derivative containing the pL-N region of phage lambda.

The phage lambda N gene, contained on a HindIII-BamHI lambda DNA fragment (lambda coordinates 38 695-34 500), was inserted into plasmid pBR322 and cloned in Escherichia coli containing a defective lambda prophage. The plasmid is called pKC30. lambda N-mediated pL transcription interfered with plasmid pKC30 maintenance. Plasmid pKC30 was stabilized (i) by repression of pL, (ii) by a nutL mutation, or (iii) by cloning an "N-unresponsive terminator" sequence downstream from N gene.