Restriction digests of the clone give the following sizes (kb): EcoRI/PstI--5.4, 2.2; BamHI--4.2, 3.4; PstI--7.6; HindIII--5.7, 1.9. Temperature-resistant derivatives arise frequently. It is important to isolate a clone that is temperature-sensitive and kanamycin resistant before use. pLDR8 is compatible with, and provides Int function for, the vectors pLDR9 (ATCC 77358), pLDR10 (ATCC 77359) and pLDR11 (ATCC 77360). Expression of int in pLDR8 is regulated by lambda PR, by the temperature sensitive cI857 repressor. Replication of pLDR8 is also temperature sensitive. Therefore, at 30C replication of the plasmid is normal and int is not expressed. At 42C, int is expressed but pLDR8 is no longer replicated, resulting in loss of int after a few cell generations. The order of the major features in this plasmid is: EcoRI - pSC101 ori - neoR - PstI - cI857 - PR promoter - int. |
