Structure and function of the repressor of bacteriophage lambda. III. Molecular cloning of the high-affinity mutant cI gene of lambda and studies of the properties of the clones.

The high-affinity mutant cI gene of lambda cIha (Nag et al. 1984) was cloned in the multicopy plasmid pBR322. In the resulting plasmid, pMD 102, a lacUV5 promoter was inserted giving the lacUV5-cIha fusion plasmid pMD 205. Bacteria carrying pMD 102 and pMD 205 contain 2.5 and 15 times, respectively, the level of repressor in a monolysogen of lambda cIha. Results of the study of certain properties of the bacteria carrying these plasmids suggest that the ha repressor also has a higher affinity for the virulent mutant operators as well as the prm promoter of lambda.