Specific binding affinity for DNA of the L phage (Salmonella typhimurium) in extracts of Escherichia coli.

The repressor gene cII of the L phage was cloned into plasmid pHC624 and expressed in E. coli. Two separate binding affinities for L phage DNA were identified during fractionation of protein extract of that strain. The activity that salts out in low concentration of ammonium sulphate belonged to the repressor, the activity that salts out in high concentrations of (NH4)2SO4 was proved to be of E. coli origin. Binding sites for the two proteins are located on different fragments of the L phage genome.