Recognition sequences of repressor and polymerase in the operators of bacteriophage lambda

Nucleotide sequences in two wild-type and six mutant operators in the DNA of phage lambda are compared. Strikingly similar 17 base pair units are found which we identify as the repressor binding sites. Each operator contains multiple repressor binding sites separated by A-T rich spacers. Elements of 2 fold rotational symmetry are present in each of the sites. Superimposed on each operator is an E. coli RNA polymerase recognition site (promoter). Similarities in the sequences of the two lambda promoters, a lac promoter, and an E. coli RNA polymerase recognition site in SV40 DNA are noted.