Completed DNA sequences and organization of repressor-binding sites in the operators of phage lambda

We complete the determination of the DNA sequences of the bacteriophage λ operators by presenting two new sequences, one about 38 base-pairs long from the left operator (O_L), and another about 42 base-pairs long from the right operator (O_R). These were determined by direct DNA sequencing. The results of experiments in which each operator was digested with nuclease in the presence of highly purified λ repressor are also described. From the new sequence information, as well as other considerations, including the results of the nuclease digestion experiments, we conclude that each operator is smaller than previously reported and consists of three repressor-binding sites. The sequence near O_R includes part of the repressor structural gene, cI.