Bacterial cells containing the ner gene of phage Mu inserted into pBR322 express a binding activity with specificity for the left-end EcoRI. C fragment of Mu DNA. Crude extracts containing either Mu repressor or ner protein have been used to localize binding sites on TaqI subfragments of the EcoRI. C fragment. There are at least 3 distinct binding sites for the Mu repressor and 1 binding site for the ner protein on the EcoRI. C fragment. The possible biological function of these binding sites is discussed.
