Homology between Escherichia coli plasmids ColE1 and p15A

The location and extent of the homology between plasmids ColE1 and p15A were determined by analysis of heteroduplexes formed between them as well as with a related plasmid, pBR322, and by hybridization of radioactive deoxyribonucleic acids to restriction fragments of p15A and ColE1. The homology between the plasmids contained the entire region of ColE1 required for its replication as well as an additional 400 base pairs downstream from the origin of replication. This region on p15A, which was 980 +/- 43 base pairs, started at 0.1 of the molecular length from one end formed by cleavage with the restriction endonuclease BglI and extended to 0.54 of the molecular length from the same end. Restriction cleavage maps for the enzymes BglI, HpaI, HaeII, HaeIII, and HincII are also presented.