Nucleotide sequence of the origin of replication of the Escherichia coli K-12 chromosome.

Abstract
The origin of replication, oriC, of the E. coli chromosome was mapped within a DNA segment of 422 base-pairs. The nucleotide sequence of this segment was determined. The source of DNA for the sequence analysis was a minichromosome constructed in vivo, consisting exclusively of chromosomal DNA and a minichromosome constructed by cloning in vitro. The nucleotide sequence of the replication origin is characterized by a high degree of repetitiveness due to both inverted and direct repeats. Sequence homologies were found between portions of the replication origins of E. coli and phages .lambda. and G4. This suggests similarities in some steps in the initiation of replication of the different replicons.