A consensus sequence of three DNA replication terminus sites on the E. coli chromosome is highly homologous to the terR sites of the R6K plasmid

Abstract

Using the “Ter assay” we developed, three separate replication terminus ( terC1, terC2, and terC3) sites on the E. coli chromosome were identified. The locations are at 28.3, 35.6, and 33.9 min on the linkage map, respectively. The terC1 site can block the counterclockwise replication fork only, while the terC2 and terC3 sites inhibit the clockwise fork traveling on the chromosome. DNA sequences of the terC sites required for termination of DNA replication are highly homologous to those of terminus ( terR) sites of the R6K plasmid, and the 21 bp consensus DNA sequence of terC is 5′-(A or T) TTAGTTACAACAT (A or C) CT (A or T) (A or T) (A or T) T-3′. In addition, all Ter active pUC- terC plasmids had a low copy number and were unstable in the host cells.