Structural elements of the E. coli origin. The E. coli origin, oriC, contains four 9-mer DNA sites (blue arrows) that bind the DnaA initiator protein. A possible fifth site deviates from the consensus sequence (not shown). The arrowheads indicate the relative direction of the 9-mers. The three 13-mer direct repeats are A=T-rich and are the locus of initial DNA strand separation (orange arrows). The oriC sequence also contains 11 GATC sites that are methylated by the Dam methylase (methylation sites indicated by arrowheads).