The Escherichia coli replication initiator DnaA is titrated on the chromosome.

DNA replication initiation is orchestrated in bacteria by the replication initiator DnaA. Two models for regulation of DnaA activity in Escherichia coli have been proposed: the switch between an active and inactive form, and the titration of DnaA on the chromosome. Although proposed decades ago, experimental evidence of a titration-based control mechanism is still lacking.