Replication cycle-coordinated change of the adenine nucleotide-bound formsof DnaA protein in Escherichia coli

The ATP-bound but not the ADP-bound form of DnaA protein is active for repl ication initiation at the Escherichia coli chromosomal origin. The hydrolys is of ATP bound to DnaA is accelerated by the sliding clamp of DNA polymera se III loaded on DNA, Using a culture of randomly dividing cells, we now ha ve evidence that the cellular level of ATP-DnaA is repressed to only simila r to 20% of the total DnaA molecules, in a manner depending on DNA replicat ion. In a synchronized culture, the ATP-DnaA level showed oscillation that has a temporal increase around the time of initiation, and decreases rapidl y after initiation. Production of ATP-DnaA depended on concomitant protein synthesis, but not on SOS response, Dam or SeqA. Regeneration of ATP-DnaA f rom ADP-DnaA was also observed. These results indicate that the nucleotide form shifts of DnaA are tightly linked with an epistatic cell cycle event a nd with the chromosomal replication system.