Regulation of DNA replication initiation by ParA is independent of location in .

Replication and segregation of the genetic information is necessary for a cell to proliferate. In , the Par system (ParA/Soj, ParB/Spo0J and ) is required for segregation of the chromosome origin () region and for proper control of DNA replication initiation. ParB binds sites clustered near the origin of replication and assembles into sliding clamps that interact with ParA to drive origin segregation through a diffusion-ratchet mechanism. As part of this dynamic process, ParB stimulates ParA ATPase activity to trigger its switch from an ATP-bound dimer to an ADP-bound monomer. In addition to its conserved role in DNA segregation, ParA is also a regulator of the master DNA replication initiation protein DnaA. We hypothesized that in the location of the Par system proximal to would be necessary for ParA to properly regulate DnaA. To test this model, we constructed a range of genetically modified strains with altered numbers and locations of sites, many of which perturbed chromosome origin segregation as expected. Contrary to our hypothesis, the results show that regulation of DNA replication initiation by ParA is maintained when a site is separated from . Because a single site is sufficient for proper control of ParA, the results are consistent with a model where ParA is efficiently regulated by ParB sliding clamps following loading at .