Model of activation of <i>V. cholerae</i> chromosome replication by Par proteins using multiple mechanisms.

<p>The upper diagram shows ParB2 interaction with the chrII origin by two mechanisms: spreading from the centromeric site <i>parS2-B</i> into a neighboring 39-mer and direct binding to another 39-mer. We suggest that these interactions promote chrII replication by out-competing initiator binding to the 39-mers. The lower diagram shows activation of chrI replication by ParA1 interaction with DnaA, which is negatively controlled by ParB1. For both chromosomes, the Par proteins target the most powerful regulators, by DNA-protein interactions for chrII and by protein-protein interactions for chrI.