What is the mechanism of ParA-mediated DNA movement?

The stable maintenance of low-copy-number plasmids requires active partitioning, with the most common mechanism in prokaryotes involving the ATPase ParA. ParA proteins undergo intricate spatiotemporal relocations across the nucleoid, dynamics that function to position plasmids at equally spaced intervals. This spacing naturally guarantees equal partitioning of plasmids to each daughter cell. However, the fundamental mechanism linking ParA dynamics with regular plasmid positioning has proved difficult to dissect. In this issue of Molecular Microbiology, Vecchiarelli et al. report on a time-delay mechanism that allows a slow cycling between the nucleoid-bound and unbound forms of ParA. The authors also propose a mechanism for plasmid movement that does not rely on ParA polymerization.