EzrA prevents aberrant cell division by modulating assembly of the cytoskeletal protein FtsZ

Summary In response to a cell cycle signal, the cytoskeletal protein FtsZ assembles into a ring structure that establishes the location of the division site and serves as a framework for assembly of the division machinery. A battery of factors control FtsZ assem- bly to ensure that the ring forms in the correct posi- tion and at the precise time. EzrA, a negative regulator of FtsZ ring formation, is important for ensuring that the ring forms only once per cell cycle and that cytokinesis is restricted to mid-cell. EzrA is distributed throughout the plasma membrane and localizes to the ring in an FtsZ-dependent manner, suggesting that it interacts directly with FtsZ to mod- ulate assembly. We have performed a series of exper- iments examining the interaction between EzrA and FtsZ. As little as twofold overexpression of EzrA blocks FtsZ ring formation in a sensitized genetic background, consistent with its predicted function. A purified EzrA fusion protein interacts directly with FtsZ to block assembly in vitro . Although EzrA is able to inhibit FtsZ assembly, it is unable to disas- semble preformed polymers. These data support a model in which EzrA interacts directly with FtsZ at the plasma membrane to prevent polymerization and aberrant FtsZ ring formation.