Mechanism of Regulation of Prokaryotic Tubulin-like GTPase FtsZ by Membrane Protein EzrA

At initiation of cell division, FtsZ, a tubulin-like GTPase, assembles into a so-called Z-ring structure at the site of division. The formation of Z ring is negatively regulated by EzrA, which ensures only one ring at the midcell per cell cycle. The mechanism leading to the negative regulation of Z-ring formation by EzrA has been analyzed. Our data reveal that the interaction between EzrA and FtsZ not only reduces the GTP-binding ability of FtsZ but also accelerates the rate of GTP hydrolysis, both of which are unfavorable for the polymerization of FtsZ. Moreover, the acceleration in rate of GTP hydrolysis by EzrA is attributed to stabilization of the transition state for GTP hydrolysis and reduction in the affinity of GDP for FtsZ. Clearly, EzrA is able to modify the GTP hydrolysis cycle of FtsZ. On the basis of these results, a model for how EzrA acts to negatively regulate Z-ring formation is proposed.