GTP-dependent polymerization of Escherichia coli FtsZ protein to form tubules.

The FtsZ protein is a GTPase that is essential for cell division in Escherichia coli. During cytokinesis, FtsZ localizes to a ring at the leading edge of septum synthesis. We report the GTP-dependent polymerization of purified FtsZ measured by sedimentation and light scattering. Electron microscopy of polymerized FtsZ revealed structures including tubules 14-20 nm in diameter with longitudinal arrays of protofilaments. FtsZ depolymerized upon removal of GTP and repolymerized after subsequent GTP addition. Mutant FtsZ84 protein polymerized inefficiently, suggesting that polymerization is important for the cellular role of FtsZ in division. The possibility that tubules of FtsZ protein form a cytoskeleton involved in septum synthesis is consistent with our data.