Protein interactions at the C‐terminus of essential cell division protein FtsZ modulate Z‐ring dynamics in Escherichia coli

Highly coordinated spatiotemporal regulation of the cell division pathway ensures the production of two identical daughter cells in Escherichia coli . Constriction and septation at midcell require the assembly of a ring‐like dynamic protein structure, called the Z‐ring, containing FtsZ, a structural homolog of tubulin that exhibits GTP‐dependent polymerization. FtsZ monomers contain an N‐terminal polymerization domain, an unstructured linker region, and a conserved C‐terminal core domain important for protein interactions. Residues near the FtsZ C‐terminus have been implicated in direct interactions with proteins that tether the Z‐ring to the membrane, including FtsA and ZipA, and proteins that promote disassembly of FtsZ polymers, including MinC and chaperone‐protease ClpXP. To test if protein interactions at the FtsZ C‐terminus are important for regulating the dynamic exchange of FtsZ subunits into and out of the Z‐ring, we monitored the fluorescence recovery of Z‐rings containing Gfp‐FtsZ in dividing cells after photobleaching. We demonstrate that multiple mutations near the FtsZ C‐terminus lead to the formation of Z‐rings that have significantly impaired dynamics in vivo. We also deleted several genes encoding proteins that promote the disassembly of FtsZ polymers in vitro, including MinC and ClpXP, and have observed that cells deleted for these genes contain Z‐rings that exchange subunits more slowly than wild type cells. These results show that proteins promoting disassembly of FtsZ polymers have a positive effect on enhancing the exchange of subunits within the FtsZ‐ring. Moreover, these results also suggest that proteins modulate Z‐ring dynamics through direct interactions with the FtsZ C‐terminus.