Dominant C-terminal deletions of FtsZ that affect its ability to localize in Caulobacter and its interaction with FtsA.

The cell division protein FtsZ is composed of three regions based on sequence similarity: a highly conserved N-terminal region of approximately 320 amino acids; a variable spacer region; and a conserved C-terminal region of eight amino acids. We show that FtsZ mutants missing different C-terminal fragments have dominant lethal effects because they block cell division in Caulobacter crescentus by two different mechanisms. Removal of the C-terminal conserved region, the linker, and 40 amino acids from the end of the N-terminal conserved region (FtsZdeltaC281) prevents the localization or the polymerization of FtsZ. Because two-hybrid analysis indicates that FtsZdeltaC281 does not interact with FtsZ, we hypothesize that FtsZdeltaC281 blocks cell division by competing with a factor required for FtsZ localization or that it titrates a factor required for the stability of the FtsZ ring. The removal of 24 amino acids from the C-terminus of FtsZ (FtsZdeltaC485) causes a punctate pattern of FtsZ localization and affects its interaction with FtsA. This suggests that the conserved C-terminal region of FtsZ is required for proper polymerization of FtsZ in Caulobacter and for its interaction with FtsA.