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 s equence similarity: a highly conserved N-terminal region of approximat e to 320 amino acids; a variable spacer region; and a conserved C-term inal region of eight amino acids. We show that FtsZ mutants missing di fferent C-terminal fragments have dominant lethal effects because they block cell division in Caulobacter crescentus by two different mechan isms. Removal of the C-terminal conserved region, the linker, and 40 a mino acids from the end of the N-terminal conserved region (FtsZ Delta C281) prevents the localization or the polymerization of FtsZ. Becaus e two-hybrid analysis indicates that FtsZ Delta C281 does not interact with FtsZ, we hypothesize that FtsZ Delta C281 blocks cell division b y competing with a factor required for FtsZ localization or that it ti trates a factor required for the stability of the FtsZ ring. The remov al of 24 amino acids from the C-terminus of FtsZ (FtsZ Delta C485) cau ses a punctate pattern of FtsZ localization and affects its interactio n with FtsA. This suggests that the conserved C-terminal region of Fts Z is required for proper polymerization of FtsZ in Caulobacter and for its interaction with FtsA.