Bacterial cell divisionprote in FtsZ is a specific substrate for the AAA family protease FtsH

The role of AAA (ATPases Associated to a variety of cellular Activities) family protease FtsH in bacterial cell division is not known, although mutations in ftsH were found to inhibit cell growth and division (1, 6, 13).\ud Overexpression of heterologous FtsH in Escherichia coli results in the formation of multinucleate ®lamentous cells due to the abolition of cell septation (8). Further, independent studies on FtsH (15) and FtsZ (2), which is the key regulator of bacterial cell division, have shown that FtsH protease and FtsZ protein are localized to the mid-cell site during septation. FtsZ protein is the prokaryotic homologue of tubulin (5, 10, 12), possessing GTP-dependent polymerization activity (4, 11). igni®cantly, the AAA family ATPase member katanin disassembles tubulin\ud polymers in an ATP-dependent manner (7). Based on these observations, we reasoned that an interaction similar to that between katanin and tubulin might hold true for FtsH and FtsZ in prokaryotes as well. To verify this hypothesis,\ud we examined whether the FtsH protease of Escherichia coli $(FtsH_{Ec})$ could degrade FtsZ of E. coli $(FtsH_{Ec})$ in vitro