A point mutation converts Escherichia coli FtsZ septation GTPase to an ATPase

The cell division protein FtsZ, essential to initiate septum formation in Escherichia coli, is a GTPase. The thermosensitive ftsZ84 mutation, which impairs the ability of FtsZ to bind and hydrolyze GTP in vitro, maps to a short glycine-rich FtsZ segment. This region is conserved in eubacterial FtsZ homologs and is strikingly similar to the proposed GTP binding motif in the eukaryotic cytoskeletal protein tubulin. Here we show that in contrast to FtsZ, FtsZ84 protein has a Mg(2+)-dependent ATPase activity in vitro. This activity, unlike the wild-type GTPase, is specifically inhibited by sodium azide, a known antagonist of F-type ATPases and the bacterial SecA protein translocation ATPase (Oliver, D., Cabelli, R. J., Dolan, K. M., and Jarosik, G. P. (1990) Proc. Natl. Acad. Sci. U.S.A. 87, 8227-8231). Conversely, aluminum fluoride abolishes FtsZ GTPase activity but only partially affects FtsZ84 ATPase. Affinity-purified anti-FtsZ antibody blocks FtsZ84 ATPase activity, indicating that this enzymatic function is intrinsic to the mutant protein. This is, to our knowledge, the first example of a missense mutation that converts a GTPase to an ATPase.