Helical tubes of FtsZ from Methanococcus jannaschii

Bacterial cell division depends on the formation of a cytokinetic ring stru cture, the Z-ring. The bacterial tubulin homologue FtsZ is required for Z-r ing formation. FtsZ assembles into various polymeric forms in vitro, indica ting a structural role in the septum of bacteria. We have used recombinant FtsZ1 protein from M. jannaschii to produce helical tubes a nd sheets with high yield using the GTP analogue GM PC PP [guanylyl (alpha,beta)-methylene -diphosphate]. The sheets appear identical to the previously reported Ca++- induced sheets of FtsZ from M. jannaschii that were shown to consist of 'th ick'-filaments in which two protofilaments run in parallel. Tubes assembled either in Ca++ or in GMPCPP contain filaments whose dimensions indicate th at they could be equivalent to the 'thick'-filaments in sheets. Some tubes are hollow but others are filled by additional protein density. Helical Fts Z tubes differ from eukaryotic microtubules in that the filaments curve aro und the filament axis with a pitch of similar to 430 Angstrom for Ca++-indu ced tubes or 590 - 620 Angstrom for GMPCPP. However, their assembly in vitr o as well-ordered polymers over distances comparable to the inner circumfer ence of a bacterium may indicate a role in vivo. Their size and stability m ake them suitable for use in motility assays.