Crystal structure of the bacterial cell-division protein FtsZ

Bacterial cell division ends with septation, the constriction of the cell wall and cell membranes that leads to the formation of two daughter cells1,2. During septation, FtsZ, a protein of relative molecular mass 40,000 which is ubiquitous in eubacteria and is also found in archaea and chloroplasts3, localizes early at the division site to form a ring-shaped septum. This septum is required for the mechanochemical process of membrane constriction4. FtsZ is a GTPase5,6 with weak sequence homology to tubulins7. The nature of FtsZ polymers in vivo is unknown, but FtsZ can form tubules, sheets and minirings in vitro8,9. Here we report the crystal structure at 2.8 Å resolution of recombinant FtsZ from the hyperthermophilic methanogen Methanococcus jannaschii. FtsZ has two domains, one of which is a GTPase domain with a fold related to one found in the proteins p21ras and elongation factor EF-Tu. The carboxy-terminal domain, whose function is unknown, is a four-stranded β-sheet tilted by 90° against the β-sheet of the GTPase domain. The two domains are arranged around a central helix. GDP binding is different from that typically found in GTPases and involves four phosphate-binding loops and a sugar-binding loop in the first domain, with guanine being recognized by residues in the central connecting helix. The three-dimensional structure of FtsZ is similar to the structure of α- and β-tubulin10.