Crystal structure of the bacterial cell-division protein FtsZ

Abstract

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 p21^ras 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.