Abstract
ABSTRACTBacterial cell division in many organisms involves a constricting cytokinetic ring that is orchestrated by the tubulin-like protein FtsZ. FtsZ forms dynamic filaments close to the membrane at the site of division that have recently been shown to treadmill around the division ring, guiding septal wall synthesis. Here, using X-ray crystallography of Staphylococcus aureus FtsZ (SaFtsZ), we reveal how an FtsZ can adopt two functionally distinct conformations, open and closed. The open form is found in SaFtsZ filaments formed in crystals and also in soluble filaments of Escherichia coli FtsZ as deduced by electron cryomicroscopy. The closed form is found within several crystal forms of two nonpolymerizing SaFtsZ mutants and corresponds to many previous FtsZ structures from other organisms. We argue that FtsZ’s conformational switch is polymerization-associated, driven by the formation of the longitudinal intersubunit interfaces along the filament. We show that such a switch provides explanations for both how treadmilling may occur within a single-stranded filament and why filament assembly is cooperative.
Highlights
Bacterial cell division in many organisms involves a constricting cytokinetic ring that is orchestrated by the tubulin-like protein FtsZ
We demonstrate that FtsZ proteins do undergo a conformational switch, that this switch is associated with polymerization and not the nucleotide hydrolysis state, and that switching provides a possible mechanism both for cooperative assembly and for single-protofilament treadmilling, which has been proposed to be the key dynamic filament behavior used to organize cell wall remodeling
We set out to generate an Staphylococcus aureus FtsZ (SaFtsZ) structure with the molecule in the closed form, which we suspected to be found in monomeric FtsZ proteins, by introducing single point mutations inhibiting polymerization in regions of the structure thought to be far away from regions involved in nucleotide binding or conformation switching
Summary
Bacterial cell division in many organisms involves a constricting cytokinetic ring that is orchestrated by the tubulin-like protein FtsZ. FtsZ forms dynamic filaments close to the membrane at the site of division that have recently been shown to treadmill around the division ring, guiding septal wall synthesis. We argue that FtsZ’s conformational switch is polymerization-associated, driven by the formation of the longitudinal intersubunit interfaces along the filament We show that such a switch provides explanations for both how treadmilling may occur within a singlestranded filament and why filament assembly is cooperative. After the localization of FtsZ, a large number of other proteins are recruited to the division site These proteins carry out remodeling and synthesis of cell wall during the division process. The precise molecular architecture of the Z ring remains unclear, it is probably composed of dynamic overlapping filaments along the circumference of the
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