title: Polymorphism of FtsZ filaments on lipid surfaces: role of monomer orientation.
abstract: FtsZ is a bacterial cytoskeletal protein involved in cell division. It forms a ringlike structure that attaches to the membrane to complete bacterial division. It binds and hydrolyzes GTP, assembling into polymers in a GTP-dependent manner. To test how the orientation of the monomers affects the curvature of the filaments on a surface, we performed site-directed mutagenesis on the E. coli FtsZ protein to insert cysteine residues at lateral locations to orient FtsZ on planar lipid bilayers. The E93C and S255C mutants were overproduced, purified, and found to be functionally active in solution, as well as being capable of sustaining cell division in vivo in complementation assays. Atomic force microscopy was used to observe the shape of the filament fibers formed on the surface. The FtsZ mutants were covalently linked to the lipids and could be polymerized on the bilayer surface in the presence of GTP. Unexpectedly, both mutants assembled into straight structures. E93C formed a well-defined lattice with monomers interacting at 60° and 120° angles, whereas S255C formed a more open array of straight thicker filament aggregates. These results indicate that filament curvature and bending are not fixed and that they can be modulated by the orientation of the monomers with respect to the membrane surface. As filament curvature has been associated with the force generation mechanism, these results point to a possible role of filament membrane attachment in lateral association and curvature, elements currently identified as relevant for force generation.
authors.affiliation: Instituto de Catálisis y Petroleoquímica, CSIC, Marie Curie, 2, Cantoblanco, 28049 Madrid, Spain.
authors.forename: Mario
authors.initials: M
authors.lastname: Encinar
authors.forename: Andrew V
authors.initials: AV
authors.lastname: Kralicek
authors.forename: Ariadna
authors.initials: A
authors.lastname: Martos
authors.forename: Marcin
authors.initials: M
authors.lastname: Krupka
authors.forename: Sandra
authors.initials: S
authors.lastname: Cid
authors.forename: Alvaro
authors.initials: A
authors.lastname: Alonso
authors.forename: Ana I
authors.initials: AI
authors.lastname: Rico
authors.forename: Mercedes
authors.initials: M
authors.lastname: Jiménez
authors.forename: Marisela
authors.initials: M
authors.lastname: Vélez
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics; D003598:Cytoskeletal Proteins / Q000737:chemistry* / Q000235:genetics; D006160:Guanosine Triphosphate / Q000494:pharmacology; D008051:Lipid Bilayers / Q000737:chemistry*; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D055503:Protein Multimerization; D020836:Protein Structure, Quaternary / Q000187:drug effects; D013499:Surface Properties
chemical_list: D001426:Bacterial Proteins; D003598:Cytoskeletal Proteins; C071525:FtsZ protein, Bacteria; D008051:Lipid Bilayers; D006160:Guanosine Triphosphate