title: FtsZ placement in nucleoid-free bacteria.
abstract: We describe the placement of the cytoplasmic FtsZ protein, an essential component of the division septum, in nucleoid-free Escherichia coli maxicells. The absence of the nucleoid is accompanied in maxicells by degradation of the SlmA protein. This protein, together with the nucleoid, prevents the placement of the septum in the regions occupied by the chromosome by a mechanism called nucleoid occlusion (NO). A second septum placement mechanism, the MinCDE system (Min) involving a pole-to-pole oscillation of three proteins, nonetheless remains active in maxicells. Both Min and NO act on the polymerization of FtsZ, preventing its assembly into an FtsZ-ring except at midcell. Our results show that even in the total absence of NO, Min oscillations can direct placement of FtsZ in maxicells. Deletion of the FtsZ carboxyl terminal domain (FtsZ*), a central hub that receives signals from a variety of proteins including MinC, FtsA and ZipA, produces a Min-insensitive form of FtsZ unable to interact with the membrane-anchoring FtsA and ZipA proteins. This protein produces a totally disorganized pattern of FtsZ localization inside the maxicell cytoplasm. In contrast, FtsZ*-VM, an artificially cytoplasmic membrane-anchored variant of FtsZ*, forms helical or repetitive ring structures distributed along the entire length of maxicells even in the absence of NO. These results show that membrane anchoring is needed to organize FtsZ into rings and underscore the role of the C-terminal hub of FtsZ for their correct placement.
authors.affiliation: Centro Nacional de Biotecnología - Consejo Superior de Investigaciones Científicas (CNB-CSIC), Madrid, Spain.
authors.forename: Manuel
authors.initials: M
authors.lastname: Pazos
authors.affiliation: Centro Nacional de Biotecnología - Consejo Superior de Investigaciones Científicas (CNB-CSIC), Madrid, Spain.
authors.forename: Mercedes
authors.initials: M
authors.lastname: Casanova
authors.affiliation: Centro Nacional de Biotecnología - Consejo Superior de Investigaciones Científicas (CNB-CSIC), Madrid, Spain.
authors.forename: Pilar
authors.initials: P
authors.lastname: Palacios
authors.affiliation: Department of Microbiology and Molecular Genetics, University of Texas Medical School at Houston, Houston, Texas, United States of America.
authors.forename: William
authors.initials: W
authors.lastname: Margolin
authors.affiliation: Centro Nacional de Biotecnología - Consejo Superior de Investigaciones Científicas (CNB-CSIC), Madrid, Spain.
authors.forename: Paolo
authors.initials: P
authors.lastname: Natale
authors.affiliation: Centro Nacional de Biotecnología - Consejo Superior de Investigaciones Científicas (CNB-CSIC), Madrid, Spain.
authors.forename: Miguel
authors.initials: M
authors.lastname: Vicente
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D002455:Cell Division; D003593:Cytoplasm / Q000378:metabolism; D003598:Cytoskeletal Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism; D054730:Protein Interaction Domains and Motifs; D021381:Protein Transport; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; D003598:Cytoskeletal Proteins; D029968:Escherichia coli Proteins; C071525:FtsZ protein, Bacteria; D011993:Recombinant Fusion Proteins; C502032:SlmA protein, E coli; D009569:Nitric Oxide