Large ring polymers align FtsZ polymers for normal septum formation

Authors

  • Muhammet E Gündoğdu,

    1. Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, Newcastle University, Newcastle, UK
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    • These authors contributed equally to this work
  • Yoshikazu Kawai,

    1. Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, Newcastle University, Newcastle, UK
    2. Nara Institute of Science and Technology, Graduate School of Information Science Functional Genomics, Ikoma, Japan
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    • These authors contributed equally to this work
  • Nada Pavlendova,

    1. Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, Newcastle University, Newcastle, UK
    2. Institute of Molecular Biology, Slovak Academy of Sciences, Bratislava, Slovak Republic
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    • These authors contributed equally to this work
  • Naotake Ogasawara,

    1. Nara Institute of Science and Technology, Graduate School of Information Science Functional Genomics, Ikoma, Japan
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  • Jeff Errington,

    1. Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, Newcastle University, Newcastle, UK
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  • Dirk-Jan Scheffers,

    1. Bacterial Membrane Proteomics Laboratory, Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Oeiras, Portugal
    2. Department of Molecular Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, NN Haren, The Netherlands
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  • Leendert W Hamoen

    Corresponding author
    1. Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, Newcastle University, Newcastle, UK
    • Corresponding author. Institute for Cell and Molecular Biosciences, Centre for Bacterial Cell Biology, Newcastle University, Richardson Road, Framlington Place, Newcastle NE2 4AX, UK. Tel.: +44 191 208 3240; Fax: +44 191 208 3205;E-mail: l.hamoen@ncl.ac.uk

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Abstract

Cytokinesis in bacteria is initiated by polymerization of the tubulin homologue FtsZ into a circular structure at midcell, the Z-ring. This structure functions as a scaffold for all other cell division proteins. Several proteins support assembly of the Z-ring, and one such protein, SepF, is required for normal cell division in Gram-positive bacteria and cyanobacteria. Mutation of sepF results in deformed division septa. It is unclear how SepF contributes to the synthesis of normal septa. We have studied SepF by electron microscopy (EM) and found that the protein assembles into very large (∼50 nm diameter) rings. These rings were able to bundle FtsZ protofilaments into strikingly long and regular tubular structures reminiscent of eukaryotic microtubules. SepF mutants that disturb interaction with FtsZ or that impair ring formation are no longer able to align FtsZ filaments in vitro, and fail to support normal cell division in vivo. We propose that SepF rings are required for the regular arrangement of FtsZ filaments. Absence of this ordered state could explain the grossly distorted septal morphologies seen in sepF mutants.

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