Novel coiled-coil cell division factor ZapB stimulates Z ring assembly and cell division

Authors

  • Gitte Ebersbach,

    1. Department of Biochemistry and Molecular Biology, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark.
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    • Present address: Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, CT 06520, USA.

  • Elisa Galli,

    1. Institute for Cell and Molecular Biosciences, Medical School, Newcastle University, Newcastle NE2 4HH, UK.
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  • Jakob Møller-Jensen,

    1. Department of Biochemistry and Molecular Biology, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark.
    2. MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, UK.
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  • Jan Löwe,

    1. MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, UK.
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  • Kenn Gerdes

    1. Institute for Cell and Molecular Biosciences, Medical School, Newcastle University, Newcastle NE2 4HH, UK.
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*E-mail kenn.gerdes@ncl.ac.uk; Tel. +44(0) 191 222 5318; Fax +44(0) 191 222 7424.

Summary

Formation of the Z ring is the first known event in bacterial cell division. However, it is not yet known how the assembly and contraction of the Z ring are regulated. Here, we identify a novel cell division factor ZapB in Escherichia coli that simultaneously stimulates Z ring assembly and cell division. Deletion of zapB resulted in delayed cell division and the formation of ectopic Z rings and spirals, whereas overexpression of ZapB resulted in nucleoid condensation and aberrant cell divisions. Localization of ZapB to the divisome depended on FtsZ but not FtsA, ZipA or FtsI, and ZapB interacted with FtsZ in a bacterial two-hybrid analysis. The simultaneous inactivation of FtsA and ZipA prevented Z ring assembly and ZapB localization. Time lapse microscopy showed that ZapB–GFP is present at mid-cell in a pattern very similar to that of FtsZ. Cells carrying a zapB deletion and the ftsZ84ts allele exhibited a synthetic sick phenotype and aberrant cell divisions. The crystal structure showed that ZapB exists as a dimer that is 100% coiled-coil. In vitro, ZapB self-assembled into long filaments and bundles. These results raise the possibility that ZapB stimulates Z ring formation directly via its capacity to self-assemble into larger structures.

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