Domain analysis of cortexillin I: Actin-bundling, PIP2-binding and the rescue of cytokinesis

Alexander Stock, Michel O. Steinmetz, Paul A. Janmey, Ueli Aebi, Günther Gerisch, Richard A. Kammerer, Igor Weber, Jan Faix

    Research output: Contribution to journalArticlepeer-review


    Cortexillins are actin-bundling proteins that form a parallel two-stranded coiled-coil rod. Actin-binding domains of the α-actinin/spectrin type are located N-terminal to the rod and unique sequence elements are found in the C-terminal region. Domain analysis in vitro revealed that the N-terminal domains are not responsible for the strong actin-filament bundling activity of cortexillin I. The strongest activity resides in the C-terminal region. Phosphatidylinositol 4,5-bisphosphate (PIP2) suppresses this bundling activity by binding to a C-terminal nonapeptide sequence. These data define a new PIP2-regulated actin-bundling site. In vivo the PIP2-binding motif enhances localization of a C-terminal cortexillin I fragment to the cell cortex and improves the rescue of cytokinesis. This motif is not required, however, for translocation to the cleavage furrow. A model is presented proposing that cortexillin translocation is based on a mitotic cycle of polar actin polymerization and midzone depolymerization.
    Original languageEnglish
    Pages (from-to)5274-5284
    Number of pages10
    JournalEMBO Journal
    Issue number19
    Publication statusPublished - 1 Oct 1999


    • Actin-based membrane flow
    • Cortexillin
    • Green fluorescent protein
    • Mitotic cleavage
    • Phosphatidylinositol 4,5-bisphosphate


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