AtFim1 is an actin filament crosslinking protein from Arabidopsis thaliana

David R. Kovar, Christopher J. Staiger, Eric A. Weaver, David W. McCurdy

Research output: Contribution to journalArticlepeer-review

108 Scopus citations


ATFIM1 is a widely expressed gene in Arabidopsis thaliana that encodes a putative actin filament-crosslinking protein, AtFim1, belonging to the fimbrin/plastin class of actin-binding proteins. In this report we have used bacterially expressed AtFim1 and actin isolated from Zea mays pollen to demonstrate that AtFim1 functions as an actin filament-crosslinking protein. AtFim1 binds pollen actin filaments (F-actin) in a calcium-independent manner, with an average dissociation constant (Kd) of 0.55 ± 0.21 μM and with a stoichiometry at saturation of 1:4 (mol AtFim1:mol actin monomer). AtFim1 also crosslinks pollen F-actin by a calcium-independent mechanism, in contrast to crosslinking of plant actin by human T-plastin, a known calcium-sensitive actin-crosslinking protein. When micro-injected at high concentration into living Tradescantia virginiana stamen hair cells, AtFim1 caused cessation of both cytoplasmic streaming and transvacuolar strand dynamics within 2-4 min. Using the 'nuclear displacement assay' as a measure of the integrity of the actin cytoskeleton in living stamen hair cells, we demonstrated that AtFim1 protects actin filaments in these cells from Z. mays profilin (ZmPRO5)-induced depolyrmerization, in a dose-dependent manner. The apparent ability of AtFim1 to protect actin filaments in vivo from profilin-mediated depolymerization was confirmed by in vitro sedimentation assays. Our results indicate that AtFim1 is s calcium-independent, actin filament-crosslinking protein that interacts with the actin cytoskeleton in living plant cells.

Original languageEnglish (US)
Pages (from-to)625-636
Number of pages12
JournalPlant Journal
Issue number5
StatePublished - 2000


  • Actin filament crosslinking
  • Arabidopsis
  • AtFim1
  • Cytoskeleton
  • Fimbrin/plastin
  • Micro-injection

ASJC Scopus subject areas

  • Genetics
  • Plant Science
  • Cell Biology


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