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Regulation of the cortical actin cytoskeleton in budding yeast by twinfilin, a ubiquitous actin monomer-sequestering protein.

Here we describe the identification of a novel 37-kD actin monomer binding protein in budding yeast. This protein, which we named twinfilin, is composed of two cofilin-like regions. In our sequence database searches we also identified human, mouse, and Caenorhabditis elegans homologues of yeast twinfilin, suggesting that twinfilins form an evolutionarily conserved family of actin-binding proteins. Purified recombinant twinfilin prevents actin filament assembly by forming a 1:1 complex with actin monomers, and inhibits the nucleotide exchange reaction of actin monomers. Despite the sequence homology with the actin filament depolymerizing cofilin/actin-depolymerizing factor (ADF) proteins, our data suggests that twinfilin does not induce actin filament depolymerization. In yeast cells, a green fluorescent protein (GFP)-twinfilin fusion protein localizes primarily to cytoplasm, but also to cortical actin patches. Overexpression of the twinfilin gene (TWF1) results in depolarization of the cortical actin patches. A twf1 null mutation appears to result in increased assembly of cortical actin structures and is synthetically lethal with the yeast cofilin mutant cof1-22, shown previously to cause pronounced reduction in turnover of cortical actin filaments. Taken together, these results demonstrate that twinfilin is a novel, highly conserved actin monomer-sequestering protein involved in regulation of the cortical actin cytoskeleton.

Pubmed ID: 9700161


  • Goode BL
  • Drubin DG
  • Lappalainen P


The Journal of cell biology

Publication Data

August 10, 1998

Associated Grants

  • Agency: NIGMS NIH HHS, Id: GM-17715
  • Agency: NIGMS NIH HHS, Id: GM-42759

Mesh Terms

  • Actin Depolymerizing Factors
  • Actins
  • Amino Acid Sequence
  • Binding, Competitive
  • Cytoplasm
  • Cytoskeleton
  • Fungal Proteins
  • Gene Deletion
  • Green Fluorescent Proteins
  • Humans
  • Luminescent Proteins
  • Microfilament Proteins
  • Molecular Sequence Data
  • Protein-Tyrosine Kinases
  • Recombinant Fusion Proteins
  • Saccharomyces cerevisiae
  • Saccharomyces cerevisiae Proteins
  • Sequence Homology, Amino Acid