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.
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
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
J. Cell Biol.
Date: Aug. 10, 1998
PubMed ID: 9700161
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