title: The unconventional myosin, Myo2p, is a calmodulin target at sites of cell growth in Saccharomyces cerevisiae.
abstract: Myo2p is an unconventional myosin required for polarized growth in Saccharomyces cerevisiae. Four lines of evidence suggest that (a) Myo2p is a target of calmodulin at sites of cell growth, and (b) the interaction between Myo2p and calmodulin is Ca2+ independent. First, as assessed by indirect immunofluorescence, the distributions of Myo2p and calmodulin are nearly indistinguishable throughout the cell cycle. Second, a genetic analysis indicates that mutations in CMD1 show allele-specific synthetic lethality with the myo2-66 conditional mutation. Mutations that inactivate the Ca(2+)-binding sites of calmodulin have little or no effect on strains carrying myo2-66, whereas an allele with a mutation outside the Ca(2+)-binding sites dramatically increases the severity of the phenotype conferred by myo2-66. Third, Myo2p coimmunoprecipitates with calmodulin in the presence of Ca2+ or EGTA. Finally, we used a modified gel overlay assay to demonstrate direct interaction between calmodulin and fusion proteins containing portions of Myo2p. Calmodulin binds specifically to the region of Myo2p containing six tandem repeats of a motif called an IQ site. Binding occurs in either Ca2+ or EGTA, and only two sites are required to observe binding.
authors.affiliation: Department of Biochemistry, University of Washington, Seattle 98195.
authors.forename: S E
authors.initials: SE
authors.lastname: Brockerhoff
authors.forename: R C
authors.initials: RC
authors.lastname: Stevens
authors.forename: T N
authors.initials: TN
authors.lastname: Davis
mesh_terms: D000483:Alleles; D001483:Base Sequence; D002118:Calcium / Q000378:metabolism; D002147:Calmodulin / Q000235:genetics / Q000378:metabolism*; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002455:Cell Division; D003598:Cytoskeletal Proteins; D004533:Egtazic Acid / Q000494:pharmacology; D005455:Fluorescent Antibody Technique; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation; D018995:Myosin Heavy Chains; D024462:Myosin Type II; D024701:Myosin Type V; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins; D029702:Schizosaccharomyces pombe Proteins
chemical_list: D002147:Calmodulin; D002352:Carrier Proteins; D003598:Cytoskeletal Proteins; D005656:Fungal Proteins; C077512:MYO2 protein, S cerevisiae; C434211:MYO2 protein, S pombe; D011993:Recombinant Fusion Proteins; C065889:SPA2 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D029702:Schizosaccharomyces pombe Proteins; D004533:Egtazic Acid; D024462:Myosin Type II; D024701:Myosin Type V; D018995:Myosin Heavy Chains; D002118:Calcium