title: An intact SH3 domain is required for myosin I-induced actin polymerization.
abstract: The yeast type I myosins (MYO3 and MYO5) are involved in endocytosis and in the polarization of the actin cytoskeleton. The tail of these proteins contains a Tail Homology 2 (TH2) domain that constitutes a putative actin-binding site. Because of the important mechanistic implications of a second ATP-independent actin-binding site, we analyzed its functional relevance in vivo. Even though the myosin tail interacts with actin, and this interaction seems functionally important, deletion of a major portion of the TH2 domain did not abolish interaction. In contrast, we found that the SH3 domain of Myo5p significantly contributes to this interaction, implicating other proteins. We found that Vrp1p, the yeast homolog of WIP [Wiskott-Aldrich syndrome protein (WASP)-interacting protein], seems necessary to sustain the Myo5p tail-F-actin interaction. Consistent with recent results implicating the yeast type I myosins in regulating actin polymerization in vivo, we demonstrate that the C-terminal domain of Myo5p is able to induce cytosol-dependent actin polymerization in vitro, and that this activity requires both an intact Myo5p SH3 domain and Vrp1p.
authors.affiliation: Biochemie Zentrum, University of Heidelberg, D-69120 Heidelberg, Germany. maribel.geli@urz.uni-heidelberg.de
authors.forename: M I
authors.initials: MI
authors.lastname: Geli
authors.forename: R
authors.initials: R
authors.lastname: Lombardi
authors.forename: B
authors.initials: B
authors.lastname: Schmelzl
authors.forename: H
authors.initials: H
authors.lastname: Riezman
mesh_terms: D000199:Actins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism; D000483:Alleles; D001665:Binding Sites; D003600:Cytosol / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D005838:Genotype; D005982:Glutathione Transferase / Q000378:metabolism; D015151:Immunoblotting; D000072235:Mating Factor; D008840:Microfilament Proteins / Q000378:metabolism; D024461:Myosin Type I; D009218:Myosins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010455:Peptides / Q000493:pharmacokinetics; D010957:Plasmids / Q000378:metabolism; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D018909:src Homology Domains
chemical_list: D000199:Actins; D005656:Fungal Proteins; C100412:MYO5 protein, S cerevisiae; D008840:Microfilament Proteins; D010455:Peptides; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; C090350:VRP1 protein, S cerevisiae; D000072235:Mating Factor; D000255:Adenosine Triphosphate; D005982:Glutathione Transferase; D024461:Myosin Type I; D009218:Myosins