A role for myosin-I in actin assembly through interactions with Vrp1p, Bee1p, and the Arp2/3 complex

Type I myosins are highly conserved actin-based molecular motors that local ize to the actin-rich cortex and participate in motility functions such as endocytosis, polarized morphogenesis, and cell migration. The COOH-terminal tail of yeast myosin-I proteins, Myo3p and Myo5p, contains an Src homology domain 3 (SH3) followed by an acidic domain. The myosin-I SH3 domain inter acted with both Bee1p and Vrp1p, yeast homologues of human WASP and WIP, ad apter proteins that link actin assembly and signaling molecules. The myosin -I acidic domain interacted with Arp2/3 complex subunits, Arc40p and Arc19p , and showed both sequence similarity and genetic redundancy with the COOH- terminal acidic domain of Bee1p (Las17p), which controls Arp2/3-mediated ac tin nucleation. These findings suggest that myosin-I proteins may participa te in a diverse set of motility functions through a role in actin assembly.