One of two redundant type-I myosins implicated in the organization of the actin cytoskeleton. Required for proper actin cytoskeleton polarization and for the internalization step in endocytosis. At the cell cortex, assembles in patch-like structures together with proteins from the actin-polymerizing machinery and promotes actin assembly. Functions redundantly with LAS17 as actin nucleation-promoting factor (NPF) for the Arp2/3 complex. Motor domain phosphorylation by PAK kinases CLA4 and STE20 promotes CDC42-regulated actin assembly. Functions together with the NPF PAN1 in late stages of endocytosis. Motor domain phosphorylation by PDK1 kinases PKH1 and PKH2, and by SGK kinases YPK1 and YPK2, promotes ligand-induced, but not constitutive endocytosis of the G protein-coupled receptor STE2 (By similarity). Interacts (via myosin motor domain) with SHE4; this interaction is important for proper localization and may regulate the interaction of the motor domain with actin. Interacts (via SH3 domain) with VRP1; this interaction is required for localization to sites of polarized growth and may regulate the interaction of the tail domain with actin. Interacts (via SH3 domain) with PAN1; this interaction is important for late stages of endocytopsis. Interacts (via SH3 domain) with BBC1 and LAS17. Interacts (via C-terminal acidic tail) with ARC19 and ARC40; ARC19 and ARC40 are Arp2/3 complex subunits. Interacts with BZZ1, PKH1, PKH2, YPK1 and YPK2 (By similarity). Localizes to cortical patch-like protein structures that assemble actin patches. Enriched at sites of polarized growth (By similarity). The myosin motor domain displays actin-stimulated ATPase activity and generates a mechanochemical force. The tail domain participates in molecular interactions that specify the role of the motor domain (By similarity). It is composed of several tail homology (TH) domains, namely a putative phospholipid-binding myosin tail domain (also named TH1), an Ala- and Pro-rich domain (TH2), followed by an SH3 domain and a C-terminal acidic domain (TH3). Phosphorylation of the TEDS site (Ser-357) is required for the polarization of the actin cytoskeleton and for ligand-induced, but not for constitutive internalization of STE2. Phosphorylation probably activates the myosin-I ATPase activity. Ser-357 is phosphorylated by YPK2 in vitro (By similarity). Belongs to the TRAFAC class myosin-kinesin ATPase superfamily. Myosin family.