Required for the assembly and the contraction of the actomyosin ring at the bud neck during cytokinesis. Interacts with myosin MYO1 and its light chain MLC1 (By similarity). Interacts with BNI1, BNR1, CLB2, CLB4, and CDC28. Forms a ring at the bud neck in a MLC1-dependent manner, which contracts at the end of cytokinesis. Rat catheter biofilm repressed. The calponin homology (CH) domain binds to actin filaments and is required for their recruitment to the bud neck. The IQ domains provide the interaction surface for the myosin light chain MLC1. The Ras-GAP domain is required for contraction of the actomyosin ring. It probably does not stimulate GTPase activity (By similarity). Hyperphosphorylated. Phosphorylation is cell cycle-dependent and peaks at the time of cytokinesis. Contains 21 consensus sites for cyclin-dependent kinases (CDKs). At least some of them are phosphorylated by the CLB2-CDC28 kinase complex. Mutation of 15 of the phosphorylation sites to Ala caused both premature assembly and delayed disassembly of the actomyosin ring, blocked interaction with the actin-nucleating proteins BNI1 and BNR1, and resulted in defects in cytokinesis.