Myosin heavy chain that is required for the cell cycle-regulated transport of various organelles and proteins for their segregation. Functions by binding with its tail domain to receptor proteins on organelles and exerting force with its N-terminal motor domain against actin filaments, thereby transporting its cargo along polarized actin cables (By similarity). Involved in endocytosis via its action in endosomal trafficking. Homodimer. A number of isoforms are produced. According to EST sequences. IQ domain mediates interaction with calmodulin. Belongs to the TRAFAC class myosin-kinesin ATPase superfamily. Myosin family. Plant myosin class VIII subfamily.