Myosins are actin-based motor molecules with ATPase activity. Unconventional myosins serve in intracellular movements. Binds actin with high affinity both in the absence and presence of ATP and its mechanochemical activity is inhibited by calcium ions. Also acts as a GTPase activator for RHOA. Plays a role in the regulation of cell migration via its role as RHOA GTPase activator. This is regulated by its interaction with the SLIT2 receptor ROBO1; interaction with ROBO1 impairs interaction with RHOA and subsequent activation of RHOA GTPase activity, and thereby leads to increased levels of active, GTP-bound RHOA. Interacts (via IQ domains) with CALM. Interacts with RHOA. Interacts (via Rho-GAP domain) with ROBO1; this inhibits the interaction with RHOA and the stimulation of RHOA GTPase activity, and thereby increases the levels of active RHOA. In undifferentiated cells colocalizes with F-actin in the cell periphery while in differentiated cells its localization is cytoplasmic with the highest levels in the perinuclear region. Expressed in the brain, heart, muscle and inner ear. Belongs to the TRAFAC class myosin-kinesin ATPase superfamily. Myosin family. Represents an unconventional myosin. This protein should not be confused with the conventional myosin-9 (MYH9).