Unconventional myosin that functions as actin-based motor protein with ATPase activity (By similarity). Plays a role in endosomal protein trafficking, and especially in the transfer of cargo proteins from early to recycling endosomes (By similarity). Required for normal planar cell polarity in ciliated tracheal cells, for normal rotational polarity of cilia, and for coordinated, unidirectional ciliary movement in the trachea. Required for normal, polarized cilia organization in brain ependymal epithelial cells (By similarity). Interacts (via the two IQ motifs) with calmodulin. Binds an additional calmodulin chain via a third, C-terminal region. Interacts with F-actin. Colocalizes with the actin cytoskeleton in the cell cortex close to the basolateral cell membrane (PubMed:20089841). Colocalizes with the actin cytoskeleton in the cell cortex close to the apical cell membrane (PubMed:20089841). Colocalizes with cytoplasmic puncta that are reminiscent of transport vesicles (By similarity). Detected in enterocytes at the intestinal brush border membrane. Detected at the tip of intestinal microvilli (at protein level). Binds a calmodulin chain via each of the two IQ domains. IQ domain 1 mediates interaction with calmodulin both in the presence and in the absence of Ca(2+). IQ domain 2 mediates interaction with calmodulin in the presence of Ca(2+). The TH1 domain is required for activity in complementing zebrafish defects in Kupffer's vesicle lumen size. 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-1 (MYH1). Contrary to the situation in zebrafish, xenopus and drosophila, mammalian MYO1D defects have no effects on left-right body asymmetry.