Unconventional myosin that functions as actin-based motor protein with ATPase activity (PubMed:30467170). Binds to membranes enriched in phosphatidylinositol 4-5-bisphosphate, and can glide along actin filaments when anchored to a lipid bilayer (PubMed:30467170). Generates left-right asymmetry at the level of single cells, organs and the whole body via its interaction with the actin cytoskeleton, both in the embryo and the adult (PubMed:16598258, PubMed:16598259, PubMed:18521948, PubMed:26073018, PubMed:25659376, PubMed:30467170). Normal left-right asymmetry of the larval midgut and hindgut requires expression in the embryonic hindgut epithelium during a critical time period, 10 to 12.75 hours after egg laying (PubMed:18521948). This period corresponds to a late stage of germband retraction, and precedes left-right asymmetric morphogenesis (PubMed:18521948). Expression in segment H1 of the imaginal ring is required at 0 to 24 hours after pupation for changes of cell shape and orientation in the H2 segment, which then gives rise to normal, dextral looping of the adult hindgut (PubMed:16598258, PubMed:26073018). Required during a critical period, 126-132 hours after egg laying, for normal, dextral rotation of the adult male genitalia (PubMed:16598258, PubMed:16598259, PubMed:22491943, PubMed:26073018, PubMed:25659376). Has a double role by promoting dextral rotation in the posterior compartment of segment A8 of the male genital disk, and in repressing sinistral looping in the anterior compartment (PubMed:16598259). Binds to F-actin (PubMed:7589814). Interacts with arm (PubMed:16598259, PubMed:22491943). Interacts with shg (PubMed:22491943). Interacts with ds (via intracellular region) (PubMed:26073018). Detected throughout the cytoplasm. Detected primarily in the basolateral cytoplasmic region of immature enterocytes. Detected also in the apical cytoplasmic region in midgut enterocytes and follicle cells (PubMed:7589814). Colocalizes with the actin cytoskeleton (PubMed:7589814, PubMed:16598258, PubMed:16598259, PubMed:25659376). Colocalizes with arm at adherens junctions (PubMed:16598259). Colocalizes with ds at cell junctions (PubMed:26073018). In the embryo, expressed in gastric caeca, midgut cells of the proventriculus, and in the mid and hindgut. In the larval gut brush border, expression is in the terminal web domain. In the adult gut brush border, expression remains in the web domain and has also moved into the microvilli. Also expressed at low levels in follicle cells during oogenesis. Expressed both maternally and zygotically throughout development to adulthood with highest levels at the end of larval development. Expression in embryogenesis is correlated with the formation of a brush border within the alimentary canal. Detected in the developing hindgut and midgut in stage 12 and stage 14 embryos (at protein level) (PubMed:16598258). In third instar larvae, detected in a symmetrical, double chevron-like pattern in the ventral section of segment A8 of the male genital disk, with one chevron in the anterior and the other in the posterior part of this segment (PubMed:16598259, PubMed:22491943). Detected in the H1 domain of the larval imaginal disk (PubMed:26073018). Detected in embryonic anterior and posterior midgut, hindgut, and in salivary gland (PubMed:25659376). The myosin motor domain contains the derminants for dextral twisting. The two IQ domains are essential for activity in determining left-right asymmetry. The actin-binding domain is essential for activity in determining left-right asymmetry. Viable and fertile (PubMed:16598258). Mutant embryos and adults display normal foregut left-right asymmetry, but inverted left-right asymmetry of the midgut and hindgut (PubMed:16598258, PubMed:18521948). RNAi-mediated knockdown in the hindgut at 0 to 24 hours after pupation leads to inverted left-right asymmetry of the adult hindgut, but knockdown at later stages has little or no effect (PubMed:16598258, PubMed:26073018). Adults display inverted left-right asymmetry of the male genitalia (PubMed:16598258). RNAi-mediated knockdown in the anterior and the posterior part of segment A8 of the male genital disk causes loss of the normal dextral rotation of the genital plate and inverted, sinistral spermiduct looping (PubMed:16598259, PubMed:26073018). Selective RNAi-mediated down-regulation in the anterior part of segment A8 of the male genital disk leads to partial dextral rotation of the genitalia, while RNAi-mediated down-regulation in the posterior part of segment A8 leads to non-rotated genitalia (PubMed:16598259). Combined RNAi-mediated knockdown of both ds and Myo31DF in the H1 segment of the imaginal ring causes mislooping of the adult hindgut (PubMed:26073018). Overexpression throughout the embryo reverses the normal left-right asymmetry of the embryonic gut, giving rise to a gut that is a mirror-image of the wild-type (PubMed:16598258). Ectopic expression in the larval epidermis causes dextral twisting of the entire larval body. Ectopic expression in tracheal precursor cells causes dextral spiraling of tracheal branches, giving rise to a spiraling ribbon shape instead of the normal smooth tube. Ectopic expression in epithelial cells causes increased elongation and a clear shift of the membrane orientation toward one side, so that the membrane is no longer perpendicular to the anterior-posterior axis (PubMed:30467170). Belongs to the TRAFAC class myosin-kinesin ATPase superfamily. Myosin family. Represents an unconventional myosin that should not be confused with the conventional myosin-1.