Type V myosins–dimeric, actin-associated motors–actively move organelles and molecules around cells. They contain a motor domain, a long neck region, a coiled-coil dimerization domain and a globular tail to which cargo binds. The neck region normally contains six calmodulin-binding IQ motifs and, in vertebrates, seems to control how fast myosin V moves around the cell. Surprisingly, on p. , Daniel Mulvihill and colleagues report that the in vivo movement of the fission yeast type V myosin Myo52 is independent of its neck domain. The authors use live-cell imaging to follow the intracellular movements of Myo52 and mutants that lack the coiled-coil domain (Myo52 CC) or the entire neck region (Myo52 IQ). Myo52, they report, moves long distances along actin filaments in an ATP-dependent manner but Myo52 CC fails to form motile foci, which indicates that dimerization is required for Myo52 movement. By contrast, Myo52 IQ moves normally in the cell. Thus, the authors suggest, the role of the neck region of myosin V proteins might vary significantly between organisms.
