myoV and actin structure. myoV, a double-headed molecular motor, is composed of a lever arm that has calmodulin (Cam) bound to six IQ domains. For fluorescence polarization measurements, a fluorescent probe (red arrow) is bound to one of the Cams. A short myoV 4IQ construct was also expressed. The actin filament track is composed of individual actin monomers, with the preferable binding site for the myoV 6IQ heads highlighted in green. Occasionally, the motor steps one monomer short (blue) or long (red) of the preferable site.