Highly purified microvillar 110 kDa polypeptide-calmodulin (110 K-cam) complex was confirmed to have ATPase activities characteristic of a myosin. The effect of F-actin on these activities was investigated. The Mg2+-ATPase is activated about 2-fold by F-actin in a dose-dependent fashion, whereas the K+-EDTA -ATPase is inhibited by > 90% by F-actin. These data provide evidence for a functional relationship between the ATPase activity of 110K-cam and its interaction with F-actin. They also extend the similarities between 110K-cam and myosin. The results suggest that higher cells contain in addition to myosin a second class of myosin-like molecules represented by 110K-cam.
