ATPase activity of the microvillar 110 kDa polypeptide‐calmodulin complex is activated in Mg2+ and inhibited in K+‐EDTA by F‐actin

Abstract

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.