Partial characterization of a rabbit liver Ca(2+)-calmodulin-dependent kinase with myosin light chain phosphorylating...

A Ca(2+)-calmodulin-dependent protein kinase that phosphorylates the regulatory light chain of hepatocyte myosin was purified from rabbit liver. The kinase catalyzed the incorporation of phosphate into the 22-k light chains of hepatocyte myosin, resulting in a 7-fold activation of the Mg(2+)-ATPase activity by F-actin. The kinase did not show any glycogen synthase kinase activity which has previously been shown to phosphorylate isolated chicken gizzard myosin light chain. ML-7, an inhibitor specific for smooth muscle myosin light chain kinase, inhibited the liver kinase with a Ki value of 13.2 microM.