Purification of myosin from Ehrlich ascites tumour cells (phosphorylation of its light chain and heavy chain).

1. The myosin molecule from Ehrlich ascites tumour cells consists of heavy chains of about 200 kDa and three species of light chains of 20, 19 and 15 kDa. 2. The heavy chain can be phosphorylated in vitro either by endogenous Ca2+-independent kinase or by casein kinase II. 3. The 20 and 19 kDa light chains can be phosphorylated either by an endogenous kinase or by myosin light chain kinase from chicken gizzard. 4. The Ca2+-ATPase activity of the purified myosin was 0.3 mumol/min mg protein. The Mg2+-ATPase activity was activated 14-fold by actin upon the light chain phosphorylation.