Phosphorylation of myosin light chain is not the main activation mechanism of smooth muscle contraction

Without affecting the actomyosin-activating activity, wortmannin represses the myosin light chain phosphorylating activity of bovine stomach's 155 kDa component, which was indistinguishable from its myosin light chain kinase as a protein. The mechanism of actomyosin-activation without phosphorylation was discussed