Phosphorylation of myosin in non-muscle and smooth muscle cells. Possible rules and evolutionary trends.

Reversible phosphorylation of myosin subunits is observed in almost all eukaryotic cells. The data concerning sites and effects of phosphorylation on actin-activated ATPase activity of myosin and on its filament formation are described. These observations are discussed in terms of possible evolutionary trends and rules which may govern the process of myosin phosphorylation.