Myosin light chain (MLC) is a subunit of the conventional myosins (e.g. myosin II). In smooth muscle and non-muscle cells conventional myosins mediate a wide variety of contractile events including cytokinesis, cell motility, and smooth muscle contraction. MLC is phosphorylated by multiple serine-threonine kinases such as Rho-kinase and PAK, however myosin light chain kinase (MLCK) acts as the primary kinase. Contractile activity of conventional myosins is regulated by phosphorylation of MLC on several residues.