MYL12B is a regulatory subunit of myosin and plays an important role in regulation of both smooth muscle and nonmuscle cell contractile activity via its phosphorylation. There are two groups of residues on the MYL12B that are phosphorylated by distinct kinases and have contrasting effects on myosin II biophysical properties.Phosphorylation at Thr18/Ser19 essentially activates the myosin molecule to produce force. The second group of phosphorylated residues is at the N-terminus of the MYL12B at Ser1, Ser2 and Thr9 and causes inhibitory effect on myosin activity.
