Myosin Light Chain 12B (MYL12B)

The activity of nonmuscle myosin II is regulated by phosphorylation of a regulatory light chain, such as MRLC2. This phosphorylation results in higher MgATPase activity and the assembly of myosin II filaments.Immunolocalization of the mutant proteins in dividing cells revealed colocalization of the 2 phosphorylated forms with actin filaments in the peripheral region and with the contractile ring, while the unphosphorylated form localized diffusely throughout the cytoplasm. Iwasaki et al. (2001) concluded that phosphorylation of MRLC2 is required for organization of stress fibers in interphase cells and the contractile ring in dividing cells. They suggested that diphosphorylated MRLC may be more effective in organizing actin filaments than monophosphorylated MRLC.