Phosphorylation of myosin regulatory light chain

Myosin light chain phosphorylation is a regulatory biochemical event primarily involving the reversible phosphate group transfer to serine or threonine residues (typically Ser19) on the myosin regulatory light chain (RLC). This modification, controlled by myosin light-chain kinase (activated by Ca2+/calmodulin) and myosin light-chain phosphatase (inhibited by various signaling pathways such as RhoA/Rho-kinase), determines the contractile activity of smooth, cardiac, and skeletal muscle, as well as non-muscle cells. Phosphorylation enhances actin-myosin interaction, muscle contraction, and cell movement, while dephosphorylation leads to relaxation and dissociation of the cross-bridge. Disrupted myosin light chain phosphorylation is implicated in heart disease, vascular disorders, cancer metastasis, and a range of cellular pathologies. Note: “Myosin light chain phosphorylation” is not a molecule or receptor, but a post-translational modification; molecular targets mediating this process include myosin light-chain kinase (MLCK) and myosin light-chain phosphatase (MLCP). For structured molecular information, use those enzyme names instead.

Other names

RLC phosphorylationMyosin II RLC phosphorylationMyosin regulatory light chain phosphorylationMLC phosphorylation

Inhibition of MLCK or activation of MLCP reduces myosin light chain phosphorylation, leading to muscle relaxation. MLCK activators increase phosphorylation, promoting contraction. Rho-kinase inhibitors disinhibit MLCP, promoting dephosphorylation.