Myosin light chain (MLC)

Myosin light chain refers to the small polypeptide subunits (typically 19–22 kDa) that associate with the neck region of myosin heavy chains, forming an essential component of the myosin molecular motor complex which is necessary for force transduction and muscle contraction in all eukaryotic cells[1][2]. There are two main classes: essential (ELC/MLC1) and regulatory (RLC/MLC2) light chains. MLC1 helps in stabilizing the myosin complex and partly in actin binding, while MLC2 undergoes phosphorylation, regulating the actin–myosin kinetics essential for muscle contraction and motility[1][2]. Myosin light chains are part of the EF-hand family of Ca²⁺-binding proteins. Phosphorylation of MLC by calcium/calmodulin-dependent myosin light chain kinase (MLCK) is crucial for activation of actin–myosin contraction, especially in smooth and non-muscle cells[3][6]. Dysfunction, abnormal phosphorylation, or altered expression of myosin light chains is implicated in cardiac disease, vascular leakage in inflammation, and several chronic inflammatory pathologies, including asthma and acute lung injury[1][4]. MLCs are not direct drug targets in clinical use, but their regulatory kinases (especially MLCK) are of therapeutic and research interest[4].

Other names

Essential light chain (ELC)Regulatory light chain (RLC)MLC1MLC2

Phosphorylation by myosin light chain kinase (MLCK) increases actin-myosin interaction and muscle contraction; targeted in research by MLCK inhibitors.