MYL9 also known as LC20, MLC2, MRLC1 plays a crucial role in muscle contraction regulation by interacting with myosin heavy chains and actin filaments. MYL9 is primarily located in the cytoplasm of smooth muscle and non-muscle cells, where MYL9 is essential for the contractile function. Phosphorylation of MYL9 by myosin light chain kinase (MLCK) in the presence of calcium and calmodulin enhances the actin-activated myosin ATPase activity, which is vital for muscle contraction and cellular motility. Additionally, MYL9 is found in striated skeletal muscle, where MYL9′s precise function is still being elucidated, highlighting MYL9′s importance in both smooth and striated muscle physiology.