Myosin regulatory light chain 2, ventricular/cardiac muscle isoform (MLC-2) also known as the regulatory light chain of myosin (RLC) is a protein that in humans is encoded by the MYL2 gene. This cardiac ventricular RLC isoform is distinct from that expressed in skeletal muscle (MYLPF), smooth muscle (MYL12B) and cardiac atrial muscle (MYL7). Ventricular myosin light chain-2 (MLC-2v) refers to the ventricular cardiac muscle form of myosin light chain 2 (Myl2). MLC-2v is a 19-KDa protein composed of 166 amino acids, that belongs to the EF-hand Ca2+ binding superfamily.[8] MLC-2v interacts with the neck/tail region of the muscle thick filament protein myosin to regulate myosin motility and function.