Myosin is composed of 2 heavy chains of about 200,000 daltons each and 4 light chains of about 20,000 daltons each. The light chains are of 2 distinct types: the phosphorylatable, regulatory, or MLC2 type, and the nonphosphorylatable, alkali, or MLC1 and MLC3 types(MYL1 according to the HGM symbols). Skeletal Myosin(Fast),, also known as MYL1, mapped to the region 2q32.1-qter.