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. Southern blots of a panel of hybrids containing different portions of human chromosome 16 localized the gene to 16p13.13-p13.12. Skeletal Myosin (slow), also known as light chain 3(MYL3), mapped to 3p. Fodor et al. (1989) found that the MYL3 gene has 7 exons, the last of which is completely untranslated 3-prime sequence.Synonyms: MYH7, MYHCB, MyHC-slow, Myosin heavy chain, Myosin heavy chain slow isoform, cardiac muscle beta, cardiac muscle beta isoform