Two pairs of smaller subunits (17–22 kDa) of hexameric myosin II, each pair being different. The two regulatory light chains (LC-2, DNTB light chains, MYL2 gene products) may directly confer calcium sensitivity on the ATPase activity, or indirectly when they are phosphorylated by calcium-regulated myosin light chain kinase. Essential light chains (LC-1, LC-3; alkali light chains, MYL3 gene products) may have a partly structural role. Multiple tissue-specific variants exist. Mutation in the gene for the essential light chains causes some types of hypertrophic cardiomyopathy.
Subjects: Medicine and Health.