Snythesis of polypeptides with the properties of myosin light chains direct by RNA extracted from muscle cultures.

Polyadenylylated RNA, extracted from differentiating primary cultures of rat muscle and the myogenic cell line L8, directs the synthesis of polypeptides in the wheat germ cell-free system which comigrate with myosin light chains under several electrophoretic conditions. The peptides also associate specifically with heavy myosin subunits during dissociation-reassociation treatment. Intact cells of primary skeletal muscle cultrues and of the myogenic line synthesize predominantly two ligh chains. RNA extracted from primary muscle cultures directs the synthesis of a third polypeptide in the cell-free system, similar to the third light chain found in myosin extracted from adult rat thigh muscle. Products of cell-free systems directly by RNA extracted from fibroblasts, reticulocytes, and myeloma cells did not contain detectable amounts of similar polypeptides.