The subunit structure of myosin from skeletal muscle of the early chick embryo.

The subunit composition and immunological properties of two types of myosins, the 3S and 6S myosin components, from skeletal muscle of early chick embryos were studied by SDS-acrylamide gel electrophoresis and immunodiffusion techniques. It was shown that the 6S myosin in the early embryonic stage was composed of two heavy chains and three kinds of light chains, as is well-known in the complete myosin molecule, having the same molecular weights and the same antigenicities as corresponding subunits of the myosin from adult chicken skeletal muscle. The heavy chain of 6S myosin was also reactive with the antibody against the heavy chain of cardiac myosin. The embryonic 3S myosin was shown to be composed of a heavy chain which was roughly the same in molecular weight but not the same in antigenicity as those of adult or embryonic 6S myosin. No light chains were detected either electrophoretically or immunologically in the 3S myosin component.