Myosin heavy chains in fast skeletal muscle of chick embryo.

The peptide map obtained by electrophoresis after digestion of purified myosin heavy chains from pectoralis muscle of embryonic chicken with the Staphylococcus aureus V8 protease, produces a peptide pattern very similar but not identical to that of adult fast myosin. In fact, some components that are present in a small amount in the map of slow adult myosin are visible in the embryonic pattern.