Identification of the essential light chains of myosin.

The molecular weights of light chains associated with adult and embryonic chick myosin have been determined by polyacrylamide gel electrophoresis in the presence of 0.1% sodium dodecyl sulfate. Adult muscle myosin contains three light chains with molecular weights averaging 27,700, 21,000, and 16,500, while the embryonic form contains only the two largest of these three. Recombination and hybridization experiments have been performed with these samples. The data clearly demonstrate that only two light chains are required for the expression of the full ATPase activity of myosin. The third light chain consistently is associated with adult myosin, but definitive evidence for its role is lacking.