Myosin light chains of avian and mammalian slow muscles: evidence of intraspecific polymorphism.

The myosin light chains of slow muscles from different species have been examined two-dimensional gel electrophoresis. While the myosin light chain 2S of mammalian soleus muscles (rabbit, rat and guinea-pig) could not be distinguished from that of avian anterior latissimus dorsi (chicken and turkey), the 1S light chain complement of myosins shows inter- and intraspecific differences. The 1S light chain varies between birds and mammals. The 1S light chain is absent in avian slow myosins and has an electrophoretic mobility peculiar to each mammalian species. Furthermore the relative amount of 1S and 1S light chains varies in different muscles of the same mammalian species and among species.