Myosin extracts of red and white muscles from mackerel (Scomber scombrus) were analyzed by native electrophoresis to investigate the existence of myosin isoforms in both kind of muscles, and by two-dimensional and SDS gel electrophoresis to study their subunit composition. Two isoforms were found in red muscle comprising one type of heavy chain and two light chains. Four isoforms were found in white muscle made up of one type of heavy chain and three types of light chains. The heavy chains from white muscle showed a higher electrophoretic mobility than that of red muscle in SDS-PAGE. Both heavy chains had an intermediate mobility between those of slow and fast myosins from rat diaphragm.
