Myosin isoenzymes of fish hearts.

1. Myosin extracted from ventricular and atrial muscles of some fish species were analysed by native and SDS gel electrophoresis. 2. Within the single heart, distinct types of native myosin were present in ventricular and atrial tissues. 3. Ventricular and atrial isomyosins contained two classes of light chain subunits. 4. The present results support the suggestion that the presence of multiple molecular forms of myosin in the heart is a common property of all vertebrates.