Light and heavy chains of myosin from atrial and ventricular myocardium of turkey and rat.

Subunit composition of myosins from atrial and ventricular cardiac muscle of turkey and rat was examined by two-dimensional polyacrylamide electrophoresis of light chains and by peptide mapping of electrophoretically purified heavy chains. In regard to light subunits in two-dimensional electrophoresis, the corresponding light chains from atrial and ventricular myocardium comigrate in the turkey. By contrast the atrial light chains LC1 and LC2 are easily distinguishable from the corresponding subunits of the ventricles in the rat. The peptide patterns of myosin heavy chains from atrial and ventricular cells were different both in turkey and rat, indicating differences in their primary structures. Therefore atrial and ventricular myosins differ in heavy chains composition in all the avian and mammalian species so far studied, suggesting that this heterogeneity represents a general feature related to the different physiological properties of atrial and ventricular cardiac cells.