Essential myosin light chain MLC-1sa decelerates actin and thin filament gliding on beta-myosin molecules

The β-myosin heavy chain expressed in ventricular myocardium and the myosin heavy chain (MyHC) in type-I fibers of slow-twitch skeletal musculus soleus are both encoded by MYH7. Thus, these myosin molecules are deemed equivalent. However, some reports suggested variations in the myosin light chain composition between soleus muscle and ventricular myosin, which could influence functional parameters such as maximum velocity of shortening. To test for functional differences of the actin gliding velocity on immobilized myosin molecules we made use of the in vitro motility assay.