Studies on the Subunit Structure of Myosin

Abstract The low molecular weight protein associated with rabbit skeletal myosin has been estimated by gel filtration studies in 5 m guanidine hydrochloride and was found to constitute 9 ± 2% of the myosin mass. We have found that 40 to 50% of the low molecular weight protein can be removed from myosin without any apparent changes in the adenosine-triphosphatase activity. Attempts to remove a larger fraction of low molecular weight protein resulted in a concomitant loss of enzymatic activity. The molecular weight of the major myosin subunit freed of low molecular weight protein has been redetermined in 5 m guanidine hydrochloride and was found to be 194,000 g per mole. The significance of its presence in assessing the molecular weight of the major subunit at low speed and high speed sedimentation equilibrium has been investigated.