Polymerization of myosin from smooth muscle of the calf aorta

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Abstract
Myosin from the smooth muscle of the calf aorta is similar to rabbit skeletal muscle myosin in MW, sedimentation coefficient and amino acid composition. When dialyzed at low ionic strength, it forms polymers that exist in equilibrium with the monomer, the position of this equilibrium is sensitive to ionic strength, pH and hydrostatic pressure. The self-association reactions for smooth muscle myosin differ from those observed for skeletal muscle myosin in several ways: aorta myosin polymerizes at a higher ionic strength to form a smaller polymer; between pH 6-8, 1 polymer boundary is observed; the result of varying total protein concentration on the myosin-polymer equilibrium cannot be analyzed by the Gilbert theory for a simple 2-species system, as was possible with skeletal myosin. This more complex polymerization behavior may be related to differences in the mode of assembly between smooth and skeletal muscle myosin.