Molecular Characteristics of Canine Cardiac Myosin

Abstract

Cardiac myosin was obtained from the hearts of normal dogs by conventional extraction and precipitation techniques, followed by ammonium sulfate fractionation in the presence of 2.0 M lithium chloride. The molecular characteristics of this protein preparation are presented. Cardiac myosin prepared by this technique shows less tendency than conventionally prepared solutions to denature when stored at 0 to 4°C, and has a significantly higher ATP ase activity. Comparison of canine cardiac myosin and skeletal muscle myosin, obtained under identical conditions, revealed no differences between these two proteins in their intrinsic viscosities, S 20. w , molecular weight, and UV absorbances, although ATP ase activity was lower for cardiac myosin.