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An Additional Low Molecular Weight Subunit in Purified Preparations of Myosin from Hypertrophied Myocardium

Summary In order to determine whether the altered contractility of hypertrophied hearts is associated with changes in the low molecular weight (MW) components of myosin, we examined rabbit heart myosin subunit composition and ATPase activity. Myosin was purified by ultracentrifugation and gel chromatography. Preparations from normal hearts exhibited two low MW components (27,000 and 20,000) on SDS-gels, compared to those from hypertrophied hearts which showed an additional low MW component (16,000). Ca2+ and EDTA-activated myosin ATPase activities were diminished in preparations from hypertrophied hearts. Thus, myosin from hypertrophied myocardium contains an additional component which may contribute to diminished contractility.