Differences between Slow and Fast Muscle Myosin

Abstract

The differences between slow and fast muscle myosin adenosine triphosphatase activity of the cat are described with reference to relative specific activities, p-chloromercuriphenylsulfonate activation, and alkaline and acid stability. The treatment of fast muscle myosin with 8 moles of p-chloromercuriphenylsulfonate per 105 g of myosin results in the release of two electrophoretically distinct proteins and loss of myosin ATPase activity. There appears to be an inverse relationship between the degree of ATPase activity lost and the amount of closely associated proteins released from fast muscle myosin. Similar treatment of slow muscle myosin releases no proteins and causes no loss of ATPase activity.