Actin from Heart Muscle: Sulfhydryl Groups

Abstract

The number and reactivity of the sulfhy-dryl groups of cardiac and skeletal actin preparations have been examined, using material from dogs and rabbits. The number of sulfhy-dryl groups of all actins was approximately six per mole, two of which could be characterized as fast-reacting and were not essential for polymerization. The time course of the reaction of the sulfhydryl groups of heart and skeletal actins with -pmercuribenzoate were identical, and the effects of Ca⁺⁺ Mg⁺⁺ and adenosinetriphosphate upon this reaction were similar for actins from the two tissues. In accord with previous structural comparisons, no difference between cardiac and skeletal actin has been detected.