Abstract
The effects of concanavalin A (Con A) on membrane Ca 2+ Mg 2+ ATPase activities as well as the characteristics of Con A binding were examined by employing rat heart sarcolemmal preparations. Con A stimulated the Ca 2+ ATPase and Mg 2+ ATPase activities in sarcolemma; maximal stimulation in these parameters was seen at a concentration of 10 μg/ml. The observed effects of Con A were blocked by α-methylmannoside. Sarcolemmal Na +-K + ATPase and Ca 2+-stimulated ATPase were not affected by Con A. Likewise, Con A did not alter the mitochondrial, sarcoplasmic reticular, and myofibrillar ATPase activities. Con A was found to bind to sarcolemma; α-methylmannoside prevented this binding. The Scatchard plot analysis of the data on specific Con A binding showed a straight line with a K d of about 530 n m and a B max of 235 pmol/mg protein, thus indicating that there was only one kind of binding site for Con A in sarcolemma. These results suggest that Con A is a specific activator of the low affinity Ca 2+ Mg 2+ ATPase system in the heart sarcolemmal membrane.
Published Version
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