A protein activator of the plasma membrane Ca++-ATPase of heart sarcolemma |
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Authors: | Leslie J Reinlib Arthur F Clark Ernesto Carafoli |
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Institution: | (1) Laboratory for Biochemistry, Swiss Federal Institute of Technology (ETH), CH-8092 Zurich, Switzerland;(2) Arrhenius Laboratory, Department for Biochemistry, Stockholm University, S-106 91 Stockholm, Sweden |
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Abstract: | A detergent extract of dog or beef heart sarcolemmal vesicles was prepared and found to have a stimulatory effect on the Ca++-ATPase of plasma membranes from human erythrocyte and cardiac sarcolemma. A procedure is described which enriches the activating fraction. The protein nature of the preparation is illustrated by its sensitivity to boiling and to the proteolytic enzyme(s) trypsin and chymotrypsin. SDS polyacrylamide gels indicate that the protein(s) involved have a molecular weight of 56 and 60 kDa. The sarcolemmal activator can stimulate the Ca++-ATPase activity of the isolated enzyme more than 100% in the presence of saturating amounts of calmodulin. The activation is calcium dependent, being greatest at approximately 10µm Ca++, free, but does not change theK
m
for Ca++. A possible physiological role for the activator is discussed. |
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Keywords: | Sarcolemma erythrocyte Ca++-ATPase Ca++-ATPase activation plasma membrane regulation Ca++ transport |
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