Stabilizing and destabilizing effects on plasma membrane Ca(2+)-ATPase activity

We have examined the temperature-dependent effects of several organic compounds on the activity of the purified Ca(2+)-ATPase of erythrocytes. The monomeric enzyme was activated either by interaction with calmodulin or by oligomerization in the absence of calmodulin. Of the four homologous solute se...

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Bibliographic Details
Published in:Molecular and cellular biochemistry 1994-10, Vol.139 (1), p.1-9
Main Authors: Kosk-Kosicka, D, Wawrzynow, A, Roszczynska, G
Format: Article
Language:English
Subjects:
Acetamides - pharmacology
Calcium-Transporting ATPases - antagonists & inhibitors
Calcium-Transporting ATPases - blood
Calmodulin - pharmacology
Enzyme Activation
Enzyme Stability
Erythrocyte Membrane - enzymology
Formamides - pharmacology
Glycerol - pharmacology
Glycols - pharmacology
Humans
Solvents - pharmacology
Structure-Activity Relationship
Temperature
Urea - pharmacology
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Summary:We have examined the temperature-dependent effects of several organic compounds on the activity of the purified Ca(2+)-ATPase of erythrocytes. The monomeric enzyme was activated either by interaction with calmodulin or by oligomerization in the absence of calmodulin. Of the four homologous solute series studied including polyols, alkanols, aprotic solvents, and N-methyl derivatives of formamide and acetamide only polyols stabilized the enzyme over a broad range of concentration and temperature. Similarity of Ca(2+)-ATPase activity patterns at 25 and 37 degrees C and in the presence of glycerol is in agreement with indirect, stabilizing interactions. Glycerol also protected the Ca(2+)-ATPase from thermal denaturation at 45 degrees C. Within each homologous series, inhibitory effects increased with increasing solute concentration and with increasing structural similarity to detergents, indicating that direct destabilizing interactions are responsible for the observed inhibition. These were comparable to the destabilizing effect of urea. Oligomers were more resistant to all inhibitory solutes as compared to calmodulin-activated monomers suggesting that the nonpolar patches of the oligomerized enzyme are less accessible to solutes.
ISSN:0300-8177
DOI:10.1007/BF00944197