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Cyclopiazonic acid reduces the coupling factor of the Ca 2+ ‐ATPase acting on Ca 2+ binding
Author(s) -
Martı́nez-Azorı́n Francisco
Publication year - 2004
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/j.febslet.2004.08.064
Subject(s) - cyclopiazonic acid , chemistry , cooperativity , atpase , calcium atpase , cooperative binding , endoplasmic reticulum , binding site , biophysics , enzyme , calcium , crystallography , biochemistry , biology , organic chemistry
The mycotoxin cyclopiazonic acid (CPA) is a potent inhibitor of the sarcoplasmic reticulum Ca 2+ ‐ATPase. The compound decreases the affinity of the Ca 2+ ‐ATPase for Ca 2+ and reduces the maximum specific activity of the enzyme. Furthermore, CPA abolishes the cooperativity of Ca 2+ transport, showing a Ca 2+ /ATP ratio ∼1 at any extent of Ca 2+ saturation. There is also an effect on the Ca 2+ ‐binding mechanism, where the addition of CPA results in binding of only half‐maximal amount of Ca 2+ observed in its absence. The experimental data suggest that in the presence of CPA, only a single Ca 2+ ion binds to the Ca 2+ ‐ATPase.