Characterization of the palytoxin effect on Ca2+-ATPase from sarcoplasmic reticulum (SERCA)
| Autor: | Fernando Soler, Ramón Coca, Francisco Fernandez-Belda |
|---|---|
| Rok vydání: | 2008 |
| Předmět: |
SERCA
ATPase Biophysics Calcium-Transporting ATPases Models Biological Biochemistry Catalysis Sarcoplasmic Reticulum Calcium-Transporting ATPases chemistry.chemical_compound Adenosine Triphosphate Cnidarian Venoms Palytoxin Animals Phosphorylation Molecular Biology chemistry.chemical_classification Acrylamides Ionophores biology Endoplasmic reticulum Cell Membrane Sarcoplasmic reticulum membrane Kinetics Sarcoplasmic Reticulum Enzyme Catalytic cycle chemistry Microsome biology.protein Calcium Female Rabbits |
| Zdroj: | Archives of Biochemistry and Biophysics. 478:36-42 |
| ISSN: | 0003-9861 |
| Popis: | The effect of palytoxin was studied in a microsomal fraction enriched in longitudinal tubules of the sarcoplasmic reticulum membrane. Half-maximal effect of palytoxin on Ca 2+ -ATPase activity yielded an apparent inhibition constant of approx. 0.4 μM. The inhibition process exhibited the following characteristics: (i) the degree of inhibition was dependent on membrane protein concentration; (ii) no protection was observed when the ATP concentration was raised; (iii) dependence on Ca 2+ concentration with a decreased maximum catalytic rate; (iv) it occurred in the absence of Ca 2+ ionophoric activity. Likewise, the inhibition mechanism was linked to: (i) rapid enzyme phosphorylation from ATP in the presence of Ca 2+ but lower steady-state levels of phosphoenzyme; (ii) more drastic effect on phosphoenzyme levels when the toxin was added to the enzyme in the absence of Ca 2+ ; (iii) decreased phosphoenzyme levels at saturating Ca 2+ concentrations; (iv) no effect on kinetics of phosphoenzyme decomposition. The palytoxin effect is related with lock of the enzyme in the Ca 2+ -free conformation so that progression of the catalytic cycle is impeded. |
| Databáze: | OpenAIRE |
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