Inhibition of sarcoplasmic reticulum Ca2+-ATPase by miconazole |
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Authors: | Lax Antonio Soler Fernando Fernandez-Belda Francisco |
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Institution: | Departamento de Bioquímica y Biología Molecular A, Facultad de Veterinaria, Universidad de Murcia, Campus de Espinardo, 30071 Espinardo, Murcia, Spain. |
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Abstract: | The inhibition of sarcoplasmic reticulumCa2+-ATPase activity by miconazole was dependent on theconcentration of ATP and membrane protein. Half-maximal inhibition wasobserved at 12 µM miconazole when the ATP concentration was 50 µMand the membrane protein was 0.05 mg/ml. When ATP was 1 mM, a lowmicromolar concentration of miconazole activated the enzyme, whereashigher concentrations inhibited it. A qualitatively similar responsewas observed when Ca2+ transport was measured. Likewise,the half-maximal inhibition value was higher when the membraneconcentration was raised. Phosphorylation studies carried out aftersample preequilibration in different experimental settings shed lighton key partial reactions such as Ca2+ binding and ATPphosphorylation. The miconazole effect on Ca2+-ATPaseactivity can be attributed to stabilization of theCa2+-free enzyme conformation giving rise to a decrease inthe rate of the Ca2+ binding transition. The phosphoryltransfer reaction was not affected by miconazole. |
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