[The specificity of modulation of sarcoplasmic reticulum Ca(2+)-ATPase by transmembrane Ca2+ gradient].
We have previously reported that transmembrane Ca2+ gradient-mediated changes in lipid fluidity could modulate the conformation and enzyme activity of sarcoplasmic reticulum (SR) Ca(2+)-ATPase. The aim of this paper is to explore the specificity of transmembrane Ca2+ gradient-mediated modulation of SR Ca(2+)-ATPase. The results showed that such specificity exhibited in two aspects: 1. The modulation could not be ascribed to transmembrane potential resulted from the transmembrane Ca2+ gradient, Dissipation of transmembrane potential by FCCP (carbonylcyanide-p-trifluoromethoxyphenylhydrazone) could not affect the activity of SR Ca(2+)-ATPase. 2. Transmembrane Sr2+ gradient had little effect on the enzyme activity of SR Ca(2+)-ATPase. A significant difference between the effect of transmembrane Ca2+ and Sr2+ gradient on the lipid fluidity was detected in the middle region of bilayer of Ca(2+)-ATPase incorporated proteoliposomes using a set of n-AS [n-(9-anthroyloxy) fatty acids] fluorescence polarization probes. It is known that Ca2+ binding domain of SR Ca(2+)-ATPase is just located in the middle region of bilayer, hence it may be deduced that possibly, membrane lipids are involved in transmembrane Ca2+ gradient-mediated modulation of Ca(2+)-ATPase.
National Laboratory of Biomacromolecules, Institute of Biophysics, Academia Sinica, Beijing, China.
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D000818:Animals; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000502:physiology*; D000252:Calcium-Transporting ATPases / Q000378:metabolism*; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects; D011817:Rabbits; D012519:Sarcoplasmic Reticulum / Q000201:enzymology*; D013324:Strontium / Q000502:physiology
D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone; D000001:Calcimycin; D000252:Calcium-Transporting ATPases; D002118:Calcium; D013324:Strontium