Functional characterization of the Ca2+-gated Ca2+ release channel of vascular smooth muscle sarcoplasmic reticulum |
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Authors: | Annegret Herrmann-Frank Edward Darling Gerhard Meissner |
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Affiliation: | (1) Department of Biochemistry and Biophysics, University of North Carolina, 27599-7260 Chapel Hill, NC, USA;(2) Present address: Department of Cell Physiology, Ruhr-University Bochum, Universitätsstrasse 150, W-4630 Bochum 1, Federal Republic of Germany |
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Abstract: | The Ca2+-gated Ca2+ release channel of aortic sarcoplasmic reticulum (SR) was partially purified and reconstituted into planar lipid bilayers. Canine and porcine aorta microsomal protein fractions were solubilized in the detergent 3-[(3-cholamidopropyl)dimethylammonio]-1-propane sulphonate (CHAPS) in the presence and absence of 3[H]-ryanodine and centrifuged through linear sucrose gradients. A single 3[H]-ryanodine receptor peak with an apparent sedimentation coefficient of 30 s was obtained. Upon reconstitution into planar lipid bilayers, the unlabelled 30 s protein fraction induced the formation of a Ca2+- and monovalent-ion-conducting channel (110 pS in 100 mM Ca2+, 360 pS in 250 mM K+). The channel was activated by micromolar Ca2+, modulated by millimolar adenosine triphosphate, Mg2+ and the Ca2+-releasing drug caffeine, and inhibited by micromolar ruthenium red. Micro- to millimolar concentrations of the plant alkaloid ryanodine induced a permanently closed state of the channel. Our results suggest that smooth muscle SR contains a Ca2+-gated Ca2+ release pathway, with properties similar to those observed for the skeletal and cardiac ryanodine receptor/Ca2+ release channel complexes. |
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Keywords: | Ca2+ Smooth muscle Sarcoplasmic reticulum Ca2+ Release channel Ryanodine receptor Ca2+-Induced Ca2+ release |
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