Properties of the 23,000-Da phosphoproteins in cardiac sarcolemma and sarcoplasmic reticulum |
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| Authors: | C F Louis M Hogan J Turnquist |
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| Affiliation: | 1. College of Horticulture, Hebei Agricultural University, Baoding 071001, Hebei, China;2. Department of Plant Biology, Faculty of Biological Sciences, Tarbiat Modares University, Tehran, Iran;1. Department of Chemistry, Mississippi State University, Starkville MS 39759, U.S.A;2. Department of Physiology and Cell Biology, College of Medicine, Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University, Columbus OH 43210, U.S.A;3. Department of Cell and Molecular Physiology, Loyola University of Chicago, Maywood Illinois 60153, U.S.A;4. Vanderbilt Center for Arrhythmia Research and Therapeutics, Nashville TN 37232, U.S.A |
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| Abstract: | The calmodulin- and cAMP-dependent protein kinase-mediated phosphorylations of isolated sarcolemma and sarcoplasmic reticulum vesicles have been compared. Similarities in the calmodulin-mediated phosphorylation of the sarcolemma and sarcoplasmic reticulum 23,000-Da phosphoproteins included their Mg2+, Na+, Ca2+, and calmodulin sensitivities, as well as the size of their dissociated subunits. In contrast, a number of differences between these phosphoproteins were indicated in their sensitivity to detergents (Triton X-100 and sodium dodecyl sulfate) and calmodulin antagonists (R24571 and trifluoperazine). Furthermore, in contrast to the sarcoplasmic reticulum phosphoprotein, the sarcolemma phosphoprotein could not be affinity labeled with 125I-calmodulin. While these results indicate the probable chemical similarity of the sarcolemma and sarcoplasmic reticulum 23,000-Da phosphoproteins, they also indicate there are differences in the lipid/phosphoprotein interactions in these two membranes. |
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