| Correlation between calmodulin-dependent increase in the rate of calcium transport and calmodulin-dependent phosphorylation of cardiac sarcoplasmic reticulum. Characterization of calmodulin-dependent phosphorylation. | |
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MedLine Citation:
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PMID: 6617659 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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The aim of the present study was to prove a correlation between the calmodulin-dependent increase in the rate of calcium transport by dog cardiac sarcoplasmic reticulum and calmodulin-dependent phosphorylation. The dependence of phosphorylation on the total calmodulin concentration at 75 microM and 1 microM free calcium gave apparent calmodulin half-saturation constants Km (CaM) of 9.4 nM and 181 nM, respectively, whilst the apparent Km (CaM) for the rate of calmodulin-stimulated calcium transport carried out at 1 microM calcium, but phosphorylated prior to the calcium uptake at 75 microM or 1 microM calcium, were 12.5 nM and 127 nM, respectively. A positive correlation was obtained between calmodulin-dependent increase in the rate of calcium transport and hydroxylamine-insensitive phosphoester formed by the calcium/calmodulin-regulated, membrane-bound protein kinase. More than 90% of incorporated [32P]phosphate is confined to a 26-28-kDa or 9-11-kDa protein as determined by polyacrylamide gel electrophoresis following solubilization in sodium dodecyl sulfate at 37 degrees C and at 100 degrees C, respectively, similar to the results obtained by phosphorylation with cAMP-dependent protein kinase. The data indicate that calmodulin-dependent phosphorylation of the above protein(s) is causally related to the stimulation of the rate of calcium transport by cardiac sarcoplasmic reticulum, which is at least partially due to a shift in the calcium dependence of the rate of calcium transport to lower free calcium concentrations, K(Ca), of 1.25 microM and 0.61 microM in controls and calmodulin-dependent phosphorylation, respectively. Activation of calmodulin-dependent phosphorylation by free calcium at total calmodulin concentrations of 300 nM, 100 nM and 30 nM gave apparent K(Ca) values of 0.83 microM, 1.44 microM and 2.3 microM and Hill coefficients of 4.13, 3.76 and 3.79, respectively, indicating that all four calcium binding sites of calmodulin have to be saturated to obtain activation of the calcium/calmodulin-regulated protein kinase. The calmodulin-dependent modulation of calcium transport in vivo is, therefore, determined to great extent by the total calmodulin concentration present in the sarcoplasm. |
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Authors:
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B Plank; C Pifl; G Hellmann; W Wyskovsky; R Hoffmann; J Suko |
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Publication Detail:
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Type: In Vitro; Journal Article; Research Support, Non-U.S. Gov't |
Journal Detail:
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Title: European journal of biochemistry / FEBS Volume: 136 ISSN: 0014-2956 ISO Abbreviation: Eur. J. Biochem. Publication Date: 1983 Oct |
Date Detail:
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Created Date: 1983-11-23 Completed Date: 1983-11-23 Revised Date: 2007-07-23 |
Medline Journal Info:
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Nlm Unique ID: 0107600 Medline TA: Eur J Biochem Country: GERMANY, WEST |
Other Details:
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Languages: eng Pagination: 215-21 Citation Subset: IM |
Export Citation:
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APA/MLA Format Download EndNote Download BibTex |
| MeSH Terms | |
Descriptor/Qualifier:
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Animals Biological Transport Calcium / metabolism* Calmodulin / physiology* Dogs Myocardium / metabolism* Phosphorylation Protein Binding Sarcoplasmic Reticulum / metabolism* |
| Chemical | |
Reg. No./Substance:
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0/Calmodulin; 7440-70-2/Calcium |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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