Document Detail

Studies on phosphorylation of canine cardiac sarcoplasmic reticulum by calmodulin-dependent protein kinase.
MedLine Citation:
PMID:  6273007     Owner:  NLM     Status:  MEDLINE    
Two endogenous protein kinase activities, cAMP-dependent and calmodulin-Ca2+-dependent, are associated with isolated cardiac sarcoplasmic reticulum (SR) vesicles. Both kinases phosphorylate an endogenous substrate of approximately 22,000 daltons (phospholamban). The phosphorylation of phospholamban by either the intrinsic or by exogenous cAMP-dependent protein kinase is found to be Ca2+-independent between 0.05 and 100 microM free Ca2+. Calmodulin-dependent phosphorylation, on the other hand, does not require cAMP and is absolutely dependent on the presence of free Ca2+ over a concentration range that corresponds to physiological levels (10(-7) to 10(-5) M). Phosphorylation of SR vesicles by both kinases is additive and the extent of saturation of the cAMP-specific sites has no effect on the degree of stimulation by calmodulin or its Ca2+-dependence. Trifluoperazine, an inhibitor of calmodulin, inhibits calmodulin-dependent phosphorylation without affecting cAMP-dependent phosphorylation, indicating the presence of two types of kinases. This is made further evident by the selectivity of each kinase for exogenous substrates. Whereas cAMP-dependent protein kinase appears to phosphorylate histone ILA (a basic protein) preferentially, calmodulin-dependent protein kinase prefers phosvitin (an acidic protein).
L M Bilezikjian; E G Kranias; J D Potter; A Schwartz
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Circulation research     Volume:  49     ISSN:  0009-7330     ISO Abbreviation:  Circ. Res.     Publication Date:  1981 Dec 
Date Detail:
Created Date:  1982-02-12     Completed Date:  1982-02-12     Revised Date:  2009-11-19    
Medline Journal Info:
Nlm Unique ID:  0047103     Medline TA:  Circ Res     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  1356-62     Citation Subset:  IM    
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MeSH Terms
Adenosine Triphosphatases / pharmacology
Calcium-Binding Proteins / pharmacology*
Calmodulin / antagonists & inhibitors,  pharmacology*
Cyclic AMP / metabolism
Egtazic Acid / pharmacology
Myocardium / enzymology*
Protein Kinases / metabolism*
Sarcoplasmic Reticulum / enzymology*
Trifluoperazine / pharmacology
Troponin / pharmacology
Grant Support
Reg. No./Substance:
0/Calcium-Binding Proteins; 0/Calmodulin; 0/Troponin; 0/phospholamban; 117-89-5/Trifluoperazine; 60-92-4/Cyclic AMP; 67-42-5/Egtazic Acid; EC 2.7.-/Protein Kinases; EC 3.6.1.-/Adenosine Triphosphatases

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