Document Detail

Cyclic AMP-stimulated protein kinases at brain synaptic junctions.
MedLine Citation:
PMID:  216697     Owner:  NLM     Status:  MEDLINE    
We have examined endogenous cyclic AMP-stimulated phosphorylation of subcellular fractions of rat brain enriched in synaptic plasma membranes (SPM), purified synaptic junctions (SJ), and postsynaptic densities (PSD). The analyses of these fractions are essential to provide direct evidence for cyclic AMP-dependent endogenous phosphorylation at discrete synaptic junctional loci. Protein kinase activity was measured in subcellular fractions using both endogenous and exogenous (histones) proteins as substrates. The SJ fraction possessed the highest kinase activity toward endogenous protein substrates, 5-fold greater than SPM and approximately 120-fold greater than PSD fractions. Although the kinase activity as measured with histones as substrates was only slightly higher in SJ than SPM fractions, there was a marked preference of kinase activity toward endogenous compared to exogenous substrates in SJ fractions but in SPM fractions. Although overall phosphorylation in SJ fractions was increased only 36% by 5 micron cyclic AMP, there were discrete proteins of Mr = 85,000, 82,000, 78,000, and 55,000 which incorporated 2- to 3-fold more radioactive phosphate in the presence of cyclic AMP. Most, if not all, of the cyclic AMP-independent kinase activity is probably catalyzed by catalytic subunit derived from cyclic AMP-dependent kinase, since the phosphorylation of both exogenous and endogenous proteins was greatly decreased in the presence of a heat-stable inhibitor protein prepared from the soluble fraction of rat brain. The specific retention of SJ protein kinase(s) activity during purification and their resistance to detergent solubilization was achieved by chemical treatments which produce interprotein cross-linking via disulfide bridges. Two SJ polypeptides of Mr = 55,000 and 49,000 were photoaffinity-labeled with [32P]8-N3-cyclic AMP and probably represent the regulatory subunits of the type I and II cyclic AMP-dependent protein kinases. The protein of Mr = 55,000 was phosphorylated in a cyclic AMP-stimulated manner suggesting autophosphorylation as previously observed in other systems.
P T Kelly; C W Cotman; M Largen
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  The Journal of biological chemistry     Volume:  254     ISSN:  0021-9258     ISO Abbreviation:  J. Biol. Chem.     Publication Date:  1979 Mar 
Date Detail:
Created Date:  1979-04-28     Completed Date:  1979-04-28     Revised Date:  2009-11-19    
Medline Journal Info:
Nlm Unique ID:  2985121R     Medline TA:  J Biol Chem     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  1564-75     Citation Subset:  IM    
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MeSH Terms
Brain / enzymology*
Cyclic AMP / pharmacology
Enzyme Activation
Molecular Weight
Protamine Kinase / metabolism
Protein Kinases / isolation & purification,  metabolism*
Subcellular Fractions / enzymology
Synapses / enzymology*
Reg. No./Substance:
60-92-4/Cyclic AMP; EC 2.7.-/Protein Kinases; EC Kinase

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