scholarly journals Calcium- and cyclic AMP-regulated protein kinases of bovine central-nervous-system myelin

1984 ◽  
Vol 218 (3) ◽  
pp. 923-932 ◽  
Author(s):  
N C Wu ◽  
F Ahmad
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Cyclic Amp ◽  
Substrate Specificity ◽  
Protein Kinases ◽  
Basic Protein ◽  
Phospholipases A2 ◽  
Dependent Protein ◽  
Myelin Fraction ◽  
Triton X

Bovine central-nervous-system myelin was found to contain both Ca2+-activated and cyclic AMP-dependent protein kinases. Each enzyme possesses unique solubility and substrate-specificity characteristics. The Ca2+-activated enzyme, like its substrate (basic protein), is probably deeply embedded in the neural membrane, whereas the cyclic AMP-dependent kinase appears to be much less tightly associated with myelin. Treatment of insoluble myelin fraction housing the Ca2+-activated kinase with phospholipase A2 and phospholipases A2 + C causes a decrease in its ability to become activated by Ca2+. This can be countered by phosphatidylserine and phosphatidylethanolamine. Whereas the activity of the Ca2+-activated membrane-associated kinase is inhibited by chlorpromazine, dibucaine, melittin and Triton X-100, it is activated by certain phorbol diesters (4 beta-phorbol 12-myristate 13-acetate, 4 beta-phorbol 12,13-didecanoate, 4 beta-phorbol 12,13-dibenzoate and 4 beta-phorbol 12,13-diacetate), which appear to exert this effect by lowering the concentration of Ca2+ normally required for the activation of this enzyme. Together these results suggest that the activation of the membrane-associated kinase by Ca2+ most probably requires certain lipids, perhaps those already present in the membrane.

scholarly journals Photoaffinity labelling of central-nervous-system myelin. Evidence for an endogenous type I cyclic AMP-dependent kinase phosphorylating the larger subunit of 2′,3′-cyclic nucleotide 3′-phosphodiesterase

1984 ◽  
Vol 221 (2) ◽  
pp. 361-368 ◽  
Author(s):  
J M Bradbury ◽  
R J Thompson
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Protein Kinase ◽  
Cyclic Amp ◽  
Cyclic Nucleotide ◽  
Type I ◽  
Phosphodiesterase Activity ◽  
Dependent Protein Kinase ◽  
Photoaffinity Labelling ◽  
Dependent Protein

Endogenous cyclic AMP-stimulated phosphorylation of a 49700-Mr Wolfgram protein component in rabbit central nervous system was investigated by using photoaffinity labelling and 2′,3′-cyclic nucleotide 3′-phosphodiesterase activity staining after electroblotting on to nitrocellulose paper. Photoaffinity labelling with 8′-azidoadenosine 3′,5′-cyclic monophosphate showed a cyclic AMP-binding protein that appeared to be intrinsic to the myelin membrane and appeared to represent the R-subunit of a type I cyclic AMP-dependent protein kinase. This photoaffinity-labelled protein was of larger apparent Mr than the protein showing cyclic AMP-stimulated phosphorylation. Blotting of one-dimensional sodium dodecyl sulphate/polyacrylamide-gel electrophoretograms followed by staining for 2′,3′-cyclic nucleotide 3′-phosphodiesterase activity showed two activity bands corresponding to the two components of the Wolfgram protein doublet. Cyclic AMP-stimulated protein phosphorylation corresponded to the upper component of this doublet. Electroblotting of two-dimensional non-equilibrium pH-gradient electrophoretograms also showed co-migration of cyclic AMP-stimulated protein phosphorylation with enzyme activity. It is proposed that central-nervous-system myelin contains an endogenous type I cyclic-AMP dependent protein kinase that phosphorylates the larger subunit of 2′,3′-cyclic nucleotide 3′-phosphodiesterase.

scholarly journals Partial characterization of the phosphotransferase system of human central-nervous-system myelin

1983 ◽  
Vol 209 (3) ◽  
pp. 789-795 ◽  
Author(s):  
N C Wu ◽  
J E Yourist ◽  
W D Rector ◽  
F Ahmad
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Cyclic Nucleotide ◽  
Basic Protein ◽  
Phosphotransferase System ◽  
Human Central Nervous System ◽  
Bivalent Cation ◽  
Triton X ◽  
Modest Activity

The phosphotransferase system of human central-nervous-system myelin was investigated. Evidence obtained indicated the presence of at least two different phosphotransferase systems (cyclic nucleotide-dependent and -independent) in myelin, which were found to be firmly associated with the membrane. The cyclic AMP-dependent kinase of myelin and white-matter cytosol preferentially phosphorylated certain histone fractions and displayed only modest activity with basic protein as substrate. On the other hand, the cyclic nucleotide-independent system showed specificity toward basic protein. Its activity was not only dependent on Mg2+ but it was greatly enhanced by this bivalent cation. Whereas the cyclic nucleotide-dependent kinase could be extracted with buffers containing Triton X-100, the bivalent cation-regulated kinase resisted solubilization from myelin under these conditions.

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