title: Cyclic AMP-stimulated phosphorylation of a high molecular weight endogenous protein substrate in sub-cellular fractions of molluscan nervous system.
abstract: Cyclic AMP stimulated the incorporation of radioactive phosphate from ATP into endogenous phosphoproteins in a 20,000 X g supernatant, as well as in a 150,000 X g supernatant, prepared from Helix nervous system homogenates. No effect of cyclic AMP was observed in the respective pellet fractions. A part (but not all) of the cyclic AMP-stimulated activity in both supernatants was due to phosphorylation of an endogenous protein substrate, of apparent molecular weight 120,000 daltons as determined from its mobility in polyacrylamide gels. Little phosphorylation of 120,000 dalton material was observed in the particulate fractions, both in the presence and absence of cyclic AMP. When the 20,000 X g pellet was incubated with radioactive ATP and an exogenous calf ovary protein kinase, cyclic AMP stimulated the phosphorylation of the 120,000 dalton material. The results suggest that both membranes and cytosol from Helix nervous system contain 120,000 dalton substrates for cyclic AMP-dependent protein kinase. However, no kinase catalyzing phosphorylation of these substrates is recovered in membrane fractions following homogenization of the tissue.
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D000242:Cyclic AMP / Q000494:pharmacology*; D003600:Cytosol / Q000378:metabolism; D006372:Helix, Snails; D008566:Membranes / Q000378:metabolism; D008970:Molecular Weight; D009420:Nervous System / Q000187:drug effects / Q000378:metabolism*; D010750:Phosphoproteins / Q000096:biosynthesis*; D011494:Protein Kinases / Q000378:metabolism
chemical_list: D010750:Phosphoproteins; D000255:Adenosine Triphosphate; D000242:Cyclic AMP; D011494:Protein Kinases