title: Phosphoproteins of the adrenal chromaffin granule membrane.
abstract: A fraction of chromaffin granule membranes contained a number of substrates for endogenous protein kinase activity as well as endogenous phosphatase activity. The major 32P-labelled polypeptide of molecular weight 43,000 appeared to be the alpha-subunit of pyruvate dehydrogenase of residual mitochondria. Several polypeptides showed cyclic AMP stimulation of phosphorylation of which the major polypeptide of molecular weight 59,000 shows half-maximal phosphorylation with 0.49 microM cyclic AMP. The phosphorylation of several other polypeptides is inhibited at high cyclic AMP concentrations. From studies with immunoprecipitation and two-dimensional electrophoresis it was found that alpha- and beta-tubulin and actin were absent from the granule membranes. However 32P labelling of a proportion of the copies of dopamine-beta-hydroxylase was demonstrated. The majority of the substrates for endogenous protein kinase activity are probably on the cytoplasmic side of the granule membrane.
mesh_terms: D000313:Adrenal Medulla / Q000648:ultrastructure*; D000818:Animals; D002417:Cattle; D002837:Chromaffin Granules / Q000378:metabolism*; D002838:Chromaffin System / Q000378:metabolism*; D000242:Cyclic AMP / Q000494:pharmacology; D004299:Dopamine beta-Hydroxylase / Q000378:metabolism; D007425:Intracellular Membranes / Q000378:metabolism; D008970:Molecular Weight; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism; D011768:Pyruvate Dehydrogenase Complex / Q000378:metabolism
chemical_list: D010750:Phosphoproteins; D011768:Pyruvate Dehydrogenase Complex; D000242:Cyclic AMP; D004299:Dopamine beta-Hydroxylase; D011494:Protein Kinases