Microtubule-associated cyclic AMP-dependent protein kinase in Drosophila melanogaster.
Microtubules were prepared from head extracts of the adult fruit fly, Drosophila melanogaster, by one-step, taxol-assisted polymerization. The microtubular fraction displayed cyclic AMP-dependent protein kinase (protein kinase A) activity, as witnessed by endogenous protein phosphorylation and by protein kinase assay. Microtubule-bound protein kinase A amounts to 4-5% of total soluble kinase activity, which is almost an order of magnitude less than in mammals. The high-molecular-weight microtubule-associated protein-2 (MAP-2), the main binding species for protein kinase A in mammalian brain microtubules, is not detectable in the fly system by protein staining and immunoblotting with anti-pig MAP-2 serum, as well as by hybridization of fly DNA with a cDNA probe for human MAP-2. Cyclic AMP removes a major part of the regulatory (R) subunit of the enzyme from Drosophila microtubules, as demonstrated by enzyme assay, autophosphorylation of R subunit, and quantitating cyclic AMP binding sites. It is proposed that permanently elevated cyclic AMP levels may elute protein kinase A from crucial intracellular binding sites, thereby interfering with signal transduction.
Adám
G
G
Institute of Enzymology, Biological Research Center, Hungarian Academy of Sciences, Budapest.
Friedrich
P
P
D000818:Animals; D000242:Cyclic AMP / Q000378:metabolism / Q000494:pharmacology*; D004331:Drosophila melanogaster / Q000201:enzymology* / Q000648:ultrastructure; D004591:Electrophoresis, Polyacrylamide Gel; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D008870:Microtubules / Q000201:enzymology*; D008970:Molecular Weight; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D011494:Protein Kinases / Q000032:analysis / Q000378:metabolism*
D008869:Microtubule-Associated Proteins; D010750:Phosphoproteins; D000242:Cyclic AMP; D011494:Protein Kinases