Phosphorylation of microtubule-associated proteins.
1. Tubulin is not an adenosine-3':5'-monophosphate-dependent (cyclic-AMP-dependent) protein kinase. Both entities have been clearly separated by sucrose gradient ultracentrifugation. With a tubulin preparation obtained by the polymerization-depolymerization technique protein kinase had a sedimentation coefficient of 8.7 S whereas tubulin sedimented with 6.4 S. After preincubation with both cyclic AMP and histone the kinase dissociated into its catalytic subunit with a sedimentation coefficient of 3.4 S. 2. Tubulin prepared by the polymerization-depolymerization technique was neither phosphorylated in vivo nor in vitro. On the contrary if this preparation was further purified by the Weisenberg's procedure (DEAE-Sephadex batch absorption) before incubation with [gamma-32 P]ATP, phosphorylation occurred. Thus, phosphorylation depended on the method used to purify tubulin i.e. was likely to an an artefact.
D001921:Brain / Q000378:metabolism*; D002499:Centrifugation, Density Gradient; D000242:Cyclic AMP / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation / Q000187:drug effects; D005459:Fluorides / Q000494:pharmacology; D007700:Kinetics; D046911:Macromolecular Substances; D008870:Microtubules / Q000378:metabolism; D008970:Molecular Weight; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D009928:Organ Specificity; D010750:Phosphoproteins / Q000096:biosynthesis*; D011494:Protein Kinases / Q000302:isolation & purification / Q000378:metabolism*; D013961:Thyroid Gland / Q000378:metabolism
D046911:Macromolecular Substances; D009419:Nerve Tissue Proteins; D010750:Phosphoproteins; D000242:Cyclic AMP; D011494:Protein Kinases; D005459:Fluorides