Phosphorylation of microtubule-associated proteins regulates their interaction with actin filaments.

摘要: We have determined the absolute phosphate content of microtubule-associated proteins (MAPs) and established that phosphorylation inhibits actin filament cross-linking activity MAPs both major MAP components, MAP-2 tau. Similar results were obtained with from rabbit muscle, hog brain, Acanthamoeba castellanii. used endogenous phosphatases kinases in brain microtubule protein to modulate level before isolating heat-stable MAPs. isolated directly twice-cycled contain 7.1 +/- 0.1 (S.E.) mol phosphate/300,000 g protein. After incubating without ATP, MAPs, had 4.9 0.6 phosphates. 1 mM ATP 5 microM cAMP 2 EGTA, 8.6 0.5 phosphates but there was also exchange three more [32P]phosphates gamma-labeled for preexisting phosphate. Incubation CaCl2 resulted no net addition fractionated preparations by gel filtration 4.3 7.5 tau 1.5 2.2 phosphate/mol depending on how we treated prior isolation. The whole MAP-2, depended MAP-phosphate content. In all cases, inhibited activity. concentration high required form a viscosity solution filaments 4 times than low During incubation [gamma-32P]ATP, only peptides are labeled. Treatment these either acid or alkaline phosphatase removes mainly an increase Thus, effect reversible.