Interaction of nerve growth factor with the mouse-brain neurotubule protein(s).

Addition of nerve growth factor to a 105,000 x g supernatant of mouse brain induces the formation of a precipitate whose main constituent is the microtubule protein(s) (tubulin). The binding of nerve growth factor to purified tubulin is not inhibited by colchicine and does not appear to depend on the presence of GTP or Mg(++). GTP, however, and divalent cations, exert a marked effect on the increased turbidity induced by interaction of nerve growth factor with tubulin. These findings are tentatively interpreted with the hypothesis that binding of the factor to tubulin and the induced aggregation is a sequential two-step process; the latter but not the former would be influenced by GTP or divalent cations.