HYDROLYSIS OF GTP ASSOCIATED WITH THE FORMATION OF TUBULIN OLIGOMERS IS INVOLVED IN MICROTUBULE NUCLEATION

Hydrolysis of GTP is known to accompany microtubule assembly, Here we show that hydrolysis of GTP is also associated with the formation of l inear oligomers of tubulin, which are precusors (prenuclei) in microtu bule assembly. The hydrolysis of GTP on these linear oligomers inhibit s the lateral association of GTP-tubulin that leads to the formation o f a bidimensional lattice, Therefore GTP hydrolysis interferes with th e nucleation of microtubules. Linear oligomers are also formed in mixt ures of GTP-tubulin and GDP-tubulin. The hydrolysis of GTP associated with heterologous interactions between GTP-tubulin and GDP-tubulin in the cooligomer takes place at a threefold faster rate than upon homolo gous interactions between GTP-tubulins. The implication of these resul ts in a model of vectorial GTP hydrolysis in microtubule assembly is d iscussed.