TABLE 1

NSC 707389 does not stabilize the colchicine binding activity of tubulin

Each final 100-μl reaction mixture contained, as described by Ludueña et al. (1989), 3.7 μM tubulin, 57 μM [³H]colchicine, 0.1 M MES (pH 6.4 with NaOH in 1 M stock solution), 0.1 mM EDTA, 1 mM GTP, 0.5 mM MgCl₂, 1 mM 2-mercaptoethanol, 1 mM EGTA, 5% (v/v) dimethyl sulfoxide, and an additional compound, as indicated, at 40 μM. The preincubation, if performed, was for 3 h at 37°C. At this point the [³H]colchicine was added to the preincubated reaction mixtures. Incubation was for 2 h at 37° C. Average results from two experiments presented in triplicate are presented as colchicine bound (percentage relative to nonpreincubated control).