Figure 1

Turbidity time course of the in vitro microtubule assembly. (A) Tubulin in presence of various ligands. Samples with 15 μM tubulin are maintained at 4°C. After addition of 8 μM Tat (line 4), 4 μM Tat (line 2) from HIV-1 HxB2 strain or 15 μM paclitaxel (line 3), the assembly reaction was started by warming the samples at 37°C (time 0, arrow) and compared to tubulin alone (line1). The ΔOD350 nm is measured every 30 sec. After 30 min the temperature was lowered to 10°C (arrow). (B) Electron microscopy of microtubules formed in the presence of Tat. Aliquot from samples reaching the ΔDO350 nm plateau at 37°C were adsorbed on coated Formvar films on copper grids. Electron micrographs of microtubules formed without Tat (Control) or with indicated concentrations of Tat and paclitaxel are presented with 4000-fold magnification. Microtubules formed with Tat at 8 μM are also presented at 40000-fold magnification. (C) Production of microtubules in the presence of Tat. Samples of 15 μM tubulin alone (Control) and with 8 μM Tat (Tat 8), 16 μM Tat (Tat 16) or 15 μM paclitaxel (Paclitaxel) at the time they reach the plateau at 37°C were ultracentrifuged and supernatant (S) and pellets (P) were analyzed on SDS-PAGE. (Tat 8) × 5 indicates a fivefold increase in the quantity of the sample loaded. The mass of tubulin (Tub 55 kDa) and Tat (Tat 10 kDa) are indicated.