Microtubules are polymers that cycle stochastically between polymerization and depolymerization, i.e. they exhibit "dynamic instability." This behavior is crucial for cell division, motility, and differentiation. Although studies in the last decade have made fundamental breakthroughs in our understanding of how cellular effectors modulate microtubule dynamics, analysis of the relationship betwe...

A series of derivatives of 5,6-diphenylpyridazin-3-one (DPP) was examined for interactions with calf brain tubulin following the demonstration that many members of the class caused significant mitotic effects in intact animals, while others had activity against murine P388 leukemia. In L1210 cells several DPP derivatives caused a rise in the mitotic index which correlated well with the cytotoxi...

Several types of non-equilibrium phenomena have been observed in microtubule polymerization, including dynamic instability, assembly overshoot and oscillations. They can be interpreted in terms of interactions between tubulin subunits (= alpha, beta heterodimers), microtubules, and a third state, oligomers, which represent intermediates between microtubule disassembly and the regeneration of as...

The important anticancer drug paclitaxel binds to the beta-subunit of the alphabeta-tubulin dimer in the microtubule in a stoichiometric ratio, promoting microtubule polymerization and stability. The conformation of microtubule-bound drug has been the subject of intense study, and various suggestions have been proposed. In previous work we presented experimental and theoretical evidence that pa...

Assembly-competent tubulin was purified from the cytoplasm of unfertilized and parthogenetically activated oocytes, and from isolated meiotic spindles of the surf clam, Spisula solidissima. At 22 degrees C or 37 degrees C, Spisula tubulin assembled into 48-51-nm macrotubules during the first cycle of polymerization and 25-nm microtubules during the third and subsequent cycles of assembly. Macro...

Dilantin (phenytoin) is a commonly used antiepileptic agent that is known to decrease conductance of sodium and calcium ions and delay outward potassium currents. Separate from its antiseizure activity, dilantin interferes with microtubule protein polymerization. It induces metaphase arrest and potentiates the effects of the antimitotics vincristine and vinblastine in cell culture. We show here...

The effect of gold nanoparticles (AuNPs) on the polymerization of tubulin has not been examined till now. We report that interaction of weakly protected AuNPs with microtubules (MTs) could cause inhibition of polymerization and aggregation in the cell free system. We estimate that single citrate capped AuNPs could cause aggregation of ∼10(5) tubulin heterodimers. Investigation of the nature of ...

The calcium concentration required to inhibit tubulin polymerization by 50% (Ca2+ sensitivity) extends from the micromolar to the millimolar range and is a function of a number of factors that include 1) a steep, inverse dependence on tubulin concentration: two-cycle tubulin has lower Ca2+ sensitivity than pure tubulin (prepared by a novel method described under "Appendix"); 2) temperature: Ca2...

A small family of structural analogues of the antimitotic tripeptides, hemiasterlins, have been designed and synthesized as potential inhibitors of tubulin polymerization. The effectiveness of a multicomponent approach was fully demonstrated by applying complementary versions of the isocyanide-based Ugi reaction. Compounds strictly related to the lead natural products, as well as more extensive...

Microtubules are dynamically unstable polymers that interconvert stochastically between polymerization and depolymerization. Compared with microtubules assembled from purified tubulin, microtubules in a physiological environment polymerize faster and transit more frequently between polymerization and depolymerization. These dynamic properties are essential for the functions of the microtubule c...