Interrelationships of tubulin-GDP and tubulin-GTP in microtubule assembly

Lin, Chii M.; Hamel, Ernest

doi:10.1021/bi00396a045

Cited by 15 publications

(7 citation statements)

References 38 publications

(82 reference statements)

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“…However, if microtubule elongation occurred at rates measured in control cells ( -4 pm/minute) [26], astral elongation would have been complete within 1-2 minutes. The slow elongation we observed may occur by incorporation of tubulin-GDP, rather than tubulin-GTP, into microtubules, a reaction that has been observed under certain in vitro conditions [5,6,17]. The dynamic instability model, however, postulates that microtubule turnover is modulated by the presence of a cap of GTP-tubulin subunits at the microtubule ends.…”

Section: Discussionmentioning

confidence: 67%

Spindle microtubule dynamics: Modulation by metabolic inhibitors

Wadsworth

Salmon

1988

Cell Motil. Cytoskeleton

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Recent experiments have shown that spindle microtubules are exceedingly dynamic. Measurements of fluorescence recovery after photobleaching (FRAP), in cells previously microinjected with fluorescent tubulin, provide quantitative information concerning the rate of turnover, or exchange, of tubulin subunits with the population of microtubules in living cells at steady state. In an effort to elucidate the pathways and factors that regulate tubulin exchange with microtubules in living cells, we have investigated the energy requirements for tubulin turnover as measured by FRAP. Spindle morphology was not detectably altered in cells incubated with 5 mM sodium azide and 1 mM 2-deoxyglucose (Az/DOG) for 5 minutes, as assayed by polarized light microscopy and antitubulin immunofluorescence. In FRAP experiments on these ATP-depleted cells, the average rate of recovery and the average percent of bleached fluorescence recovered were reduced to 37% and 30% of controls, respectively. When the inhibitors were removed, cells continued through mitosis, and rapid FRAP was restored. In the presence of azide and glucose, the rate of recovery and percent of fluorescence recovered were only slightly reduced, demonstrating that energy production via glycolysis can support microtubule turnover. Longer incubations with Az/DOG altered the microtubule organization in mitotic cells: astral microtubules lengthened and spindle fibers shortened. Furthermore, both astral and spindle microtubules became resistant to nocodazole-induced disassembly under these conditions. Together these observations indicate that microtubule dynamics require ATP and suggest a relationship between microtubule organization and turnover.

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Section: Discussionmentioning

confidence: 67%

Spindle microtubule dynamics: Modulation by metabolic inhibitors

Wadsworth

Salmon

1988

Cell Motil. Cytoskeleton

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“…Taken together these facts suggest the following plau-sible mechanism for the polymerization oscillations that we observe. Under limiting GTP conditions and in the presence of a GTP regenerating system, GTP-tubulin will initially accumulate to 80% of the total tubulin [11]. Then nucleation occurs and microtubule growth proceeds.…”

Section: Discussionmentioning

confidence: 99%

Monotonic versus oscillating microtubule assembly: a cryo‐electron microscope study

Wade¹,

Pirollet²,

Margolis³

et al. 1989

Biology of the Cell

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Depending on the free GTP concentration, microtubules can assemble following either a monotonic or an oscillatory mode. We have used cryoelectron microscopy to compare the tubulin assemblies characteristic of each polymerization pathway. We focus on the first assembly peak. At this particular time point, despite their strikingly different subsequent evolution, both systems are similar with regard to the extent of tubulin polymerization and to the microtubule length distribution. The present study shows that whilst the observed microtubule structures are the same in both systems, the oscillatory system shows quantities of closed ring-like tubulin oligomers, far in excess of those observed in the monotonic system. Furthermore, the conversion of the oscillating system to a monotonic one by GTP addition during the first oscillation is accompanied by a marked decrease in the number of rings. Based on these results we propose that the GTP dependent step which governs microtubule oscillations is the opening of inactive tubulin oligomers.

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“…Whilst the experimental evidence for TU • GDP supporting MT elongation has been a matter of debate for a long time, it now seems sure that TU" GDP can indeed be incorporated during copolymerization with TU. GTP (Bayley and Manser 1985;Hamel et al 1986;Lin and Hamel 1987;Hyman et al 1992). …”

Section: Destabilization By Tu Gdp According To the Lateralmentioning

confidence: 99%

A model of microtubule oscillations

Marx

Mandelkow

1994

Eur Biophys J

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Simulations of microtubule oscillations have been obtained by a kinetic model including nucleation of microtubules, elongation by addition of GTP-loaded tubulin dimers, disassembly into oligomers, and dissolution of oligomers followed by nucleotide exchange at the free dimers. Dynamic instability is described by the on and off rates for dimer association in the growth phase, the rate of rapid shortening, and the transition rates for catastrophe and rescue. The latter are assumed to be completely determined by the current state of the system ("short cap hypothesis"). Microtubule oscillations and normal polymerizations measured by time-resolved X-ray scattering were used to test the model. The model is able to produce oscillations without further assumptions. However, in order to obtain good fits to the experimental data one requires an additional mechanism which prevents rapid desynchronization of the microtubules. One of several possible mechanisms that will be discussed is the destabilization of microtubules by the products of disassembly.

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Interrelationships of tubulin-GDP and tubulin-GTP in microtubule assembly

Cited by 15 publications

References 38 publications

Spindle microtubule dynamics: Modulation by metabolic inhibitors

Spindle microtubule dynamics: Modulation by metabolic inhibitors

Monotonic versus oscillating microtubule assembly: a cryo‐electron microscope study

A model of microtubule oscillations

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