Dilution-induced disassembly of microtubules: Relation to dynamic instability and the GTP cap
Article first published online: 4 FEB 2005
Copyright © 1991 Wiley-Liss, Inc.
Cell Motility and the Cytoskeleton
Volume 18, Issue 1, pages 55–62, 1991
How to Cite
Voter, W. A., O'Brien, E. T. and Erickson, H. P. (1991), Dilution-induced disassembly of microtubules: Relation to dynamic instability and the GTP cap. Cell Motil. Cytoskeleton, 18: 55–62. doi: 10.1002/cm.970180106
- Issue published online: 4 FEB 2005
- Article first published online: 4 FEB 2005
- Manuscript Accepted: 13 SEP 1990
- Manuscript Received: 3 APR 1990
- purified tubulin;
- computer simulations;
- polymer loss
Microtubules were assembled from purified tubulin in the buffer originally used to study dynamic instability (100 mM PIPES, 2 mM EGTA, 1 mM magnesium, 0.2 mM GTP) and then diluted in the same buffer to study the rate of disassembly. Following a 15-fold dilution, microtubule polymer decreased linearly to about 20% of the starting value in 15 sec. We determined the length distribution of microtubules before dilution, and prepared computer simulations of polymer loss for different assumed rates of disassembly. Our experimental data were consistent with a disassembly rate per microtubules of 60 μm/min. This is the total rate of depolymerization for microtubules in the rapid shortening phase, as determined by light microscopy of individual microtubules (Walker et al.: Journal of Cell Biology 107:1437–1448, 1988). We conclude, therefore, that microtubules began rapid shortening at both ends upon dilution. Moreover, since we could detect no lag between dilution and the onset of rapid disassembly, the transition from elongation to rapid shortening apparently occurred within 1 sec following dilution. Assuming that this transition (catastrophe) involves the loss of the GTP cap, and that cap loss is achieved by the sequential dissociation of GTP-tubulin subunits following dilution, we can estimate the maximum size of the cap based on the kinetic data and model interpretation of Walker et al. The cap is probably shorter than 40 and 20 subunits at the plus and minus ends, respectively.