Measurements and simulations of microtubule growth imply strong longitudinal interactions and reveal a role for GDP on the elongating end
Abstract
Microtubule polymerization dynamics result from the biochemical interactions of αβ-tubulin with the polymer end, but a quantitative understanding has been challenging to establish. We used interference reflection microscopy to make improved measurements of microtubule growth rates and growth fluctuations in the presence and absence of GTP hydrolysis. In the absence of GTP hydrolysis, microtubules grew steadily with very low fluctuations. These data were best described by a computational model implementing slow assembly kinetics, such that the rate of microtubule elongation is primarily limited by the rate of αβ-tubulin associations. With GTPase present, microtubules displayed substantially larger growth fluctuations than expected based on the no GTPase measurements. Our modeling showed that these larger fluctuations occurred because exposure of GDP-tubulin on the microtubule end transiently 'poisoned' growth, yielding a wider range of growth rates compared to GTP only conditions. Our experiments and modeling point to slow association kinetics (strong longitudinal interactions), such that drugs and regulatory proteins that alter microtubule dynamics could do so by modulating either the association or dissociation rate of tubulin from the microtubule tip. By causing slower growth, exposure of GDP tubulin at the growing microtubule end may be an important early event determining catastrophe.
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Author details
Funding
National Science Foundation (MCB-1615938)
- Tae Kim
- Lauren A McCormick
- Luke M Rice
National Institutes of Health (R01-GM135565)
- Lauren A McCormick
- Luke M Rice
National Institutes of Health (R35-GM139568)
- Joseph M Cleary
- William O Hancock
National Institutes of Health (T32-GM108563)
- Joseph M Cleary
National Institutes of Health (T32-GM008297)
- Tae Kim
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Copyright
© 2022, Cleary et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
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