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Insights into the mechanism for microtubule dynamics from computational modeling and cryo electron tomographyтезисы доклада
Информация о цитировании статьи получена из
Web of Science
Дата последнего поиска статьи во внешних источниках: 29 мая 2019 г.
- Авторы: Gudimchuk N., Ulyanov E.V., Eileen O’Toole, Vinogradov D.S., Ataullakhanov F.I., and, McIntosh J.R.
- Сборник: Molecular Biology of the Cell
- Серия: 26
- Том: 29
- Тезисы
- Год издания: 2018
- Издательство: American Society for Cell Biology
- Местоположение издательства: United States
- Первая страница: 3063
- Последняя страница: 3063
- DOI: 10.1091/mbc.E18-10-0647
- Аннотация: Microtubules (MTs) are tubulin polymers whose dynamic instability is essential for many cellular processes. The propensity of tubulins to polymerize into MTs depends on an associated nucleotide: GTP vs. GDP. However, despite decades of research, it remains unclear how and to what extent tubulin conformation and/or inter-tubulin bonds are affected by the associated nucleotide. Some studies using cryo-electron microscopy have reported very different structures at the tips of growing and shortening MTs, suggesting different conformations for GTP- and GDP-tubulin. However, crystallographic data, small angle X-ray scattering measurements and allocolchicine binding experiments have indicated that the conformation of free tubulin dimers is not sensitive to the nucleotide bound. Consistent with that, we have recently shown that the tips of growing and shortening MTs both exhibit curved protofilaments (PFs) of very similar curvatures (McIntosh et al., J. Cell Biol 2018). Based on that observation, we have proposed a Brownian dynamics model and a new mechanism for MT assembly in which MT elongation results from the straightening of curved GTP-bound PFs due to thermal fluctuations and the formation of lateral bonds between tubulins in adjacent PFs. Here we provide both experimental and theoretical evidence supporting that model. We have examined model behavior as a function of its key parameters, such as tubulin bending stiffness, the strengths of lateral and longitudinal bonds, and the concentration of soluble tubulin. Stiffnesses in the range of 35-95 kcal/mol/rad2 are sufficient to explain pulling forces of 26-65 pN per MT. Calibrated at those bending stiffnesses, the model correctly describes the dependence of MT assembly rate on soluble tubulin concentration. The shapes and lengths of PFs at growing MT tips are strikingly similar at different tubulin concentrations – a model prediction that we have verified by cryo-electron tomography. Additionally, we find that growing MT tip configurations remain similar in vitro at different concentrations of a TOG polymerase derived from XMAP215. Modest changes in lateral bonds between tubulins in simulations are sufficient to drive a switch from assembly to disassembly, whereas the longitudinal bonds largely determine the lengths of curved PFs at the MT tip. We conclude that our MT growth model can account for MT assembly, dynamic instability and the development of pulling force during MT depolymerization. This revised view of growing MT tip structure and MT dynamics has important implications for our understanding of MT regulation and the mechanics of MT attachment to kinetochores. Supported by RFBR grants №16-34-60113 mol_a_dk and №16-04-01862 A to N.Gudimchuk and NIH grant GM033787 to J.R. McIntosh.
- Добавил в систему: Гудимчук Никита Борисович