15 Microtubules - BME 418, Quantitative Cell Biology #15:...

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BME 418, Quantitative Cell Biology Alan J. Hunt #15: Microtubules Microtubules are central to mitosis since they are the principal structural element of the mitotic spindle, and serve as tracks along which chromosomes move. Brief review of important points: - Polymerized from tubulin dimers, the asymmetry of which confers a polarity on a microtubule. The faster growing plus end is located distal to the microtubule organizing center, or distal to the spindle poles during mitosis. - A non-exchangeable GTP molecule is always bound to the α-tubulin. An exchangeable molecule of GTP is bound to the β-tubulin before polymerization, and is hydrolyzed to GDP shortly after incorporation into a microtubule. - Energy released by GTP hydrolysis drives “dynamic instability”, the process of alternation between periods of slow growth and rapid shortening. The energy released during dynamic instability may be harnessed to move chromosomes during mitosis.
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Alan J. Hunt Dynamics instability is an unusual behavior that is not exhibited by any other known polymers. During this process a microtubule transitions between different states that have very different kinetic parameters. A transition from “growth” to “rapid shortening” is called a “catastrophe”, and a transition back to growth is called a rescue. What does this tell us about tubulin energetics?
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15 Microtubules - BME 418, Quantitative Cell Biology #15:...

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