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BIOL 2201 Lecture Notes - Lecture 7: Feedback, Ubiquitin, Phosphatase

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8 Dec 2017

School

Carleton University

Department

Course

Professor

Mohsen Hooshyar

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Document Summary

Microtubules have a hollow cylinder of protofilaments. Starts from the centrosome, on gama-tubulin starting point. Start growing out from centromeres and at the same time they shrink. Always grow at the plus end and shrink at the minus end. If the microtubules reach another molecule, then it will stabilize and will not depolamarize. This whole process is called dynamic instability. (independent process) Tubulin carried gtp are more stable than tubulin bound to gdp. If the process of hydrolysis is faster than the addition of new tubulin with gtp, at some point hydrolysis will catch up. Newly tubulin added can only be added to the tubulin whose already bounded with. When only have gdp bound then no more addition of tubulin is possible. (shrinking microtubule) Taxol (stabilize microtubules) and col-chesin (destabilize microtubules) types of drugs. Growing microtubules cannot attach to kinetochores cell cycle wont start, leading to cell death, Three things you get out of microtubules: motor proteins.

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Related Questions

Activity: Dynamic Instability of Microtubules

Part A

What causes catastrophe of the microtubule in vitro?

the lack of tubulin heterodimers

non-motor Microtubule Associated Proteins (MAPs)

mutation of the Î²-tubulin

Part B

What is the role of GTP in microtubule polymerization?

GTP binds the alpha and beta tubulin subunits together to form the tubulin monomer.

GTP hydrolysis provides the energy for the polymerization of the microtubule.

GTP is a second messenger that signals the need for polymerization/de-polymerization.

GTP stabilizes the tip of the microtubule, allowing more monomers to be added.

Part C

What would happen in the treadmilling experiment if a non-hydrolyzable analogue of GTP were used?

The monomers would be unable to add to the plus end, and the microtubules would shrink until they disappeared.

The microtubule would treadmill until the new tubulin, with non-hydrolyzable GTP, reached the minus end, and then it would only extend at the plus end.

The microtubule would add monomers at both the plus and minus ends, growing in both directions.

The non-hydrolyzable GTP would stabilize both ends, causing treadmilling to stop.

Part D

What is the difference between the plus and minus ends of the microtubule in in vitro experiments?

The beta subunit of the tubulin is exposed on the minus end.

Polymerization occurs at the plus end.

The plus end has a lower critical concentration for tubulin heterodimers.

Catastrophe occurs at the minus end.

Part E

How would the drug taxol affect the in vitro dynamic instability and treadmilling experiments?

Taxol would block catastrophe at the plus end in the dynamic instability experiment but not depolymerization at the minus end in the treadmilling experiment.

Taxol would block the addition of tubulin in both experiments, leading to a destruction of the microtubules.

Taxol would stabilize the microtubules in both experiments, leading to polymerization without catastrophe.

Taxol would block depolymerization at the minus end in the treadmilling experiment but not catastrophe at the plus end in the dynamic instability experiment.