8 - Cytoskeleton I Microtubules

8 - Cytoskeleton I Microtubules - Lecture 8: Microtubules,...

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Lecture 8: Microtubules, Motors, and Dynamic Instability
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Three major types of cytoskeletal filament: Microtubules (today’s subject) actin (thin filaments; next week) intermediate filaments IFs form coiled-coils that form strong lateral bonds as they are bundled into structures with rope-like properties and provide structural stability to cells. lamin vimentin desmin keratin neurofilament proteins
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Key facts about microtubules made out of the proteins α - and β -tubulin form hollow tubes constructed of 13 ‘protofilaments’ of alternating α - and β - tubulin asymmetric, with – ( α ) and + ( β ) ends α - and β -tubulin bind GTP, β -tubulin hydrolyzes it. This results in non- equilibrium behavior of MTs at steady- state. typically require ‘seed’ to nucleate assembly
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Figure 16-11 Molecular Biology of the Cell (© Garland Science 2008) Structural organization of microtubules
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Dynamics of Microtubule Growth
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Figure 16-2 Molecular Biology of the Cell (© Garland Science 2008) The microtubule cytoskeleton is highly dynamic and can re-organize within minutes
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Cell injected with bio-tubulin and imaged 50 sec later Total tubulin Bio-tubulin Whole cell Blow up
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Bio- Tub total Tub 5 min 15 min Cell imaged x minutes after injection with Bio-tubulin
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What is the basis for the dynamic behavior of microtubules? Study the assembly properties. low tubulin high tubulin So far so good. behaves like a simple equilibrium polymer (e.g. salt crystallization). C c can be thought of as the concentration at which the rate of assembly = rate of disassembly. i.e.
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polymer’ hypothesis. Based on the measured k on and C c , one can calculate k off and predict that it should take 1000 min to disassemble a 500 μM-long MT. However, during the normal course of development,
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This note was uploaded on 01/12/2012 for the course BI 9 taught by Professor Aravin during the Spring '10 term at Caltech.

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8 - Cytoskeleton I Microtubules - Lecture 8: Microtubules,...

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