Dynamic Instability - depolymerization If the rate of...

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Dynamic Instability Individual microtubules alternate between cycles of growth and shrinkage. This dynamic behavior is termed dynamic instability. This behavior stems from the intrinsic capacity of tubulin subunits to hydrolyze GTP. Each free tubulin dimer contains one tightly bound GTP molecule that is hydrolyzed to GDP shortly after the subunit is added to the microtubule. GTP associated subunits pack tightly together while GDP associated subunits bind less strongly to one another. When polymerization is proceeding rapidly, tubulin molecules add to the plus end faster than the GTP that they carry is hydrolyzed. A cap (the GTP cap) prevents
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Unformatted text preview: depolymerization. If the rate of polymerization slows, the GTP at plus end will be hydrolyzed to GDP. If this occurs, the GDP-bound tubulin will dissociate resulting in rapid depolymerization. Now, the microtubule can depolymerize by loosing subunits from the plus end. Function of this behavior: the centrosome is continually shooting out new microtubules in an exploratory fashion in different directions and retracting them through depolymerization. A microtubule can be prevented from disassembling if its plus end is stabilized by attachment to another molecule or cell structure. Analogy to fisherman "waiting for a bite"....
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This document was uploaded on 11/03/2011 for the course BIOLOGY MCB2010 at Broward College.

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