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Lecture 6--the cytoskeleton-1

The right one or the left the older subunits are

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Unformatted text preview: d first, theyve been in polymer longer so longer time to be hydrolzed. now theyre all being GDP bound, and that causes the protofilament to nbe weakr; protofilament curves, both curvid and GDP binding reduce the affinitiy of the dimers to eachtohers so they start to fall off; grpwig and shrinking on same end; (+) side stablized by gamma tubulin Figure 16-16b Molecular Biology of the Cell (© Garland Science 2008) dark green: GTP bound dimers stability of microtubul es canbe affected by other proteins when addig new dimers. start on right side; over time, those on the plus end start to hydrolyze as long as the ones on the end are GTP bound theyare stable and can light green circles: GDP bound continue to grow dimers hydroysis can catch up to the end, cap is lost, protofilaments droop, individual dimers fall off, andget a vary rapid shrinkage pf the microtubule, consquenc e caled catastrophy (shrnking when cap is gone). as it shrinks, dimers are released, and those dimers can exchange GDP for GTP and theyre ready to add again to the (+) end) dynamic instability: important for function of tubulin; can mess up tubulinwith things that stabilize and destabilize them. taxol, chemotherapy drug, actually stabilizes microtubules but it is preventing the cycle of growth and catastrophy. Figure 16-16a Molecular Biology of the Cell (© Garland Science 2008) Microtubule associated proteins (MAPS1-4) they can : promote drpolimerization, but often think of them as providing stability. MAP2 cell that is completing mytosis has a spindle it has to take apart. MAP2 microtubule • • MAPs can function as cross-bridges connecting microtubules. They can affect microtubule rigidity and assembly rate. example of cell expressing lots of MAP2, one thing does is maintain the space between microtubules; it is helping stablize and arrange them Figure 16-41 Molecular Biology of the Cell (© Garland Science 2008) tau is protein with strongest association to alzeihmers disease. mutation causes TAU to aggregate. aggregated TAU clogs axons so that thinga can...
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