Microtubule Dynamics

• Assembly occurs at 37°C and disassembly at 4°C (Fig. 19.9a).
• Assembly above the critical concentration, Cc (Fig. 19.9b).
• Near critical concentration microtubules oscillate between lengthening ans shortening.
• Linear polymers of alpha/beta anr joined together to forms shees and then circular tubules that serve as a nucleation site.  Polymerization then continues by addition of dimers to each end (Fig. 19.11).
• Microtubule-associated proteins (MAPs) bind microtubules and keep them from depolymerizing, organize them into bundles, and cross-link them to membranes and intermediate filaments (Table 19.1, Fig. 19.18)

• Kinesin (Fig. 19.23) and dynein protein families serve as motors that travel along microtubules.
• These motors attach to vesicles and carry them in specific directions (Fig. 19.24).
• Each type has specific cargo to carry (Table 19.2).
• Dynein-associated microtubule binding proteins tether cargo to microtubules (Fig. 19.25).

General model for kenesin- and dynein-mediated transport on the cytoplamic microtubule network (Fig. 19.26).

Model for dynein-mediated sliding of axonemal out doublet microtubules (Fig. 19.31).

Stages of mitosis and cytokinesis in an animal cell (Fig. 19.34) (Movie).
 
 
 

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