Microtubules growth

S. lijima, T. Ichihashi, Y. Ando, Pentagons, heptagons, and negative curvature in graphitic microtubule growth, Nature, voi. 356, pp. 776-778,1992. 

Iijima, S., Ichihashi, T. Ando, Y. 1992 Pentagons, heptagons and negative curvature in graphite microtubule growth. Nature, Lond. 356, 776-778. 

Brandt R, Lee G (1993) Functional organization of microtubule-associated protein tau. Identification of regions which affect microtubule growth, nucleation, and bundle formation... 

Mitchison T, Kirschner M. Dynamic instabibty of microtubule growth. Nature 1984 312 237-242. 

Jordan MA, Kamath K, Manna T, Okouneva T, Miller HP, Davis C, Littlefield BA, Wilson L. The primary antimitotic mechanism of action of the synthetic halichondrin E7389 is suppression of microtubule growth. Mol. Cancer Ther. 2005 4 1086-1095. 

Pentagons, heptagons and negative curvature in graphite microtubule growth... 

Pentagons, Heptagons and Negative Curvature in Graphite Microtubule Growth... 

Microtubule systems are used in the cell for many other functions, such as transport of organelles and vesicles, and separating genetic material on the mitotic spindle and other motile events of the cell cycle. Substances that interfere with microtubule growth or turnover, or with microtubule interaction with motor proteins, will disrupt these... 

Under appropriate In vitro conditions, some individual microtubules oscillate between growth and shortening phases (Figure 20-9). In all cases, the rate of microtubule growth is much slower than the rate of shortening. When first discovered, this behavior of microtubules, termed dynamic instability, was surprising to researchers because they expected that under any condition all the microtubules in a solution or the same cytosol would behave identically. 

FIGURE 20-11 Dynamic instability model of microtubule growth and shrinkage. GTP-bound a(3-tubulin subunits (red) add preferentially to the (-t) end of a preexisting microtubule. After incorporation of a subunit, the GTP (red dot) bound to the (i-tubulin monomer is hydrolyzed to GDP Only microtubules whose (+) ends are associated with GTP-tubulin (those with a GTP cap) are stable and can serve as primers for the polymerization of additional tubulin. Microtubules with GDP-tubulin (blue) at the (+) end (those with a GDP cap) are rapidly depolymerized and may disappear within 1 minute. At high concentrations of unpolymerized GTP-tubulin, the rate of addition of tubulin is faster than the rate of hydrolysis of the GTP bound in the microtubule or the rate of dissociation of GTP-tubulin from microtubule ends thus the microtubule grows. At low concentrations of unpolymerized GTP-tubulin, the rate of addition of tubulin is decreased consequently, the rate of GTP hydrolysis exceeds the rate of addition of tubulin subunits and a GDP cap forms. Because the GDP cap is unstable, the microtubule end peels apart to release tubulin subunits. [See T Mitchison and M. Kirschner, 1984, Nature 312 237 ... 

The check the validity of the arguments a series of model calculations based on the reaction mechanism of Fig. 10 were performed [19], details to be published). They are based on a set of coupled differential equations and on the assumption that the phase transition between microtubule growth and shrinkage can be explained by cooperative interactions between tubulin subunits at microtubule ends. Two examples are shown in Fig. 13 where the rate of GTP hydrolysis following the incorporation of tubulin into microtubules was varied. When this rate is fast (Fig. 13 a) one finds pronounced oscillations (this is equivalent to an intermediate stability of microtubules, compare Fig. lib). When the rate of hydrolysis is reduced (Fig. 13 b) the oscillations disappear because microtubules are effectively stabilized, and they remain assembled in a steady state (compare Fig. 11 a). 

Mitchison, T., and Kirschner, M., Dynamic instability of microtubule growth. Nature (London) 312, 237 (1984). 

Mitchison T and Kirschner M 1984 Dynamic instability of microtubule growth Nature 213 237-42... 

---