The name is absent

GTP is hydrolyzed to GDP. Eventually the oligomers will join to form the ringed
microtubule. The hydrolysis of GTP of course is facilitated at a temperature of
37⁰C and stopped at temperatures of 4⁰C. As the oligomers assemble, they form
a series of rings, 25 nm in diameter.

In the cell itself, microtubules are formed in an area near the nucleus called
aster. This is also called the microtubule organizing center (MTOC), or
centrosome. Microtubules are polar with a plus end (fast growing) and a minus
end (slow growing). Usually the minus end is the anchor point in the MTOC. The
plus end carries the GTP molecules, which may be hydrolyzed to GDP.
Hydrolysis is not necessary, however. Tests have shown that microtubules will
form normally with nonhydrolyzable GTP analog molecules attached, however
they will not be able to depolymerize.

It should be stressed that in neurons the microtubule severing by specific
enzyme called katanin (Quarmby, 2000) is important for the production of
non-centrosomal microtubules, which are stable and thus good candidate for
quantum computation. Ahmad et al. (1999) have shown that in neurons a large
number of non-centrosomal microtubules is required for the growth and
maintenance of neuronal processes.

Injection of an anti-katanin antibody into neurons leads to an accumulation of
centrosomal microtubules and a loss of neuronal processes, which indicates that
centrosomal katanin, is important for the production of non-centrosomal
microtubules primarily through severing of the microtubules near the centrosome.
In the neurons the minus end might be capped, which would allow the
persistence of centrosome-free microtubules (Rodionov et al., 1999).

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