Dimers of a- and ¿8-tubulin (MW 54 kDa); y-tubulin found in MTOC is necessary for nucleation of microtubules
GTP hydrolytic activity
Yes; minus (-) end is nongrowing end embedded in MTOC; plus (+) end is the growing end
At the nucleation site, a- and /3-tubulin dimers are added to y tubulin ring in an end-to-end fashion; each tubulin dimer molecule binds GTP before it becomes incorporated into the microtubule; polymerization also requires the presence of Mg2^; GTP-tubulin complex is polymerized, and after incorporation, GTP is hydrolyzed to GDP
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